Cole, PA
1996
Roving GC/MS: Mapping VOC Gradients and Trends in Space and Time
McClennen, W.H.; Vaughn, C.L.; Cole, P.A.; Sheya, S.A.N.; Wager, D.J.; Mott, T.J.; Dworzanski, J.P.; Meuzelaar, H.L.C. and Arnold, N.S.
Field Analytical Chemistry and Technology, 1(2):109-116, 1996. Funded by Hewlett Packard and ACERC.
Obtaining representative VOC (volatile organic compound) measurements in ambient environments that exhibit complex concentration gradients and/or trends is difficult when relying upon limited numbers of analyses obtained by simple pooling or averaging techniques. A more effective approach is to perform large numbers of analyses over a period of time to permit detailed mapping of profiling of local gradients and trends. Until recently, use of GC/MS (gas chromatography/mass spectrometry) techniques for rapid profiling or mapping operations was not feasible because of sample speed limitations. This article describes a roving GC/MS system based on the combination of a Hewlett-Packard model 5972 MSD (mass selective detector), a FemtoScan Enviroprobe repetitive vapor sampling inlet with short capillary GC column, and Alcatel Micro HV oil-less vacuum pump stack and a Pentium notebook PC running under Windows 95. The roving system is further equipped with differential GPS (global positioning system) and radio transceiver capabilities thereby permitting remote tracking of vehicle location and local VOC concentrations. Laboratory tests demonstrate lower detection limits of approx 4 ppb for BTX (benzene, toluene, and zylene), corresponding to minimum detectable quantities of a mixture of volatile ketones. Demonstrated outdoor performance, using a zero-emission electric vehicle, includes measurement of low ppb BTX levels along a 6 km urban route at 15 s (~ 150 m) intervals while moving at an estimated average speed of 35 km/hr. Indoor measurements of toluene concentrations in the low to mid ppm range at 6 s (~5 cm) intervals along a 6 m long path reveal a high degree of spatial and temporal variability in VOC concentrations. Mobility, specificity, sensitivity and speed of the roving GC/MS method make this a promising candidate method for rapid outdoor and indoor screening, monitoring and mapping of VOCs.
1993
The Next Horizon in Portable GC/MS for Field Air Monitoring Applications
Arnold, N.S.; Cole, P.A.; Hu, D.W.; Watteyne, B.; Urban, D.T. and Meuzelaar, H.L.C.
International Symposium on Field Screening Methods for Hazardous Wastes & Toxic Chemicals, Pittsburgh, PA, 2, 915-931, 1993. ( Also presented at 1993 International Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, February 1993 and presented at the 41st ASMS Conference on Mass Spectrom. All. Topics, San Francisco, CA, January 1993). Funded by Hewlett Packard and ACERC.
Over the past few years, GC/MS has struggled out of the laboratory and into field applications. In spite of its complexity and size limitations, the sheer analytical power of this hyphenated technique has helped it earn its place in the field. A number of workers have demonstrated "transportable" GC/MS systems that may be moved to a field site and operated via personnel bringing samples to the instrument or via long heated sample transfer lines. The next horizon is to bring truly field-portable equipment to the field analytical problem. This horizon can be reached via the so-called "man-portable" GC/MS systems that can be operated while moving with an individual and are thus capable of addressing problems in situ, rather than just on-site.
The requirements of such systems are stringent. We suggest that realistic goals include high speed GC separation, low ppb sensitivity, remote control capability for hazardous environments, 25 lbs total system weight and 60 W total system power consumption. To obtain these goals innovative low power pumping techniques, lightweight materials and small mass analyzers are an absolute necessity. The present paper discusses the engineering design specifications of an integrated man-portable GC/MS system. Trade-offs to obtain sufficient GC flow rates and operating pressures are considered together with weight and power consumption issues for various mass analyzer configurations. The available pumping technology and its ability to meet stringent power and weight requirements will also be considered.
An existing demonstration prototype system developed in our laboratory and utilizing an HP 5971A mass analyzer system, an automated vapor sampling "transfer line" GC interface and a novel bulk getter pumping system along with remote laptop computer operation will be used as a benchmark. This system has already broken through the 100 W barrier with an approx. 50 lbs weight while utilizing a trap-and-desorb approach to obtain ppb level sensitivities. It is already clear that this system can meet many of the analytical challenges posed, but some discussion will be presented of the remaining hurdles required to meet power and weight requirements.
Development of Field-Portable Mass Spectrometric Techniques for Particulate Organic Matter in PM-10
Dworzanski, J.P.; Meuzelaar, H.L.C.; Maswadeh, W.; Nie, X.; Cole, P.A. and Arnold, N.S.
Proceedings of the International Symposium on Field Screenings Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, February 1993. Funded by Southwest Center for Environmental Research and Policy, and the Environmental Protection Agency.
The chemical composition and structure of particulate organic matter can provide important information regarding origin, distribution and fate of respirable aerosols (PM-10) in the environment. Nevertheless, because of a lack of fast and reliable methods for chemical characterization of the organic components of the PM-10 fraction, most source apportionment studies focus exclusively on specification of inorganic components. In view of its inherent sensitivity, specificity and quantitative response, mass spectrometry (MS) offers obvious promise for characterization of the organic fraction. Consequently, special collection and sampling modules suitable for MS analysis of PM-10 have been developed in our laboratory and field-tested. The modules consist of a sampling unit and a low-dead volume Curie-point thermal desorption/pyrolysis inlet interfaced to a temperature programmable "transfer line" capillary column which is coupled to a ruggedized, miniaturized Finnigan MAT ion trap mass spectrometer (ITMS).
From among the PM-10 collection methods for MS investigated in our laboratory quartz fiber filters were selected because of inherent simplicity and high collection efficiency. After PM-10 collection, quartz filters underwent thermal desorption or pyrolysis followed by on-line GC/MS analysis. This approach was used to characterize the organic matter in particulate samples collected at 3-hour intervals at the US/Mexican border. Subsequent principal component analysis of selected mass profiles together with particle density and size distribution data as well as meteorological parameters allowed tentative identification of several PM-10 sources, including automotive emissions, food preparation and wood burning.
1992
Development of a Single Chamber EDB/ITMS System for Laser Pyrolysis MS Analysis of Individual Microparticles
Arnold, N.S.; Hars, G.; Cole, P.A. and Meuzelaar, H.L.C.
US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, Aberdeen Proving Ground, MD, November 1992. Funded by Army Research Office.
A novel technique for laser mass spectrometry of individual particles, e.g. microorganisms, is being developed. Present paper gives a detailed discussion on the theoretical and experimental aspects of trapping a submicron size charged particles pressures from atmospheric down to <10-7 torr. The ability to trap particles under UHV conditions has provided a new opportunity to study "ion trajectories" as they perform the solution of Mathieu equation.
Individual microparticles, mainly microorganisms, have been aerosolized and charged by a quasi-electrospray technique. A Paul type three-dimensional quadruple "trap" was constructed to combine the properties of an EDB (Electro-Dynamic Balance), capable of capturing the stabilizing micro-sized particles, with those of an ITMS (Ion Trap Mass Spectrometer), capable of trapping and mass selectivity detecting ionic species up to several thousand amu. A TEA CO2 laser (300 mJ per 200 µsec pulse) with focusing optics designed to produce a 50-80 µm beam waist through the center of the trap is used. A typical analysis cycle starts with the trap in EDB mode, thereby enabling capture and stabilization of one or more particles, followed by evacuation of the trap to high vacuum (<10-3 torr).
Cole, PA
1996
Roving GC/MS: Mapping VOC Gradients and Trends in Space and Time
McClennen, W.H.; Vaughn, C.L.; Cole, P.A.; Sheya, S.A.N.; Wager, D.J.; Mott, T.J.; Dworzanski, J.P.; Meuzelaar, H.L.C. and Arnold, N.S.
Field Analytical Chemistry and Technology, 1(2):109-116, 1996. Funded by Hewlett Packard and ACERC.
Obtaining representative VOC (volatile organic compound) measurements in ambient environments that exhibit complex concentration gradients and/or trends is difficult when relying upon limited numbers of analyses obtained by simple pooling or averaging techniques. A more effective approach is to perform large numbers of analyses over a period of time to permit detailed mapping of profiling of local gradients and trends. Until recently, use of GC/MS (gas chromatography/mass spectrometry) techniques for rapid profiling or mapping operations was not feasible because of sample speed limitations. This article describes a roving GC/MS system based on the combination of a Hewlett-Packard model 5972 MSD (mass selective detector), a FemtoScan Enviroprobe repetitive vapor sampling inlet with short capillary GC column, and Alcatel Micro HV oil-less vacuum pump stack and a Pentium notebook PC running under Windows 95. The roving system is further equipped with differential GPS (global positioning system) and radio transceiver capabilities thereby permitting remote tracking of vehicle location and local VOC concentrations. Laboratory tests demonstrate lower detection limits of approx 4 ppb for BTX (benzene, toluene, and zylene), corresponding to minimum detectable quantities of a mixture of volatile ketones. Demonstrated outdoor performance, using a zero-emission electric vehicle, includes measurement of low ppb BTX levels along a 6 km urban route at 15 s (~ 150 m) intervals while moving at an estimated average speed of 35 km/hr. Indoor measurements of toluene concentrations in the low to mid ppm range at 6 s (~5 cm) intervals along a 6 m long path reveal a high degree of spatial and temporal variability in VOC concentrations. Mobility, specificity, sensitivity and speed of the roving GC/MS method make this a promising candidate method for rapid outdoor and indoor screening, monitoring and mapping of VOCs.
1993
The Next Horizon in Portable GC/MS for Field Air Monitoring Applications
Arnold, N.S.; Cole, P.A.; Hu, D.W.; Watteyne, B.; Urban, D.T. and Meuzelaar, H.L.C.
International Symposium on Field Screening Methods for Hazardous Wastes & Toxic Chemicals, Pittsburgh, PA, 2, 915-931, 1993. ( Also presented at 1993 International Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, February 1993 and presented at the 41st ASMS Conference on Mass Spectrom. All. Topics, San Francisco, CA, January 1993). Funded by Hewlett Packard and ACERC.
Over the past few years, GC/MS has struggled out of the laboratory and into field applications. In spite of its complexity and size limitations, the sheer analytical power of this hyphenated technique has helped it earn its place in the field. A number of workers have demonstrated "transportable" GC/MS systems that may be moved to a field site and operated via personnel bringing samples to the instrument or via long heated sample transfer lines. The next horizon is to bring truly field-portable equipment to the field analytical problem. This horizon can be reached via the so-called "man-portable" GC/MS systems that can be operated while moving with an individual and are thus capable of addressing problems in situ, rather than just on-site.
The requirements of such systems are stringent. We suggest that realistic goals include high speed GC separation, low ppb sensitivity, remote control capability for hazardous environments, 25 lbs total system weight and 60 W total system power consumption. To obtain these goals innovative low power pumping techniques, lightweight materials and small mass analyzers are an absolute necessity. The present paper discusses the engineering design specifications of an integrated man-portable GC/MS system. Trade-offs to obtain sufficient GC flow rates and operating pressures are considered together with weight and power consumption issues for various mass analyzer configurations. The available pumping technology and its ability to meet stringent power and weight requirements will also be considered.
An existing demonstration prototype system developed in our laboratory and utilizing an HP 5971A mass analyzer system, an automated vapor sampling "transfer line" GC interface and a novel bulk getter pumping system along with remote laptop computer operation will be used as a benchmark. This system has already broken through the 100 W barrier with an approx. 50 lbs weight while utilizing a trap-and-desorb approach to obtain ppb level sensitivities. It is already clear that this system can meet many of the analytical challenges posed, but some discussion will be presented of the remaining hurdles required to meet power and weight requirements.
Development of Field-Portable Mass Spectrometric Techniques for Particulate Organic Matter in PM-10
Dworzanski, J.P.; Meuzelaar, H.L.C.; Maswadeh, W.; Nie, X.; Cole, P.A. and Arnold, N.S.
Proceedings of the International Symposium on Field Screenings Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, February 1993. Funded by Southwest Center for Environmental Research and Policy, and the Environmental Protection Agency.
The chemical composition and structure of particulate organic matter can provide important information regarding origin, distribution and fate of respirable aerosols (PM-10) in the environment. Nevertheless, because of a lack of fast and reliable methods for chemical characterization of the organic components of the PM-10 fraction, most source apportionment studies focus exclusively on specification of inorganic components. In view of its inherent sensitivity, specificity and quantitative response, mass spectrometry (MS) offers obvious promise for characterization of the organic fraction. Consequently, special collection and sampling modules suitable for MS analysis of PM-10 have been developed in our laboratory and field-tested. The modules consist of a sampling unit and a low-dead volume Curie-point thermal desorption/pyrolysis inlet interfaced to a temperature programmable "transfer line" capillary column which is coupled to a ruggedized, miniaturized Finnigan MAT ion trap mass spectrometer (ITMS).
From among the PM-10 collection methods for MS investigated in our laboratory quartz fiber filters were selected because of inherent simplicity and high collection efficiency. After PM-10 collection, quartz filters underwent thermal desorption or pyrolysis followed by on-line GC/MS analysis. This approach was used to characterize the organic matter in particulate samples collected at 3-hour intervals at the US/Mexican border. Subsequent principal component analysis of selected mass profiles together with particle density and size distribution data as well as meteorological parameters allowed tentative identification of several PM-10 sources, including automotive emissions, food preparation and wood burning.
1992
Development of a Single Chamber EDB/ITMS System for Laser Pyrolysis MS Analysis of Individual Microparticles
Arnold, N.S.; Hars, G.; Cole, P.A. and Meuzelaar, H.L.C.
US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, Aberdeen Proving Ground, MD, November 1992. Funded by Army Research Office.
A novel technique for laser mass spectrometry of individual particles, e.g. microorganisms, is being developed. Present paper gives a detailed discussion on the theoretical and experimental aspects of trapping a submicron size charged particles pressures from atmospheric down to <10-7 torr. The ability to trap particles under UHV conditions has provided a new opportunity to study "ion trajectories" as they perform the solution of Mathieu equation.
Individual microparticles, mainly microorganisms, have been aerosolized and charged by a quasi-electrospray technique. A Paul type three-dimensional quadruple "trap" was constructed to combine the properties of an EDB (Electro-Dynamic Balance), capable of capturing the stabilizing micro-sized particles, with those of an ITMS (Ion Trap Mass Spectrometer), capable of trapping and mass selectivity detecting ionic species up to several thousand amu. A TEA CO2 laser (300 mJ per 200 µsec pulse) with focusing optics designed to produce a 50-80 µm beam waist through the center of the trap is used. A typical analysis cycle starts with the trap in EDB mode, thereby enabling capture and stabilization of one or more particles, followed by evacuation of the trap to high vacuum (<10-3 torr).