Overview of conventional extraction techniques applied to the extraction of surfactants and their metabolites from solid samples.
\\n\\n
IntechOpen was founded by scientists, for scientists, in order to make book publishing accessible around the globe. Over the last two decades, this has driven Open Access (OA) book publishing whilst levelling the playing field for global academics. Through our innovative publishing model and the support of the research community, we have now published over 5,700 Open Access books and are visited online by over three million academics every month. These researchers are increasingly working in broad technology-based subjects, driving multidisciplinary academic endeavours into human health, environment, and technology.
\\n\\nBy listening to our community, and in order to serve these rapidly growing areas which lie at the core of IntechOpen's expertise, we are launching a portfolio of Open Science journals:
\\n\\nAll three journals will publish under an Open Access model and embrace Open Science policies to help support the changing needs of academics in these fast-moving research areas. There will be direct links to preprint servers and data repositories, allowing full reproducibility and rapid dissemination of published papers to help accelerate the pace of research. Each journal has renowned Editors in Chief who will work alongside a global Editorial Board, delivering robust single-blind peer review. Supported by our internal editorial teams, this will ensure our authors will receive a quick, user-friendly, and personalised publishing experience.
\\n\\n"By launching our journals portfolio we are introducing new, dedicated homes for interdisciplinary technology-focused researchers to publish their work, whilst embracing Open Science and creating a unique global home for academics to disseminate their work. We are taking a leap toward Open Science continuing and expanding our fundamental commitment to openly sharing scientific research across the world, making it available for the benefit of all." Dr. Sara Uhac, IntechOpen CEO
\\n\\n"Our aim is to promote and create better science for a better world by increasing access to information and the latest scientific developments to all scientists, innovators, entrepreneurs and students and give them the opportunity to learn, observe and contribute to knowledge creation. Open Science promotes a swifter path from research to innovation to produce new products and services." Alex Lazinica, IntechOpen founder
\\n\\nIn conclusion, Natalia Reinic Babic, Head of Journal Publishing and Open Science at IntechOpen adds:
\\n\\n“On behalf of the journal team I’d like to thank all our Editors in Chief, Editorial Boards, internal supporting teams, and our scientific community for their continuous support in making this portfolio a reality - we couldn’t have done it without you! With your support in place, we are confident these journals will become as impactful and successful as our book publishing program and bring us closer to a more open (science) future.”
\\n\\nWe invite you to visit the journals homepage and learn more about the journal’s Editorial Boards, scope and vision as all three journals are now open for submissions.
\\n\\nFeel free to share this news on social media and help us mark this memorable moment!
\\n\\n\\n"}]',published:!0,mainMedia:{caption:"",originalUrl:"/media/original/237"}},components:[{type:"htmlEditorComponent",content:'
After years of being acknowledged as the world's leading publisher of Open Access books, today, we are proud to announce we’ve successfully launched a portfolio of Open Science journals covering rapidly expanding areas of interdisciplinary research.
\n\n\n\nIntechOpen was founded by scientists, for scientists, in order to make book publishing accessible around the globe. Over the last two decades, this has driven Open Access (OA) book publishing whilst levelling the playing field for global academics. Through our innovative publishing model and the support of the research community, we have now published over 5,700 Open Access books and are visited online by over three million academics every month. These researchers are increasingly working in broad technology-based subjects, driving multidisciplinary academic endeavours into human health, environment, and technology.
\n\nBy listening to our community, and in order to serve these rapidly growing areas which lie at the core of IntechOpen's expertise, we are launching a portfolio of Open Science journals:
\n\nAll three journals will publish under an Open Access model and embrace Open Science policies to help support the changing needs of academics in these fast-moving research areas. There will be direct links to preprint servers and data repositories, allowing full reproducibility and rapid dissemination of published papers to help accelerate the pace of research. Each journal has renowned Editors in Chief who will work alongside a global Editorial Board, delivering robust single-blind peer review. Supported by our internal editorial teams, this will ensure our authors will receive a quick, user-friendly, and personalised publishing experience.
\n\n"By launching our journals portfolio we are introducing new, dedicated homes for interdisciplinary technology-focused researchers to publish their work, whilst embracing Open Science and creating a unique global home for academics to disseminate their work. We are taking a leap toward Open Science continuing and expanding our fundamental commitment to openly sharing scientific research across the world, making it available for the benefit of all." Dr. Sara Uhac, IntechOpen CEO
\n\n"Our aim is to promote and create better science for a better world by increasing access to information and the latest scientific developments to all scientists, innovators, entrepreneurs and students and give them the opportunity to learn, observe and contribute to knowledge creation. Open Science promotes a swifter path from research to innovation to produce new products and services." Alex Lazinica, IntechOpen founder
\n\nIn conclusion, Natalia Reinic Babic, Head of Journal Publishing and Open Science at IntechOpen adds:
\n\n“On behalf of the journal team I’d like to thank all our Editors in Chief, Editorial Boards, internal supporting teams, and our scientific community for their continuous support in making this portfolio a reality - we couldn’t have done it without you! With your support in place, we are confident these journals will become as impactful and successful as our book publishing program and bring us closer to a more open (science) future.”
\n\nWe invite you to visit the journals homepage and learn more about the journal’s Editorial Boards, scope and vision as all three journals are now open for submissions.
\n\nFeel free to share this news on social media and help us mark this memorable moment!
\n\n\n'}],latestNews:[{slug:"webinar-introduction-to-open-science-wednesday-18-may-1-pm-cest-20220518",title:"Webinar: Introduction to Open Science | Wednesday 18 May, 1 PM CEST"},{slug:"step-in-the-right-direction-intechopen-launches-a-portfolio-of-open-science-journals-20220414",title:"Step in the Right Direction: IntechOpen Launches a Portfolio of Open Science Journals"},{slug:"let-s-meet-at-london-book-fair-5-7-april-2022-olympia-london-20220321",title:"Let’s meet at London Book Fair, 5-7 April 2022, Olympia London"},{slug:"50-books-published-as-part-of-intechopen-and-knowledge-unlatched-ku-collaboration-20220316",title:"50 Books published as part of IntechOpen and Knowledge Unlatched (KU) Collaboration"},{slug:"intechopen-joins-the-united-nations-sustainable-development-goals-publishers-compact-20221702",title:"IntechOpen joins the United Nations Sustainable Development Goals Publishers Compact"},{slug:"intechopen-signs-exclusive-representation-agreement-with-lsr-libros-servicios-y-representaciones-s-a-de-c-v-20211123",title:"IntechOpen Signs Exclusive Representation Agreement with LSR Libros Servicios y Representaciones S.A. de C.V"},{slug:"intechopen-expands-partnership-with-research4life-20211110",title:"IntechOpen Expands Partnership with Research4Life"},{slug:"introducing-intechopen-book-series-a-new-publishing-format-for-oa-books-20210915",title:"Introducing IntechOpen Book Series - A New Publishing Format for OA Books"}]},book:{item:{type:"book",id:"8970",leadTitle:null,fullTitle:"Tourism",title:"Tourism",subtitle:null,reviewType:"peer-reviewed",abstract:"Tourism was booming until 2019 when the COVID-19 pandemic hit. Since then, tourism and related industries have suffered from negative economic impacts. This book examines current challenges and opportunities in the tourism industry using case studies from different parts of the world. It also examines the challenges and obstacles faced by the tourism sector due to lack of environmental policies, high crime rates, and poverty.",isbn:"978-1-83962-173-4",printIsbn:"978-1-83962-172-7",pdfIsbn:"978-1-83962-174-1",doi:"10.5772/intechopen.82932",price:139,priceEur:155,priceUsd:179,slug:"tourism",numberOfPages:348,isOpenForSubmission:!1,isInWos:null,isInBkci:!1,hash:"4b086129cadc323ba152b00c6386c2c8",bookSignature:"Syed Abdul Rehman Khan",publishedDate:"October 6th 2021",coverURL:"https://cdn.intechopen.com/books/images_new/8970.jpg",numberOfDownloads:7817,numberOfWosCitations:0,numberOfCrossrefCitations:2,numberOfCrossrefCitationsByBook:0,numberOfDimensionsCitations:2,numberOfDimensionsCitationsByBook:0,hasAltmetrics:0,numberOfTotalCitations:4,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"June 2nd 2020",dateEndSecondStepPublish:"June 23rd 2020",dateEndThirdStepPublish:"August 22nd 2020",dateEndFourthStepPublish:"November 10th 2020",dateEndFifthStepPublish:"January 9th 2021",currentStepOfPublishingProcess:5,indexedIn:"1,2,3,4,5,6",editedByType:"Edited by",kuFlag:!1,featuredMarkup:null,editors:[{id:"254664",title:"Prof.",name:"Syed Abdul Rehman",middleName:null,surname:"Khan",slug:"syed-abdul-rehman-khan",fullName:"Syed Abdul Rehman Khan",profilePictureURL:"https://mts.intechopen.com/storage/users/254664/images/system/254664.jpg",biography:null,institutionString:"Xuzhou University of Technology",position:null,outsideEditionCount:0,totalCites:0,totalAuthoredChapters:"8",totalChapterViews:"0",totalEditedBooks:"6",institution:{name:"Nanjing University",institutionURL:null,country:{name:"China"}}}],equalEditorOne:null,equalEditorTwo:null,equalEditorThree:null,coeditorOne:null,coeditorTwo:null,coeditorThree:null,coeditorFour:null,coeditorFive:null,topics:[{id:"71",title:"Hospitality Management",slug:"hospitality-management"}],chapters:[{id:"73393",title:"Challenges and Advances in the Planning of Tourism with Amazon River Dolphins in the Brazilian Amazon",doi:"10.5772/intechopen.93894",slug:"challenges-and-advances-in-the-planning-of-tourism-with-amazon-river-dolphins-in-the-brazilian-amazo",totalDownloads:445,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Being considered charismatic cetaceans are among the animals most sought after in tourist interactions that may involve observation, touch, swimming, and provisioning food. This tourism model has the potential to generate socioeconomic and conservationist benefits. However, when carried out in a disorderly manner, this can have a negative impact on cetaceans and tourists alike. In this chapter, we discuss the challenges and advances within the process of participatory planning of tourism with Amazon River dolphins (Inia geoffrensis). Our goal is to present strategies that can support the development of projects and public policies aimed at management of wildlife tourism in other areas. Since its implementation at the Anavilhanas National Park - Brazil, the activity had never had its impact monitored by any competent bodies, and this has led to problems and quick spreading to other sites. The rules and guidelines implemented in have significantly reduced risks for tourists and dolphins alike, improving tourist experience and promoting the awareness of animal life. However, many issues remain and need to be solved, especially in the protected areas. These include reduced staff levels, which limits the ability to implement and monitor planned actions. Such shortcomings lead to setbacks in the development of tourist activities with cetaceans.",signatures:"Marcelo Derzi Vidal, Priscila Maria da Costa Santos, Maria do Perpétuo Socorro Rodrigues Chaves and Robert Swett",downloadPdfUrl:"/chapter/pdf-download/73393",previewPdfUrl:"/chapter/pdf-preview/73393",authors:[{id:"322901",title:"Dr.",name:"Marcelo Derzi",surname:"Vidal",slug:"marcelo-derzi-vidal",fullName:"Marcelo Derzi Vidal"},{id:"329272",title:"MSc.",name:"Priscila Maria da Costa",surname:"Santos",slug:"priscila-maria-da-costa-santos",fullName:"Priscila Maria da Costa Santos"},{id:"329274",title:"Dr.",name:"Maria do Perpétuo Socorro Rodrigues",surname:"Chaves",slug:"maria-do-perpetuo-socorro-rodrigues-chaves",fullName:"Maria do Perpétuo Socorro Rodrigues Chaves"},{id:"329275",title:"Dr.",name:"Robert",surname:"Swett",slug:"robert-swett",fullName:"Robert Swett"}],corrections:null},{id:"76910",title:"From Eco to Sustainable Tourism, the Contradictions and Challenges of Nature-Based Tourism: The Case of Polar Cruises",doi:"10.5772/intechopen.96914",slug:"from-eco-to-sustainable-tourism-the-contradictions-and-challenges-of-nature-based-tourism-the-case-o",totalDownloads:279,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Polar tourism includes all leisure travel products set in the Antarctic and Arctic regions. As such, it is conditioned by an interest for nature in extreme settings (polar desert, cold climate, harsh travel conditions – when by sea. The Arctic adds an additional interest for indigenous cultures. Trying to met those tourism interests, a specialized cruise tourism branch developed in the late 1980s (thu sporadic cruises were held back from the XIXth century onward) providing exclusive access the most difficult and far distant latitudes of the High Arctic and opposite Antarctic coastline. In any form of tourism, operators must protect the resources their economic activities rest upon as any deterioration they suffer will sooner or later impact the experiente and its viability. Hence a paradox: how to protect the ecological (and cultural) integrity of these features for sustained competitiveness? Since its emergence, as an industry some 40 years ago, the polar cruising has followed trends in environmental and social management, referring in their marketing and travel policies to both eco- and sustainable tourism. Serving the wealthy customers, initially the well traveled elderly, the ship-based polar industry kept a simple programme of lecture and soft-oriented activities, namely inflatable cruising in icy bays and close-to-shore trekking. Yet, with an increasing clientele of younger middle-age tourists, operators have also diversified their excursion products to offer more sportive-oriented activities off-ship. As long as these activities were non-fuel based, the operators enforced their ecological management claims. But with more fuel-based activities (helicopter, Zodiac sightseeing), and therefore a more invasive approach to the sensitive ecosystems visited, can this industry continue to claim to be sustainable? Based on the sustainable claims made by two important polar cruise operators, this study ams to underlines that while the polar cruise industry, as a whole, might seek to improve its ecological footprint, there remains many contradiction between their will to be environmental and the desire to conquer the environment.",signatures:"Alain A. Grenier",downloadPdfUrl:"/chapter/pdf-download/76910",previewPdfUrl:"/chapter/pdf-preview/76910",authors:[{id:"324497",title:"Prof.",name:"Alain A.",surname:"Grenier",slug:"alain-a.-grenier",fullName:"Alain A. Grenier"}],corrections:null},{id:"73547",title:"The Light-Up of Dark Bali Tourism: A Qualitative Study",doi:"10.5772/intechopen.93389",slug:"the-light-up-of-dark-bali-tourism-a-qualitative-study",totalDownloads:329,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Tourism world currently stumbles due to Corona virus case that limits all human activities including those related to traveling. Various efforts in every country have been conducted to rebuild tourism to the normal condition; however, each country has its own obstacles. This study aims to create a strategic model in developing tourism based on cultural values or local wisdom to rebuild tourism passion to support economy. This study is a qualitative study using cultural approaches with ethnomethodology tools. Data are collected through in-depth interview with tourism actors: government and communities represented by traditional village leaders. The qualitative results indicate that cultural values summarized in a harmonization concept—harmony with God, harmony with fellow human being, and harmony with environment—become a model core that influences human behavior in developing tourism, namely: natural tourism, cultural tourism, spiritual tourism, culinary tourism, conference tourism, and so on. Traditional villages become the second pillar in developing tourism and it supports by local government. Another finding is that Bali will conduct a shift in tourism from cultural-based tourism to those that give more emphasis on natural tourism based on cultural and religious values as a promoter. The strategy will support health protocol related to physical distancing between tourists.",signatures:"I. Putu Astawa, Tjokorda Gde Raka Sukawati and I. Nyoman Gede Sugiartha",downloadPdfUrl:"/chapter/pdf-download/73547",previewPdfUrl:"/chapter/pdf-preview/73547",authors:[{id:"322956",title:"Prof.",name:"I. Putu",surname:"Astawa",slug:"i.-putu-astawa",fullName:"I. Putu Astawa"},{id:"322967",title:"Dr.",name:"Tjokorda Gde Raka",surname:"Sukawati",slug:"tjokorda-gde-raka-sukawati",fullName:"Tjokorda Gde Raka Sukawati"},{id:"323920",title:"Dr.",name:"I. Nyoman Gede",surname:"Sugiartha",slug:"i.-nyoman-gede-sugiartha",fullName:"I. Nyoman Gede Sugiartha"}],corrections:null},{id:"73254",title:"Opportunities and Obstacles in the Global Tourism Industry: A Story of Post-Covid-19",doi:"10.5772/intechopen.93683",slug:"opportunities-and-obstacles-in-the-global-tourism-industry-a-story-of-post-covid-19",totalDownloads:752,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"The rapid spread of Covid-19 has had far-reaching consequences for people’s daily lives in almost all parts of the world. Furthermore, it creates a negative impact on trade and economic activities, which further has spillover social problems, including unemployment and poverty. Moreover, in the tourism sector, millions of people lost their jobs, and hundreds of airlines are nearly bankrupt. This chapter is intended to investigate the link between the outbreak of Covid-19 and its effect on the tourism sector. The discussion reveals that due to the Covid-19, tourism sector declined sharply, but it provides an opportunity to transform our polluted world into a green one, which will have a significant and positive impact on global tourism in upcoming years. Finally, the chapter provides practical implications and recommendations, which will help policymakers to formulate an eco-friendly mechanism in the tourism sector.",signatures:"Syed Abdul Rehman Khan, Laeeq Razzak Janjua and Zhang Yu",downloadPdfUrl:"/chapter/pdf-download/73254",previewPdfUrl:"/chapter/pdf-preview/73254",authors:[{id:"254664",title:"Prof.",name:"Syed Abdul Rehman",surname:"Khan",slug:"syed-abdul-rehman-khan",fullName:"Syed Abdul Rehman Khan"},{id:"300373",title:"Dr.",name:"Zhang",surname:"Yu",slug:"zhang-yu",fullName:"Zhang Yu"},{id:"328959",title:"Dr.",name:"Laeeq Razzak",surname:"Janjua",slug:"laeeq-razzak-janjua",fullName:"Laeeq Razzak Janjua"}],corrections:null},{id:"74482",title:"Applying and Promoting the Seaport Quality System (SQS) and Spatial Interaction Model (SIM) for the Sustainable Development of the Recreational Seaport Industry in Malaysia",doi:"10.5772/intechopen.93765",slug:"applying-and-promoting-the-seaport-quality-system-sqs-and-spatial-interaction-model-sim-for-the-sust",totalDownloads:310,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"The recreational seaport industry carries out many critical functions, including transport circulation, logistics, commercial, and spatial ones. They influence local economic growth and determine the quality of recreational seaport. However, the definition of recreational seaport quality has remained elusive among the community, at present. Hence, this chapter explores the current literature by using the Systematic Literature Review (SLR) to derive at the definition of seaport quality based on three categories: seaport effectiveness, seaport reliability, and seaport governance, which will be main pillars for the development of marinas. This chapter proposes the Seaport Quality System (SQS) and Spatial Interaction Model (SIM) as a way to develop approaches and strategies that support sustainable planning and management of recreational seaports and marinas in countries with extensive coastlines. It is proposed that in order to offer sustainable and quality services, marinas must adopt the SQS model based on identifying and managing quality and risks. In addition, SIM can be utilised to improve the marinas operations by adopting key components in cruise activities, economic corridors and seaport regionalisation. The combination of both models are essential to enhance the growth momentum of marinas in this country.",signatures:"Mohamad Rosni Othman, Jagan Jeevan, Nurul Haqimin Salleh and Noor Azwa Noralam",downloadPdfUrl:"/chapter/pdf-download/74482",previewPdfUrl:"/chapter/pdf-preview/74482",authors:[{id:"322938",title:"Dr.",name:"Jagan",surname:"Jeevan",slug:"jagan-jeevan",fullName:"Jagan Jeevan"},{id:"329107",title:"Prof.",name:"Mohamad Rosni",surname:"Othman",slug:"mohamad-rosni-othman",fullName:"Mohamad Rosni Othman"},{id:"329109",title:"Dr.",name:"Nurul Haqimin",surname:"Salleh",slug:"nurul-haqimin-salleh",fullName:"Nurul Haqimin Salleh"},{id:"329110",title:"Ms.",name:"Noor Azwa",surname:"Noralam",slug:"noor-azwa-noralam",fullName:"Noor Azwa Noralam"}],corrections:null},{id:"74446",title:"Tourism Impact on Environmental Sustainability: A Focus on the Cruise Industry",doi:"10.5772/intechopen.93922",slug:"tourism-impact-on-environmental-sustainability-a-focus-on-the-cruise-industry",totalDownloads:150,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"The growth of the Global Economy and in particular the Caribbean Islands has been for the last two decades fueled by the cruise shipping industry. However, the growth in this industry gives rise to the expansion in ship size and the number of destinations. Unfortunately, the cruise line industry is responsible for the largest volume of waste, pollutants and destruction to marine lives when compared to other maritime industry sector. This chapter seeks to highlight the correlation between the industry and the growing global need for vibrant economies, a high quality of life, while protecting the environment and sustaining the world’s natural resources. A review of several literature has shown that within the last twenty years, the cruise lines have invested a lot of time and money correcting the negative environmental impacts created. Several proactive and green shipping initiatives designed to improve environmental management were successfully implemented by the industry. These diverse initiatives are group as follows: Research and Innovation, Corporate Social Responsibility (CSR) and Marketing, Awareness raising/environmental education initiative, and Green technologies. Emanating from these initiatives are: reduce or obviate of harmful environmental emissions and environmental management improvements and ultimately an environment that is experiencing an increased level of sustainability and economic activities.",signatures:"Kirkland Robert Anderson",downloadPdfUrl:"/chapter/pdf-download/74446",previewPdfUrl:"/chapter/pdf-preview/74446",authors:[{id:"267131",title:"Dr.",name:"Kirkland Robert",surname:"Anderson",slug:"kirkland-robert-anderson",fullName:"Kirkland Robert Anderson"}],corrections:null},{id:"73876",title:"Development of a Destination Image Recovery Model for Enhancing the Performance of the Tourism Sector in the Developing World",doi:"10.5772/intechopen.93854",slug:"development-of-a-destination-image-recovery-model-for-enhancing-the-performance-of-the-tourism-secto",totalDownloads:477,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"This chapter is based on a doctoral thesis on the development of a destination image (DI) recovery model for enhancing the performance of the tourism sector in Zimbabwe. The study was prompted by the failure of African destinations to develop DI image recovery models. A pragmatist paradigm, a convergent parallel mixed methodology research approach and a cross sectional survey were adopted. A sample of three hundred and nineteen comprising international tourists, service providers and key informants was used. A structured, semi-structured questionnaire and semi-structured interview guide were used respectively. Quantitative data was analyzed using the Statistical Package for Social Sciences (SPSS) and AMOS version 25 while qualitative data was analyzed using NVivo version 12. Tests were conducted using descriptive statistics, exploratory factor analysis, and confirmatory factor analysis. Structural Equation Modeling (SEM) was used to analyze the multiple independent variables. The major findings were that price, ancillary services and amenities significantly influenced affective image while ancillary services significantly influenced destination performance. The study recommended that the Ministry of Environment, Climate, Tourism and Hospitality Industry trains tourism stakeholders including the host community in order to achieve sustainable destination image recovery.",signatures:"Phillip Farayi Kanokanga, Marian Tukuta and Oliver Chikuta",downloadPdfUrl:"/chapter/pdf-download/73876",previewPdfUrl:"/chapter/pdf-preview/73876",authors:[{id:"324894",title:"Dr.",name:"Phillip Farayi",surname:"Kanokanga",slug:"phillip-farayi-kanokanga",fullName:"Phillip Farayi Kanokanga"},{id:"329365",title:"Prof.",name:"Marian",surname:"Tukuta",slug:"marian-tukuta",fullName:"Marian Tukuta"},{id:"329366",title:"Dr.",name:"Oliver",surname:"Chikuta",slug:"oliver-chikuta",fullName:"Oliver Chikuta"}],corrections:null},{id:"74265",title:"Contribution of Domestic Tourism to Sustainable Tourism Development",doi:"10.5772/intechopen.93646",slug:"contribution-of-domestic-tourism-to-sustainable-tourism-development",totalDownloads:590,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Tourism literature is awash with evidence of the value of domestic tourism to the tourism industry in general. However; there is limited knowledge of how domestic tourism is contributing towards sustainable tourism development especially in developing countries. This study explored the contribution of domestic tourism to sustainable tourism development in Zimbabwe, one developing country in Southern Africa. Using qualitative methodologies, data were collected and thematically analysed. The study revealed that domestic tourism has both positive and negative contributions to sustainable tourism development in unique ways. In conclusion, it was noted that without domestic tourism, Zimbabwe as a tourism destination would be struggling to grow its tourism product offering and expand its market share on the global tourism market.",signatures:"Forbes Kabote",downloadPdfUrl:"/chapter/pdf-download/74265",previewPdfUrl:"/chapter/pdf-preview/74265",authors:[{id:"324488",title:"Dr.",name:"Forbes",surname:"Kabote",slug:"forbes-kabote",fullName:"Forbes Kabote"}],corrections:null},{id:"71919",title:"Vein Thrombosis Risk in Women and Travel",doi:"10.5772/intechopen.92229",slug:"vein-thrombosis-risk-in-women-and-travel",totalDownloads:660,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:1,abstract:"Deep vein thrombosis (DVT) of the lower limbs is a serious condition that can lead to pulmonary embolism (PE) in about 15–24% of cases. If it is not diagnosed/treated timely, nearly 15% of these PE are lethal. The relationship between travel and staying in the same position for a long time is well-known since World War II. Generally, it is more frequent in air flights. It is also associated with the economic downturn in airplanes because passengers have limited space and have greater difficulty of moving. It is estimated that approximately 1–6% of long-haul passengers arrive at their destination with a clot in their veins, but most DVT are asymptomatic.",signatures:"Panagiotis Tsikouras, Xanthoula Anthoulaki, Theodora Deftereou, Anna Chalkidou, Anastasia Bothou, Fotini Gaitatzi, Eleftherios Chatzimichael, Selma Gyroglou, Arsou Chalil Bourazan, George Stanulov, Spyridon Michalopoulos, John Tsirkas, Irene Babageogaka, Werner Rath, Georg-Friedrich Von Tempelhoff, Stefanos Zervoudis, Georgios Iatrakis, Georgios Galazios and Nikolaos Nikolettos",downloadPdfUrl:"/chapter/pdf-download/71919",previewPdfUrl:"/chapter/pdf-preview/71919",authors:[{id:"48837",title:"Prof.",name:"Panagiotis",surname:"Tsikouras",slug:"panagiotis-tsikouras",fullName:"Panagiotis Tsikouras"},{id:"229224",title:"Ms.",name:"Theodora",surname:"Deftereou",slug:"theodora-deftereou",fullName:"Theodora Deftereou"},{id:"229225",title:"Ms.",name:"Anna",surname:"Chalkidou",slug:"anna-chalkidou",fullName:"Anna Chalkidou"},{id:"229226",title:"Ms.",name:"Xanthoula",surname:"Anthoulaki",slug:"xanthoula-anthoulaki",fullName:"Xanthoula Anthoulaki"},{id:"229227",title:"Ms.",name:"Anastasia",surname:"Bothou",slug:"anastasia-bothou",fullName:"Anastasia Bothou"},{id:"229230",title:"Prof.",name:"Stefanos",surname:"Zervoudis",slug:"stefanos-zervoudis",fullName:"Stefanos Zervoudis"},{id:"229232",title:"Dr.",name:"Georgios",surname:"Iatrakis",slug:"georgios-iatrakis",fullName:"Georgios Iatrakis"},{id:"229233",title:"Dr.",name:"Georgios",surname:"Galazios",slug:"georgios-galazios",fullName:"Georgios Galazios"},{id:"290371",title:"Mrs.",name:"Fotini",surname:"Gaitatzi",slug:"fotini-gaitatzi",fullName:"Fotini Gaitatzi"},{id:"290372",title:"Mr.",name:"Ioannis",surname:"Tsirkas",slug:"ioannis-tsirkas",fullName:"Ioannis Tsirkas"},{id:"290373",title:"Mrs.",name:"Arsou",surname:"Chalil Bourazan",slug:"arsou-chalil-bourazan",fullName:"Arsou Chalil Bourazan"},{id:"290374",title:"Prof.",name:"Werner",surname:"Rath",slug:"werner-rath",fullName:"Werner Rath"},{id:"298197",title:"Mrs.",name:"Eirini",surname:"Bampageorgaka",slug:"eirini-bampageorgaka",fullName:"Eirini Bampageorgaka"},{id:"299669",title:"Prof.",name:"Georg-Friedrich",surname:"Von Tempelhoff",slug:"georg-friedrich-von-tempelhoff",fullName:"Georg-Friedrich Von Tempelhoff"},{id:"300195",title:"Mr.",name:"George",surname:"Stanulov",slug:"george-stanulov",fullName:"George Stanulov"},{id:"303163",title:"Dr.",name:"Spyridon",surname:"Michalopoulos",slug:"spyridon-michalopoulos",fullName:"Spyridon Michalopoulos"},{id:"317103",title:"Prof.",name:"Nikolaos",surname:"Nikolettos",slug:"nikolaos-nikolettos",fullName:"Nikolaos Nikolettos"},{id:"317104",title:"Dr.",name:"Selma",surname:"Gyroglou",slug:"selma-gyroglou",fullName:"Selma Gyroglou"},{id:"317105",title:"Mr.",name:"Eleftherios",surname:"Chatzinmichael",slug:"eleftherios-chatzinmichael",fullName:"Eleftherios Chatzinmichael"}],corrections:null},{id:"74326",title:"Manta Ray Tourism",doi:"10.5772/intechopen.93924",slug:"manta-ray-tourism",totalDownloads:412,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Manta rays are flagship species for marine conservation because of a number of threats including anthropogenic, overfishing, plastics (microplastics), over tourism, commercial trade (gills for medicine), and chaotic shipping lines where they often injured or killed. Because of these reasons, manta ray face risk of extinction and listed on the Red List of IUCN. A number of studies present the value of this fish estimated millions of dollars per year from tourism which show much greater valuable alive than dead. Responsible manta ray tourism encourages stakeholders to protect the species by generating incentives from tourism while develop conservations initiatives to protect the species. Desk study on current literatures were reviewed to identify the role of stakeholders in supporting the sustainable management of manta ray tourism. This chapter explored the operations of manta ray tourism in Indonesia as the study areas. In summary, to reach the positive contributions from manta ray tourism, there is an important role of co-management between stakeholders to ensure the sustainable operations and conservation of the ecology, economy, and socio-culture.",signatures:"Maulita Sari Hani",downloadPdfUrl:"/chapter/pdf-download/74326",previewPdfUrl:"/chapter/pdf-preview/74326",authors:[{id:"323655",title:"Dr.",name:"Maulita Sari",surname:"Hani",slug:"maulita-sari-hani",fullName:"Maulita Sari Hani"}],corrections:null},{id:"73258",title:"Effective Leadership in the 21st Century: Lessons for the Tourism Sector in the African Continent",doi:"10.5772/intechopen.93844",slug:"effective-leadership-in-the-21st-century-lessons-for-the-tourism-sector-in-the-african-continent",totalDownloads:326,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Although Africa has been one of the world’s fastest growing tourism regions, when comparing it to the rest of the world, tourism still lags behind. Tourism is a dynamic and a competitive industry that continues to develop whilst the tourists’ preferences are changing. Consequently, leading and managing in the tourism sector is of great importance, particularly in the 21st century. The purpose of this paper is to explore leadership concepts to draw lessons for the tourism sector in the African continent. Leadership in the African continent remains questionable and controversial; the nature of effective leadership has been the subject of great debate. The findings reveal the prominent African leadership concepts from Ubuntu, Culturally embedded values, Communalism, Common good and Paternalism as some of the existing leadership concepts that could be applicable to an effective leader in the 21st century in the tourism sector in Africa.",signatures:"Portia Pearl Siyanda Sifolo",downloadPdfUrl:"/chapter/pdf-download/73258",previewPdfUrl:"/chapter/pdf-preview/73258",authors:[{id:"324889",title:"Dr.",name:"Portia Pearl Siyanda",surname:"Sifolo",slug:"portia-pearl-siyanda-sifolo",fullName:"Portia Pearl Siyanda Sifolo"}],corrections:null},{id:"76067",title:"Model of Virtual Tourism as an Alternative of the Concept of Architecture Tourism Post Covid-19 in Bandung City, Indonesia",doi:"10.5772/intechopen.94015",slug:"model-of-virtual-tourism-as-an-alternative-of-the-concept-of-architecture-tourism-post-covid-19-in-b",totalDownloads:225,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"The tourism sector as one of the sectors that has been hit by the Covid-19 pandemic needs a new breakthrough to enter a new normal era. Amid the ongoing paradigm shift and a number of new protocols will be implemented to welcome the new normal conditions in the tourism industry. The tourism sector in Indonesia, which has been absorbing many jobs, has been hit hard by the Covid-19 pandemic. Coupled with the difficulty of predicting when the pandemic will end, it is necessary to take smart steps in maintaining the sustainability of the tourism industry in entering an era of new norms. The new normal era brings new roles, new roads and expectations in the tourism sector. Digitalization that is growing rapidly and rapidly requires adaptation to new conditions and rearranging business strategies and models so that they can survive in the new normal era by adjusting technological developments. The development method used in this research is the Multimedia Development Life Cycle (MDLC). MDCL as a method for designing multimedia tools by emphasizing the 6 stages of multimedia development. The tools used in this application are PT GUI, Eclipse, and Google Maps. The objects of historical and heritage buildings that become the Sate Building, Villa Isola, the Geological Building, the Asian Africa Museum, and the Merdeka Building are made using immersive photography techniques. By representing information in the form of panoramic images, the 3600 makes it easy for users to visually display information from historical and heritage buildings in Bandung. The tourism model is virtually a possible form of tourism in the future.",signatures:"Asep Yudi Permana, Aathira Farah Salsabilla Permana and Karto Wijaya",downloadPdfUrl:"/chapter/pdf-download/76067",previewPdfUrl:"/chapter/pdf-preview/76067",authors:[{id:"322928",title:"Dr.",name:"Asep Yudi",surname:"Permana",slug:"asep-yudi-permana",fullName:"Asep Yudi Permana"}],corrections:null},{id:"73374",title:"Eco-Cultural Tourism: Sustainable Development and Promotion of Natural and Cultural Heritage",doi:"10.5772/intechopen.93897",slug:"eco-cultural-tourism-sustainable-development-and-promotion-of-natural-and-cultural-heritage",totalDownloads:583,totalCrossrefCites:2,totalDimensionsCites:2,hasAltmetrics:0,abstract:"Ecotourism has the eradication of poverty and environmental protection at its core. Both of these goals were established by the United Nations in 2012 though their development began in the 1980s. The purpose of this chapter is to analyse, using a comparative methodology, global and local eco-cultural tourism (natural, rural and urban areas) in tourist destinations of countries with emerging economies (Asia: China, Malaysia, Thailand), developed countries (Europe: Spain), and developing nations (South America: Peru, Argentina, Bolivia). The working hypothesis states that local, sustainable planning, endorsed by all the tourist agents is required, and should be led by the load capacity and the economic and environmental balance (green economies and ideologies), in order to answer to poverty and climate change problems by means of Tourist Projects directed by governmental policies and administrations. The outcomes suggest a need for a logistical change of policies, to prevent economies from generating pollution and carrying out abrasive activities associated with tourism. This change will create sustainable tourist destinations, the inclusion of populations, and the protection and conservation of natural and cultural heritage.",signatures:"Violante Martínez Quintana",downloadPdfUrl:"/chapter/pdf-download/73374",previewPdfUrl:"/chapter/pdf-preview/73374",authors:[{id:"322905",title:"Mrs.",name:"Violante",surname:"Martínez Quintana",slug:"violante-martinez-quintana",fullName:"Violante Martínez Quintana"}],corrections:null},{id:"73647",title:"Gen Y: Emotions and Functions of Smartphone Use for Tourist Purposes",doi:"10.5772/intechopen.94245",slug:"gen-y-emotions-and-functions-of-smartphone-use-for-tourist-purposes",totalDownloads:508,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:1,abstract:"Smartphones have revolutionized the tourism industry due to their ability to create and improve the tourist experience, mostly among young users, especially those belonging to the Generation Y (Gen Y). Millennials, as the Generation Y is often referred to, stand out for their ability to travel more frequently and for longer periods, as well as for their often-addictive use of smartphones. Despite nomophobia is not a recent phenomenon, there are few research works on information and communication technologies and tourism that address the effects of smartphone use on the tourist experience. The objective of this exploratory study is to describe the feelings Gen Y experiences as a result of use smartphones during their travels, their tourism functionality, and the relationship between the two. The study is based on the application of an online survey to a representative sample. The results confirm the problems associated with smartphone use, especially among young people (16–19) and the existence of a correlation between smartphone use for tourist purposes and a positive travel experience. It has confirmed that they experience negative feelings and emotions. The study presents crucial information that destination marketing organizations can use to successfully integrate smartphones into their digital marketing and communication strategies.",signatures:"Alba-María Martínez-Sala, Concepción Campillo-Alhama and Irene Ramos-Soler",downloadPdfUrl:"/chapter/pdf-download/73647",previewPdfUrl:"/chapter/pdf-preview/73647",authors:[{id:"316359",title:"Dr.",name:"Alba-María",surname:"Martínez-Sala",slug:"alba-maria-martinez-sala",fullName:"Alba-María Martínez-Sala"},{id:"329491",title:"Dr.",name:"Concepción",surname:"Campillo-Alhama",slug:"concepcion-campillo-alhama",fullName:"Concepción Campillo-Alhama"},{id:"329492",title:"Dr.",name:"Irene",surname:"Ramos-Soler",slug:"irene-ramos-soler",fullName:"Irene Ramos-Soler"}],corrections:null},{id:"74136",title:"Tourism Routes for the Diversification of Rural Livelihoods: A Methodological Approach",doi:"10.5772/intechopen.94871",slug:"tourism-routes-for-the-diversification-of-rural-livelihoods-a-methodological-approach",totalDownloads:288,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Tourism routes are the configuration of resources and services into an experience. They are structured based on the characteristics of the local setting but also considering the tourists’ expectations motivations and interests. The objective of this manuscript is to present a methodological approach for the configuration and evaluation of tourism routes, using the municipality of Tenancingo, Mexico as a case study. The methodology followed consisted of three phases: 1) the identification and classification of resources; 2) the qualitative evaluation of the resources; and 3) the use of a route evaluation index to determine the suitability. The study concluded that the methodology allowed for the evaluation of different configurations, and the identification of the tourism route with the most potential, according to its characteristics.",signatures:"Emmanuel Mérida Velazquez, Tirzo Castañeda Martínez and Gandhi González-Guerrero",downloadPdfUrl:"/chapter/pdf-download/74136",previewPdfUrl:"/chapter/pdf-preview/74136",authors:[{id:"325521",title:"Prof.",name:"Gandhi",surname:"González-Guerrero",slug:"gandhi-gonzalez-guerrero",fullName:"Gandhi González-Guerrero"},{id:"337481",title:"M.Sc.",name:"Emmanuel",surname:"Mérida Velázquez",slug:"emmanuel-merida-velazquez",fullName:"Emmanuel Mérida Velázquez"},{id:"337482",title:"Dr.",name:"Tirzo",surname:"Castañeda Martínez",slug:"tirzo-castaneda-martinez",fullName:"Tirzo Castañeda Martínez"}],corrections:null},{id:"73267",title:"Developing a Rural Tourism Destination Brand Framework from the Perspective of a Relationship-Based Approach",doi:"10.5772/intechopen.93839",slug:"developing-a-rural-tourism-destination-brand-framework-from-the-perspective-of-a-relationship-based-",totalDownloads:456,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"The aim of this paper is to develop a destination brand framework for rural tourism destination. Bario a rural community in Sarawak (Borneo) in Malaysia was chosen as a study context. The choice of Bario over other pre-selected rural destinations is because of its unique remote destination. The primary data collection method for this paper was the in-depth interview with 48 participants; this was supplemented by participant observation and documentary evidence. From the perspective of relationship-based approach adopted in this paper, the findings outline three components for a theoretical construction of rural tourism destination brand framework that comprise tourism destination appeals, branding strategies, and stakeholders’ roles. Findings also indicate that the development of rural tourism destination brand should be from the bottom-up, where community-driven strategies can be most effectively delegated to the local leadership system and community’s association. Implications for practice and host community well-being are discussed in detail.",signatures:"Samuel Adeyinka-Ojo",downloadPdfUrl:"/chapter/pdf-download/73267",previewPdfUrl:"/chapter/pdf-preview/73267",authors:[{id:"323647",title:"Dr.",name:"Samuel",surname:"Adeyinka-Ojo",slug:"samuel-adeyinka-ojo",fullName:"Samuel Adeyinka-Ojo"}],corrections:null},{id:"71912",title:"Traveler’s Infections: Overview of Hepatitis B Virus Infection",doi:"10.5772/intechopen.92174",slug:"traveler-s-infections-overview-of-hepatitis-b-virus-infection",totalDownloads:504,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"Hepatitis B virus (HBV) is a double-stranded circular DNA virus that infects the hepatocytes. HBV infection is considered as an important public health concern globally especially with one-third of the world’s population been infected. Local and international migrants are one of those population at high risk of the infection. Many factors interplay in the acquisition of HBV such as purpose of travel, destination endemicity rate of the virus, time of stay of the traveler, inadequate prevention and control measures, among others, understanding the genotypes of HBV is critical in correlating the evolution of the virus and migration of humans and also treatment responses of infected population. The symptom of the virus ranges from fever to jaundice and to a liver cirrhosis and hepatocellular carcinoma (HCC). Transmission of HBV is commonly via horizontal route in developing regions and in the developed regions; transmission occur more often among adults that use injectable drugs and high-risk sexual behaviors. Therefore, the Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) have recommended HBV screening and vaccination to all travelers without an HBV immunization history before traveling to endemic regions. This chapter gives an overview on HBV as a potential traveler’s infection.",signatures:"Victor B. Oti",downloadPdfUrl:"/chapter/pdf-download/71912",previewPdfUrl:"/chapter/pdf-preview/71912",authors:[{id:"245062",title:"Mr.",name:"Victor B.",surname:"Oti",slug:"victor-b.-oti",fullName:"Victor B. Oti"}],corrections:null},{id:"73322",title:"Marketing Cultural Resources as a Tourism Product",doi:"10.5772/intechopen.93869",slug:"marketing-cultural-resources-as-a-tourism-product",totalDownloads:523,totalCrossrefCites:0,totalDimensionsCites:0,hasAltmetrics:0,abstract:"This chapter presents the marketing aspect of cultural tourism resources by taking evidence from Sidama, Southern Ethiopia. It identifies the major cultural tourism resources of Sidama, and assesses their market readiness state through the lenses of tourists. It also presents the profile of cultural tourists visiting endowments in Sidama using descriptive research approach. Brief introduction of marketing approaches to cultural tourism and a review of literature on cultural tourism products and cultural tourists is also provided. As to its significance, the chapter offers analysis of cultural tourism assets and their marketability as a tourism product in a developing destination context. Practical implications for sound cultural tourism marketing are also discussed in the chapter.",signatures:"Amare Yaekob Chiriko",downloadPdfUrl:"/chapter/pdf-download/73322",previewPdfUrl:"/chapter/pdf-preview/73322",authors:[{id:"324979",title:"Assistant Prof.",name:"Amare Yaekob",surname:"Chiriko",slug:"amare-yaekob-chiriko",fullName:"Amare Yaekob Chiriko"}],corrections:null}],productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},subseries:null,tags:null},relatedBooks:[{type:"book",id:"8603",title:"Green Practices and Strategies in Supply Chain Management",subtitle:null,isOpenForSubmission:!1,hash:"cfd8838aeddebe04b84b2fbc553b6887",slug:"green-practices-and-strategies-in-supply-chain-management",bookSignature:"Syed Abdul Rehman Khan",coverURL:"https://cdn.intechopen.com/books/images_new/8603.jpg",editedByType:"Edited by",editors:[{id:"254664",title:"Prof.",name:"Syed Abdul 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",isbn:"978-1-80356-591-0",printIsbn:"978-1-80356-590-3",pdfIsbn:"978-1-80356-592-7",doi:null,price:0,priceEur:0,priceUsd:0,slug:null,numberOfPages:0,isOpenForSubmission:!0,isSalesforceBook:!1,isNomenclature:!1,hash:"65dc94eb0a8dd733522f67d95b2c2d48",bookSignature:"Dr. Afsheen Raza",publishedDate:null,coverURL:"https://cdn.intechopen.com/books/images_new/11680.jpg",keywords:"Inhibitory Receptors, NK Cells, Activating Receptors, Tumor Immune Escape, Cancer Immunotherapy, Mechanisms of Targeting, Checkpoint Cells Targeting, Clinical Trials, Biomarkers, Immune Checkpoint Cells, Immune Checkpoint Inhibitors, Future Perspectives",numberOfDownloads:null,numberOfWosCitations:0,numberOfCrossrefCitations:null,numberOfDimensionsCitations:null,numberOfTotalCitations:null,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"March 16th 2022",dateEndSecondStepPublish:"May 25th 2022",dateEndThirdStepPublish:"July 24th 2022",dateEndFourthStepPublish:"October 12th 2022",dateEndFifthStepPublish:"December 11th 2022",dateConfirmationOfParticipation:null,remainingDaysToSecondStep:"8 hours",secondStepPassed:!1,areRegistrationsClosed:!1,currentStepOfPublishingProcess:2,editedByType:null,kuFlag:!1,biosketch:"Dr. Raza has been trained in Cancer Biology and Therapeutics at Harvard Medical School, USA, and in Molecular Biology at Aga Khan University. 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They are a wide range of chemicals characterized by their amphiphilic nature. Thus, their molecules consist of an hydrophilic / polar head group (either charged or uncharged) and an hydrophobic / nonpolar hydrocarbon tail. As a consequence, surfactants show solubility in polar and nonpolar liquids, ability to form micelles, adsorption to phase boundaries and reduction of the surface tension of water. They are economically important due to their specific properties that allow using them as washing, wetting, emulsifying and dispersing agents. Therefore, surfactants are mainly used in the formulation of detergents, personal care products, paints, textiles, pesticide formulations, pharmaceutical, and many other products [1, 2]. Many different types of these compounds have been synthesized, although they can be classified into three main groups according to their charge: (1) anionics, (2) non-ionics, and (3) cationics (Figure 1); the first and second groups accounting for the highest production volumes. Thus, the European Committee of Organic Surfactants and their Intermediates (CESIO) reported a production of 1200 ktons of anionic and 1400 ktons of non-ionic surfactants in Europe in 2010, which represents 90% of the total European production of surfactants.
Linear alkylbenzenesulfonates (LAS), alkyl ethoxysulfates (AES) and alkyl sulfates (AS) are the most widely used anionic surfactants. LAS are commercially available as a mixture containing homologues with alkyl chains ranging from 10 to 14 carbon units, and isomers resulting from the different attachment positions of the phenyl group along that chain (Figure 1a). The chemical structure of AS comprises a C12-16alkyl chain with a terminal sulfate group. AES share the same structure than AS but they also have a variable number of ethylene oxide (EO) units (Figure 1b). All these compounds are commonly employed in household and laundry detergents, hand dishwashing liquids, shampoos, and other personal care products [3-5]. Among the nonionic surfactants, alcohol polyethoxylates (AEOs) are currently produced in the greatest volume (e.g., 747000 tons in Europe in 2000), and alkylphenolethoxylates (APEOs) are in second place by volume as a consequence of the restrictions on their use in recent years, due to the estrogenicity showed by some of their degradation intermediates [6-8]. AEOs are a mixture of homologues having from 12 to 18 carbon atoms in their alkyl chain, which is connected via an ether bond to an ethylene oxide (Figure 1c). APEOs are mixtures of a wide range of ethoxymers (from 1 to 20 EO units), and isomers, depending on the degree of branching of the alkyl chain (Figure 1d). Both, AEOs and APEOs, are widely employed in domestic and industrial applications [9] (e.g., detergents, emulsifiers, wetting and dispersing agents, industrial cleaners, textile, pulp and paper processing). Finally, quaternary ammonium-based compounds (QACs) are the main class of cationic surfactants, being constituted of at least one hydrophobic hydrocarbon chain linked to a positively charged nitrogen atom, and other alkyl groups which are mostly short-chain substituents such as methyl or benzyl groups (Figure 1e). Major uses of QACs are as fabric softeners and antiseptic agents in laundry detergents as well as other industrial uses [2]. Since the 1960’s, the most commonly used active ingredient in fabric softeners has been dehydrogenated tallow dimethyl ammonium chloride (DTDMAC), with industry-wide European annual volumes exceeding 32000 tons through 1990. However, esterquat surfactants were introduced into the European market in the early 1990’s because, due to their structure, they were more accessible to hydrolysis and biodegradation than DTDMAC. Hence, most fabric conditioners marketed now are comprised of esterquat types, with a volume of 130000 tons/year used in detergent products in the European Union [10-13].
Chemical structures of (a) linear alkylbenzenesulfonates (LAS), (b) alkyl ethoxysulfates (AES), (c) alcohol polyethoxylates (AEOs), (d) alkylphenolpolyethoxylates (APEOs), and (e) quaternary ammonium-based compounds (QACs).
Once used, the major fraction ofsynthetic surfactants are disposed down the drain to sewers, where it has been estimated that 50% by volume is degraded, 25% sorpted to suspended solids and 25% dissolved [14, 15]. Later, these chemicals are commonly removed between 81 and 99.9% in wastewater treatment plants (WWTPs) [16-18], although they are frequently detected in sewage effluents showing concentrations up to 872 µg/L for LAS [16], between 0.24 and 3 µg/L for AES [19], up to 4 µg/L for QACs [20], and from 0.2 to 23 µg/L for AEOs and APEOs [21, 22]. Secondary treatment in active sludge units is considered the most important process to eliminate surfactants through aerobic biodegradation, but a considerable fraction is also removed by sorption / precipitation in sludges originated from several decantations (Figure 2) (e.g., 15-37% of total LAS [14, 15, 23] and more than 90% of nonylphenol [24]). These sludges are also a potential source of contamination for soils, groundwater and adjacent rivers as they tend to contain high concentrations of organic contaminants and are often used in agriculture after anaerobic digestion. High levels of surfactants have been measured in treated sludges: up to 5400 mg/kg dry weight for LAS [15, 25], from 119.3 to 380.5 mg/kg for APEOs, AEOs and AES [25], and up to 5870 mg/kg for QACs [26, 27].Any environmental compartment (surface waters, sediment, biota…) is susceptible of being contaminated by these compounds and/or their degradation metabolites [2, 28]. As example, a considerable number of studies have reported the presence of LAS in surface waters [29-31] at levels typically ranging from less than 1 ng/L to several hundreds of µg/L respectively, depending on the distance from urban wastewater discharge sources and the type of wastewater treatment. Available studies about the presence, environmental behavior and distribution of non-ionic surfactants are mainly focused on NPEOs (nonylphenolpolyethoxylates, which are the major fraction of APEOs). Concentrations of these compounds have been reported in surface waters all around the world: <0.1 to 100 µg/L in rivers in Mexico [32],Holland [33], Japan [34] and Taiwan [29], and from<1 to 38.5 µg/Lin coastal waters of United States [35], Italy [30], Spain [36] and Israel [37]. Levels of surfactants in surface sediments are usually higher by several orders of magnitude than those measured in water due to their moderate to high sorption capacity. Thus, the presence of LAS [31, 38-40] and NPEOs [22, 41-44] has been widely detected in sediments, with levels ranging from less than 1 to more than 200 mg/kg and from less than 0.1 to 28.5 mg/kg respectively. Available data concerning to the presence of aliphatic anionic (AES) and nonionic (AEOs) surfactants, as well as cationic surfactants of any class, are rather limited. There are only a few papers about the occurrence of AEOs [36, 40, 43, 44] and AES [19, 31] in sediments, showing levels ranging from <0.1 to 23 mg/kg. Some authors have also measured concentrations between <0.1 and 72 µg/L for AES [19, 31] and AEOs [36, 40, 43] in surface waters. QACs have been measured at levels ranging from less than 2 µg/L in surface waters [20] to more than 100 mg/kg in sediments [45, 46].
Flowsheet and sampling points of a wastewater treatment plant (WWTP). Figure shows mass balance of dissolved (d) and adsorbed/precipitated (a) of LAS and non-ionic surfactants. Absolute amount (average value in kg/day) and percentage with respect to raw water (adapted from reference [
Summarizing, huge volumes of surfactants are used every day, entering the environment, where these compounds and/or their degradation products may cause damage depending on their concentrations. Therefore, it becomes necessary developing reliable analytical methodologies that allow determining the levels of surfactants in environmental matrices, which may be complicated due several reasons. First, surfactants are often sold as commercial mixtures which can comprise hundreds of different homologues, isomers and/orethoxymers with different physico-chemical properties. Separation and quantification of these components require the use of chromatographic techniques, mainly gas chromatography (GC) and liquid chromatography (LC). Achieving a successfully identification of every component in the mixture is also desirable for a better understanding of their environmental behavior as they may suffer differential degradation or sorption. There is also an additional challenge when dealing with target compounds that tend to be present at trace levels. In these cases it is necessary to develop reliable extraction, purification, and preconcentration protocols in order to remove as many interferences as possible before analysis without sacrificing high recovery values. Some of the techniques used to this end are also based on chromatographic techniques, such as solid phase extraction (SPE), directly derived from column chromatography. Thus, in this chapter we present the main problems posed by analysis of surfactants in environmental samples from two points of view:
Isolation and/or preconcentration of surfactants from different types of samples;
Separation, identification and quantification of analytes in properly prepared extracts.
Correct sampling of environmental samples is indispensable to provide representative information of the environmental compartments from which they are taken and, on the other hand, it is important to preserve the target compounds during storage [1]. Generally,water samples are often immediately preserved upon collection by the addition of biocides such as formaldehyde up to a concentration of 4% [17, 47], chloroform or sodium azide [20], or by filtering through a 0.45 µm membrane filter [16]. Then, aliquots are kept at low temperatures and are often analyzed within a short period of time (48 h) in order to minimize the biodegradation of surfactants. Solid samples (sewage sludges, soils or sediments) are also kept at low temperature once they are collected to avoid any degradation of the analytes during the transport to the laboratory. Later, they are usually dried in a heater [47], at room temperature[25], or frozen at -20 ºC and later freeze-dried [48]. Once dried, samples are milled and strained through a sieve to a particle size of less than 2 mm, and then stored at 4 to -20 ºC for further extraction and analysis.
Surfactants are often found at trace levels (ppb or less) in environmental matrices, frequently below the limits of detection of most analytical techniques. Therefore, it is necessary to carry out not only their extraction but also their isolation and preconcentration to achieve proper identification and quantification. Those methodologies more commonly used at this preliminary stage are commented next for both solid and aqueous samples.
For several decades now, Soxhlet extraction and solid-liquid extraction (SLE) have been the most commonly used techniques for the extraction of surfactants and many other organic compounds from solid matrices. These methodologies are cheap and allow simple extraction, although they have also several disadvantages, including the large volume of solvent needed (from 150 to 500 mL [27, 49, 50]), the long time required, which can take 4-18 hours per sample [20, 51, 52], and the production of toxic liquid wastes. Soxtec is an alternative extraction method based on Soxhlet, but the addition of several boiling and rinsing steps reduces the extraction time to 45 min and solvent consumption to 50-100 mL [53, 54]. Application of ultrasounds followed by centrifugation or filtration to separate extracts from solid matrices is another cheap option for extracting surfactants due to the high extraction efficiency in a short time [40, 55, 56]. On the other hand, it also shows the same problems than SLE and Soxhlet extraction (high volume of organic solvents and toxic wastes). Table 1 summarizes the conditions used for the extraction of surfactants employing these conventional extraction techniques. As example, LAS and their degradation intermediates, sulfophenyl carboxylic acids (SPCs), have been extracted from sediments using methanol (MeOH) as solvent [50, 52, 57, 58] by means of Soxhlet extraction and SLE. For APEOs and their metabolites, methodologies have been similar to those used for LAS [30, 59, 60], although methanol tends to be substituted by other less polar solvents (e.g., hexane [51] or dichloromethane (DCM) [61]), in order to enhance the extractability of the more hydrophobic compounds such as nonylphenol (NP). With respect to the extraction of aliphatic surfactants (AEOs and AES) and their main degradation products (polyethylenglycols, PEGs) from solid matrices, most authors have employed methanol [19, 40, 62, 63] and dichloromethane [55, 64] during Soxhlet or Soxtec extraction, SLE and sonication. There are still a few studies dealing with the application of all these techniques for extraction of QACs [26, 27, 65], but acidified methanol is used as solvent in most cases.
LAS, AES, AS | Sediment | Soxhlet, PLE | MeOH | Time: 5 h, Temperature: 125 ºC Pressure: 1500 psi | SPE (C18) | [62] |
NPEO, NP | Sediment | Soxhlet, Sonication | Hexane/ isopropanol, Hexane/ acetone | Time: 18 h,Not spec. | SPE (cyanopropil) | [51] |
QAC | Sediment, sludge | Soxhlet | MeOH/ HCl | Time: 18 h | LLE (CHCl3, water) | [20] |
NPEO, OPEO, AEO | Sludge | SLE | DCM | Time: 2 h | - | [64] |
LAS | Soil | Soxtec | MeOH | Time: 45 min | - | [54] |
NPEO, OPEO, NP, OP, AEO | Sludge | Soxtec | MeOH | Time: 45 min | SPE (C18) | [53] |
LAS, SPC, NPEO, NPEC, AEO, PEG | Sediment | Sonication | MeOH | Time: 30 min x 3 | SPE (HLB) | [40] |
QAC | Sediment | Sonication | MeOH/ HCl | Time: 1 h x 3 | LLE (CHCl3, water) + SPE (anion exchange) | [65] |
NP1-3EO, OP1-3EO | Sediment | Sonication | MeOH | Time: 7 min | SPE (aminopropyl silica) + LCcolumn (C18) | [60] |
Overview of conventional extraction techniques applied to the extraction of surfactants and their metabolites from solid samples.
New extraction methods have been developed within the last decade not only to save time, but also to reduce solvent consumption without losing extraction efficiency. Table 2 shows some examples of the application of new techniques for the extraction of surfactants from solid environmental matrices. Microwave-assisted extraction (MAE) is suitable for the extraction of different anionic [66] and non-ionic [67] surfactants from sediments and sludges. Extractions are often achieved quickly at 120 ºC using low solvent volumes (mainly MeOH [68] or DCM/MeOH [69]). Another advantage of MAE is that it can also be combined with Soxhlet extraction [70] in order to increase its efficiency. Less solvent demand and higher extraction rates compensate the high initial cost of acquiring a MAE unit. Pressurized fluid extraction (PFE), also known as accelerated solvent extraction (ASE) or pressurized liquid extraction (PLE), is a technique based on the use of high temperatures (100-200 ºC) and pressures (1500-3000 psi) to prevent solvents from boiling and to increase the kinetics of extraction. Therefore, PLE allows a faster extraction of organic compounds from solid samples (15-20 min per sample) with a lower uptake of organic solvent than more conventional techniques and without sacrificing high recovery values. Recently anionic [62, 71], cationic [72] and non-ionic [47, 73, 68] surfactants have been extracted using PLE and methanol or mixtures containing hexane, acetone, acetonitrile (ACN) or even water as solvents. However, Petrovic et al. [74] observed the volatilization of some APEOs and their metabolites under these conditions, so they suggested keeping the extraction temperature under 60 ºC in this case. Supercritical fluid extraction (SFE) is another extraction technique that has been recently applied to the extraction of ionic and non-ionic surfactants, using CO2 [75] or water [25] instead of toxic organic solvents to carry out the extraction in a short time and without requiring further clean-up steps [26]. Sometimes, the mobile phase (CO2, H2O) is modified with the addition of low molecular weight alcohols (e.g., MeOH) to improve the efficiency in the extraction of polar or ionic compounds [76, 77]. However, better extraction recoveries for nonpolar compounds, possibility of using water as extraction solvent and automation of PLE has result in a lower interest of using SFE instead PLE for extraction of surfactants.
LAS, SPC, AES, AS, NPEO, APEC, AEO | Sediment | PLE | MeOH | Time: 15 min Temperature: 120 ºC Pressure: 1500 psi | SPE (C18) | [47] |
LAS, SPC | Soil | PLE | MeOH/H2O | Time: 15 min Temperature: 120 ºC Pressure: 1500 psi | SPE (C18) | [71] |
NP1-5EO, OP1-5EO, NP, OP | Sediment | PLE | Acetone/hexane | Time: 15 min Temperature: 100 ºC Pressure: 1500 psi | SPE (aminopropyl silica) | [73] |
QAC | Sediment | PLE | ACN/H2O | Temperature: 120 ºC Pressure: 1500 psi | SPE (polymeric) | [72] |
NPEO, NP | Sediment | Soxhlet, PLE, MAE | MeOH | Time: 10 h, Time: 10 min Temperature: 100 ºC Pressure: 1500 psi, Time: 20 min | LC column (alumina) | [68] |
LAS | Sludge | SFE | CO2 | Time: 15 min | Not required | [75] |
QAC | Sludge | SFE | CO2/MeOH | Time: 45 min | LLE (CHCl3, water) + LC column (anion exchange) | [77] |
LAS, AS, AES, AEO, NPEO, NPEC, AP | Sludge | SFE | Water | Time: 27 min | SPE (carbograph 4) | [25] |
NP, OP | Sediment | MAE | DCM/MeOH | Time: 25 min | SPE (polyestyrene-divinylbenzene) | [69] |
LAS | Sludge | MAE | MeOH | Time: 10 min | Not required | [66] |
Overview of modern extraction techniques applied to the extraction of surfactants and their metabolites from solid samples.
There is a wide variety of techniques to carry out purification and preconcentration of extracts from solid samples, as well as aqueous samples, before proceeding with analysis of surfactants and their degradation metabolites. Liquid-liquid extraction (LLE) is among the first techniques that have been widely applied for the extraction of ionic and non-ionic surfactants. Target compounds are isolated from the sample according to their relative solubilities in two different immiscible o partially miscible liquid phases, usually water and an organic solvent. Several cationic [20, 65] and anionic compounds [78, 79] have been extracted from aqueous samples using chloroform, whereas dichloromethane [80] and ethyl acetate [81] have been used to isolate non-ionic surfactants from water. The main advantage of LLE is that it can be used to determine total concentrationof these compounds in water in spite of their solid particle matter level. However, the tendency of surfactants to concentrate at phase boundaries leads to the formation of emulsions, and phase separation during LLE becomes very difficult. This can be avoided by the formation of liphopilic ion pairs between surfactants and ion-pair reagents [1] (e.g., disulphine blue dyes or LAS for cationic surfactants [65, 77, 82], methylene blue [78, 79, 83] or methylene green for anionic surfactants [84], modified Dragendorff reagent for non-ionic [81]).
Nowadays, solid-phase extraction (SPE) is the most extended purification and preconcentration technique for surfactants. LLE requires large amounts of sample (100-500 mL) and high consumption of toxic organic solvents, while SPE is generally faster and needs lower sample and solvent volumes (7-100 mL and 5-20 mL, respectively). Briefly, SPE consists on passing the aqueous sample or extract (mobile phase) through a specific material (solid phase) that retains analytes whereas water, salts and other interferences are discarded. Later, target compounds can be eluted from the solid phase using a minimal amount of solvent (few milliliters) so a clean and low volume extract is obtained. Table 3 shows general information about protocols developed for the isolation of surfactants using both SPE and LLE. SPE has been widely applied to isolate anionic surfactants from aqueous samples. More specifically, octadecylsilica (C18) has been used as the main solid phase to extract LAS and their degradation products (SPCs) from water samples [62, 71], while methanol is commonly employed as elution solvent. Due to the negative charge of these analytes, strong anionic-exchange (SAX) resins have been also employed, alone or combined with C18, for a better purification [52, 85], using a mixture of methanol and hydrochloric acid as elution solvent [57, 58]. Lowering the pH of the sample and/or adding significant amounts of salts such as sodium chloride [52, 71] (salting-out effect) is also convenient to improve the retention of most polar components (e.g., SPCs). Other authors have preferred using graphitized black carbon (GBC) [29, 86] or polystyrene-divinylbezene SDB-1 cartridges [87] instead, also showing good extraction recoveries. Other anionic surfactants (AES and AS) have been successfully isolated by octadecylsilica [62, 85] and GBC [25, 88] SPE cartridges from river, marine and wastewater samples, as well as sludge and sediment extracts. Regarding non-ionic surfactants, a wide variety of different protocols has been developed to extract AEOs and APEOs and their degradation products from liquid samples. Thus, GBC [89, 90] and silica (C2 to C18) cartridges [53, 91, 92], along with methanol, dichloromethane, ethyl acetate and/or acetonitrile as elution solvents, have been employed, sometimes combined with strong cationic-exchange (SCX) and SAX cartridges [90, 92] for the removal of potential anionic and cationic interferences as non-ionic compounds are not retained due to their neutral charge. Additionally, octadecylsilica has been applied to extract the most hydrophobic group of NPEOs metabolites, constituted by NP and short chain oligomers (NP1-3EOs), using mainly methanol, acetone or dichloromethane as elution solvents [60, 73]. SAX disks have been also used instead of conventional SPE cartridges to isolate nonylphenolpolyethoxycarboxylates (NPECs), NPEO polar degradation products, from sludge extracts. Cassani and co-workers [93] also employed disks (C18) for determination of AEOs in sludge samples and wastewaters. Overall, most authors employ C18 [47,55]and GBC cartridges [25,88] because they are suitable for simultaneous isolation of a wide range of anionic (LAS and AES) and non-ionic (AEOs and NPEOs) surfactants, as well as their polar metabolites (PEGs, NPECs and SPCs), in a single stage by fractional elution using mixtures of hexane, dichloromethane, methanol, acetone and ethyl acetate.New polymeric materials are also currently being tested for the extraction of these compounds [51, 73, 69]. Thus, the hydrophilic-lipophilic copolymer Oasis HLB has been presented by Lara-Martín and co-workers [40] as an alternative for the simultaneous isolation of LAS, NPEOs, their carboxylated metabolites (SPCs and NPECs), and AEOs and their polar degradation intermediates (PEGs) from liquid samplesin one single purification step. On the other hand, research on the isolation of cationic surfactants using SPE from water samples [94-97] and sediment extracts [72] is more limited. Nonpolar silica sorbents (e.g., C18) are not suitable for QACs because the strong interaction of these compounds with the silanolgroups results in very broad elution bands [98]. This issue has been partially solved employing neutral polymeric sorbents instead [72, 96], although better results are obtained using sodium dodecyl sulphate (SDS) hemimicelles attached to alumina or anion exchange resins [94, 95, 97]. Despite this, LLE is still considered to be more effective than SPE for extraction of cationic surfactants from liquid samples [27].
In the past few years, advances in SPE have led to new related techniques such as matrix solid-phase dispersion (MSPD), which is used to extract and purify target compounds simultaneously from solid matrices. In the case of surfactants, this extraction protocol has been mainly applied to fish samples [99], where aliquots are taken and mixed with octadecyl silica in a column, in order to isolate LAS and SPCs, as well as non-ionic surfactants. Afterwards, strong non-polar solvents (e.g., hexane) and methanol are used to remove fats in a first clean-up stage and to extract surfactants after another elution,respectively. There are other simple and low cost extraction techniques which reduce the time needed for sample preparation, and decrease or eliminate solvent consumption [100-111]. As example, dispersive liquid-liquid microextraction (DLLME) is a novel method based on the migration of analytes to a cloudy solution, caused by the dispersion of the extraction solvent (low soluble in water, e.g., chloroform) as very fine droplets due to the appropriate mixture with a dispersant (soluble in water, e.g., acetone) in the aqueous sample. Then, these dispersed fine particles of the extraction phase containing analytes are sedimented in the bottom of a test tube by centrifugation [100]. The main difficulties associated with DLLME are the vulnerability of solvent drop to physic forces and automation issues. This problem of physical instability could be solved by the application of hollow fiber membranes which are impregnated by an organic solvent (e.g., 1-octanol) and placed into the water sample for
QAC | 100 mL | LLE | Solvent: chloroform (15 mL) Washing: water Ion-par reagent: Patent Blue V | [82] | |
LAS, SPC | 500-1000 mL | LLE | Solvent: chloroform (3 x 4 mL) Ion-par reagent: methylene green | [84] | |
NP1-2EO, NP, OP | 300 mL | LLE | Solvent: DCM (300 mL) | [80] | |
QAC | 20 mL | LLE | Solvent: chloroform (5 mL) Ion-par reagent: disulphine blue | [79] | |
LAS, AES, AS | 10-200 mL | SPE | C18+SAX (LAS) C2 (AES, AS) | 1. Conditioning: MeOH, water 2. Washing: MeOH/water 3. Elution: MeOH + HCl/MeOH 1. Conditioning: MeOH/isopropanol, water 2. Washing: water 3. Elution: MeOH/isopropanol | [85] |
AEOs | 50-2000 mL | SPE | C2+SCX+ SAX | 1. Conditioning: Not spec. 2. Fractionation: ACN 3. Fractionation: MeOH/ethyl acetate/water | [92] |
QAC | 50 mL | SPE | Alumina | 1. Passing solution with SDS 2. Elution: MeOH | [95] |
NPEO, NPEC | 100 mL | SPE | GBC | 1. Conditioning: DCM, DCM/formic acid, MeOH, acidified water 2. Washing: MeOH/water, MeOH 3. Elution: DCM/formic acid | [89] |
LAS, SPC | 25-250 mL | SPE | C18+SAX | 1. Conditioning: MeOH, water 2. Washing: water, acidified water 3. Elution: MeOH + acidified MeOH | [52] |
QAC | 100 mL | SPE | Strata-X | 1. Conditioning: ACN, water 2. Washing: water 3. Elution: ACN/acetic acid/water | [96] |
LAS, NPEO, NPEC, AEO, PEG, NP, OP | 200 mL | SPE | C18 | 1. Conditioning: MeOH, water 2. Fractionation: hexane/DCM 3. Fractionation: MeOH/DCM | [55] |
Overview of LLE and SPE techniques used for clean-up and preconcentrationof surfactants from environmental samples.
equilibrium extraction of the target compounds. Finally, the fiber is removed from the sample and extracted analytes are desorbed by diffusion into a different solvent (e.g., MeOH) [101]. This technique has been recently applied to isolation of cationic [101, 102], non-ionic [103] and anionic surfactants [104] from aqueous samples. Solid-phase microextraction (SPME) and stir-bar sorptive extraction (SBSE) can be also considered for rapid isolation of surfactants. Both techniques are based on the diffusion of analytes from the sample directly, without requiring any organic solvent, into a fiber or bar made of a specific polymer. The amount of polymer changes from 0.5 µL in SPME fibers up to 300 µL in SBSE bars, therefore improving the sensitivity of target compounds. Different types of fibers have been tested during application of SPME for isolation of anionic (polydimethylsiloxane (PDMS) [105], polyacrylate (PA) [106]) and non-ionic surfactants (carbowax/template resin (CWAX/TR) [107], PDMS/divinylbenzene (DVB), PA [108]).So far, the use of SBSE is limited to the extraction of NP and octylphenol (OP) from liquid samples [109]. Once they are captured by the polymer in the fiber or the bar, analytes are released by heat in the injection port of GC systems (thermal desorption), or by reduced amount of solvents before injection on LC systems (liquid desorption).
Over the last decades, analysis of surfactants in environmental samples has been carried out using several instrumental techniques. So far, spectrophotometric, potentiometric titrametration (PT) and tensammetrictecniques have been optimized to measure the total content of ionic [112-114] and non-ionic surfactants [115, 116], although their sensitivity and/or specifity tend to be low compared to chromatographic techniques coupled to several types of detectors. Generally, one of the main applications of spectrophotometric techniques has been routine environmental analysis due to their quickness and simplicity. They involve the formation of ion associates of analytes with specific ion-pair reagents and their extraction into appropriated organic solvents. After phase separation, the absorbance of the organic phase is measured. However, despite the advantages described above, the use of spectrophotometry generates very toxic wastes (e.g., chloroform) and is only limited to the analysis of total amount of surfactants [117-119]. PT and tensammetric techniques [120, 121] are based on the changes in electric properties caused by the presence of analytes in environmental samples. They can be only applied to the determination of total ionic and nonionic compounds, being impossible for both techniques to discriminate among individual components from surfactant mixtures. Besides, there are also issues associated with reproducibility and signal stability [113]. Nowadays, it is necessary to go beyond quantification of the total concentration of target analytes and, in most cases, chromatographic techniques (gas chromatography, GC, or high-performance liquid chromatography, HPLC) coupled to various types of detectors are preferred to separate and identify each individual compound from surfactant mixtures.
Less frequently used than HPLC for analysis of surfactants, the main drawback of GC is that all anionic and non-ionic compounds and their metabolites need to be derivatized with specific agents to solve sensitivity, separation or volatilization issues before injecting them into the system. Most commonly used derivatizing agents are trifluoroethanol [29, 58], diazomethane [84], N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) [53, 59, 122], acetic anhydride [61, 109] and hydrogen bromide [90], among other reactants. In any case, some low molecular mass metabolites of non-ionic surfactants (NP and short-chain NPEOs) have been analyzed directly by GC [67, 80] as they are volatile enough, although better results can be obtained if derivatization is performed. There are also some advantages in using GC over HPLC. Thus, GC columns have a better capability for achieving complete separation of homologues and isomers of many surfactants after derivatization. This may be a key aspect for those studies on the biodegradability or toxicity of surfactants such as LAS or NPEO, which can change depending on the length of the alkyl chain and/or the position of the phenyl ring [123] (Figures 3a and b). In most cases, anionic and non-ionic surfactants have been separated by nonpolar capillary columns containing 5%-phenyl-95%-dimethylpolysiloxane (e.g., HP-5 [58, 75, 67], SE-54 [76], DB-5 [84, 103, 109]), and a mobile phase comprised of high purity helium as carrier gas with a flow rate from 0.58 to 3.4 mL/min. Regarding cationic surfactants, the application of GC to their separation and analysis has not been mentioned in any paper so far [1]. Table 4 describes general information about some analytical protocols for determination of anionic and nonionic surfactants by means of GC in environmental samples.
Several types of detectors can be used after gas chromatography for the analysis of target compounds, such as flame-ionization detectors (FID), which were used for the analysis of
Selected GC-EI-MS characteristic ion chromatograms from a river sample, showing resolution of the derivatives of (a) LAS [
anionic surfactants in water samples [124]. Nowadays, single quadrupole (MS) or tandem mass spectrometers (MS-MS) are commonly preferred because they allow unequivocal identification of analytes by measuring their parent masses and displaying specific fragmentation patterns after their ionization and rupture, respectively. Hence, there are several papers dealing with the analysis of anionic and non-ionic surfactants using GC coupled to MS [69, 105, 108] or MS-MS [125]. Target compounds can be detected by electron impact (EI) or chemical ionization (CI), being more widely used the first mode, although higher sensitivity may be reached using CI for analysis of some anionic compounds.
LAS | Wastewater, seawater | Ion pair SPME Derivatization in GC injection port (tetrabutyl ammonium) | - | - | BPX5 (capillary column, 30 m, 0.25 mm ID, 0.25 µm) | EI(+)-MS | 0.16-0.8 ng/ mL | [105] |
NP1-3EO, NP NP1-3EC LAS, SPC | River water, wastewater | SPE (without derivatization) Derivatization (C3H7OH/ CH3COCl) Derivatization (SOCl2/ CF3CH2OH) | 81-90 (NP) 75-112 (LAS, SPC) | - | DB-5 (capillary column, 30 m, 0.25 mm ID, 0.25 µm) | EI/CI(+)-MS | ≤0.01 µg/L (LOQ) | [29,143,144] |
AEOs (C12-C15) | Wastewater, river water | SPE Derivatization (HBr) | 65-102 | Helium | Rtx-1 (capillary column, 60 m, 0.25 mm ID, 0.25 µm) | EI(-)-MS | 0.001-0.01 mg/L | [90] |
NP1-2EO, NP | Marine sediment | MAE, SPE (without derivatization) | 100 | Helium (2 mL/min) | HP-5 (capillary column, 30 m, 0.25 mm ID, 0.25 µm) | EI(+)-MS | 100 ng | [67] |
NP, OP | River water | DLLME Derivatization in situ (methyl chloroformate) | 88.3-106.7 | Helium (1 mL/min) | DB-5 (fused silica capillary column, 30 m, 0.25 mm ID, 0.25 µm) | EI(+)-MS | 0.002- 0.03 µg/L | [103] |
NP,OP | River water, sediment | MAE, SPE Derivatization (BSTFA) | 77-109 | Helium (1 mL/min) | HP-5 (capillary column, 30 m, 0.25 mm ID, 0.25 µm) | EI(+)- MS-MS | 0.01-0.1 ng/L 0.08-0.14 ng/g | [125] |
Key aspects of GC analysis of surfactants in different environmental matrices.
High-performance liquid chromatography (HPLC) is currently the most commonly used technique for separation and analysis of commercial mixtures of surfactants in the environment, mainly due to its advantages over GC because HPLC is suitable for determining non volatileanalytes from low to high molecular weight and derivatization is unnecessary in most cases. Reverse-phase columns,mainly RP-18 [47, 96, 106] and RP-8 [52, 95], are often employed for chromatographic separations of anionic, non-ionic, cationic surfactants and their degradation products. Mobile phases are solvent mixtures containing deionized water, acetonitrile and/or methanol. Separation can be improved by adding some additives (e.g., ammonium acetate (AMAC), triethylamine) to the mobile phase, as well as acetic (AA) or formic acid (FA) as modifiers [72, 71, 89]. There are also a few works showing efficient separation of NPEOs ethoxymers, some of their metabolites [126] and QACs [101] by amino-silica or cyanopropyl normal phase columns, although the elution order is reversed (more hydrophobic compounds, such as NP, elute first and NPEOs last). In these cases, stronger non-polar solvents (e.g., hexane, chloroform and isopropanol) are preferred. Additionally, some researchers have used new stationary phases that are specific for the separation of ethoxylated surfactants. As example, Lee Ferguson and co-workers [60, 127] tested a mixed-mode HPLC system using a column packed with a polymeric phase capable of separating NPEO and NP components by both size-exclusion and reversed-phase adsorption mechanisms (Figure 4a). Other authors have also applied this technique with some modifications to quantify OP and octylphenolethoxylates (OPEOs) in environmental samples [73]. Alternative packing materials containing hydrophobic (alkyl chains) and hydrophilic (amide) functional groups to improve the simultaneous separation of cationic, anionic and non-ionic surfactants have also been occasionally employed [128].
Some surfactant classes (e.g., LAS and NPEOs) and their metabolites are still good candidates, due to the presence of an aromatic ring in their molecular structure, to be analyzed by the first quantitative methods based on the use of HPLC coupled to ultraviolet (UV) or fluorescence detectors (FL) [68, 66, 126, 129, 130]. The presence of a benzene group also facilitates the use of UV for identifying some specific cationic surfactants such as benzalkonium chlorides (BACs) [97]. Moreover, HPLC coupled to FL detector was employed by Natkae and co-workers [131] to achieve partial separation of positional isomers and obtain information on the alkyl chain distributions of LAS in river water samples. However, aliphatic surfactants (e.g., AEOs and AES) have not been monitored so much due to their lack of UV absorbance or fluorescence. Prior derivatization using phenyl-isocyanate [132], naphthylisocyanate and naphthyl chloride (NC) [88, 133], among others, must be carried out. Nowadays, however, this kind of surfactants, along with LAS, NPEOs and many other organic microcontaminants, are preferably determined by HPLC-MS, which offers several advantages over other detectors such as sensitivity, selectivity, and simultaneous identification and confirmation of multiple analyte classes by means of their molecular weight, retention time and mass spectra. In this sense, considerable progress has been achieved in the environmental analysis of surfactants over the last decade due to the development of atmospheric pressure ionization (APCI) or electrospray ionization (ESI) interfaces that allow coupling HPLC to MS. Before this, mass spectrometry was used only for identification of a wide range of surfactants from their mass spectra by flow-injection analysis (FIA) [134].
a) Mixed-mode HPLC-ESI-MS total current ion chromatogram of NPEOs (A= NP, B=n-NP3EO, 0=NP, 1=NP1EO, etc.) from a sediment sample, switching MS polarity from positive to negative ion mode at retention time 25.8 min [
Among different types of mass analyzers used for the identification and quantification of surfactants, there are several authors that have employed single quadrupole HPLC-MS systems operating in selected ion monitoring (SIM) mode [25, 55]. However, isobaric interferences may lead to sensitivity and resolution issues, which have been commonly solved by means of triple quadrupole [27, 106, 135] or ion trap MS detectors [47, 94]. In recent years, both techniques, especially the first one, have been the main tool for trace analysis of surfactants and many other organic contaminants because their respective MS-MS (triple quadrupole) and MSn (ion trap) capabilities allow scanning for daughter ions, increasing sensitivity and selectivity (especially for analysis of environmental samples which contain compounds showing the same molecular ions and retention times than those for selected analytes) [72] (Figures 4b and c). As example, discrimination and quantification of the 20 positional isomers of LASwas achieved recently by Lunar and co-workers [136] by monitoring specific fragment ions resulting from the benzylic cleavage of the carbon alkyl chain on both sides of the LAS phenyl group. As a drawback of this type of MS detectors, there is a limited number of predetermined ions that can be monitored during a single experiment and, although less frequent than in single quadrupole MS, interferences may lead to overestimation in the concentration of target compounds. Time-of-flight (ToF) LC-MS systems are less commonly used than other MS analyzers for environmental analysis of surfactants, but their full scan spectral sensitivity in a wide mass range and accurate mass measurement allow the identification and quantification of a large number of target, non-target surfactants and their metabolites in all kinds of matrices [40, 65, 137], constituting a recent alternative to address the issues mentioned above. Occasionally, hybrid systems like quadrupole time-of-flight (Q-ToF) detectors have been applied to determine a wide range of surfactants and some of their degradation products, such as alkylphenols and their carboxylates, in textile wastewaters [138], or to identify for the first time the molecular structure of LAS anaerobic degradation metabolites [139], although due to their high cost and relatively lower sensitivity compared with HPLC-MS-MS they are not often used for routine analysis of these compounds in environmental samples.
Table 5 provides general information about some analytical procedures aimed to the determination of surfactants in different environmental matrices by HPLC-MS (and some other detectors). So far, LAS and SPCs have been determined in both freshwater [71] and marine environments [40] using several kinds of MS detectors coupled to HPLC under negative ion (NI) mode due to the presence of a sulfonate group. Quasi-molecular ions [M-H]-and a characteristic fragment m/z = 183 were used for their identification and quantification. AES have also been monitored in aquatic systems [62, 140] in a similar way, but m/z = 97, corresponding to HO – SO3-,was selected as the main fragment ion. On the other hand, identification of QACs relies upon measurement oftheir molecular ions (M+) in positive ionization mode (PI), and further confirmation can be achieved by mass measurement of main characteristic ions such as m/z = 60 for alkyltrimethylammonium chlorides (ATACs) [141] or m/z = 91 for BACs [94]. Non-ionic surfactants lack charge or acid/base functional groups, so the most widely used option for ionization of ethoxylated compounds, such as NPEOs and AEOs, is to form adducts as the oxygen atoms in the polyethoxylate chain can donate their free electrons to a selected cation agent and the flexible structure of the chain allows the molecule to “wrap” itself around that cation [64]. Thus, sodium acetate [60, 74], ammonium acetate [89, 142] or different acids [53] are commonly added to the samples or to the mobile phase to increase the MS response of NPEOs and AEOs and to stabilize the generation of [M+Na]+, [M+NH4]+ or [M+H]+ ions, among others. Additionally, this ability to form different adducts can be used to obtain multiple confirmation points in full-scan mode [40]. Another advantage of MS compared to other detectors is that several types of surfactants can be analyzed within a single run (e.g., NPEOs and AEOs can be separated, using an adequate gradient, and later analyzed under PI [53, 64]). Most recent methodologies allow simultaneous determination of anionic and non-ionic surfactants and their metabolites in environmental samples [47, 55].
BAC, DADMAC | Marine sediment | Sonication, LLE, SPE | 98-118 (DADMAC) | ACN/H2O, isopropanol, FA, AMAC | Luna C18 (150 mm, 2mm, 5 µm) | ESI(+)- ToF-MS | 0.1-2.6 ng/g (LOQ) | [65] |
LAS, SPC | Seawater, marine sediment | Soxhlet, SPE | 75-105 | MeOH/H2O, H2O, tetraethyl ammonium hydrogensulfate | LiChrosorb RP-8 (250 mm, 4.6 mm, 10.6 µm) | FL | 0.2-0.4 µg/L 5-10 µg/Kg | [52] |
NPEO, NP | Marine sediment, sewage | Sonication, SPE LLE | 64-127 (sediment) | H2O, MeOH, sodium acetate | MSpak GF-310 4D filtration column (150 mm, 4.6 mm) | ESI-MS NPEO (ESI+) NP (ESI-) | 0.78-37.3 ng/g | [127] |
LAS, SPC, NPEO, NP1-2EC, AEO, PEG | Sewage, marine sediment, seawater, s. solids | Sonication, SPE | 26-117 (AEOs, PEGs) 60-108 (NPEOs, NP1-2EC) 37-101 (LAS, SPC) | ACN, H2O, FA, ammonium formate | Luna C18 (150 mm, 2mm, 5 µm) | ESI-ToF-MS LAS, SPC, NP1-2EC (ESI-) NPEO, AEO (ESI+) | 0.1-11.8 ng/L 0.1-23.7 µg/Kg | [40] |
AEO, NP1-3EO, NP, NP1-2EC | Marine sediment | Sonication, SPE | 34-88 | ACN, H2O, FA, ammonium formate | Purospher STAR RP-18 UHPLC column (50 mm, 2 mm, 1.8 µm) | ESI(+)-MS-MS | <0.1-27.3 ng/g | [44] |
BAC, ATAC, DADMAC | River sediment, sludge | Soxhlet, LLE | 67-95 | ACN/H2O, isopropanol, FA, AMAC | Luna C18 (150 mm, 2mm, 5 µm) | ESI(+)-MS-MS | 0.6-5 µg/Kg (LOQ) | [27] |
QAC | River water, sewage | Microporous membrane liquid-liquid extraction | - | Chloroform, ethanol, ammonia, heptanoic acid | Cyanopropyl column (250 mm, 2mm) | UV | 0.7-5 µg/L | [101] |
Key aspects of HPLC analysis of surfactants in different environmental matrices.
Today, mass spectrometry is often combined with ultra-performance liquid chromatography (UPLC), which uses sub-2-µm column particles that provide enhanced separation, faster analysis, and improved sensitivity over HPLC, boosting laboratory efficiency by saving time and decreasing solvent consumption. Most researchers have started to benefit from this combination, although there are still a few examples on its use for analysis of surfactants. So far, UPLC-Q-ToF-MS has been used for structural elucidation of SPC isomers [139] and for environmental screening of several anionic and non-ionic surfactants in wastewater [138]. UPLC-MS-MS [44] has allowed achieving fast analysis (less than 10 min per sample) of NPEO metabolites and AEOs at trace levels in aquatic environments.
The assessment of the behavior and final fate of synthetic surfactants in the environment is a crucial matter due to the huge volumes of these chemicals that are discharged into aquatic and terrestrial ecosystems. A significant number of analytical protocols have been developed over the last decades aimed to the individual or simultaneous extraction, isolation and determination of different types of surfactants in environmental samples. Nowadays, the most widely used sample preparation protocols are based on SPE, directly derived from column chromatography. However, the trend is to research on new techniques, such as SPME or SBSE, aimed to reduce, or even eliminate, solvent consumption, as well as saving money by using reusable fibers and bars rather than disposable cartridges. Regarding the separation, identification and quantification of surfactants, HPLC-MS and, to a lesser extent due to the non volatility of most analytes, GC-MS, are the main tools currently employed as they allow for determination of every single homologue, ethoxymer and/or isomer from surfactant mixtures in different environmental matrices (solids, water and biota). Most recently, different classes of time-of-flight and triple quadrupole mass spectrometers have started to be combined with UPLC, which provides enhanced separation, faster analysis, higher confidence, and lower detection limits than more conventional HPLC-MS or HPLC-MS-MS approaches, as well as improves identification of unknown surfactant metabolites and other non target compounds within the same run.
AA, Acetic acid; ASE,Accelerated solvent extraction; ACN, Acetonitrile;AEOs,Alcohol polyethoxylates; AES,Alkyl ethoxysulfates; AS, Alkyl sulfates; ATACs, Alkyltrimethylammonium chlorides; AP, Alkylphenol; APEOs, Alkylphenolpolyethoxylates; APEC, Alkylphenolpolyethoxycarboxylate; AMAC, Ammonium acetate; APCI, Atmospheric pressure ionization; BACs, Benzalkonium chlorides; BSTFA, N,O-bis(trimethylsilyl)trifluoroacetamide; CWAX/TR, Carbowax/template resin; CI, Chemical ionization; DTDMAC, Dehydrogenated tallow dimethyl ammonium chloride; DADMAC, Dialkyldimethylammonium chlorides; DCM, Dichloromethane; DLLME, Dispersive liquid-liquid microextraction; EI, Electron impact ionization; ESI, Electrospray ionization; EO, Ethylene oxide;CESIO,European Committee of Organic Surfactants and their Intermediates; FID, Flame-ionization detectors; FIA,Flow-injection analysis; FL, Fluorescence detectors; FA, Formic acid; GC, Gas chromatography; GBC, Graphitized black carbon; HPLC, High-performance liquid chromatography; HLB, Hydrophilic-lipophilic balance; LOD, Limit of detection; LOQ, Limit of quantification; LAS, Linear alkylbenzenesulfonates;LC, Liquid chromatography; LLE, Liquid-liquid extraction; MS, Mass spectrometry; MSPD, Matrix solid-phase dispersion;MeOH, Methanol; MLD, Method limit detection; MAE, Microwave-assisted extraction; NC,Naphthyl chloride; NI, Negative ionization; NP, Nonylphenol; NPEOs, Nonylphenolpolyethoxylates; NPECs, Nonylphenolpolyethoxycarboxylates; OP, Octylphenol; OPEOs, Octylphenolpolyethoxylates; PA, Polyacrylate; PEGs, Polyethylenglycols; SDB, Polystyrene-divinylbezene;PDMS/DVB, Polydimethylsiloxane/divinylbenzene;PI, Positive ionization; PT, Potentiometric titrametration; PFE, Pressurized fluid extraction; PLE, Pressurized liquid extraction;Q-ToF, Quadrupole time-of-flight; QACs, Quaternary ammonium-based compounds; SIM, Selected ion monitoring; SDS, Sodium dodecyl sulphate; SLE, Solid-liquid extraction; SPE, Solid phase extraction;SPME, Solid phase microextraction; SBSE, Stir-bar sorptive extraction; SAX, Strong anionic-exchange; SCX, Strong cationic-exchange; SPCs, Sulfophenyl carboxylic acids; SFE, Supercritical fluid extraction; MS-MS, Tandem mass spectrometry;ToF, Time-of-flight; UPLC, Ultra performance liquid chromatography; UV, Ultraviolet detectors; WWTPs, Wastewater treatment plants.
High-entropy alloys (HEAs) are a new class of materials and have attracted a great deal of attention [1, 2]. The concept of HEA was originally proposed for a face-centered-cubic (fcc), body-centered-cubic (bcc), or hexagonal-closed packing (hcp) structure. The most prominent feature of a HEA is that more than five elements, each having an atomic percentage between 5% and 35%, randomly occupy one crystallographic site (see also Figure 1(a)). This produces a large mixing entropy, and HEAs exhibit the combination of high yield strength and ductility [3], high strength at elevated temperatures [4], strong resistance to corrosion and oxidation [5], and so on. The high-entropy concept is extensively adapted in various materials such as oxides, chalcogenides, and halides [6, 7].
Crystal structure of compounds with (a) fcc and (b) Mn5Si3-type structures. In (a), a multicolored ball means a random occupation by constituent elements.
One of the novelties of HEAs is a cocktail effect, which indicates an enhancement of physical properties beyond the simple mixture of those of components. For example, several bcc HEAs show superior mechanical properties compared to conventional hard materials. Another example is found in magnetic spinel oxide (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)Al2O4. The high-entropy type spinel oxide interestingly shows enhanced magnetic frustration [8]. The cocktail effect is also reported in the structural stability of high-entropy-type materials. A γ-type disilicate structure is stable from room temperature to 1900°C in (Gd1/6Tb1/6Dy1/6Tm1/6Yb1/6Lu1/6)2Si2O7. The outstanding thermal stability is ascribed to the high-entropy state at the rare-earth site [9]. The other novelty of HEAs is the tuning of physical properties via the change of microstructure. The manufacturing process of HEAs considerably affects their microstructures, which are often deeply related to their physical properties. Fe15Co15Ni20Mn20Cu30 shows a spinodal decomposition after the heat treatment [10]. The spinodally decomposed sample exhibits enhanced Curie temperature and magnetization compared to the homogenized single-phase sample. The tuning of magnetic properties is also reported in dual-phase HEAs [11, 12, 13].
One of the new research topics in HEA is the superconductivity found in 2014 [14]. Transition metal-based superconductors, forming simple crystalline structures, follow the so-called Matthias rule. When the superconducting critical temperature
In the typical HEAs with fcc, bcc, or hcp structure, the superconductivity seems to appear in bcc or hcp HEAs. According to the classification by VEC, single-phase fcc HEA is stabilized for VEC larger than 8.0 [1, 2], where
The concept of HEA is now used in superconducting materials with the crystal structures possessing multiple Wyckoff positions. For example, CsCl-type, α-Mn-type, A15, NaCl-type, σ-phase and CuAl2-type HEA superconductors are reported [29, 30, 31, 32, 33, 34, 35, 36, 37]. High degree-of-freedom in such a multisite HEA design would promote the investigations of multisite HEA superconductors. The second purpose of this chapter is the materials research on the hexagonal Mn5Si3-type HEAs, possessing multiple Wyckoff positions. Recently, several superconductors with the Mn5Si3-type—or its ordered derivative Ti5Ga4-type—structure have been found and attract much attention [38, 39, 40, 41, 42, 43, 44]. Besides, many intermetallic compounds are crystallizing into these crystal structures [45, 46]. Figure 1(b) shows the crystal structure of the Mn5Si3-type compound represented by M5X3. The space group is
In this chapter, we report the synthesis and characterization of the fcc and the Mn5Si3-type HEA samples. The measurement of AC magnetic susceptibility checked the superconducting state. We also present the phase analyses of both kinds of samples. Finally, the future direction of materials research on superconducting HEAs is mentioned.
All samples were synthesized by a home-made arc furnace in an Ar atmosphere. The constituent elements as listed in Table 1 were arc-melted on a water-cooled Cu hearth. The samples were turned over and melted several times. The Mn5Si3-type HEAs were annealed at 800°C for four days in evacuated quartz tubes.
Element | Supply company | Purity (%) | Crystal structure | Atomic radius (Å) | VEC |
---|---|---|---|---|---|
Zr | Soekawa Chemicals, Tokyo, Japan | 99 | A3 (hcp) | 1.6025 | 4 |
Nb | Nilaco, Tokyo, Japan | 99.9 | A2 (bcc) | 1.429 | 5 |
V | Kojundo Chemical Laboratory, Sakado, Japan | 99.9 | A2 (bcc) | 1.316 | 5 |
Ru | Soekawa Chemicals, Tokyo, Japan | 99.9 | A3 (hcp) | 1.3384 | 8 |
Ir | Furuya Metal, Tokyo, Japan | 99.99 | A1 (fcc) | 1.3573 | 9 |
Rh | Soekawa Chemicals, Tokyo, Japan | 99.9 | A1 (fcc) | 1.345 | 9 |
Pd | Tanaka Kinzoku Kogyo, Tokyo, Japan | 99.9 | A1 (fcc) | 1.3754 | 10 |
Cu | Soekawa Chemicals, Tokyo, Japan | 99.99 | A1 (fcc) | 1.278 | 11 |
Sc | Furuya Metal, Tokyo, Japan | 99.9 | A3 (hcp) | 1.641 | 3 |
Ti | Nilaco, Tokyo, Japan | 99.9 | A3 (hcp) | 1.4615 | 4 |
Ga | Kojundo Chemical Laboratory, Sakado, Japan | 99.99 | All | 1.392 | 3 |
Si | Soekawa Chemicals, Tokyo, Japan | 99.999 | A4 | 1.153 | 4 |
Ge | Soekawa Chemicals, Tokyo, Japan | 99.999 | A4 | 1.24 | 4 |
Pt | Tanaka Kinzoku Kogyo, Tokyo, Japan | 99.9 | A1 (fcc) | 1.387 | 10 |
Materials used in this study. The supply company, purity, crystal structure at room temperature, atomic radius [47], and VEC are also listed.
A powder X-ray diffractometer (XRD-7000 L, Shimadzu, Kyoto, Japan) with Cu-Kα radiation was employed to detect the X-ray diffraction (XRD) patterns of prepared samples. The microstructure of each sample was examined by a field emission scanning electron microscope (FE-SEM, JSM-7100F; JEOL, Akishima, Japan). The atomic compositions of the samples were checked by an energy dispersive X-ray (EDX) spectrometer equipped to the FE-SEM.
To confirm the diamagnetic signal due to the superconducting state, the temperature dependence of the AC magnetic susceptibility
The starting compositions of prepared Nb-containing samples were determined, considering the conventional design rule [1, 2]: a
No. | Sample | Composition of Phase I, II or III | VEC | |
---|---|---|---|---|
1 | Cu20Nb15Pd25Rh30V10 | 3.52 | 8.65 | |
Phase I | Cu8.3(8)Nb21.2(8)Pd21.6(4)Rh42.9(5)V6.0(5) | 3.14 | 8.29 | |
Phase II | Cu14.4(5)Nb12.6(5)Pd28(1)Rh26.4.(8)V18.6(5) | 3.26 | 8.32 | |
Phase III | Cu65(5)Nb2(1)Pd28(2)Rh2(1)V3(1) | 3.56 | 10.38 | |
2 | Cu21Ir21Nb15Pd22Rh21 | 3.45 | 9.04 | |
Phase I | Cu1.4(6)Ir36.4(8)Nb24.3(4)Pd10.1(9)Rh27.8(3) | 2.52 | 8.16 | |
Phase II | Cu8.5(7)Ir6(1)Nb12.5(6)Pd46(3)Rh27(2) | 2.66 | 9.13 | |
Phase III | Cu40(5)Nb4(1)Pd52(3)Rh4(1) | 3.74 | 10.16 | |
3 | Cu21Nb15Pd22Rh21Zr21 | 8.00 | 7.99 | |
Phase I | Cu19.3(3)Pd37.2(2)Rh19.2(4)Zr24.3(5) | 8.30 | 8.54 | |
Phase II | Cu7(1)Nb41(1)Pd8(1)Rh27(1)Zr17(1) | 6.60 | 6.73 | |
Phase III | Cu57(1)Pd13(1)Rh9(1)Zr21(1) | 9.33 | 9.22 | |
4 | Cu20Nb15Pd24Rh25V10Zr6 | 5.62 | 8.34 | |
Phase I | Cu14.5(3)Nb15.7(5)Pd31(1)Rh23.1(5)V7(1)Zr8.7(5) | 5.98 | 8.26 | |
Phase II | Cu15.0(5)Nb24(1)Pd18(1)Rh27.2(5)V15.8(8) | 3.72 | 7.89 | |
Phase III | Cu86(1)Pd14(1) | 2.62 | 10.86 | |
5 | Cu40Nb20Pd30V10 | 4.44 | 8.9 | |
Phase I | Cu21.1(2)Nb27.6(2)Pd39.7(7)V11 5(7) | 4.05 | 8.25 | |
Phase II | Cu89.2(5)Pd10.8(5) | 2.35 | 10.89 | |
6 | Ir10Nb17Pd33Rh28Ru12 | 2.21 | 8.54 | |
Phase I | Ir15.5(2)Nb17.7(8)Pd20.3(7)Rh29.7(2)Ru16.8(5) | 2.30 | 8.33 | |
Phase II | Ir4.0(6)Nb16.0(5)Pd51(1)Rh22(1)Ru7.0(7) | 2.02 | 8.8 |
and
where
Shown in Figure 2 is the XRD patterns of prepared samples. In the upper five samples, all containing Nb, Pd, and Cu atoms, Cu20Nb15Pd25Rh30V10 and Cu21Ir21Nb15Pd22Rh21 possess dominant fcc phases. On the other hand, the XRD patterns of Zr-containing samples (Cu21Nb15Pd22Rh21Zr21 and Cu20Nb15Pd24Rh25V10Zr6) cannot be characterized by fcc phases. These results suggest that Zr is unfavorable for the formation of an fcc structure. In order to further investigate the formation condition of the single fcc phase, the quaternary alloy Cu40Nb20Pd30V10 was synthesized. As shown in Figure 2, this sample exhibits two fcc phases with quite different lattice parameters. The XRD pattern of the sample with no Cu atom (see the bottom of Figure 2) can be explained by an fcc phase. The lattice parameters of all fcc phases were obtained by the least-square method [48, 49] and are shown in Figure 2.
XRD patterns of Nb-containing samples. The origin of each pattern is shifted by an integer value.
Figures 3(a)–(f) display the SEM images of samples, all indicating multi-phases. In Cu20Nb15Pd25Rh30V10 (Figure 3(a)) and Cu21Ir21Nb15Pd22Rh21 (Figure 3(b)), three contrast phases I, II and III were detected. In each case, the brightest area (phase I) showed a dendritic morphology, which is surrounded by phase II with the median contrast. The darkest area (phase III) would be the precipitate that formed in the final solidification process. A part of Cu21Nb15Pd22Rh21Zr21 (Figure 3(c)) or Cu20Nb15Pd24Rh25V10Zr6 (Figure 3(d)) showed a eutectic-like structure formed by phase I and phase II (see, for example, the green elliptic closed-curve). As shown in Figure 3(e), Cu40Nb20Pd30V10 possesses two phases, both of which would be fcc phases taking into account the XRD results. Ir10Nb17Pd33Rh28Ru12 displays two contrast areas (see phases I and II in Figure 3(f)). The shape of the main phase has a dendritic-like morphology. The compositions of all phases determined by EDX are listed in Table 2.
Back-scattered electron (15 keV) images of (a) Cu20Nb15Pd25Rh30V10, (b) Cu21Ir21Nb15Pd22Rh21, (c) Cu21Nb15Pd22Rh21Zr21, (d) Cu20Nb15Pd24Rh25V10Zr6, (e) Cu40Nb20Pd30V10, and (f) Ir10Nb17Pd33Rh28Ru12, respectively.
Here, we discuss the fcc phase stability, viewed from the parameters of
We have prepared five Mn5Si3-type HEAs as listed in Table 3, and the XRD patterns are given in Figure 4. All XRD patterns are well indexed by the hexagonal Mn5Si3-type structure, and the determined lattice parameters are displayed in Figure 4. The SEM images of all samples are presented in Figures 5 and 6, and
No. | Sample | Composition of main phase | Composition of minor phase | VEC |
---|---|---|---|---|
1 | (NbScTiVZr)(GaGeSi) | (Nb13.0(1)SC15.5(1)Ti11.2(1)V4.6(2)Zr19.0(1))(Ga4.4(2)Ge19.3(1)Si13.1(1)) | Ga7(1)Ge6(1)Nb19(1)Sc8(1) Si7(1)Ti17(1)V28(1)Zr8(1) | 4 |
2 | (Nb1.25Sc1.25Ti1.25Zr1.25) (Ge1.8Si1.2) | (Nb17(1)Sc14(1)Ti16(1)Zr17(1)) (Ge22(1)Si14(1)) | — | 4 |
3 | (Nb1.25Sc1.25Ti1.25Zr1.25) (Ge1.55Ru0.47Si0.98) | (Nb18.0(2)Sc13.5(4)Ti12.3(5)Zr20.5(6)) (Ge21.4(2)Si14.3(4)) | Nb28(4)Ru31(4)Sc6(2)T31(3)Zr4(1) | 4.234 |
4 | (Nb1.4ScTiZr1.6) (Ge1.6Pt0.3Si1.1) | (Nb20.8(3)Sc8.4(5)Ti10.9(3)Zr24(1)) (Ge19.9(5)Pt1.0(4) Si15.0(5)) | Ge5.5(7)Sc37(2)Si1.7(2)Ti15(1)Pt40.7(7) | 4.275 |
5 | (Nb1.4ScTiZr1.6) (Ge1.6Ir0.3Si1.1) | (Nb20.4(2)Sc8.9(5)Ti10.9(1)Zr24.5(4)) (Ge20.3(3)Si15.0(2)) | Ge5.3(5)Ir27.7(9)Nb9.3(5) Sc20.5(9)Si4.0(6)Ti16.4(5) Zr16.7(8) | 4.238 |
Chemical compositions of phases detected by EDX measurements for Mn5Si3-type HEA samples. VEC of each starting composition is also shown.
XRD patterns of Mn5Si3-type HEAs. The simulation pattern is also shown. Each pattern is shifted by an integer value for clarity.
Back-scattered electron (15 keV) images of (a) (NbScTiVZr)(GaGeSi), and (b) (Nb1.25Sc1.25Ti1.25Zr1.25)(Ge1.8Si1.2), respectively. The elemental mappings are also shown.
Back-scattered electron (15 keV) images of (a) (Nb1.25Sc1.25Ti1.25Zr1.25)(Ge1.55Ru0.47Si0.98), (b) (Nb1.4ScTiZr1.6)(Ge1.6Pt0.3Si1.1), and (c) (Nb1.4ScTiZr1.6)(Ge1.6Ir0.3Si1.1), respectively.
Temperature dependences of
We have started from (NbScTiVZr)(GaGeSi), which shows a diamagnetic signal (see Figure 7). However, as shown in Figure 5(a), the elemental mapping has revealed the inhomogeneous distribution of constituent elements, which is obviously signaled by the V atom. The atomic compositions determined by EDX are (Nb13.0(1)Sc15.5(1)Ti11.2(1)V4.6(2) Zr19.0(1))(Ga4.4(2)Ge19.3(1)Si13.1(1)) for the V-poor phase and Ga7(1)Ge6(1)Nb19(1)Sc8(1)Si7(1)Ti17(1)V28(1) Zr8(1) for the V-rich phase, respectively. The separately synthesized latter phase crystallizes into a bcc structure. This compound also shows the diamagnetic signal at approximately 5 K, which is identical to that of (NbScTiVZr)(GaGeSi). Therefore, (NbScTiVZr)(GaGeSi) would be an intrinsically normal state down to 3 K. The result of the chemical composition of the Mn5Si3-type phase in (NbScTiVZr)(GaGeSi) suggests the difficulty of incorporation of V and Ga atoms in a Mn5Si3-type HEA. Taking into account this experimental result, we have synthesized (Nb1.25Sc1.25Ti1.25Zr1.25)(Ge1.8Si1.2). As shown in Figure 4, the sample is almost single phase, which is also supported by homogeneous elemental mapping (see also Figure 5(b)). The determined atomic composition is (Nb17(1)Sc14(1)Ti16(1)Zr17(1))(Ge22(1)Si14(1)), which agrees well with the starting composition. While the single-phase Mn5Si3-type HEA is successfully obtained, the diamagnetic signal cannot be confirmed down to 3 K, as shown in Figure 7.
One of the conceivable reasons for no superconductivity in the samples mentioned above is that the VEC value is slightly less than the optimal value (see also Table 3). As pointed out in the review [28], multisite HEA superconductors follow the respective Matthias rule, which means the important role of the density of states at the Fermi level. The VEC values of Mn5Si3-type superconductors Zr5Sb3 and Zr5Ge2.5Ru0.5 are 4.375 and 4.25, respectively [40, 42], while the VEC value of (NbScTiVZr)(GaGeSi) or (Nb1.25Sc1.25Ti1.25Zr1.25)(Ge1.8Si1.2) is 4. Thus, aiming at increasing the VEC, we substituted Ru, Pt, or Ir atoms at the Si site of Mn5Si3-type HEA. The prepared samples were (Nb1.25Sc1.25Ti1.25Zr1.25)(Ge1.55Ru0.47Si0.98), (Nb1.4ScTiZr1.6)(Ge1.6Pt0.3Si1.1), and (Nb1.4ScTiZr1.6)(Ge1.6Ir0.3Si1.1) with the respective VEC value of 4.234, 4.275, and 4.238. In each sample, the main phase of XRD pattern is well characterized by the Mn5Si3-type structure (see Figure 4). However, the atomic composition, deviating from the starting one, as shown in Table 3, indicates that Ru, Pt, or Ir atoms cannot replace the atoms at the Si site. The SEM images of these samples show the precipitation of impurity phases at the grain boundaries of hexagonal-shaped main phases (see Figure 6(a)–(c)).
We have carried out materials research on the fcc and the Mn5Si3-type HEA superconductors. In the study of fcc HEA superconductors, we employed the Nb element, taking into account that the inclusion of rather high
The conclusions regarding the manufacturing process or microstructure in HEA superconductors are bulleted below.
If one wants to obtain a single-phase sample with bcc, hcp, or fcc type structure by the arc-melting method, it would be a rather hard task due to an appearance of secondary phase and/or of phase with a slightly different composition.
Eutectic HEAs receive much attention due to the rich functions arising from the microstructures [53]. In some cases, eutectic superconductors show enhanced superconducting critical temperatures. Therefore, the study of the eutectic phase in HEA superconductors might be interesting.
Mechanical alloying has been widely used to produce HEAs [54]. The mechanical alloying process is different from the arc-melting one. So this is another route to obtain single-phase HEA superconductors.
The formation of single-phase fcc HEA is realized at VEC larger than 8.0. According to the Matthias rule of transition metal alloys,
Nb5Ir3O, crystallizing into the Ti5Ga4-type structure, which is the ordered derivative of Mn5Si3-type structure, is well known as a two-band superconductor [41]. By substituting Pt into Ir, the crossover to single-band superconductivity is observed [44], which is a rare phenomenon. This result promotes us to investigate multisite HEA superconductors for further search of the crossover phenomenon, and the high-entropy state may be a new route of controlling the superconducting band. Another interesting aspect of HEA is the cocktail effect. In bcc HEA superconductors, we have shown that the peculiar enhancement of
J.K. is grateful for the support provided by Comprehensive Research Organization of Fukuoka Institute of Technology.
The authors declare no conflict of interest.
"Open access contributes to scientific excellence and integrity. It opens up research results to wider analysis. It allows research results to be reused for new discoveries. And it enables the multi-disciplinary research that is needed to solve global 21st century problems. Open access connects science with society. It allows the public to engage with research. To go behind the headlines. And look at the scientific evidence. And it enables policy makers to draw on innovative solutions to societal challenges".
\n\nCarlos Moedas, the European Commissioner for Research Science and Innovation at the STM Annual Frankfurt Conference, October 2016.
",metaTitle:"About Open Access",metaDescription:"Open access contributes to scientific excellence and integrity. It opens up research results to wider analysis. It allows research results to be reused for new discoveries. And it enables the multi-disciplinary research that is needed to solve global 21st century problems. Open access connects science with society. It allows the public to engage with research. To go behind the headlines. And look at the scientific evidence. And it enables policy makers to draw on innovative solutions to societal challenges.\n\nCarlos Moedas, the European Commissioner for Research Science and Innovation at the STM Annual Frankfurt Conference, October 2016.",metaKeywords:null,canonicalURL:"about-open-access",contentRaw:'[{"type":"htmlEditorComponent","content":"The Open Access publishing movement started in the early 2000s when academic leaders from around the world participated in the formation of the Budapest Initiative. They developed recommendations for an Open Access publishing process, “which has worked for the past decade to provide the public with unrestricted, free access to scholarly research—much of which is publicly funded. Making the research publicly available to everyone—free of charge and without most copyright and licensing restrictions—will accelerate scientific research efforts and allow authors to reach a larger number of readers” (reference: http://www.budapestopenaccessinitiative.org)
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The Open Access publishing movement started in the early 2000s when academic leaders from around the world participated in the formation of the Budapest Initiative. They developed recommendations for an Open Access publishing process, “which has worked for the past decade to provide the public with unrestricted, free access to scholarly research—much of which is publicly funded. Making the research publicly available to everyone—free of charge and without most copyright and licensing restrictions—will accelerate scientific research efforts and allow authors to reach a larger number of readers” (reference: http://www.budapestopenaccessinitiative.org)
\n\nIntechOpen’s co-founders, both scientists themselves, created the company while undertaking research in robotics at Vienna University. Their goal was to spread research freely “for scientists, by scientists’ to the rest of the world via the Open Access publishing model. The company soon became a signatory of the Budapest Initiative, which currently has more than 1000 supporting organizations worldwide, ranging from universities to funders.
\n\nAt IntechOpen today, we are still as committed to working with organizations and people who care about scientific discovery, to putting the academic needs of the scientific community first, and to providing an Open Access environment where scientists can maximize their contribution to scientific advancement. By opening up access to the world’s scientific research articles and book chapters, we aim to facilitate greater opportunity for collaboration, scientific discovery and progress. We subscribe wholeheartedly to the Open Access definition:
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\n\nAs a firm believer in the wider dissemination of knowledge, IntechOpen supports the Open Access Initiative Protocol for Metadata Harvesting (OAI-PMH Version 2.0). Read more
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\n\nBook chapters published in edited volumes are distributed under the Creative Commons Attribution 3.0 Unported License (CC BY 3.0). IntechOpen upholds a very flexible Copyright Policy. There is no copyright transfer to the publisher and Authors retain exclusive copyright to their work. All Monographs/Compacts are distributed under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0). Read more
\n\nPeer Review Policies
\n\nAll scientific works are Peer Reviewed prior to publishing. Read more
\n\nOA Publishing Fees
\n\nThe Open Access publishing model employed by IntechOpen eliminates subscription charges and pay-per-view fees, enabling readers to access research at no cost. In order to sustain operations and keep our publications freely accessible we levy an Open Access Publishing Fee for manuscripts, which helps us cover the costs of editorial work and the production of books. Read more
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\n\nIntechOpen is committed to ensuring the long-term preservation and the availability of all scholarly research we publish. We employ a variety of means to enable us to deliver on our commitments to the scientific community. Apart from preservation by the Croatian National Library (for publications prior to April 18, 2018) and the British Library (for publications after April 18, 2018), our entire catalogue is preserved in the CLOCKSS archive.
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They are considered as the biotechnologically valuable bacteria that are exploited for its secondary metabolite production. Approximately, 10,000 bioactive metabolites are produced by Actinobacteria, which is 45% of all bioactive microbial metabolites discovered. Especially Streptomyces species produce industrially important microorganisms as they are a rich source of several useful bioactive natural products with potential applications. Though it has various applications, some Actinobacteria have its own negative effect against plants, animals, and humans. On this context, this chapter summarizes the general characteristics of Actinobacteria, its habitat, systematic classification, various biotechnological applications, and negative impact on plants and animals.",book:{id:"5056",slug:"actinobacteria-basics-and-biotechnological-applications",title:"Actinobacteria",fullTitle:"Actinobacteria - Basics and Biotechnological Applications"},signatures:"Ranjani Anandan, Dhanasekaran Dharumadurai and Gopinath\nPonnusamy Manogaran",authors:[{id:"48914",title:"Dr.",name:"Dharumadurai",middleName:null,surname:"Dhanasekaran",slug:"dharumadurai-dhanasekaran",fullName:"Dharumadurai Dhanasekaran"}]},{id:"42319",doi:"10.5772/50364",title:"Lactic Acid Bacteria in Hydrogen-Producing Consortia: On Purpose or by Coincidence?",slug:"lactic-acid-bacteria-in-hydrogen-producing-consortia-on-purpose-or-by-coincidence-",totalDownloads:3766,totalCrossrefCites:29,totalDimensionsCites:85,abstract:null,book:{id:"2796",slug:"lactic-acid-bacteria-r-d-for-food-health-and-livestock-purposes",title:"Lactic Acid Bacteria",fullTitle:"Lactic Acid Bacteria - R & D for Food, Health and Livestock Purposes"},signatures:"Anna Sikora, Mieczysław Błaszczyk, Marcin Jurkowski and Urszula Zielenkiewicz",authors:[{id:"143688",title:"Dr.",name:"Urszula",middleName:null,surname:"Zielenkiewicz",slug:"urszula-zielenkiewicz",fullName:"Urszula Zielenkiewicz"},{id:"146985",title:"Dr.",name:"Anna",middleName:null,surname:"Sikora",slug:"anna-sikora",fullName:"Anna Sikora"},{id:"162424",title:"Prof.",name:"Mieczysław",middleName:null,surname:"Błaszczyk",slug:"mieczyslaw-blaszczyk",fullName:"Mieczysław Błaszczyk"},{id:"162425",title:"Mr.",name:"Marcin",middleName:null,surname:"Jurkowski",slug:"marcin-jurkowski",fullName:"Marcin Jurkowski"}]},{id:"42328",doi:"10.5772/47766",title:"Lactic Acid Bacteria as Source of Functional Ingredients",slug:"lactic-acid-bacteria-as-source-of-functional-ingredients",totalDownloads:7580,totalCrossrefCites:21,totalDimensionsCites:50,abstract:null,book:{id:"2796",slug:"lactic-acid-bacteria-r-d-for-food-health-and-livestock-purposes",title:"Lactic Acid Bacteria",fullTitle:"Lactic Acid Bacteria - R & D for Food, Health and Livestock Purposes"},signatures:"Panagiota Florou-Paneri, Efterpi Christaki and Eleftherios Bonos",authors:[{id:"140984",title:"Prof.",name:"Panagiota",middleName:null,surname:"Florou-Paneri",slug:"panagiota-florou-paneri",fullName:"Panagiota Florou-Paneri"},{id:"142773",title:"Dr.",name:"Efterpi",middleName:null,surname:"Christaki",slug:"efterpi-christaki",fullName:"Efterpi Christaki"},{id:"142774",title:"Dr.",name:"Eleftherios",middleName:null,surname:"Bonos",slug:"eleftherios-bonos",fullName:"Eleftherios Bonos"}]},{id:"42337",doi:"10.5772/50839",title:"Exopolysaccharides of Lactic Acid Bacteria for Food and Colon Health Applications",slug:"exopolysaccharides-of-lactic-acid-bacteria-for-food-and-colon-health-applications",totalDownloads:6363,totalCrossrefCites:18,totalDimensionsCites:46,abstract:null,book:{id:"2796",slug:"lactic-acid-bacteria-r-d-for-food-health-and-livestock-purposes",title:"Lactic Acid Bacteria",fullTitle:"Lactic Acid Bacteria - R & D for Food, Health and Livestock Purposes"},signatures:"Tsuda Harutoshi",authors:[{id:"141928",title:"Dr.",name:"Harutoshi",middleName:null,surname:"Tsuda",slug:"harutoshi-tsuda",fullName:"Harutoshi Tsuda"}]},{id:"42322",doi:"10.5772/51282",title:"The Current Status and Future Expectations in Industrial Production of Lactic Acid by Lactic Acid Bacteria",slug:"the-current-status-and-future-expectations-in-industrial-production-of-lactic-acid-by-lactic-acid-ba",totalDownloads:9076,totalCrossrefCites:18,totalDimensionsCites:46,abstract:null,book:{id:"2796",slug:"lactic-acid-bacteria-r-d-for-food-health-and-livestock-purposes",title:"Lactic Acid Bacteria",fullTitle:"Lactic Acid Bacteria - R & D for Food, Health and Livestock Purposes"},signatures:"Sanna Taskila and Heikki Ojamo",authors:[{id:"139705",title:"Dr.",name:null,middleName:null,surname:"Taskila",slug:"taskila",fullName:"Taskila"},{id:"142916",title:"Prof.",name:"Heikki",middleName:null,surname:"Ojamo",slug:"heikki-ojamo",fullName:"Heikki Ojamo"}]}],mostDownloadedChaptersLast30Days:[{id:"49873",title:"An Introduction to Actinobacteria",slug:"an-introduction-to-actinobacteria",totalDownloads:8003,totalCrossrefCites:27,totalDimensionsCites:97,abstract:"Actinobacteria, which share the characteristics of both bacteria and fungi, are widely distributed in both terrestrial and aquatic ecosystems, mainly in soil, where they play an essential role in recycling refractory biomaterials by decomposing complex mixtures of polymers in dead plants and animals and fungal materials. They are considered as the biotechnologically valuable bacteria that are exploited for its secondary metabolite production. Approximately, 10,000 bioactive metabolites are produced by Actinobacteria, which is 45% of all bioactive microbial metabolites discovered. Especially Streptomyces species produce industrially important microorganisms as they are a rich source of several useful bioactive natural products with potential applications. Though it has various applications, some Actinobacteria have its own negative effect against plants, animals, and humans. On this context, this chapter summarizes the general characteristics of Actinobacteria, its habitat, systematic classification, various biotechnological applications, and negative impact on plants and animals.",book:{id:"5056",slug:"actinobacteria-basics-and-biotechnological-applications",title:"Actinobacteria",fullTitle:"Actinobacteria - Basics and Biotechnological Applications"},signatures:"Ranjani Anandan, Dhanasekaran Dharumadurai and Gopinath\nPonnusamy Manogaran",authors:[{id:"48914",title:"Dr.",name:"Dharumadurai",middleName:null,surname:"Dhanasekaran",slug:"dharumadurai-dhanasekaran",fullName:"Dharumadurai Dhanasekaran"}]},{id:"55303",title:"Classification of Anti‐Bacterial Agents and Their Functions",slug:"classification-of-anti-bacterial-agents-and-their-functions",totalDownloads:9107,totalCrossrefCites:10,totalDimensionsCites:18,abstract:"Bacteria that cause bacterial infections and disease are called pathogenic bacteria. They cause diseases and infections when they get into the body and begin to reproduce and crowd out healthy bacteria or to grow into tissues that are normally sterile. To cure infectious diseases, researchers discovered antibacterial agents, which are considered to be the most promising chemotherapeutic agents. Keeping in mind the resistance phenomenon developing against antibacterial agents, new drugs are frequently entering into the market along with the existing drugs. In this chapter, we discussed a revised classification and function of the antibacterial agent based on a literature survey. The antibacterial agents can be classified into five major groups, i.e. type of action, source, spectrum of activity, chemical structure, and function.",book:{id:"5867",slug:"antibacterial-agents",title:"Antibacterial Agents",fullTitle:"Antibacterial Agents"},signatures:"Hamid Ullah and Saqib Ali",authors:[{id:"201024",title:"Dr.",name:"Hamid",middleName:null,surname:"Ullah",slug:"hamid-ullah",fullName:"Hamid Ullah"},{id:"202624",title:"Dr.",name:"Saqib",middleName:null,surname:"Ali",slug:"saqib-ali",fullName:"Saqib Ali"}]},{id:"58507",title:"Probiotics and Ruminant Health",slug:"probiotics-and-ruminant-health",totalDownloads:2783,totalCrossrefCites:5,totalDimensionsCites:9,abstract:"Probiotics are viable microorganisms with beneficial health effects for humans and animals. They are formulated into many functional foods and animal feed. There is a growing research interest in the application and benefits of probiotics in ruminant production. Several recent studies have evaluated the potential of probiotics in animal nutrition and health. In this chapter, we have reviewed current research on the benefits of probiotics on gut microbial communities in ruminants and their impact on ruminant production, health and overall wellbeing.",book:{id:"6425",slug:"probiotics-current-knowledge-and-future-prospects",title:"Probiotics",fullTitle:"Probiotics - Current Knowledge and Future Prospects"},signatures:"Sarah Adjei-Fremah, Kingsley Ekwemalor, Mulumebet Worku and\nSalam Ibrahim",authors:[{id:"107905",title:"Prof.",name:"Salam",middleName:null,surname:"Ibrahim",slug:"salam-ibrahim",fullName:"Salam Ibrahim"},{id:"218786",title:"Dr.",name:'Mulumebet "Millie"',middleName:null,surname:"Worku",slug:'mulumebet-"millie"-worku',fullName:'Mulumebet "Millie" Worku'},{id:"218789",title:"Dr.",name:"Kingsley",middleName:null,surname:"Ekwemalor",slug:"kingsley-ekwemalor",fullName:"Kingsley Ekwemalor"},{id:"223195",title:"Dr.",name:"Sarah",middleName:null,surname:"Adjei-Fremah",slug:"sarah-adjei-fremah",fullName:"Sarah Adjei-Fremah"}]},{id:"49285",title:"Morphological Identification of Actinobacteria",slug:"morphological-identification-of-actinobacteria",totalDownloads:8467,totalCrossrefCites:18,totalDimensionsCites:43,abstract:"Actinobacteria is a phylum of gram-positive bacteria with high G+C content. Among gram-positive bacteria, actinobacteria exhibit the richest morphological differentiation, which is based on a filamentous degree of organization like filamentous fungi. The actinobacteria morphological characteristics are basic foundation and information of phylogenetic systematics. Classic actinomycetes have well-developed radial mycelium, which can be divided into substrate mycelium and aerial mycelium according to morphology and function. Some actinobacteria can form complicated structures, such as spore, spore chain, sporangia, and sporangiospore. The structure of hyphae and ultrastructure of spore or sporangia can be observed with microscopy. Actinobacteria have different cultural characteristics in various kinds of culture media, which are important in the classification identification, general with spores, aerial hyphae, with or without color and the soluble pigment, different growth condition on various media as the main characteristics. The morphological differentiation of actinobacteria, especially streptomycetes, is controlled by relevant genes. Both morphogenesis and antibiotic production in the streptomycetes are initiated in response to starvation, and these events are coupled.",book:{id:"5056",slug:"actinobacteria-basics-and-biotechnological-applications",title:"Actinobacteria",fullTitle:"Actinobacteria - Basics and Biotechnological Applications"},signatures:"Qinyuan Li, Xiu Chen, Yi Jiang and Chenglin Jiang",authors:[{id:"175852",title:"Dr.",name:"Chen",middleName:null,surname:"Jiang",slug:"chen-jiang",fullName:"Chen Jiang"}]},{id:"68772",title:"Multidrug-Resistant Bacterial Foodborne Pathogens: Impact on Human Health and Economy",slug:"multidrug-resistant-bacterial-foodborne-pathogens-impact-on-human-health-and-economy",totalDownloads:1032,totalCrossrefCites:3,totalDimensionsCites:7,abstract:"The drug abuse known to occur during growth of animals intended for food production, because of their use as either a prophylactic or therapeutic treatment, promotes the emergence of bacterial drug resistance. It has been reported that at least 25% of the foodborne isolates show drug resistance to one or more classes of antimicrobials (FAO 2018). There are diverse mechanisms that promote drug resistance. It is known that the use of sub-therapeutic doses of antibiotics in animals intended for food production promotes mutations of some chromosomal genes such as gyrA-parC and mphA, which are responsible for quinolone and azithromycin resistance, respectively. Also, the horizontal transfer of resistance genes as groups (“cassettes”) or plasmids makes the spread of resistance to different bacterial genera possible, among which there could be pathogens. The World Health Organization considers the emergence of multidrug-resistant pathogenic bacteria as a health problem, since the illnesses caused by them complicate the treatment and increase the morbidity and mortality rates. The complication in the illness treatment caused by a multidrug-resistant pathogen causes economic losses to patients for the payment of long stays in hospitals and also causes economic losses to companies due to the absenteeism of their workers.",book:{id:"8133",slug:"pathogenic-bacteria",title:"Pathogenic Bacteria",fullTitle:"Pathogenic Bacteria"},signatures:"Lilia M. Mancilla-Becerra, Teresa Lías-Macías, Cristina L. 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Much of biochemistry is devoted to enzymes, proteins that catalyze chemical reactions, enzyme structures, mechanisms of action and their roles within cells. Biochemistry also studies small signaling molecules, coenzymes, inhibitors, vitamins, and hormones, which play roles in life processes. Biochemical experimentation, besides coopting classical chemistry methods, e.g., chromatography, adopted new techniques, e.g., X-ray diffraction, electron microscopy, NMR, radioisotopes, and developed sophisticated microbial genetic tools, e.g., auxotroph mutants and their revertants, fermentation, etc. More recently, biochemistry embraced the ‘big data’ omics systems. Initial biochemical studies have been exclusively analytic: dissecting, purifying, and examining individual components of a biological system; in the apt words of Efraim Racker (1913 –1991), “Don’t waste clean thinking on dirty enzymes.” Today, however, biochemistry is becoming more agglomerative and comprehensive, setting out to integrate and describe entirely particular biological systems. The ‘big data’ metabolomics can define the complement of small molecules, e.g., in a soil or biofilm sample; proteomics can distinguish all the comprising proteins, e.g., serum; metagenomics can identify all the genes in a complex environment, e.g., the bovine rumen. This Biochemistry Series will address the current research on biomolecules and the emerging trends with great promise.",coverUrl:"https://cdn.intechopen.com/series/covers/11.jpg",latestPublicationDate:"May 24th, 2022",hasOnlineFirst:!0,numberOfPublishedBooks:27,editor:{id:"31610",title:"Dr.",name:"Miroslav",middleName:null,surname:"Blumenberg",slug:"miroslav-blumenberg",fullName:"Miroslav Blumenberg",profilePictureURL:"https://mts.intechopen.com/storage/users/31610/images/system/31610.jpg",biography:"Miroslav Blumenberg, Ph.D., was born in Subotica and received his BSc in Belgrade, Yugoslavia. He completed his Ph.D. at MIT in Organic Chemistry; he followed up his Ph.D. with two postdoctoral study periods at Stanford University. Since 1983, he has been a faculty member of the RO Perelman Department of Dermatology, NYU School of Medicine, where he is codirector of a training grant in cutaneous biology. Dr. Blumenberg’s research is focused on the epidermis, expression of keratin genes, transcription profiling, keratinocyte differentiation, inflammatory diseases and cancers, and most recently the effects of the microbiome on the skin. He has published more than 100 peer-reviewed research articles and graduated numerous Ph.D. and postdoctoral students.",institutionString:null,institution:{name:"New York University Langone Medical Center",institutionURL:null,country:{name:"United States of America"}}},editorTwo:null,editorThree:null},subseries:{paginationCount:4,paginationItems:[{id:"14",title:"Cell and Molecular Biology",coverUrl:"https://cdn.intechopen.com/series_topics/covers/14.jpg",isOpenForSubmission:!0,editor:{id:"165627",title:"Dr.",name:"Rosa María",middleName:null,surname:"Martínez-Espinosa",slug:"rosa-maria-martinez-espinosa",fullName:"Rosa María Martínez-Espinosa",profilePictureURL:"https://mts.intechopen.com/storage/users/165627/images/system/165627.jpeg",biography:"Dr. Rosa María Martínez-Espinosa has been a Spanish Full Professor since 2020 (Biochemistry and Molecular Biology) and is currently Vice-President of International Relations and Cooperation development and leader of the research group 'Applied Biochemistry” (University of Alicante, Spain). Other positions she has held at the university include Vice-Dean of Master Programs, Vice-Dean of the Degree in Biology and Vice-Dean for Mobility and Enterprise and Engagement at the Faculty of Science (University of Alicante). She received her Bachelor in Biology in 1998 (University of Alicante) and her PhD in 2003 (Biochemistry, University of Alicante). She undertook post-doctoral research at the University of East Anglia (Norwich, U.K. 2004-2005; 2007-2008).\nHer multidisciplinary research focuses on investigating archaea and their potential applications in biotechnology. She has an H-index of 21. She has authored one patent and has published more than 70 indexed papers and around 60 book chapters.\nShe has contributed to more than 150 national and international meetings during the last 15 years. Her research interests include archaea metabolism, enzymes purification and characterization, gene regulation, carotenoids and bioplastics production, antioxidant\ncompounds, waste water treatments, and brines bioremediation.\nRosa María’s other roles include editorial board member for several journals related\nto biochemistry, reviewer for more than 60 journals (biochemistry, molecular biology, biotechnology, chemistry and microbiology) and president of several organizing committees in international meetings related to the N-cycle or respiratory processes.",institutionString:null,institution:{name:"University of Alicante",institutionURL:null,country:{name:"Spain"}}},editorTwo:null,editorThree:null},{id:"15",title:"Chemical Biology",coverUrl:"https://cdn.intechopen.com/series_topics/covers/15.jpg",isOpenForSubmission:!0,editor:{id:"441442",title:"Dr.",name:"Şükrü",middleName:null,surname:"Beydemir",slug:"sukru-beydemir",fullName:"Şükrü Beydemir",profilePictureURL:"https://s3.us-east-1.amazonaws.com/intech-files/0033Y00003GsUoIQAV/Profile_Picture_1634557147521",biography:"Dr. Şükrü Beydemir obtained a BSc in Chemistry in 1995 from Yüzüncü Yıl University, MSc in Biochemistry in 1998, and PhD in Biochemistry in 2002 from Atatürk University, Turkey. 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He worked on the structure-function relationships of glycoconjugates and his main project was the investigations on the biological roles of the de-N-glycosylation enzymes (Endo-N-acetyl-β-D-glucosaminidase and peptide-N4-(N-acetyl-β-glucosaminyl) asparagine amidase). From 2002 he contributes to the understanding of the Blood-brain barrier functioning using proteomics approaches. He has published more than 70 papers. 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She gained considerable experience in developing and validating new methodologies whose applications allowed her to determine both the amount of biomarkers (Desmosine and Isodesmosine) in the urine of patients affected by COPD, and the activity of proteolytic enzymes (HNE, Cathepsin G, Pseudomonas aeruginosa elastase) in the sputa of these patients. Simona Viglio was also involved in research dealing with the supplementation of amino acids in patients with brain injury and chronic heart failure. She is presently engaged in the development of 2-DE and LC-MS techniques for the study of proteomics in biological fluids. The aim of this research is the identification of potential biomarkers of lung diseases. 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