Uses of Portable Gas Chromatography Mass Spectrometers

Abstract

Gas chromatography mass spectrometry (GCMS) technology, whether in a laboratory or in the field allows scientists to identify and quantitate volatile and semi-volatile chemical compounds at low levels. It was not until the 1990s, well after the birth of GCMS in the 1950’s, that portable GCMS technology became possible. GCMS miniaturization along with a need for scientists to test samples outside of the laboratory drove the development of portable GCMS systems. Currently, scientists in the environmental, emergency response, government, military sectors, and private manufacturing industries use portable GCMS technology to monitor and quantitate various chemicals such as low levels of hazardous compound exposure in the environment. Successful implementation of portable GCMS also required that many sample preparatory techniques used in the laboratory must be modified for application in the field to maintain simplicity and robustness of the analysis of complex matrices like soil or water. This chapter will describe portable GCMS technology along with the current uses and sample preparatory techniques utilized.

1. Introduction

Portable gas chromatography mass spectrometers (GCMS) have been used by people in the environmental science, emergency response, government, military, and private manufacturing sectors [1]. Common analysis targets in the field have been narcotics, explosives, hazardous industrial environmental contaminants, and even food/beverage biomarkers for counterfeit prevention. These systems can identify and quantitate volatile and semi-volatile compounds contained in gases, liquids, and solids [1]. The sensitivity of this technique is high with the limit of detection for some chemical targets ranging from parts-per-billion to parts-per-trillion.

This section gives an overview of the topics reviewed in this chapter including portable GCMS technology, user requirements, and method development. Section 2 contains information about the basic technology behind portable GCMS systems. This includes information on low thermal mass gas chromatography column technology. It also includes key technology differences including available sample preparation devices for the following commercial portable GCMS systems: Perkin Elmer Torion T-9series, FLIR Griffin 500 series, and Infincon Hapsite ER series. All systems have different, yet similar characteristics that need to be evaluated by users to establish the best system for their specific methods and deployment criteria. Section 3 will provide specific case studies highlighting the different systems and techniques.

Section 3.1 will give characteristics important to users. The users for a Homeland Security study designed testing parameters to evaluate different portable GCMS technology specifically to see which characteristics were most important for first responders or investigators in the field. The study suggested that many different parameters were important, but again each user would need to evaluate which parameters fit better with their specific application.

Section 3.2 contains a method development review for headspace needle trap quantitation of butylated hydroxy toluene using a portable GCMS. The method will describe the effort involved in creating a purge and trap method for the analyte of interest and comparison with established GCMS preparatory methods. This work allowed for better quality control of cosmetics containing butylated hydroxy toluene using portable GCMS technology.

Section 3.3 contains a method development review for measuring 24 different illicit drugs with adulterants which could interfere with quantitation using portable GCMS technology. Method development was needed to show that the results created with the portable GCMS technology matched benchtop GCMS technology in a laboratory.

Section 3.4 showed that by using focusing agents for thermal desorption some portable GCMS technology had better precision when measuring chemical weapons agents. These focusing agents were necessary to decrease the relative standard deviation in order to show good chemical weapon agent quantitation reproducibility in the field using portable GCMS technology. These study descriptions show the amount of data required to create reliable quantitation methods for portable GCMS technology out the field.

2. Characteristic portable GCMS technology

Different commercialized portable GCMS technology have unique features overlaying a set of common core elements. In this next section, the technology that makes portable GCMS distinct from laboratory based GCMS technology will be discussed in detail to show why this technology can be deployed outside of the laboratory. In addition, vendor specific sample preparatory technology will be discussed. Review of the product brochures and vendor specific documentation are included to describe the following portable GCMS systems: Perkin Elmer Torion T-9, FLIR Griffin G510, and Hapsite ER systems. These three instruments are the most up to date examples of portable GCMS systems in the literature.

2.1 Low thermal mass gas chromatography column technology

Besides the GCMS column selectivity, the temperature programming is one of the most important factors in contributing to a successful GCMS separation. Temperature programming is a process of increasing and decreasing column temperature during a GC run [2]. The temperature changes over a GC run contribute to the separation of compounds with different boiling points, and can be used to change detection limits, help with peak symmetry, and facilitate column cleaning of high boiling point compounds [2].

For normal GC systems, a convection oven requiring 220 volts is used to heat a silica capillary column to achieve the programmed temperature control mentioned above. The heating of normal GCMS ovens requires a lot of energy and is relatively fast. The cool down time of the oven can be much longer as the oven approaches room temperature since it is only cooled by a fan. All the materials that make up the oven store the heat which in turn need to be cooled.

The temperature programming of a portable GCMS column allows for faster changes in temperature rates for heating and cooling and has roughly 1% of the energy usage compared to a laboratory based GCMS system [3]. The technology used to achieve this is called low thermal mass (LTM) GC. Unlike a convection oven of a normal GC system, the LTM GC technology combines silica column, heating elements, insulation, and temperature sensors in one assembly as to require less material to heat up and cool down. Less required energy means less time required to heat up and cool LTM GC columns [3]. This is important for GCMS miniaturization for portable systems to conserve energy on battery power and to maintain the ability to run with a column up to 30 meters in length.

The LTM GC column assemblies consist of the following parts: insulated silica capillary column, insulated heating wire, resistive temperature detector (as a temperature sensor), and metal foil. Each component is bundled together and then twisted into a torus shape formed by rotating the closed loop of bundled components to create a smaller loop. Figure 1 shows the composition of the LTM GC column torus configuration along with the cross section of the bundle. This configuration allows for a high surface area and thus rapid heating and cooling potential while maintaining low power consumption due to the fact there is no large GC oven, just the heating wires in the torus bundle. The absence of a large GC oven means the overall heat capacity of the system is smaller and thus the amount of energy required to heat or cool is much smaller. Faster heating and cooling rates allow for smaller runtimes and potentially better peak resolution depending on specific methodology required.

Figure 1.

A diagram of the LTMGC assembly and a cross section of the bundle.

2.2 Commercialized portable GCMS systems

As discussed above, the LTM GC column set up is shared among many of the portable GCMS systems. In this section, three of the following commercialized portable GCMS systems will be discussed from literature available from the manufacturer: Perkin Elmer Torion T-9series, FLIR Griffin 500 series, and Infincon Hapsite ER series. Method development required to create methods in the field will be discussed later in the Section 3 case studies. As of the writing of this chapter, these three instruments are the most up to date examples of portable GCMS systems in the literature. In addition, the vendor-specific sample preparation technology associated with each portable GCMS technology will be discussed.

2.2.1 Perkin Elmer Torion T-9 GCMS product brochure information

The weight of the Torion T-9 portable GCMS is 32 pounds. Battery power is up to 2.5 hours. This system has the option of an internal disposable helium cylinder or an external hookup for a larger helium container. From a cold start, the system is ready to run samples within 5 minutes. Automated startup performance validation is done to check system performance [4]. The LTM GC column allows for the analysis of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) with the ability to match performance from lab based GCMS systems. Small diameter GC columns along with rapid temperature programming allows for shorter GC analysis times. The maximum temperature ramp rate is 2.5°C per minute.

The Toroidal ion trap allows for large trapping volumes which can increase signal to noise and spectral quality with a scan range of 41–500 m/z [4]. The color touchscreen allows for easy changes in the method and for data analysis. On-board automated Chromion^® software/option PC integration allow for the potential of compound deconvolution and identification with the National Institute of Standards and Technology (NIST) libraries [4].

Some of the Perkin Elmer sample preparation technologies for portable GCMS systems technologies are as follows for Custodian^® Sampling Devices: Solid Phase Micro Extraction (SPME), Coil Microextraction (CME), and Needle Trap (NT). The Custodian^® devices are made of hard plastic and have a push button trigger that allows certain parts of the extraction devices to exit and retract into a 19-gauge needle [5]. The SPME device exposes a SPME fiber PDMS / DVB 65 μm to concentrate volatile compounds when exposed to sealed headspace or direct immersion into water/liquid samples [5]. The CME device exposes a steel coil that draws up dissolved solid and liquid samples [5]. The solvent is then allowed to evaporate before it is retracted into the 19-guage needle and is often best for SVOCs [5, 6]. The NT device contains a protected tribed Tenax TA, Carboxen 1016 and Carboxen 1003 fiber [5]. This fiber can be exposed to liquid samples when coupled thermal desorption units or a pump can pump air through it with a purge and trap apparatus for air samples [5]. All fiber sorbents or coils that have been retracted into the Custodian^® device can be inserted into the heated GCMS inlet for volatilization according to specific parameters of the matrix holding the chemical compounds.

2.2.2 FLIR Griffin 500 GCMS

The weight of the FLIR Griffin 500 portable GCMS is 36 pounds. Battery power is 2 to 4 hours depending on the scanning mode. This system also has the option of an internal disposable helium cylinder or an external hookup for a larger helium container. From a cold start, the system is ready to run samples within 15 minutes. This system also uses a LTM GC column assembly for the analysis of VOCs and SVOCs with the ability to match performance from lab based GCMS systems. The mass spectrometer in this system is a linear quadrupole that allows scanning from 15 to 515 m/z [7]. The color touchscreen allows for any changes in the method and for data analysis. On-board software allows for the potential of compound deconvolution and identification with the NIST and Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) libraries [7].

The Griffin portable GCMS systems have many different sample introduction techniques which include air, liquid, and solid samples. There is an integrated heated sample probe that can intake air sample from the environment during survey mode [7]. Split/splitless injection ports are present for different forms of sample introduction including air, liquid and SPME fibers. Syringes can be used to inject gas or liquid samples into the GCMS [8]. SPME fibers can be either used in sealed headspace experiments or immersed in liquids like water or solvents to concentrate the chemical compounds. Any commercial SPME fiber can be used and then put into the Griffin GCMS injection port. External headspace heating devices are available for purchase. When many liquid samples need to be injected into the GCMS with reproducible volume measurements, Griffin offers an autosampler that can hold up to 120 samples. Another sample prep device is the PSI-Probe. It is used with the Touch-and-Go (TAG) technology to collect solid or liquid samples just by touching the TAG sampler to the sample and then dropping it into the probe for thermal desorption. No solvents or sample prep is needed according to FLIR [8]. External headspace heating devices are also available for purchase. In addition, GERSTEL-Twister bars, spin plate bars coated in sorbent, can be used to extract compounds from liquid samples. The bars are said to be more sensitive than SPME and can be dropped into the PSI-probe once they are dry [8].

2.2.3 Infincon Hapsite ER portable GCMS system

The weight of the Inficon Hapsite ER portable GCMS is 42 pounds. Battery power is between 2 to 3 hours. This system has the option of an internal disposable nitrogen cylinder or an external hookup for a larger nitrogen container. Tuning occurs with an internal gas cylinder containing an internal standard [9]. This system also uses a LTM GC column assembly for the analysis of VOCs and SVOCs with the ability to match performance from lab based GCMS systems. The mass spectrometer allows scanning from 41 to 300 m/z [9]. The touchscreen allows for any changes in the method and for data analysis. On-board software does compound data processing with the National Institute for occupational Safety and Health (NIOSH) database. The NIST library is also available on a laptop for processing [9].

The Inficon Hapsite ER system has many options to introduce samples into the system. The air probe introduces volatiles compounds directly into the portable GC system [8]. In addition, the air probe can be hooked up to other available accessories. The headspace sampling system is a battery-operated accessory that can heat liquid and solid samples in vials, create headspace volatiles, and then the headspace is pumped directly into the Hapsite system with the air sampling probe [9]. The Thermal Desorber Sampling System can be attached directly to the Hapsite ER universal interface to allow suction of air for defined times through a TDU sorbent tube and then subsequent desorption of that sorbent into the mass spec for analysis [8]. The SPME sampling System can also be attached to the Hapsite ER universal interface for SPME fiber introduction which can extract samples from gas headspace or liquid samples [9]. Also, the Situ Probe Purge and Trap GCMS is a battery-operated accessory allowing for purge and trap sampling of water head space samples directly to the Hapsite ER system through the air sampling probe [8].

2.3 Commercialized portable GCMS conclusions

There are some characteristics of commercialized portable GCMS systems that were not included in the discussion. The previous sections showed that portable GCMS systems have some similar features such as LTM GC columns and sample preparation techniques. Each manufacturer has different variants of how to perform SPME and headspace. Overall, every user will have to evaluate each characteristic and potentially request a demo model to evaluate which system is best for their required method and their required deployment area such as a war zone, manufacturing facility or storage facility for illicit drugs.

3. What aspects of portable GCMS systems are useful to the user?

3.1 Important considerations for portable GCMS users in the field

What are the important considerations relevant to using portable GCMS in the field according to the experts? Many first responders, scientists, and other portable GCMS users have shared what portable GCMS characteristics are important to them as part of the System Assessment and Validation for Emergency Responders (SAVER) program which is under the National Urban Security Technology Laboratory (NUSTL) and the U.S. Department of Homeland Security (DHS).

The SAVER program gathers product information on commercially available equipment, conducts impartial testing led by experts in the first responder community, and then provides the results to allow for better informed decision-making when users buy equipment [1].

The SAVER program assessed several commercially available portable GCMS systems in order to demonstrate the important characteristics required by expert users in the field. The case studies in Sections 3.1.1 and 3.1.2 describe the study parameters used by the SAVER program to determine the characteristics important to users. The experts used in this study each had 8 to 20+ years in firefighting, public health, law enforcement, national guard weapons of mass destruction, civil support, and hazardous materials management. This information was then published for users to make informed decisions on capabilities of portable GCMS technology [1]. This section is provided to familiarize the reader with general portable GCMS function and what functions are important to GCMS users in the field and outside of the controlled laboratory environment. Different samples were analyzed to assess the following portable GCMS systems for usability, ease of deployment, maintainability, and capability: Griffin G-510, Torion T-9, and Hapsite ER. Sample preparation techniques/technology will be discussed in more detail in Section 3 as it pertains to method development.

3.1.1 Unknown analysis of portable GCMS systems

Each portable GCMS system was assessed for the ability to analyze for volatile or semi-volatile compounds in vapor from a sample. This test analyzed the following consumer products: isopropyl alcohol, ethyl acetate-based, and acetone-based nail polish remover [1]. All of these products contained volatile organic compounds with large vapor pressures in simplistic matrices for preliminary testing.

Each instrument had different ways of introducing the samples into the system. The testers used vapor sampling probes for the Griffin G-150 and Hapsite ER systems and a Solid Phase Micro Extraction (SPME) fiber collection device for the Torion T-9 to introduce the samples into the GCMS systems.

All the systems were able to identify isopropyl alcohol, ethyl acetate, and acetone in each of the consumer products along with relative chemical compositions listed by the manufacturers [1]. The evaluation then moved onto the second stage of chemical composition testing.

3.1.2 Liquid and solid sample testing

The next round included each evaluator testing at least one liquid and one solid sample. The liquid samples available for testing were fabric spot cleaner, mentholated electronic cigarette liquid, caffeinated beverage, oral analgesic spray lubricant, and liniment. The solid samples available for testing included wintergreen candy, wood filler, ibuprofen, aspirin pill, and caffeine pill [1]. These solid and liquid samples were included not only for the complex matrix, but also because of the semi-volatile/higher molecular weight ingredients. These compounds required longer analysis time compared to the volatile compounds in the previous experiments due to higher molecular weight/semi-volatile compounds having physical properties which cause longer elution times on the GC columns.

The evaluators repeated the use of the sampling probes and the SPME fibers from the previous section to extract any volatile compounds from the liquid and solid samples. Also, the solid and liquid samples were dissolved and diluted in organic solvent. These samples were then injected into the sample injection port of the Griffin G-150 with a calibrated GC syringe accounting for specific volumes to measure the analyte concentration. The samples dissolved in organic solvent were also extracted by submerging a Coiled Microextraction (CME) device manufactured by PerkinElmer. This CME device was then injected into the Torion T-9 using the instrument’s sample injection port.

Additional samples were also analyzed due to availability in their immediate environment. The sample vapor probes for the Griffin G-150 and Hapsite ER instruments were used to collect emissions from vehicles in a parking lot. The same vapors were also sampled with a SPME fiber and then inserted into the Torion T-9 for a full GCMS analysis. The volatile organic compounds emitted by pine trees next to the parking lot were sampled with the sample probes of the G-150 and Hapsite ER. Sampling occurred either next to the pine needles or at the top of a vial containing harvested pine needles. In addition, a SPME fiber was used to collect the volatile pine needle compounds from the headspace of a vial and then the SPME fiber was put into the Torion T-9. Another sampling technique for the Torion T-9 included a battery-operated air sampler. This device sucked air/ vapor close to the branch of a pine tree. This air sampler contained a detachable needle trap device (NTD) with sorbent. This device was then detached and inserted into the Torion T-9. Samples were analyzed with full scan GCMS.

The chemical composition of each analysis contained compounds that matched reported chemical compositions in the literature. In addition, to evaluate accessibility and usability while wearing personal protective equipment, experts used Level A gloves from encapsulated suits commonly used to completely protect users during hazardous materials/biological/chemical spills.

3.1.3 Report summary about major considerations for portable GCMS acceptability

This evaluation used the testing procedures described above to decide what were the most important characteristics of portable GCMS systems in the following categories: usability, ease of deployment, maintainability, and capability. The scores of each portable GCMS system will not be discussed in this section, but the main characteristics of portable GCMS systems required for successful experiments will be discussed.

The usability or ease of performing analyses in the field increases the chance of successful experiments. Easy to learn interfaces with the built-in touch screen along with intuitive operating systems were important. The touch screen could even be operated while the experts were wearing Level A gloves in a self-encapsulated hazardous materials suit. The software’s ability to switch between basic settings and advanced settings would allow the user experience to be varied based on user availability in the field. Remote function of the system would be beneficial if the instrument had to be mounted to a robotic system for remote transport into extremely hazardous conditions. Ease of sampling with sampling probes or cheap/innovative consumables gives the user more flexibility in the field when the matrix may be gas, liquid, or solid. With more use also comes the necessity to count injection to estimate carrier gas usage of the internal helium or nitrogen gas cylinders in the system. Some users suggested internal gas pressure levels to directly measure the gas, an integral part of the system. In addition, the inclusion of multiple gas cylinders within a system would allow the possibility of gas cylinder replacement without having to shut down the instrument. All these observations would increase the chances of successful experiments in the field.

The deployment and maintainability, along with ease of basic setup and startup in the field, were important to the end users. Multiple batteries to power the system was desirable to lengthen the analysis time. In addition, charging capabilities must be as fast as possible with the inclusion of vendor independent batteries for ease and cost of replacement. Operating temperature of the instrument must be able to handle both hot and cold environments. Remote access and diagnosis of problems by vendors was suggested to prevent instrument downtime and detachable/replaceable parts like inlet covers were required to allow for decontamination, if necessary, in toxic environments.

The main instrument capability category or scientific measurement ranges were also evaluated. Large ranges in atomic mass units from small to large were essential for an expert to measure volatile or semi-volatile compounds that could range in size in an unknown matrix. A wide column temperature range would also help in this aspect so that separation from a complex matrix would be possible. Automated data analysis/processing tools used with mass spectral library identification, report generation, and sending reports by email were highly rated in this process.

In summary, many different aspects of portable GCMS systems were evaluated. None of the portable GCMS systems failed the analytical testing performed by the experts. Usability with sample preparation, ease of sample introduction, temperature limits, mass scanning limits, and ability to swap battery and gas canisters were important to the experts. This report gave general opinions about operation and usability parameters important to portable GCMS systems. Each system needs to be evaluated by target users to determine if those parameters are important for their specific applications.

3.2 Case study 1

3.2.1 Case study 1: Introduction

Case study 1 relates to creating a method for measuring butylated hydroxytoluene (BHT) in cosmetics [10]. As seen in Figure 2, BHT is one of many antioxidants used in skin care products. Antioxidants are included in these products to help prevent the appearance of dark spots, wrinkles, and changes in skin elasticity. The antioxidants act directly to eliminate free radicals which damage skin DNA, lipids, and proteins which in turn causes the signs of skin aging described above. The free radicals come from exposure to sun and other environmental contaminants [10, 11].

Figure 2.

Butylated hydroxy toluene structure.

BHT penetrates the skin, acts on free radicals, and then any residual BHT remains within the layers of the skin. It is suggested that long term exposure to the skin can contribute to increased toxicity in various organ systems in the human body [10, 12]. Toxicity issues may be mitigated by decreasing exposure dosage or exposure duration. Despite having potential toxicity issues, products do contain this antioxidant. Methods of measurement are required to serve as quality control tests for manufactures to prevent overages that may be excessive.

A previous GCMS methods available for quantitating BHT included solvent extraction/Solid Phase Extraction (SPE) in water and then evaporation for GCMS analysis [13]. This method was made to be simpler and more robust than other techniques in order to rapidly quantitate BHT in cosmetics in manufacturing facilities using a portable GCMS system. This study chose lotion with BHT as a representative cosmetic since lotions have long exposure times on human skin due to the method of use.

3.2.2 Case study 1: Portable GCMS parameters

The Torion Tridion-9 portable GCMS system was used to analyze for BHT in this study [10]. As previously mentioned, this portable GCMS system can accept Solid Phase Micro Extraction (SPME) fibers or tubes/devices containing sorbent material. Once the objects containing the sorbent material were inserted into the portable GCMS, the analytes of interest bound to the sorbent were desorbed and entered the GCMS for analysis both with split and splitless sample flow. The inlet temperature was 280°C to ensure complete desorption. As the sample was desorbing, the resulting volatized compounds were drawn into the GCMS. The inlet desorption method was the following: 280°C hold for 1 second splitless air flow, 10:1 sample air split flow for 10 seconds, and a 50:1 sample air flow split for 30 seconds. The splitless and split air flow sections were combined to balance higher sensitivity (splitless) with high enough air sample flow rates (split) to desorb samples fast enough to maintain good peak shape of the matrix and BHT [10]. The oven method was as follows: 37°C for 2 seconds, increase to 220°C at a rate of 2°C per second, and then a 50 second hold at 220°C (approximate chromatographic separation of 2.4 minutes). GC ion-trap heater was 155°C and transfer line temperature was 250°C. Calibration and performance validation was done with Perkin Elmer’s Calion-13 standard mixture. The portable GCMS mass analyzer was run at 70 eV with an in-trap electron gun source. The GCMS scanned from 43 to 500 Da with a scan time of 50 ms.

3.2.3 Case study 1: SPME headspace method

This study performed several sample preparation techniques to compare results and see if any differences appeared between methods. The first method started with a standard addition calibration curve to quantitate BHT in lotion due to a matrix interference potential affecting the signal. Known quantities of BHT were spiked into the lotion matrix which contained an unknown starting BHT concentration. This method was also repeated with lotion which did not contain BHT. BHT standards of 10, 7, 5, 3, and 1 μg/mL were prepared by diluting a stock with acetone to obtain the desired concentrations. Ten microliters of each standard was spiked onto separate 0.1 g samples of the lotion suspended in 4 mL of water. Each sample was vortexed for 5 minutes and then further mixed with a rotating apparatus for 5 minutes at 1200 rpm. Due to the volatility of the BHT, the vials were heated for 30 minutes at 60°C to force the BHT into the headspace of the sealed vials. The headspace was exposed to a 65 μm DVB/PDMS SPME fiber punctured through the septum for 10 minutes. The SPME fiber bound the BHT present in the headspace during these 10 minutes. The fiber was then inserted into the inlet of a Torion Tridion-9 Portable GCMS to be heated and desorbed for analysis. Each spiked sample was prepared in triplicate. The calibration curves (with and without BHT) were created with the original unknown concentration of BHT in the spiked lotion matrix being y = 0.

3.2.4 Case study 1: head space needle trap method

The second method used a needle trap device (NTD) for binding the BHT. NTDs are needles with sorbent material on the inside of the needle that can bind volatile organic compounds (VOCs) or semi-volatile organic compounds (SVOCs) [14]. One end of the needle is connected to a suction pump and the other end of the needle remains open to draw gaseous sample into it to interact with the sorbent. The NTD can then be inserted into a GCMS inlet to be heated to desorb any bound chemical compounds.

The same calibration curve creation procedure with the SPME fiber in Section 3.2.3 was performed with the NTD with the setup portrayed in Figure 3. There were two needles inserted through the cap septum. The first needle was a purge needle which would flow helium through the spiked lotion solution. The BHT and other compounds would be volatilized easier with the gas flow through the solution. The second needle (NTD) was attached to a suction pump which would cause the headspace of the sample to be sucked through the sorbent. The NTD contained Tenax/CAR sorbent. Approximately 10 mL of gas passed through the NTD at a rate of 10 mL per minute. No breakthrough of the BHT occurred over this time and flow rate was based on the study coupling two NTDs in series previously. At one minute the runtime for this method was significantly less than the 10 minutes required for the SPME fiber to bind the BHT. The NTD was injected into a Torion-9 portable GCMS system. Again, the calibration curves created quantitated the original unknown BHT concentration in the lotion.

Figure 3.

NTD device setup.

3.2.5 Case study 1: thin film liquid injection

Thin film (TF) liquid injection was used to help confirm the amounts of BHT extracted from the lotion in the standard addition curves. The TF method put small amounts of liquid with predetermined concentrations of analytes on a thin film membrane [15]. The membrane containing the liquid with the analyte of interest was placed into a SPS-3 PerkinElmer thermal desorption unit (TDU). The TDU device when connected to a NTD via a sorbent tube, transferred the analyte from the TF to the NTD. The NTD was then put into the portable GCMS inlet and heated at 250°C to desorb the BHT and analyze it in the portable GCMS. This allowed neat, liquid BHT standards to be injected into the instrument to correlate amount of BHT to the instrument response. A calibration curve was obtained when different BHT concentrations were injected using the TF method. BHT amounts put onto the TF ranged from 0.15 μg to 3 μg. This was done to confirm the amount of BHT extracted from the spiking with the standard curve creation and to observe any instrument response differences caused by interfering peaks from the lotion. This method also served as an external calibration method.

3.2.6 Case Study 1: results

The results for head space needle trap sampling coupled to a portable GCMS for testing BHT in cosmetics are shown in Table 1. The instrument responses from the TF BHT method were used to transform the NTD and SPME extraction responses to the amount of BHT injected on column versus spiked BHT standard extracted from the lotion. These values allowed for the quantitation of the BHT in the lotion using headspace/SPME BHT. The retention time of the BHT in the GCMS method was 95.4 seconds with no co-eluting peaks detected when comparing the standard addition curves of lotion with and without BHT.

	BHT (μg)	BHT (μg)
Non-BHT containing body lotion	Spiked	Recovered	Extraction Efficiency
Sample 1	7	6.5	92.8
Sample 2	5	5.4	108.0
Sample 3	15	15.2	101.3
	Calculated from standard addition curve	Calculated from external calibration curve
BHT containing body lotion	5.6	6.1	108.9

Table 1.

Spike recoveries and comparison of NTD standard addition curve and external calibration.

Injecting three replicates showed that variability was less than 10% and had good linearity with a R² value of 0.98. As mentioned above, the NTD and SPME standard addition curves that originally had response versus spiked BHT standard were transformed to the amount of BHT extracted versus spiked BHT standard. The amount of BHT originally in the lotion was calculated when the value of y was set to zero in y = mx + b. There was good agreement between the NTD and SPME standard curves with only a 7.4% difference between the slopes of each curve. Spiked recoveries and comparison between the NTD standard addition and the external calibration are shown in Table 1.

A 0.005% BHT concentration was estimated based on the data from the standard addition curves. The results show that the NTD was able to concentrate the BHT from the headspace effectively even when mixed with the lotion matrix. Even with dilution by the helium, the headspace NTC method was able to achieve less than 10% relative standard deviation between replicates. Extracting from the headspace was a method advantage because some protocols may call for a dilute and shoot GC method for the lotion which would be problematic for the instrumentation.

3.2.7 Case 1 study: conclusion

The new method described in this case study was a headspace needle trap method used for the rapid determination of BHT using a portable GCMS. The sample preparation used a purge and trap method that included only diluting the lotion sample in solvent and then enriching the BHT sample on the NTD sorbent. Laborious sample preparation procedures, such as liquid-liquid partitioning, were avoided to obtain a simpler and faster procedure. The NTD method results agreed well with the SPME results which further strengthened the method validity. In addition, due to the air flow across the NTD, theoretically the NTD can concentrate more analyte in a shorter amount of time compared to SPME.

Future work suggested in this study would be a longer extraction NTD time with higher temperatures to make the method more exhaustive if the sample matrix is changed. This method allowed for rapid determination of BHT in non-laboratory environments lending to better quality control in factories or storage facilities if inspections of those locations were required.

3.3 Case study 2

3.3.1 Case study 2: introduction

Adulterants may be added to illicit drugs to either boost the drug’s effects or increase profits [16]. The mixing of different compounds together can lead to unforeseen negative side effects if ingested, even leading to death. In addition, these adulterants can also be mixed with ingredients that do not have any pharmacological effect such as sugars and bicarbonates [16].

Identifying adulterants in crime labs is often not done due to the lack of analytical method development for these compounds and the adulterants are not considered illegal compounds of abuse [16]. Including these compounds in the analytical methods would benefit clinicians when diagnosing the treatment for acute toxicity from drug mixtures, help investigate chronic health impacts of these mixtures and even serve as chemical fingerprints when tracking illicit drugs since certain illicit drug manufacturers have signature recipes [16].

This study was meant to develop and validate a method for illicit drug analysis along with potential adulterants using a FLIR Griffin G510 portable GCMS system and then compare the results to a laboratory based GCMS system.

3.3.2 Case study 2: methodology

A FLIR Griffin G510 portable GCMS was used in this study. A 5 m × 0.18 mm × 0.18 μm DB-5 column was the low thermal mass GC column used for analytical separation. The carrier gas was helium supplied by the internal helium cartridges of the G510. The programmed temperature gradient was as follows: ramp of 30°C per minute from 50°C to 340°C and hold at 340°C for 4 min (total runtime of 13.6 minutes). Full scan mode was used (43 to 425 m/z) with 275°C injection port temperature and a 1 μL splitless injection.

An Agilent GCMS 6890 N/5975B was used as the laboratory based GCMS to confirm the test results from the portable GCMS system. This GCMS was operated in full scan mode from 40 to 550 m/z. The GC column was a DB-1 column (12 m X 22 mm X 0.3 μm). The following parameters were used: 1 μL injection volume, splitless mode injection at 265°C and detector at 300°C with a 1.2 mL/min helium flow rate. The temperature program for the GC method was as follows: ramp 30°C per minute from 50°C to 340°C and hold at 340°C for 2.33 min (total runtime of 12 minutes).

The main compounds of interest were as follows: alprazolam, amphetamine, aminopyrine, benzocaine, caffeine, cocaine, codeine, diltiazem, ephedrine, fentanyl, fenethylline, furanylfentanyl, heroin, hydroxyzine, levamisole, lidocaine, methamphetamine, morphine, noramidopyrine (a marker of metamizole), phencyclidine, phenacetin, procaine, strychnine and xylazine. Stocks were made to a concentration of 1 mg per mL and diluted to 0.1 mg per mL for method validation. Each solution was injected separately to establish retention time and confirm NIST library match scores. To mimic field conditions, a protocol was made to weigh approximately 1 mg of powder into 10 mL of methanol to give a 0.1 mg per mL concentration. This was an approximate concentration since analytical balances would not be brought into the field. The five main parameters to create a validated method for the 24 above compounds on a portable GCMS system were interference, precision, limit of detection, robustness, and carryover.

To analyze precision, each of the target compounds was injected 10 times every day for 3 days. In addition, fresh solutions were made every day. Confirmation of each peak included setting a 0.3-minute retention time variation limit and a NIST library match score of at least 65 or above. If the criteria were not met, then the peak seen in the GC run was not identified as one of the 24 compounds of interest.

Possible interferences would be the adulterants, and according to this study they were commonly found in seized illegal drugs [16]. The interferences evaluated were as follows: salicylic acid, atropine, cannabidiol, delta 9-THC, diphenhydramine, ibuprofen, methadone, mitragynine, nicotine, quinine, lactose, creatine, acetaminophen, thebaine and theophylline [16]. Stock solutions of 0.1 mg per mL were made and analyzed in duplicate to establish retention times and the most abundant mass fragments from the mass spectrum. The mass spectrum allowed for the identification of any unique fragments for each compound which showed selectivity in differentiating between signal features.

Limit of detection (LOD) was established by analyzing the lower concentrations to identify the point when the signal to noise ratios were less than 3:1. This reproducible 3:1 instrument response plus the 0.3-minute retention time window and the NIST score greater than or equal to 65 were all criteria in identifying the LOD and confirming the identity of the compound. All these values were used to help with the validation of this method.

The carryover was tested by injecting 0.2, 0.5, and 1.0 mg per mL of the drugs of abuse and the adulterants. Two solvent blanks (methanol) were then injected in duplicate. The concentration at which the method did not have carryover was designated as the highest analyte concentration at which none of the illicit drug samples or adulterants were observed in the blank.

To evaluate the robustness of the instrument or the portable GCMS instrument performance reliability, small changes were made to see any fluctuations in instrument response. The injector temperature was varied plus or minus 5°C and the injection volume was varied plus or minus 0.2 μL. Each of the variations was done in duplicate and the criteria for peak identification of each of the 24 analytes along with the adulterants were retention time windows of 0.3 minutes and GCMS library match scores greater than or equal to 65.

After validation of the portable GCMS method, tests were performed to show the method could correctly identify the drugs of abuse and adulterants. Fifty different seized drug lots were tested for this purpose. The benchtop GCMS results were run alongside the portable GCMS to confirm the reliability of drug testing results from the portable GCMS. This study described using a method called Receiver Operating Characteristic (ROC) analysis to show the reliability of the portable GCMS results [16]. The ROC analysis assigned different categories to the portable GCMS data when it was compared to the benchtop GCMS. As above, identification criteria were established with specific parameters related to retention time and GCMS library identification score. True positive (TP) samples showed positive identifications on both the portable GCMS and benchtop GCMS for target analytes. True negative (TN) samples showed negative identifications on both portable and benchtop GCMS. False positive (FP) samples screened positive on the portable GCMS for a target analyte, but it was confirmed absent on the benchtop GCMS. False negative (FN) results showed an absence of target analytes on the portable GCMS results, but positive identification of the targets was confirmed on the benchtop GCMS. Based on the results, each compound in the 50 seized drug lots received a TP, TN, FP, or FN designation, and these values were used to calculate the following performance parameters describes in Table 2: sensitivity, specificity, accuracy, positive predictive values (PPV), and negative predictive values (NPV).

Parameter	Formula (%)	Definition
Sensitivity	100 × (TP#) / (TP# + FN#)	% Positively identified results in confirmed positive samples
Specificity	100 × (TN#) / (TN# + FP#)	% Negatively identified results in confirmed negative samples
Accuracy	100 × (TP# + TN#) / (TP# + TN# + FP# + FN#)	% Similarity between portable GCMS and benchtop GCMS
Positive Predictive Value (PPV)	(TP#) / (TP# + FP#)	Ratio of true positive results
Negative Predictive Value (NPV)	(TN#) / (FN# + TN#)	Ratio of true negative results

Table 2.

Performance parameters use to score portable GCMS performance.

3.3.3 Case study 2: results

Some of the 24 target compounds had similar retention times to several adulterants, but the mass spectrum of each of the co-eluting peaks were distinct enough to resolve/differentiate these compounds. There was no carryover of the analytes of interest or adulterants using the concentrations described in the previous section. Carryover was important to test since sample concentration variability was expected to be high in the field without calibrated glassware or analytical balances. Confirming the absence of carryover ensured a lower chance of false positives when there was high sample preparation variability causing the concentration to be greater than 1 mg/mL. Limits of detection ranged from 0.01 to 0.1 mg/mL depending on the analytes of interest in this study.

Thirty injections at 0.1 mg/mL of each of the standards were made to measure the precision. Heroin and morphine were not detected in 1 out of the 30 injections while diltiazem and fenethylline were not detected in 3 out of 30 injections. The precision for the other analytes were not mentioned. Many aspects of manual injection can change the results such as air bubbles, injection speed, and injection timing. It is important for the analyst in the field to emphasize reproducible injection technique.

Fifty seized illegal drug samples composing of mainly cocaine, methamphetamine, and heroin underwent screening with the validated portable GCMS method using the FLIR Griffin 510. Data was confirmed with a benchtop GCMS system. The data showing the results of the Receiver Operating Characteristic (ROC) are in Table 3. The data confirmed the presence or absence of adulterants and other illicit drugs mixed with the cocaine, methamphetamine, and heroin samples. Only 5 samples (10%) were true positives for one substance and 19 samples (38%) had two substances from the above list. Ten samples (20%) contained three of the above compounds, and 16 samples (32%) had four or more of the above drugs and or adulterants. The study did not specify which samples contained the adulterants. The data did not include all the compounds developed for the portable GCMS method because the samples tested in Table 3 only contained the compounds with true positive or false negative hits. Refer to the methods for definitions of TP, FN, FP, and TN.

Drug	TP#	FN#	FP#	TN#	Sensitivity	Specificity	Accuracy	PPV	NPV
Amphetamine	7	1	0	42	87.5	100.0	98.0	100.0	97.6
Benzocaine	0	1	0	49	—	100.0	98.0	—	98.0
Caffeine	13	4	0	33	76.4	100.0	92.0	100.0	89.1
Cocaine	20	0	0	30	100.0	100.0	100.0	100.0	100.0
Diltiazem	4	0	0	46	100.0	100.0	100.0	100.0	100.0
Ephedrine	2	0	0	48	100.0	100.0	100.0	100.0	100.0
Fentanyl	2	0	0	48	100.0	100.0	100.0	100.0	100.0
Furanyl Fentanyl	3	0	0	47	100.0	100.0	100.0	100.0	100.0
Heroin	12	3	0	35	80.0	100.0	94.0	100.0	92.1
Hydroxyzine	3	0	0	47	100.0	100.0	100.0	100.0	100.0
Levamisole	7	0	0	43	100.0	100.0	100.0	100.0	100.0
Lidocaine	2	1	0	47	66.6	100.0	98.0	100.0	97.9
Methamphetamine	15	0	0	35	100.0	100.0	100.0	100.0	100.0
Morphine	2	0	0	48	100.0	100.0	100.0	100.0	100.0
Noramidopyrine	3	0	0	47	100.0	100.0	100.0	100.0	100.0
Phenacetin	9	0	0	41	100.0	100.0	100.0	100.0	100.0
Procaine	2	2	0	46	50.0	100.0	96.0	100.0	95.8

Table 3.

Results comparing Portable GCMS data to benchtop GCMS results. Sensitivity, specificity, accuracy, PPV, and NPV were % values.

Some additional facts of the data need to be discussed. Accuracy values from the portable GCMS that were in high agreement with the lab based GCMS had higher values in the accuracy column. As Noted in from the methods section, the sensitivity, accuracy, and NPV were affected by the number of false negatives as seen with caffeine, heroin, procaine, amphetamine, lidocaine, and benzocaine. Most compounds had high values, but each method had limitations such as benzocaine having a PPV that could not be calculated since there were no true positive samples.

3.3.4 Case study 2: conclusion

The screening method developed in this study measured 24 different illicit drugs along with several adulterants on a FLIR Griffin 510 portable GCMS. To confirm the results, a laboratory based GCMS was used to set criteria for measuring sensitivity, specificity, accuracy, and the probability of predicting whether a compound would be present or absent. Through this process, the portable GCMS method was validated to show a relatively high degree of accuracy for correctly screening the presence or absence of these compounds in 50 seized drug samples. The adulterants did not significantly affect the performance of the method, and this method was prepared for monitoring of these adulterants as needed.

3.4 Case study 3

3.4.1 Case study 3: introduction

The need exists to detect and quantitate chemical warfare agents (CWAs) in the field in order to protect those who may be at risk of exposure. The portable GCMS systems are most advantageous since deployment in the field yields shorter data turnaround times as samples do not have to be transported to laboratories for analysis [17, 18]. Besides short turnaround time, reproducible CWA absolute quantitation data for portable GCMS is very important due to the high toxicity of these substances. Shown in Figure 4, the analytes of interest in this study were the G-series nerve agents tabun, sarin, soman, and cyclosarin and the blistering agent sulfur mustard [18]. Previous work showed the possibility of using response factors (analyte peak area/internal standard peak area) for quantitating G-series nerve agents using Hapsite and Hapsite ER portable GCMS systems [19]. The results showed significant carryover effects from concentrator sorbent, air sampling robe, and transfer line. In addition, the Hapsite ER system built-in internal standard, bromopentafluorobenzene (BPFB) showed 26.3% relative standard deviation (%RSD) between days and 32.9% RSD within a day. Both high % RSD values showed that the BPFB was not a good candidate for calculating relative response factor CWA calibration curves.

Figure 4.

Nerve agents and blistering agents.

This case study sought to show that better? %RSD values for the above compounds could be achieved by spiking potential candidate compounds (Figure 5) onto thermal desorption (TD) tubes. These compounds served as focusing agents allowing relative response factors (RRFs) to be used to create calibration curves with better %RSD values and thus better quantitation parameters for portable GCMS systems [18]. The focusing agents in Figure 5 were as follows: 2-chloroethyl ethyl sulfide (2-CEES), diisopropyl fluorophosphate (DIFP), diethyl methylphosphonate (DEMP), diethyl malonate (DEM), methyl salicylate (MES), and dichlorvos (DCV). In addition, the stability of the focusing agents 14 days after spiking was also determined at multiple conditions. Another goal was to reproduce the data across multiple Hapsite portable GCMS systems to show inter-instrument feasibility for low % RSD quantitation of the CWAs.

Figure 5.

Structures of focusing agents used in study.

3.4.2 Case study 3: methodology

The study used Supelco Tenax^® TA (35/60) TD tubes to measure sarin, tabun, soman, cyclosarin, and sulfur mustard on multiple Hapsite ER portable GCMS systems. The TDU sampling system was set to 310°C and nitrogen gas was used to transfer the desorbed sample to a tri-bed concentrator. This concentrator was then held at 45°C for 12 minutes, 280°C for 11 seconds, and then the desorbed sampled entered a DB-1 ms GC column (15 m, 0.25 mm ID, 1.0 μm d_f). The total run time of the method was 15 minutes 30 seconds. The programmed temperature method was as follows: hold at 60°C for 1 minute 15 seconds, ramp of 8°C per minute for 3 minutes 45 seconds, after reaching 90°C ramp at 25°C per minute for 4 minutes 24 seconds with a maximum temperature at 200°C. Hapsite portable GCMS system were used with scanning from 45 to 300 m/z [18].

The TD tubes were spiked with 1, 2, 5, 10, and 50 ng of each of the previously mentioned focusing agents. Stability, carry-over, and remaining residual focusing agent were tested with two Hapsite ER portable GCMS systems. Carryover was determined by desorbing a spiked TD tube and then desorbing a blank TD tube. Residual focusing agent remaining on the TD tube was analyzed by desorbing spiked TD tubes multiple times. Stability was determined by measuring the mid-point signal response of 5 ng of each of the focusing agents spiked on a TD tube over a 14-day time period with multiple time points in between. External calibration curves were made with the system internal standard but had a %RSD value of around 24.2%. RRFs used area values determined by Hapsite ER IQ software and Automated Mass Spectral Deconvolution and Identification System (AMDIS) version 2.72 [18]. TD tubes were conditioned before spiking with dry purging rates of 50 mL of nitrogen per minute and temperature hold of 280°C for 120 minutes.

RRFs were calculated by dividing the (CWA Area X mass of focusing agent) by the (Focusing agent area X mass of the CWA). Six-point calibration curves were made for 1, 2, 5, 10, 20, and 50 ng of each CWA in relation to the RRF of each CWA and focusing agent.

3.4.3 Case study 3: results

The goal of this study was to improve the quantitation method of sarin, tabun, soman, cyclosarin, and sulfur mustard on a portable GCMS using the focusing agents listed above. The retention times of the CWAs and the focusing agents were mostly chromatographically resolved. Soman (retention time 6 minutes 13 seconds) was close to DEMP (retention time 5 minutes 52 seconds) and DEM (retention time 6 minutes 31 seconds). Cyclosarin (retention time 7 minutes 44 seconds) was not chromatographically resolved from focusing agent MES (retention time 7 minutes 48 seconds) in the total ion chromatogram, but the quantitation was done on specific and distinct mass spectral features [18]. If the mass spectral data was not present, quantitation of cyclosarin would be potentially less accurate.

All CWAs and focusing agents were analyzed on a single TD tube with 5 ng of each focusing agent. The measured peak areas were used to calculate the RRFs and calibration curves for each of the CWAs in triplicate across four Hapsite ER portable GCMS systems. Carry over of the CWAs was established to be low. For tabun, sarin, soman, and cyclosarin, the carryover was as follows: 0.26%, 0.04%, 0.01% 0.02%. Carryover for sulfur mustard was not given in the study. The residual BPFB internal standard was around 58%, and the carryover was less than 0.1%.

All RRFs were combined for six-point calibration curves for each of the CWAs of 1, 2, 5, 10, 20 and 50 ng of each CWA. The RRFs for the calibration curves were tested over 14 days and the % RSD values of each of the CWAs with each of the focusing agents are included in Table 4. All calibration curves were linear and had R² values of at least 0.983.

	%RSD
CWA	2-CEES	DIFP	DEMP	DEM	MES	DCV
Tabun	45	14	12	22	30	20
Sarin	51	3	8	10	21	9
Soman	37	18	25	9	2	9
Cyclosarin	41	12	18	2	9	3
Sulfur Mustard	29	32	37	22	12	23

Table 4.

Average RRF %RSD values for CWAs over 14 days.

All % RSD values were compared to the % RSD of the internal BPFB internal standard of 32.9%. Most of the %RSD values were lower than the 32.9% except for the CWAs with 2-CEES. Sulfur mustard had high % RSD for most of the focusing agents but MES seemed to be the best for this specific compound. This was a significant improvement over the BPFB and thus allowed for greater confidence in the CWA quantitation. DIFP, DEMP, and DEM had the lowest overall %RSD for most of the CWAs. The overall difference in area responses for all CWAs between two Hapsite instruments were as follows: 2-CEES 21%, DIFP 6%, DEMP 6%, DEM 16%, MES 13%, and DCV 7%. The similar values for DIFP and DEMP showed that the calibration curves were transferable between Hapsite instruments and were not just limited to one portable GCMS.

3.4.4 Case study 3: conclusion

This study showed that thermal desorption calibration techniques on the Hapsite portable GCMS system could be used to improve quantitation reproducibility of CWAs. By using focusing agents, the intra-instrument relative standard deviation was greatly reduced below the 32% using the internal BPFB standard. In addition, the inter-instrument variability was also shown to be much lower than that of the BPFB standard. This study successfully showed that CWA quantitation on portable GCMS equipment in the field can have high reproducibility and thus be more valid as absolute quantitation numbers.

4. Conclusions

As shown in this chapter, many different fields such as manufacturing, government, and first responders elect to use portable gas chromatography mass spectrometers (GCMS) for analysis. For each field, compound analysis targets are different, but testing is required for public safety such as with illegal drugs, chemical weapons, or potentially harmful ingredients in cosmetics. These systems are used for their mobility and sensitivity for analyzing complex mixtures in the field. Without portable GCMS technology, toxic samples may have to be shipped to laboratories which would delay data analysis and decision making.

Section 2 of this chapter reviewed the technology behind portable GCMS systems. The GC columns are low thermal mass column technology allowing for miniaturization and 1% the power requirements of a laboratory based GCMS. The following commercial portable GCMS systems were discussed in the chapter: Perkin Elmer Torion T-9series, FLIR Griffin 500 series, and Infincon Hapsite ER series. All have similar specifications, but slightly different sample introduction and sample preparation technologies. The characteristics of each system require user evaluation to choose which system would be better for their specific methods and deployment criteria.

Section 3.1 reviewed a Homeland Security report on the portable GCMS characteristics which were important to users in the first responder fields. Many different evaluation tests were done to evaluate the three different portable GCMS systems. Many of the criteria were similar on the different systems, but ease of use and deployment were important to most users. Again, a user evaluation would be required before purchase to match system requirements to user method development requirements.

Section 3.2 contained a method for the quantitation of butylated hydroxy toluene using a portable GCMS and needle trap technology for a purge and trap method. This work created a method which would allow researchers to decrease the time it would take for quality control testing.

Section 3.3 described the development of a new method for evaluation of 24 different illicit drugs with adulterants which could interfere with quantitation using portable GCMS technology. Method development showed that the portable GCMS results were the same as the benchtop GCMS technology in a laboratory.

Section 3.4 reviewed that focusing agents used on TDU tubes allowed for better precision when measuring the chemical weapon agents on portable GCMS systems. Reliable quantitation of these compounds was vital when the lives of personal would be put in danger. Also, depending on the application needs, these instrument can perform in-field analysis just as well as instruments in laboratory settings.

Conflict of interest

The authors declare no conflict of interest.