Kim, M-G
1994
Performance Advances in Ion Mobility Spectrometry by Combination with High-Speed Vapor Sampling, Preconcentration, and Separation Techniques
Dworzanski, J.P.; Kim, M.-G.; Snyder, A.P.; Arnold, N.S. and Meuzelaar, H.L.C.
Anal. Chimica Acta, 293:219-235, 1994. Funded by US Army Chemical Research Development and Engineering Center and Battelle.
Rugged, low weight, hand-held ion mobility spectrometry devices, initially developed for chemical warfare detection purposes, possess attractive characteristics as field-portable instruments for paramilitary (treaty verification, chemical demilitarization, drug interdiction, counterterrorism operations) and civilian (environmental monitoring, forensic characterization, process control) applications. Generally, however, such devices tend to exhibit limited resolution, narrow dynamic range, nonlinear response and long clearance times which severely limit their usefulness for qualitative and quantitative analysis of mixtures. To overcome these restrictions a prototype combined gas chromatography/ion mobility spectrometry (GC/IMS) unit was constructed by replacing the membrane inlet of a military IMS device known as the CAM (Chemical Agent Monitor) with suitable front-end modules. These modules enable high speed automated vapor sampling (AVS), microvolume preconcentration/thermal desorption, and isothermal GC preseparation of analytes using a short capillary column while operating the IMS source and cell at subambient pressures as low as 0.5 atm. The AVS-GC/IMS methodology sharply reduces competitive ionization and facilitates identification of mixture components, thereby enabling quantification of volatile and semivolatile compounds over a broad range of concentrations in air. At higher concentral levels (e.g.>1 ppm) using the AVS inlet in automatic attenuation control (AAC) mode maintains excellent linear response. At ultralow concentration levels, e.g. < 10 ppb, a microvolume, trap-and-desorb type preconcentration module, maintains adequate signal to noise levels, thereby expanding the effective dynamic range of the method to appox. 6 orders to magnitude (100 pp 5-100 ppm). The resulting "hyphenated" GC/IMS technique has the potential of evolving into the first hand-portable combined chromatography/spectroscopy instruments for field screening applications.
1993
Novel Automated Chromatographic and Spectroscopic Techniques for On-Line Combustion By-Product Monitoring
Meuzelaar, H.L.C.; McClennen, W.H.; Arnold, N.S.; Dworzanski, J.P. and Kim, M.-G.
Incineration of Hazardous Wastes-2; Toxic Combustion By Products: 513-530, (in press). Funded by Consortium for Fossil Fuel Liquefaction and ACERC.
A new generation of on-line combustion product and by-product monitoring techniques based on the combination of a novel, automated vapor sampling (AVS) concept with so-called "transfer line gas chromatography" (TLGC) and any of several possible spectroscopic techniques is described. The automated vapor sampling method is characterized by the exclusive presence of quartz glass surfaces in the path of sample molecules between sampling point and detector, as well as by very short vapor sampling times (typically ˜ 1 sec), thereby facilitating rapid chromatographic separation using a short length (e.g., 1-6 ft) of fused silica capillary GC column. Laboratory test data are provided for three different instrumental configurations, namely AVS-TLGC in combination with: (1) mass spectrometry (MS); (2) MS and Fourier transform infrared spectroscopy (FTIR); and (3) ion mobility spectrometry (IMS).
Whereas on-line GC/MS monitoring is clearly the preferred approach when maximum specificity and sensitivity are required, GC/IR has important advantages for monitoring gaseous combustion products and distinguishing isomeric species and on-line GC/IMS appears to offer a sensitive, relatively inexpensive and simple monitoring tool for selected target compounds.
Portable Hand-Held Gas Chromatography/Ion Mobility Spectrometry Device
Snyder, A.P.; Harden, C.S.; Brittain, A.H.; Kim, M.-G.; Arnold, N.S. and Meuzelaar, H.L.C.
Analytical Chemistry, 65:299-306, 1993. Funded by US Army and University of Utah.
The concept of a portable gas chromatography/Ion mobility spectrometry (GC/IMS) device is introduced. The potential of the GC/IMS unit is investigated for the separation and characterization of vapor mixtures of various chemical classes. Parameters such as internal cell pressure, GC column flow rate, and column temperature were varied to determine the effects on speed and resolution for separating and characterizing mixtures. It was generally found that by reducing both the internal IMS cell pressure and the isothermal GC column temperature, the peak widths, retention times, and peak overlap could be varied for different classes of analytes. The GC/IMS system shows versatility in the various compound classes that can conveniently be analyzed by a hand-portable version. Mixtures included phosphonates, phosphates, alkyl ketones, and chlorophenois with total separation times in the 7-s to 2-min time range. Positive or negative ion polarities in IMS were used depending upon the functional group.
Performance Advances in Ion Mobility Spectrometry through Combination with High-Speed Vapor Sampling, Preconcentration and Separation Techniques
Dworzanski, J.P.; Kim, M.-G.; Snyder, A.P.; Arnold, N.S. and Meuzelaar, H.L.C.
Anal. Chimica Acta, 1993 (in press). Funded by Chemical Research Development and Engineering Center and Battelle.
Rugged, low weight, hand-held ion mobility spectrometry devices, initially developed for chemical warfare detection purposes, possess attractive characteristics as field-portable instruments for paramilitary (treaty verification, chemical demilitarization, drug interdiction, counterterrorism operations) and civilian (environmental monitoring, forensic characterization, process control) applications. Generally, however, such devices tend to exhibit limited resolution, narrow dynamic range, nonlinear response and long clearance times which severely limit their usefulness for qualitative and quantitative analysis of mixtures. To overcome these restrictions a prototype combined gas chromatography/ion mobility spectrometry (GC/IMS) unit was constructed by replacing the membrane inlet of a military IMS device known as the CAM (Chemical Agent Monitor) with suitable front-end modules. These modules enable high speed automated vapor sampling (AVS), microvolume preconcentration/thermal desorption, and isothermal GC preseparation of analytes using a short capillary column while operating the IMS source and cell at subambient pressures as low as 0.5 atm. The AVS-GC/IMS methodology sharply reduces competitive ionization and facilitates identification of mixture components, thereby enabling quantitative of volatile and semivolatile compounds over a broad range of concentrations in air. At higher concentral levels (e.g.>1 ppm) using the AVS inlet in automatic attenuation control (AAC) mode maintains excellent linear response. At ultralow concentration levels, e.g. < 10 ppb, a microvolume, trap-and-desorb type preconcentration module, maintains adequate signal to noise levels, thereby expanding the effective dynamic range of the method to appox. 6 orders to magnitude (100 pp 5-100 ppm). The resulting "hyphenated" GC/IMS technique has the potential of evolving into the first hand-portable combined chromatography/spectroscopy instruments for field screening applications.
Portable, Handheld Instrumentation: Gas Chromatography/Ion Mobility Spectrometer
Snyder, A.P.; Harden, C.S.; Brittain, A.H.; Kim, M.-G.; Arnold, N.S. and Meuzelaar, H.L.C.
Proceedings of the International Symposium on Field Screening Methods for Hazardous Waste and Toxic Chemicals: 831-841, Las Vegas, NV 1993. Funded by US Army and University of Utah.
The concept of a one hand-portable gas chromatography/ion mobility spectrometry (GC/IMS) device is introduced. The potential of the GC/IMS unit is investigated for the separation and characterization of vapor mixtures of various chemical classes. The column temperature was varied to determine the effects on speed and resolution for separating and characterizing mixtures. The GC/IMS system shows versatility in the various compound classes that can conveniently be analyzed by a hand-portable version. Mixtures included amines, alcohols and drug synthesis/purification solvents with total separation times in the 7-30 sec time range, and all were analyzed in the positive ion mode.
Performance Advances in Combined Gas Chromatography/Ion Mobility Spectrometry through High-Speed Vapor Sampling, Preconcentration, and Pyrolysis Techniques
Dworzanski, J.P.; Meuzelaar, H.L.C.; Arnold, N.S.; Kim, M.-G. and Snyder, A.P.
Proceedings of US Army Electrical Research Development and Engineering Center Science Conference on Chemical Defense Research, Aberdeen, MD, November 1993 (in press). Funded by US Department of Defense Electrical Research Development and Engineering Center and Battelle.
Detection and characterization of low volatile and nonvolatile organic matter as well as extension of the effective dynamic range of ion mobility spectrometry (IMS) for analysis of volatile organic compounds are achieved by interfacing handheld IMS units to special inlet modules. Modules consist of a high-speed adsorption/desorption or pyrolysis unit (Curie-point heating technique) coupled to an automated vapor sampling (AVS) inlet and a short (2-3m), isothermal GC column. The AVS-GC/IMS methodology allows quantitation of compounds over a broad range of concentrations (i.e., 10 ppb - 100 ppm) in air through a computer-controlled, variable sampling time technique. Minimum detectable concentrations can be further reduced (e.g., to 90 ppt) by means of a microvolume, trap-and-desorb type preconcentration module, thereby expanding the effective dynamic range to approx. 6 orders of magnitude. Finally, when operating in pyrolysis mode the instrument can be used to obtain reproducible and characteristic GC/IMS pyrograms for a broad range of polymers.
1992
Portable, Hand-Held Gas Chromatography/Ion Mobility Spectrometer
Snyder, A.P.; Harden, C.S.; Brittain, A.H.; Kim, M.-G.; Arnold, N.S. and Meuzelaar, H.L.C
Analytical Chemistry, 1992 (in press). (Also included in American Laboratory, October:32B, 1992). Funded by US Army/Chemical Research Development and Engineering Center.
The general applicability of gas chromatography (GC) in combination with its reliability, to more complex chemical mixtures has made this technology particularly valuable in environmental and medical applications. Such monitoring are conducted in laboratory settings, in mobile field laboratories, and increasingly, in the field with hand-held portable analyzers. Hand-held systems have made significant technical gains in recent years to complement existing logistical attractions of coat and speed of analysis.
Ion mobility spectrometry (IMS) is an attractive technique in conjunction with GC for the determination of constituents in a mixture. The analyses of mixtures of amines, alcohols, and, in particular, the drug solvents performed in this study illustrate the effectiveness of IMS as a true additional dimension of detection for a GC system. Significant advantages to rapid screening, detection, and identification of both indoor and outdoor scenarios can be realized with the GC-IMS concept as a hand-held portable device.
Optimization of Transfer Line Gas Chromatography for Direct Atmospheric Vapor Sampling Ion Mobility Spectrometry Application
Arnold, N.S.; Kim, M.-G.; McClennen, W.H. and Dworzanski, J.P.
Workshop on Ion Mobility Spectrometry, Mescalaro, AZ, June 1992. Funded by US Army/Chemical Research Development and Engineering Center.
An automated vapor sampling (AVS) device has proved powerful for atmospheric (and other) vapor sampling applications when coupled with the "preseparation" available via rapid transfer line gas chromatography (TLGC) prior to detection by a "smart" detector. Initial applications of AVS TLGC utilized mass spectrometric (MS) detection along with rapid repetitive sampling to monitor on-line test reactors and industrial processes. Subsequent work extended this technique to AVS TLGC/FTIR for the monitoring of evolution products from a thermogravimetric analyzer. Most recently this technique has been extended to ion mobility spectrometry (IMS).
Because the AVS device samples directly from the ambient environment at the inlet into the GC column without any intervening mechanical parts (e.g. syringes, pumps, etc.), the GC column itself must function as a pressure restrictor between the sampled environment and a detector operated at reduced pressure. This technique found its first application in AVS TLGC/MS where the merits of vacuum outlet GC and the requirement of capillary flow restriction are obvious. Yet, the extension to detectors that are ordinarily operated at atmospheric pressure (i.e., IMS and FTIR) by pulling up to ½ atmosphere of vacuum on the detector cell has also proved successful.
These successes have motivated a search for "optimal" performance based upon the selection of appropriate column parameters for both separation and flow restriction criteria. Specifically, this paper evaluated the performance for AVS TLGC/IMS separations from the perspective of resolution, speed of separation and sensitivity.
1991
Hand-Portable Gas Chromatography/Ion Mobility Spectrometry: The "Poor Man's" CB System?
Meuzelaar, H.L.C.; Kim, M.-G.; Arnold, N.S.; Kalousek, P. and Snyder, A.P.
US Army Research Office Workshop on Spectrometry and Spectroscopy for Biologicals, Cashiers, NC, 1991. Funded by US Army/Chemical Research Development and Engineering Center and US Department of Defense/Army Research Office.
The capabilities of ion mobility spectrometry (IMS) with regard to the detection and identification of chemical warfare agents are widely recognized. Tens of thousands of IMS based CAM® (Chemical Agent Monitor) systems manufactured by Graseby Ionics (Watford, U.K.) are currently in use by NATO forces, including US Army Marine Corps.
The hand-held, battery powered CAM draws approx. 500 ml. min-1 of ambient air over a heated silicone rubber membrane covering the entrance to the ionization chamber (a Ni-63 source) and the IMS drift tube region both of which are being operated slightly below ambient pressure. A Faraday cup detector registers the arrival time of mobile ion species traversing the drift tube at different velocities after being admitted into the drift tube region by gating pulses at 20 msec intervals. Typical drift times ("mobilities") of ion species representing volatile organic compounds are in the 5-10 msec range. The CAM can be operated in either positive or negative ion detection mode (switch selectable).
In spite of the successful development and application of the CAM for detecting chemical warfare agents, several remaining shortcomings inherent to IMS based detection devices (e.g., limited ability to distinguish between individual components in complex mixtures as well as low dynamic range and lack of linear response), seriously hamper its application as a quantitative detection tool. Moreover, only organic species that readily pass through the silicone rubber membrane can be detected. This prevents the use of the CAM for detection of nonvolatile materials such as most biological warfare agents.
1990
Man-Portable Gas Chromatography/Ion Mobility Spectrometry System: GC/CAM
Meuzelaar, H.L.C.; Kim, M.-G.; Arnold, N.S.; Urban, D.T. ; Kalousek, P.; Snyder, A.P. and Eiceman, G.A.
US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, Aberdeen Proving Grounds, Maryland, 1990. Funded by US Army Chemical Research Development and Engineering Center.
Currently there is widespread interest in extending the capabilities of ion mobility spectrometry (IMS) to various military as well as nonmilitary fields of application, including chemical demilitarization, treaty verification, drug enforcement, explosives detection and environmental monitoring. Characteristic features of IMS are high sensitivity, fast response, low weight, small size, low power requirements, and relatively low cost. An attractive approach is to add a front-end module capable of performing "transfer line gas chromatography" (TLGC). In its present form the TLGC/IMS system consists of a special automated air sampling valve, a short (1-2 m long) capillary GC column with isothermal oven, a Chemical Agent Monitor (CAM) and a small laptop PC. The IMS system is operated below ambient pressures.
Kim, M-G
1994
Performance Advances in Ion Mobility Spectrometry by Combination with High-Speed Vapor Sampling, Preconcentration, and Separation Techniques
Dworzanski, J.P.; Kim, M.-G.; Snyder, A.P.; Arnold, N.S. and Meuzelaar, H.L.C.
Anal. Chimica Acta, 293:219-235, 1994. Funded by US Army Chemical Research Development and Engineering Center and Battelle.
Rugged, low weight, hand-held ion mobility spectrometry devices, initially developed for chemical warfare detection purposes, possess attractive characteristics as field-portable instruments for paramilitary (treaty verification, chemical demilitarization, drug interdiction, counterterrorism operations) and civilian (environmental monitoring, forensic characterization, process control) applications. Generally, however, such devices tend to exhibit limited resolution, narrow dynamic range, nonlinear response and long clearance times which severely limit their usefulness for qualitative and quantitative analysis of mixtures. To overcome these restrictions a prototype combined gas chromatography/ion mobility spectrometry (GC/IMS) unit was constructed by replacing the membrane inlet of a military IMS device known as the CAM (Chemical Agent Monitor) with suitable front-end modules. These modules enable high speed automated vapor sampling (AVS), microvolume preconcentration/thermal desorption, and isothermal GC preseparation of analytes using a short capillary column while operating the IMS source and cell at subambient pressures as low as 0.5 atm. The AVS-GC/IMS methodology sharply reduces competitive ionization and facilitates identification of mixture components, thereby enabling quantification of volatile and semivolatile compounds over a broad range of concentrations in air. At higher concentral levels (e.g.>1 ppm) using the AVS inlet in automatic attenuation control (AAC) mode maintains excellent linear response. At ultralow concentration levels, e.g. < 10 ppb, a microvolume, trap-and-desorb type preconcentration module, maintains adequate signal to noise levels, thereby expanding the effective dynamic range of the method to appox. 6 orders to magnitude (100 pp 5-100 ppm). The resulting "hyphenated" GC/IMS technique has the potential of evolving into the first hand-portable combined chromatography/spectroscopy instruments for field screening applications.
1993
Novel Automated Chromatographic and Spectroscopic Techniques for On-Line Combustion By-Product Monitoring
Meuzelaar, H.L.C.; McClennen, W.H.; Arnold, N.S.; Dworzanski, J.P. and Kim, M.-G.
Incineration of Hazardous Wastes-2; Toxic Combustion By Products: 513-530, (in press). Funded by Consortium for Fossil Fuel Liquefaction and ACERC.
A new generation of on-line combustion product and by-product monitoring techniques based on the combination of a novel, automated vapor sampling (AVS) concept with so-called "transfer line gas chromatography" (TLGC) and any of several possible spectroscopic techniques is described. The automated vapor sampling method is characterized by the exclusive presence of quartz glass surfaces in the path of sample molecules between sampling point and detector, as well as by very short vapor sampling times (typically ˜ 1 sec), thereby facilitating rapid chromatographic separation using a short length (e.g., 1-6 ft) of fused silica capillary GC column. Laboratory test data are provided for three different instrumental configurations, namely AVS-TLGC in combination with: (1) mass spectrometry (MS); (2) MS and Fourier transform infrared spectroscopy (FTIR); and (3) ion mobility spectrometry (IMS).
Whereas on-line GC/MS monitoring is clearly the preferred approach when maximum specificity and sensitivity are required, GC/IR has important advantages for monitoring gaseous combustion products and distinguishing isomeric species and on-line GC/IMS appears to offer a sensitive, relatively inexpensive and simple monitoring tool for selected target compounds.
Portable Hand-Held Gas Chromatography/Ion Mobility Spectrometry Device
Snyder, A.P.; Harden, C.S.; Brittain, A.H.; Kim, M.-G.; Arnold, N.S. and Meuzelaar, H.L.C.
Analytical Chemistry, 65:299-306, 1993. Funded by US Army and University of Utah.
The concept of a portable gas chromatography/Ion mobility spectrometry (GC/IMS) device is introduced. The potential of the GC/IMS unit is investigated for the separation and characterization of vapor mixtures of various chemical classes. Parameters such as internal cell pressure, GC column flow rate, and column temperature were varied to determine the effects on speed and resolution for separating and characterizing mixtures. It was generally found that by reducing both the internal IMS cell pressure and the isothermal GC column temperature, the peak widths, retention times, and peak overlap could be varied for different classes of analytes. The GC/IMS system shows versatility in the various compound classes that can conveniently be analyzed by a hand-portable version. Mixtures included phosphonates, phosphates, alkyl ketones, and chlorophenois with total separation times in the 7-s to 2-min time range. Positive or negative ion polarities in IMS were used depending upon the functional group.
Performance Advances in Ion Mobility Spectrometry through Combination with High-Speed Vapor Sampling, Preconcentration and Separation Techniques
Dworzanski, J.P.; Kim, M.-G.; Snyder, A.P.; Arnold, N.S. and Meuzelaar, H.L.C.
Anal. Chimica Acta, 1993 (in press). Funded by Chemical Research Development and Engineering Center and Battelle.
Rugged, low weight, hand-held ion mobility spectrometry devices, initially developed for chemical warfare detection purposes, possess attractive characteristics as field-portable instruments for paramilitary (treaty verification, chemical demilitarization, drug interdiction, counterterrorism operations) and civilian (environmental monitoring, forensic characterization, process control) applications. Generally, however, such devices tend to exhibit limited resolution, narrow dynamic range, nonlinear response and long clearance times which severely limit their usefulness for qualitative and quantitative analysis of mixtures. To overcome these restrictions a prototype combined gas chromatography/ion mobility spectrometry (GC/IMS) unit was constructed by replacing the membrane inlet of a military IMS device known as the CAM (Chemical Agent Monitor) with suitable front-end modules. These modules enable high speed automated vapor sampling (AVS), microvolume preconcentration/thermal desorption, and isothermal GC preseparation of analytes using a short capillary column while operating the IMS source and cell at subambient pressures as low as 0.5 atm. The AVS-GC/IMS methodology sharply reduces competitive ionization and facilitates identification of mixture components, thereby enabling quantitative of volatile and semivolatile compounds over a broad range of concentrations in air. At higher concentral levels (e.g.>1 ppm) using the AVS inlet in automatic attenuation control (AAC) mode maintains excellent linear response. At ultralow concentration levels, e.g. < 10 ppb, a microvolume, trap-and-desorb type preconcentration module, maintains adequate signal to noise levels, thereby expanding the effective dynamic range of the method to appox. 6 orders to magnitude (100 pp 5-100 ppm). The resulting "hyphenated" GC/IMS technique has the potential of evolving into the first hand-portable combined chromatography/spectroscopy instruments for field screening applications.
Portable, Handheld Instrumentation: Gas Chromatography/Ion Mobility Spectrometer
Snyder, A.P.; Harden, C.S.; Brittain, A.H.; Kim, M.-G.; Arnold, N.S. and Meuzelaar, H.L.C.
Proceedings of the International Symposium on Field Screening Methods for Hazardous Waste and Toxic Chemicals: 831-841, Las Vegas, NV 1993. Funded by US Army and University of Utah.
The concept of a one hand-portable gas chromatography/ion mobility spectrometry (GC/IMS) device is introduced. The potential of the GC/IMS unit is investigated for the separation and characterization of vapor mixtures of various chemical classes. The column temperature was varied to determine the effects on speed and resolution for separating and characterizing mixtures. The GC/IMS system shows versatility in the various compound classes that can conveniently be analyzed by a hand-portable version. Mixtures included amines, alcohols and drug synthesis/purification solvents with total separation times in the 7-30 sec time range, and all were analyzed in the positive ion mode.
Performance Advances in Combined Gas Chromatography/Ion Mobility Spectrometry through High-Speed Vapor Sampling, Preconcentration, and Pyrolysis Techniques
Dworzanski, J.P.; Meuzelaar, H.L.C.; Arnold, N.S.; Kim, M.-G. and Snyder, A.P.
Proceedings of US Army Electrical Research Development and Engineering Center Science Conference on Chemical Defense Research, Aberdeen, MD, November 1993 (in press). Funded by US Department of Defense Electrical Research Development and Engineering Center and Battelle.
Detection and characterization of low volatile and nonvolatile organic matter as well as extension of the effective dynamic range of ion mobility spectrometry (IMS) for analysis of volatile organic compounds are achieved by interfacing handheld IMS units to special inlet modules. Modules consist of a high-speed adsorption/desorption or pyrolysis unit (Curie-point heating technique) coupled to an automated vapor sampling (AVS) inlet and a short (2-3m), isothermal GC column. The AVS-GC/IMS methodology allows quantitation of compounds over a broad range of concentrations (i.e., 10 ppb - 100 ppm) in air through a computer-controlled, variable sampling time technique. Minimum detectable concentrations can be further reduced (e.g., to 90 ppt) by means of a microvolume, trap-and-desorb type preconcentration module, thereby expanding the effective dynamic range to approx. 6 orders of magnitude. Finally, when operating in pyrolysis mode the instrument can be used to obtain reproducible and characteristic GC/IMS pyrograms for a broad range of polymers.
1992
Portable, Hand-Held Gas Chromatography/Ion Mobility Spectrometer
Snyder, A.P.; Harden, C.S.; Brittain, A.H.; Kim, M.-G.; Arnold, N.S. and Meuzelaar, H.L.C
Analytical Chemistry, 1992 (in press). (Also included in American Laboratory, October:32B, 1992). Funded by US Army/Chemical Research Development and Engineering Center.
The general applicability of gas chromatography (GC) in combination with its reliability, to more complex chemical mixtures has made this technology particularly valuable in environmental and medical applications. Such monitoring are conducted in laboratory settings, in mobile field laboratories, and increasingly, in the field with hand-held portable analyzers. Hand-held systems have made significant technical gains in recent years to complement existing logistical attractions of coat and speed of analysis.
Ion mobility spectrometry (IMS) is an attractive technique in conjunction with GC for the determination of constituents in a mixture. The analyses of mixtures of amines, alcohols, and, in particular, the drug solvents performed in this study illustrate the effectiveness of IMS as a true additional dimension of detection for a GC system. Significant advantages to rapid screening, detection, and identification of both indoor and outdoor scenarios can be realized with the GC-IMS concept as a hand-held portable device.
Optimization of Transfer Line Gas Chromatography for Direct Atmospheric Vapor Sampling Ion Mobility Spectrometry Application
Arnold, N.S.; Kim, M.-G.; McClennen, W.H. and Dworzanski, J.P.
Workshop on Ion Mobility Spectrometry, Mescalaro, AZ, June 1992. Funded by US Army/Chemical Research Development and Engineering Center.
An automated vapor sampling (AVS) device has proved powerful for atmospheric (and other) vapor sampling applications when coupled with the "preseparation" available via rapid transfer line gas chromatography (TLGC) prior to detection by a "smart" detector. Initial applications of AVS TLGC utilized mass spectrometric (MS) detection along with rapid repetitive sampling to monitor on-line test reactors and industrial processes. Subsequent work extended this technique to AVS TLGC/FTIR for the monitoring of evolution products from a thermogravimetric analyzer. Most recently this technique has been extended to ion mobility spectrometry (IMS).
Because the AVS device samples directly from the ambient environment at the inlet into the GC column without any intervening mechanical parts (e.g. syringes, pumps, etc.), the GC column itself must function as a pressure restrictor between the sampled environment and a detector operated at reduced pressure. This technique found its first application in AVS TLGC/MS where the merits of vacuum outlet GC and the requirement of capillary flow restriction are obvious. Yet, the extension to detectors that are ordinarily operated at atmospheric pressure (i.e., IMS and FTIR) by pulling up to ½ atmosphere of vacuum on the detector cell has also proved successful.
These successes have motivated a search for "optimal" performance based upon the selection of appropriate column parameters for both separation and flow restriction criteria. Specifically, this paper evaluated the performance for AVS TLGC/IMS separations from the perspective of resolution, speed of separation and sensitivity.
1991
Hand-Portable Gas Chromatography/Ion Mobility Spectrometry: The "Poor Man's" CB System?
Meuzelaar, H.L.C.; Kim, M.-G.; Arnold, N.S.; Kalousek, P. and Snyder, A.P.
US Army Research Office Workshop on Spectrometry and Spectroscopy for Biologicals, Cashiers, NC, 1991. Funded by US Army/Chemical Research Development and Engineering Center and US Department of Defense/Army Research Office.
The capabilities of ion mobility spectrometry (IMS) with regard to the detection and identification of chemical warfare agents are widely recognized. Tens of thousands of IMS based CAM® (Chemical Agent Monitor) systems manufactured by Graseby Ionics (Watford, U.K.) are currently in use by NATO forces, including US Army Marine Corps.
The hand-held, battery powered CAM draws approx. 500 ml. min-1 of ambient air over a heated silicone rubber membrane covering the entrance to the ionization chamber (a Ni-63 source) and the IMS drift tube region both of which are being operated slightly below ambient pressure. A Faraday cup detector registers the arrival time of mobile ion species traversing the drift tube at different velocities after being admitted into the drift tube region by gating pulses at 20 msec intervals. Typical drift times ("mobilities") of ion species representing volatile organic compounds are in the 5-10 msec range. The CAM can be operated in either positive or negative ion detection mode (switch selectable).
In spite of the successful development and application of the CAM for detecting chemical warfare agents, several remaining shortcomings inherent to IMS based detection devices (e.g., limited ability to distinguish between individual components in complex mixtures as well as low dynamic range and lack of linear response), seriously hamper its application as a quantitative detection tool. Moreover, only organic species that readily pass through the silicone rubber membrane can be detected. This prevents the use of the CAM for detection of nonvolatile materials such as most biological warfare agents.
1990
Man-Portable Gas Chromatography/Ion Mobility Spectrometry System: GC/CAM
Meuzelaar, H.L.C.; Kim, M.-G.; Arnold, N.S.; Urban, D.T. ; Kalousek, P.; Snyder, A.P. and Eiceman, G.A.
US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, Aberdeen Proving Grounds, Maryland, 1990. Funded by US Army Chemical Research Development and Engineering Center.
Currently there is widespread interest in extending the capabilities of ion mobility spectrometry (IMS) to various military as well as nonmilitary fields of application, including chemical demilitarization, treaty verification, drug enforcement, explosives detection and environmental monitoring. Characteristic features of IMS are high sensitivity, fast response, low weight, small size, low power requirements, and relatively low cost. An attractive approach is to add a front-end module capable of performing "transfer line gas chromatography" (TLGC). In its present form the TLGC/IMS system consists of a special automated air sampling valve, a short (1-2 m long) capillary GC column with isothermal oven, a Chemical Agent Monitor (CAM) and a small laptop PC. The IMS system is operated below ambient pressures.