Arnold, NS

1996

Field Evaluation of a Prototype Man-Portable GC/MS

Arnold, N.S.; Du, W.H.; Sheya, S.A.N.; Mihamou, H.; Dworzanski, J.P.; Hall, D.L.; McClennen, W.H. and Meuzelaar, H.L.C.
Proceedings of the Ninth International Symposium On Field Screening Methods for Hazardous Wastes and Toxic Chemicals, 2:903-910, 1996. Funded by ACERC, US Army Electrical Research Development and Engineering Center.

In recent years, a man-portable gas chromatography/mass spectrometry (GC/MS) system has been developed based on a Hewlett-Packard 5971 MSD and a unique automated vapor sampling (AVS) transfer-line (TL) GC system for direct sampling of ambient chemical vapors [1,2]. The vacuum system and power supplies were replaced to facilitate operation on 24 V DC batteries for up to 4 hours after startup on a transportable docking station. The gas chromatography was performed on a short (2 m) capillary column under isothermal conditions in a small oven to minimize power usage. Repetitive samples were taken at 10 to 60 s intervals using an automated vapor-sampling inlet.

In initial testing, the prototype system has been used for monitoring of gasoline vapors. Ambient levels of 6.0 ppm benzene, 4.1 ppm toluene, 0.22 ppm ethylbenzene, 1.1 ppm m-and p-xylene and 0.25 ppm 0-xylene were measured near a busy gas station. The gradient mapping or source tracking capabilities of the backpack-mounted system have also been demonstrated in tests with a simulated gasoline leak.

This paper will describe recent work to further evaluate the capabilities and limitations of the prototype system. Results will be described in terms of the practical utility of portable GC.NS for identification and quantification of unknown vapors.

 

Design Considerations for a Novel Miniaturized Tandem GC Method for Field Screening Applications

Sheya, S.A.N.; Dworzanski, J.P.; McClennen, W.H.; Meuzelaar, H.L.C. and Arnold, N.S.
Proceedings of the Ninth International Symposium On Field Screening Methods for Hazardous Wastes and Toxic Chemicals, 1:213-220, 1996. Funded by ACERC.

Development of a potentially field-portable tandem GC (GC/GC) method involving a novel, dynamic coupling between two short capillary GC columns-each of which is independently optimizable with regard to temperature and flow-is described. The relatively slow (5-25 sec wide), GC peaks eluting from the first (1.2 m x 530 µm) column are sampled repetitively at 1-5 sec. Intervals into the second (0.8 m x 100 µm) column. Dynamic coupling by means of fluidic AVS (Automated Vapor Sampling) technology, rater than through trap-and-desorb interfaces, reduces power requirements. Further power reduction is achieved by isothermal operation of both columns. If properly designed and optimized the sensitivity of dynamic GC/GC techniques should approach that of one-dimensional GC, depending on the type of detector used. Since a universally responsive, subambient pressure, low weight and low power detector for field-portable GC/GC has not yet been found, a Hewlett Packard MSC (Mass Selective Detector) was used throughout the present study. At a maximum scan rate of 35 spectra (over 5 amu mass range), the minimum practical GC peak width eluting from the second column is limited to approximately 100 msec. The feasibility of producing comprehensive, two-dimensional chromatograms of multicomponent mixtures, volatile compounds, including C3-C6 ketones, is demonstrated.

 

Hyphenated Techniques: The Next Generation of Field-Portable Analytical Instruments?

Meuzelaar, H.L.C.; McClennen, W.H.; Dworzanski, J.P.; Sheya, S.A.N.; Snyder, A.P.; Harden, C.S. and Arnold, N.S.
Proceedings of the Ninth International Symposium On Field Screening Methods for Hazardous Wastes and Toxic Chemicals, 1:38-46, 1996. Funded by ACERC, Consortium for Fossil Fuel Liquefaction Science, US Army Electrical Research Development and Engineering Center, Hewlett Packard, Finnigan MAT Corporation, and Femto Scan Corporation.

The first field-portable (i.e., transportable) hyphenated analytical instruments, including commercially available MS/MS and GC/MS systems as well as a specially built GC/MS system, were introduced during the past seven years. Since then further miniaturization and ruggedization of hyphenated systems by several laboratories has resulted in fully man-portable (backpack and briefcase style) GC/MS systems and a hand portable GC/IMS prototype. The main pitfall to be avoided in developing a hyphenated, field portable system is incompatibility between the coupled techniques. Carefully designed hyphenated techniques incorporating compatible methods such as GC and MS can provide dramatic increases in resolution and chemical specificity which may be traded for speed or sensitivity gains, if needed. Novel developments currently underway in the laboratory include roving GC/MS platforms, personalized GC/IMS devices, high speed GC/GC methods and, last but not least, Virtual Reality techniques.

 

 

 

1994

High Speed, Two-Wavelength Radiation Thermometry of Single Micro Particles During CO2 Laser Heating

Maswadeh, W.; Tripathi, A.; Arnold, N.S.; DuBow, J. and Meuzelaar, H.L.C.
Journal of Analytical and Appl. Pyrolysis, 28:55-70, 1994. Funded by ACERC.

A high speed, two-wavelength radiation thermometer that is capable of monitoring the surface temperature of 50-150 µm diameter particles in the 600-2000 K range at heating rates of up to 106 K/s, characteristic of pulverized coal combustion, was designed and constructed. To meet the above characteristics, special attention was paid to detector wavelength range and speed, detection electronics and optical system alignment. The thermometer was calibrated using an in-house constructed, black cavity radiation source. Spherocarb model particles, which have a more uniform size; physical properties and emissivity than coal particles, were used to demonstrate the level of short-term reproducibility attainable. Consistent, reproducible temperature-time profiles obtained for particles from different coals indicate that non-grey effects do not dominate these measurements.

Field Portable Hyphenated Instrumentation: The Birth of the Tri-Corder?

McClennen, W.H.; Arnold, N.S. and Meuzelaar, H.L.C.
Trends in Analytical Chemistry, 13(7):286-293, 1994. Funded by Hewlett Packard and US Army.

The "tricorder," the tiny universal sensor of "Star Trek" science fiction fame, might be the ultimate objective for developers of field-portable instrumentation. The advantages of multi-dimensional ("hyphenated") analytical methods over one-dimensional techniques in working toward such a goal are based upon the degree of correlation of the information from the combined analytical techniques. With appropriately selected techniques that yield complementary (orthogonal) information, the actual resolution of the hyphenated technique is the product of the resolution of the two techniques. In effect, the whole of a suitable hyphenated system is greater than the sum of its parts.

The most widely used hyphenated method, combined gas chromatography-mass spectrometry (GC-MS), is regarded as the definitive method for certain applications and has become the officially required procedure for numerous environmental, clinical and occupational health or safety related tests. In fact, in most laboratories GC-MS has all but replaced the use of one-dimensional GC and MS techniques. Consequently, results based on characterization of complex environmental samples by GC or MS alone would tend to be disregarded or seen as tentative, at best. Yet, the use of one-dimensional GC and MS techniques represents the present state-of-the-art in field screening methods. The demonstration of hyphenated analytical techniques in field application via the use of mobile laboratories has been established in the last 10 years by a number of researchers using MS-MS or GC-MS techniques. However, it is appropriate to consider whether a field laboratory constitutes a truly field-portable analytical technique.

In-situ applications are an area of field portability where the use of hyphenated methods is a recent phenomenon that can be expected to continue due to the considerable power of these approaches. However, the large-scale acceptance of these techniques in the field will depend upon overcoming the constraints of inherent higher cost, complexity, size, weight and power requirements.

On the other hand, hyphenated techniques should certainly not be seen as a panacea for every analytical problem, whether in the laboratory or in the field. Although the information provided by a multi-dimensional method is often much greater than the summed information obtainable from the component techniques, a poorly designed hyphenated experiment may end up amplifying the characteristic weaknesses and shortcomings of the component methods and provide little or no useful information. In effect, the use of sophisticated hyphenated methods is certainly not a satisfactory way to compensate for a poor analytical technique!

 

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

On-Line Monitoring of Formaldehyde in Combustion Gases Using Gas Chromatography/Mass Spectrometry

McClennen, W.H.; Sheya, S.A.N.; Arnold, N.S.; Meuzelaar, H.L.C.; Larsen, F.S. and Silcox, G.D.
Incineration of Hazardous Wastes-2; Toxic Combustion By-Products:545-555, (in press). Funded by Consortium for Fossil Fuel Liquefaction and ACERC.

This paper describes a method for on-line gas chromatography/mass spectrometry (GC/MS) of formaldehyde in combustion gases. The method uses a recently developed vapor-sampling inlet to monitor the concentration of formaldehyde and other products of incomplete combustion (PICs) from the burning of plain and phenol-formaldehyde resin treated wood chips. Other PICs that were simultaneously monitored included ketene, propylene, propyne and acetaldehyde. The direct analysis method has detection limits of less than 1 ppm for the reactive formaldehyde and excellent selectivity for determinations in the complex mixtures of combustion products. The rapid sampling technique allows monitoring of transient events of only a few minutes or less duration. Examples of the technique include the detection of sample line problems and the comparison of PIC concentrations from different points in the combustion exhaust stream.

 

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.

 

Thermogravimetry/Gas Chromatography/Mass Spectrometry and Thermogravimetry/Gas Chromatography/Fourier Transform Infrared Spectroscopy: Novel Hyphenated Methods in Thermal Analysis

McClennen, W.H.; Buchanan, R.M.; Arnold, N.S.; Dworzanski J.P. and Meuzelaar, H.L.C.
Analytical Chemistry, 65:2819-1823, 1993. Funded by Hewlett Packard and ACERC.

Two doubly hyphenated, thermogravimetry-based analytical techniques, viz. TG/GC/MS and TG/GC/IR, are described. A valveless, quartz, heated sample path between TG furnace and GC column minimizes losses of products. Furthermore, combination of a pulsed automated vapor-sampling inlet and a transfer line type GC column permits high-speed GC identification of individual TG products while maintaining sufficiently high temporal resolution with the ~1-min sampling interval to provide kinetic information about the underlying reaction mechanisms. Example analyses on poly (alpha-methylstyrene), a styrene-isoprene block copolymer, and wood demonstrate the techniques' capability for monitoring specific minor products and isomers.

 

Interfacting High-Speen Transfer Line Gas Chromatography to Ion Trap Mass Spectrometry; Advantages and Limitations

Arnold, N.S.; McClennen, W.H. and Meuzelaar, H.L.C.
Proceedings of the 41st ASMS Conference on Mass Spectrometry and Allied Topics, San Francisco, CA, June 1993. Funded by US Army/Electrical Research Development and Engineering Center and ACERC.

The Ion Trap Detector (ITD, Finnigan-MAT) was originally introduced as a gas chromatography (GC) detector for laboratory bench top GC/MS analyses. Its introduction coincided with a rising interest in a vacuum outlet short column GC/MS for high-speed chromatographic separations. Advantages for such short column applications, including high operating pressures (10-3 torr) sensitivities (.1 fg/s) and scan speeds (5500 amu/s) relative to conventional quadruple instruments, have fueled interest in ion trap based instruments for high speed, high resolution GC/MS analyses. Subsequent interest has been fueled by new developments in mobile instruments, high sensitivity MSn capability, AGC-based dynamic range enhancement, and axial modulation based resolution enhancement.

 

The Next Step in Miniaturization Toward Personal GC/IMS

Arnold, N.S.; Dworzanski, J.P.; Meuzelaar, H.L.C. and McClennen, W.H.
Proceedings of US Army Electrical Research Development and Engineering Center Science Conference on Chemical Defense Research, Aberdeen, MD, November 1993. Funded by US Air Force.

Field portable gas chromotography/ion mobility spectrometry (GC/IMS) techniques have been identified as an important area of development for CW detection. Recent developments of smaller, personal IMS detection devices offer new prospects for miniaturization of a combined personal GC/IMS unit that would have considerable size and cost advantages over its larger predecessors. The following is a preliminary examination of feasibility of personal GC/IMS based on an automated vapor sampling-transfer line gas chromatography (AVS-TLGC) approach previously used in developing hand portable GC/IMS instrumentation. Special focus is placed upon developing low power GC interfacing strategies for an existing prototype miniature IMS device. Parameters such as GC column position and flow as well as IMS purge flows are examined for their effects on sensitivity and resolution.

 

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.

 

Chemical Characterization of Single Aerosol Particles Via Combined Electrodynamic Balance/Ion Trap Mass Spectrometry Techniques

Hars, G.; Arnold, N.S., Meuzelaar, H.L.C.
Proceedings of American Chemical Society Meeting, Chicago, IL, August 1993. Funded by US Army Research Office.

A multifunction Paul trap is described capable of trapping, stabilizing and analyzing electrostatically charged microparticles as well as a broad range of ions and macro-ions. Typically, particles in the 0.1-10 µm range are introduced by aerosolization from an aqueous suspension, although quasi-electrospray and dry powder type introduction methods can also be used. A new particle trajectory pattern, observed in the equatorial plane, was found to offer a nondestructive, optical method for determining the m/z value of microparticles and macro-ions, with a present accuracy of 1:103 and a potential maximum resolution of 1:106. Recent addition of a more powerful laser (Nd YAG, operating at 1.06 µm) has enabled us to generate laser fragmentation/ionization mass spectra of 1 µm dia polystyrene particles and of Bacillus subtilis spores. Current shot-to-shot reproducibility is still unsatisfactory and some as yet unresolved, mass calibration problems have been encountered. Nonetheless, the high intensity and apparent complex organic nature of the ion signals obtained might herald the emergence of a novel MS technique for chemical and physical characterization of single microorganisms and other components of respirable aerosols.

 

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.

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).

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.

 

On-Line GC/MS Analysis of High Pressure Reactions

Dworzanski, J.P.; Huai, H.; Arnold, N.S. and Meuzelaar, H.L.C.
Proceedings of the Fortieth ASMS Conference on Mass Spectrometry and Allied Topics, 762-767, Washington, DC, 1992. Funded by Consortium for Fossil Fuel Liquefaction, Rocketdyne and ACERC.

The growing demand for real-time monitoring of industrial processes performed in reactors under conditions of high pressure and temperature indicates that MS technology, especially in combination with GC preseparation potential could fulfill many current requirements. To achieve these goals we have expanded the application of our valveless vapor sampling inlet for on-line analysis of atmospheric gases and vapors by "transfer line" GC/MS to monitor chemical processes at high pressures (1000-2000 psi) through the construction of a special capillary restrictor to reduce the pressure to near ambient conditions. The restrictor effluent is coupled to the automatic vapor-sampling inlet via a dilution chamber. This allows repetitive GC/MS analyses to be obtained at 1-15 minute intervals.

Kinetic parameters and yields of primary and secondary decomposition products of jet fuels as well as model compounds in coal liquefaction processes have been obtained in a fraction of time needed for conventional off-line measurements and indicate that the proposed approach may be easily applied to a broad range of existing reactor types and potential processing environments.

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

On-Line Monitoring of Formaldehyde in Comubustion Gases Using Gas Chromatography/Mass Spectrometry

McClennen, W.H.; Sheya, S.A.N.; Arnold, N.S.; Meuzelaar, H.L.C.; Deng, X.-X.; Larsen, F.S. and Silcox, G.D.
Combustion Science and Technology, 1991 (in press). Funded by ACERC.

This paper describes a method for on-line gas chromatography/mass spectrometry (GC/MS) of formaldehyde in combustion gases. The method uses a recently developed vapor-sampling inlet to monitor the concentration of formaldehyde and other products of incomplete combustion (PICs) from the burning of plain and phenol-formaldehyde resin treated wood chips. Other PICs that were simultaneously monitored included ketene, propylene, propyne and acetaldehyde. The direct analysis method has detection limits of less than 1 ppm for the reactive formaldehyde and excellent selectivity for determinations in the complex mixtures of combustion products. The rapid sampling technique allows monitoring of transient events of only a few minutes or less duration. Examples of the technique include the detection of sample line problems and the comparison of PIC concentrations from different points in the combustion exhaust stream.

 

Vapor Sampling Device for Direct Short Column Gas Chromatography/Mass Spectrometry Analyses of Atmospheric Vapors

Arnold, N.S.; McClennen, W.H. and Meuzelaar, H.L.C.
Analytical Chemistry, 63:299-304, 1991. Funded by ACERC.

A number of methods are currently used for atmospheric vapor and gas sampling with mass spectrometric detection and identification. Direct mass spectrometry (MS) sample introduction methods include fixed molecular tasks, atmospheric pressure ionization, trap and desorb, and membrane separation, while gas chromatography/mass spectrometry (GC/MS) methods employ trap and desorb, direct bubbler solvent injection, sample loops, and pressurized gas plug introduction. Approaches vary depending upon whether MS, tandem MS, or GC/MS analyses are desired. Direct MS and tandem MS analyses typically give quick response times and high repetition rates but are often sensitive to interferents, including atmospheric constituents, while GC/MS analyses offer greater specificity but with typically lower results.

 

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.

 

Feasibility of Drone-Portable Ion Mobility Spectrometry

Arnold, N.S.; Meuzelaar, H.L.C.; Dworzanski, J.P.; Cole, P.C. and Snyder, A.P.
US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, Arberdeen Proving Grounds, MD, November 1991. Funded by US Department of Defense/Army Research Office.

The feasibility of telemetry based, drone-portable IMS (ion mobility spectrometry) and GC/IMS (gas chromatography/-ion mobility spectrometry) for real-time detection and monitoring of atmospheric concentrations of target vapors in otherwise inaccessible locations has been demonstrated using primarily "off the shelf" technology. The test configuration involved a Graseby Ionics CAM (Chemical Agent Monitor) with an ASP type PC interface, a Compaq 386 mother-board with 1 Mbyte RAM, two H-Cubed Corp. and Tekk Corp. digital radio transmitter and receiver sets, CoSession (Triton Technology) communications software and a remote, 386 level computer workstation. On-board system components weigh <15 lbs and use <30W of battery power. Preliminary test results indicate the feasibility of transmitting ion mobility data at up to 9600 baud, corresponding to approximately 20 spectra per minute. Typical range of the tested transceiver system is 1-2 miles. Potential applications include military or law enforcement operations as well as environmental and industrial screening or monitoring.

 

Remotely Operated, Field Portable Gas Chromatography/Mass Spectrometry System for Monitoring Hazardous Atmosphere Vapors

Arnold, N.S.; Urban, D.T.; Watteyne, R.L.; Cole, P.C. and Meuzelaar, H.L.C.
Proceedings of the 39th Annual ASMS Conference on Mass Spectrometry and Allied Topics, 671-672, Nashville, TN, May 1991. Funded by US Department of Defense and ACERC.

In order to protect and inform personnel involved in monitoring, containment and remediation of hazardous volatiles materials, it is important that exposure to such materials be limited and that personnel working in such environments have sensitive and easily handled tools that do not limit mobility or vision. In order to meet these requirements a man-portable GC/MS system described previously has been modified to meet four objectives: (1) to allow remote instrument operation via a serial data transfer protocol compatible with broadband radio telemetry; (2) to reduce system size for placement in a single backpack or in a small, unmanned reconnaissance plane (drone); (3) to reduce system weight under 50 lbs for worker mobility in man-portable mode and to meet payload requirements for drone aircraft; (4) to increase pumping speed for greater sample throughput and lower detection limits.

The Application of a Mobile Ion Trap Mass Spectrometer System to Environmental Screening and Monitoring

McClennen, W.H.; Arnold, N.S.; Meuzelaar, H.L.C.; Ludwig, E. and Lighty, J.S.
2nd International Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, February 1991. Funded by ACERC, Environmental Protection Agency, Finnigan MAT Corp., US Army Chemical Research Development and Engineering Center and Utah Power and Light.

This paper presents examples of the use of a mobile Ion Trap Mass Spectrometer (ITMS, Finnigan MAT) for on-site environmental screening and monitoring of vapors by gas chromatography/mass spectrometry (GC/MS). The instrument is built around a miniaturized ITMS system, with a novel direct vapor-sampling inlet and coupled to a high-speed transfer line GC column (short capillary column with fixed pressure drop). The column is temperature controlled inside the standard ion trap transfer line housing. This provides for high-speed analyses at 10-60 s intervals using an automated sampling system constructed with only inert materials in the sample path.

Specific laboratory and field applications exemplify key characteristics of the system including sensitivity, specificity for a broad range of compounds, ruggedness for field-testing in harsh environments, and general speed for field-testing in harsh environments, and general speed and versatility of the analytical technique. The system has been calibrated for alkylbenzenes at concentrations as low as 4 ppb in air and used to monitor these compounds in an office space. Both the MINITMASS and a simpler Ion Trap Detector (ITD) based system have been used to monitor organic vapors from acetone through 5 ring polycyclic aromatic hydrocarbons produced in laboratory scale reactors for studying the thermal desorption and incinerations of hazardous wastes. The ruggedness of the MINITMASS system has been demonstrated by vapor sampling in the Utah summer desert and at a 600 MW coal fired power plant. Finally, the analysis speed and versatility are described for vapor monitoring of volatile organic compounds at an EPA national priority list waste site.

 

Development and Testing of a Man-Portable Gas Chromatography/Mass Spectrometry System for Air Monitoring

Meuzelaar, H.L.C.; Urban, D.T. and Arnold, N.S.
2nd International Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals, Las Vegas, NV, February 1991. Funded by Environmental Protection Agency, US Department of Defense, Finnigan MAT Corp., Utah Power and Light, Hewlett Packard Corp. and ACERC.

In situations involving special military or law enforcement operations, as well as industrial accidents or natural disaster, mobile laboratories may be of little use because of limited site access restrictions due to contamination or terrain constraints. Under such conditions man-portable analytical instruments may offer the only acceptable means of carrying out on-site analyses. The current prototype weighs approx 70-75 lbs and uses 150-200 W of battery power. The mass spectrometer and computer are carried in front of the operator by means of a shoulder harness whereas battery pack, carrier gas supply and roughing vacuum system are carried as a backpack. Air samples can be analyzed using a special automated air-sampling inlet. The man-portable GC/MS system is supported by a vehicle transportation "docking station."

 

1990

Laser Pyrolysis-Transfer Line Chromatography/Mass Spectrometry of Single, Levitated Coal Particles

Maswadeh, W.; Arnold, N.S. and Meuzelaar, H.L.C.
Proc. of the 38th ASMS Conference on Mass Spectrometry and Allied Topics, Tucson, AZ, 599-600, 1990. (Also presented at Pyrolysis 90, Amsterdam, The Netherlands, 1990; ACS Joint 45th Northwest/Rocky Mountain Regional Meeting, Salt Lake City, UT, 1990; ACS Division of Fuel Chemistry and Preprints for Papers Presented at the 200th ACS National Meeting, 35 (3), 755-762, Washington, D.C., 1990). Funded by ACERC.

A laser pyrolysis transfer line gas chromatography/mass spectrometry (laser Py-TLGC/MS) system based on the combination of an electronically pulsed CW C02 laser with an electrodynamic balance (EDB), a heated capillary ("transfer line") GC column and an ion trap mass spectrometer (ITMS) was constructed.

The main purpose of the system is to study the devolatilization behavior of single, levitated coal particles at very high heating rates, e.g., 105 - 106 K/sec, while comparing the composition of the devolatilization products to those observed at much lower heating rates, e.g., 10-2 - 10-2 K/sec.

 

Development of Novel, Mass Spectrometric Combustion Monitoring Techniques

McClennen, W.H.; Arnold, N.S.; Sheya, S.A.N.; Lighty, J.S. and Meuzelaar, H.L.C.
Preprints for Papers Presented at the 200th ACS National Meeting, 35 (3), 713-720, Washington, D.C., 1990. Funded by ACERC.

An on-line gas and vapor analysis method has been developed to monitor combustion products by short column ("transfer line") Gas Chromatography/Mass Spectrometry. An automated vapor-sampling inlet with only inert materials (quartz and fused silica) in the sample path is utilized to introduce flue gases into a 1 m long "transfer line" capillary GC column for rapid, repetitive chromatographic separation of products. The column effluent is introduced directly into the source of an ion trap type mass spectrometer. Combustion products from a gas fired rotary kiln were monitored by this method using a standard Ion Trap Detector (ITD). Detection limits of 20 to 50 ppb were obtained for various substituted benzenes. Monitoring of polycyclic aromatic hydrocarbons (PAHs) from the thermal desorption of contaminated soils in a fixed bed reactor utilized a modified Ion Trap Mass Spectrometer (ITMS). Varying isothermal column temperature allowed analysis of PAHs from naphthalene through 6 ring PAHs. The ITMS system provides higher sensitivity (~4 ppb for benzene) in addition to tandem MS and chemical ionization capabilities for unambiguous identification of combustion products incompletely resolved by the transfer line GC approach.

Fast, Repetitive GC/MS Analysis of Thermally Desorbed Polycyclic Aromatic Hydrocarbons (PAHs) from Contaminated Soils

McClennen, W.H.; Arnold, N.S.; Roberts, K.A.; Meuzelaar, H.L.C.; Lighty, J.S. and Lindgren, E.R.
Combustion Science and Technology, 1990 (In press). Sponsored by Remediation Technology, Gas Research Institute, ACERC, Finnigan Corp. and IT Corporation.

A system for on-line analysis of organic vapors by short column gas chromatography/mass spectrometry (GC/MS) has been used to monitor products from a thermal soil desorption reactor. The system consists of a unique air-sampling inlet with a 1-meter long capillary column coupled directly to a modified Ion Trap Mass Spectrometer (Finnigan MAT) with demonstrated detection limits for alkylbenzenes in the low ppb range. In this work the mobile instrument is used for repetitive GC/MS and GC/MS (tandem MS) analysis at 30 to 60 sec intervals of PAH products from coal tar contaminated soils in a bed characterization reactor.

Results for napthalene through dibenzanthracenes are compared to conventional, more detailed GC/MS analyses of extracts from the soil before and after thermal treatment.

A combustion map of burnout values was made using the laboratory nozzle at an A/S of 0.7, swirl number of 1.5 and SR of 1.1.

Vapor Sampling Device for Direct, Short Column Gas Chromatography/Mass Spectrometry Analyses of Atmospheric Vapors

Arnold, N.S.; McClennen, W.H. and Meuzelaar, H.L.C.
Analytical Chemistry, 1990 (In press). Funded by ACERC.

A number of methods are currently used for atmospheric vapor and gas sampling with mass spectrometric detection and identification. Direct mass spectrometry (MS) sample introduction methods include fixed molecular tasks (1), atmospheric pressure ionization (2,3), trap and desorb (4), and membrane separation (5), while gas chromatography/mass spectrometry (GC/MS) methods employ trap and desorb (6), direct bubbler solvent injection (7,8), sample loops (9), and pressurized gas plug introduction (10). Approaches vary depending upon whether MS, tandem MS, or GC/MS analyses are desired. Direct MS and tandem MS analyses typically give quick response times and high repetition rates but are often sensitive to interference, including atmospheric constituents, while GC/MS analyses offer greater specificity but with typically lower results.

On-Line GC/MS Sampling of Exhaust Gas from a Rotary Kiln Simulator

Lighty, J.S.; Wagner, D.; Deng, X.-X.; Pershing, D.W.; McClennen, W.H.; Sheya, S.A.N.; Arnold, N.S. and Meuzelaar, H.L.C.
AWMA Specialty Conference on Waste Combustion in Boilers and Industrial Furnaces, Kansas City, MO, 1990. Funded by ACERC.

An on-line, short-column gas chromatography/mass spectrometry (GC/MS) system has been used to monitor the evolution of trace amounts of hydrocarbons evolving from a material which has been combusted in a rotary-kiln simulator. The system uses the isothermally heated, 1-m long transfer line of an Ion Trap Detector (ITD) as the gas chromatograph. The fused silica capillary normally used in the transfer line is replaced by a 1 m, 0 .15-mm inside diameter, 1.2 micron thick methyl silicone stationary phase (DB-1) GC column. Given the short column length and using a direct vapor sampling inlet, the exhaust gas can be sampled quickly, approximately every 10 s in these experiments. Since the column is isothermal, only a limited range of compounds can be analyzed for any given experiment.

 

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.

 

Development and Testing of a Man-Portable Gas Chromatography/Mass Spectrometry System for Air Monitoring

Meuzelaar, H.L.C.; Urban, D.T. and Arnold, N.S.
Proceedings of the 1990 US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense, Aberdeen Proving Grounds, Maryland, 1990. Funded by Hewlett Packard Corp. and ACERC.

In situations involving special military or law enforcement operations, as well as industrial accidents or natural disaster, mobile laboratories may be of little use because of limited site access restrictions due to contamination or terrain constraints. Under such conditions man-portable analytical instruments may offer the only acceptable means of carrying out on-site analyses. The current prototype weighs approx 70-75 lbs and uses 150-200 W of battery power. The mass spectrometer and computer are carried in front of the operator by means of a shoulder harness whereas battery pack, carrier gas supply and roughing vacuum system are carried as a backpack. Air samples can be analyzed using a special automated air-sampling inlet. The man-portable GC/MS system is supported by a vehicle transportation "docking station."

 

Progress in CB Detection by Transfer Line GC/MS Using a Miniaturized Ion Trap Mass Spectrometer

Meuzelaar, H.L.C.; Arnold, N.S.; McClennen, W.H. and Snyder, A.P.
Proceedings of the 1989 US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense, 373-379, 1990. Funded by ACERC, US Army Chemical Research Development and Engineering Center, and Finnigan Corp.

A novel direct vapor-sampling inlet has been tested in combination with Transfer Line Gas Chromatography/Mass Spectrometry (TLGC/MS) using the MINITMASS (Miniaturized Ion Trap Mass Spectrometer) system developed at the University of Utah. Typically, 0.2-0.5 s wide air pulses are injected into the 1 m long transfer line at 15-60 s intervals. Even with relatively complex mixtures of vapors, e.g., produced by desorption and combustion of model compounds in a laboratory-scale fixed bed reactor, sufficient GC separation may be obtained to allow positive identification of minor reaction products by direct library search and matching procedures. Moreover, the high sensitivity of the MINITMASS allows tandem MS analysis of subpicogram quantities of selected model compounds.

 

1989

Laser Pyrolysis Mass Spectrometry of Single Levitated Coal Particles

Maswadeh, W.; Roberts, K.A.; McClennen, W.H.; Meuzelaar, H.L.C. and Arnold, N.S.
37th ASMS Conference on Mass Spectrometry and Allied Topics, Miami Beach, Florida, 304-305, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates), US Department of Energy, and the State of Utah.

A laser pyrolysis mass spectrometry experiment was designed to study the devolatilization behavior of individual coal particles at high heating rates (104-106 K/s), characteristic of pulverized coal combustion reactors. The experimental set-up consists of an electrostatic particle levitation cell, also known as an "electrodynamic balance", a 50 W cw CO2 laser and a Finnigan-MAT ITMS system. The particle levitation cell was constructed by modifying a regular ion trap electrode assembly in such a way as to provide line-of-sight access to the center of the cell for the CO2 laser beam as well as for visual observation by means of a stereo microscope. Typical cell operating parameters for levitating a 120 mm dia. Spherocarb particle are: ring electrode 3000 V (60 Hz ac), upper end-cap +100 V dc, lower end-cap -100 V dc. The CO2 laser (Apollo 3050 OEM) is capable of electronic pulsed beam operation. The 8 mm dia. beam is split equally into 2 opposing beams focused at the center of the levitation cell (beam waist ca. 400 um, power density ca. 4-10 MW/m2), as a co-linear parfocal HeNe laser beam permits positioning the levitated particle in the optical and electrical center of the cell. Two IR detectors measure the integrated pulse and time-resolved pulse energy.

A heated transfer line column (2m x .18 mm DB5) equipped with a special air sampling inlet enables intermittent sampling of volatiles from the center of the levitation cell into the ITMS vacuum system. Feasibility studies were performed on 120-150 mm Spherocarb particles impregnated with an alkylnaphthalenes mixture and heated with a single 10 ms CO2 laser pulse. Ample signal intensities were obtained with the first laser pulse to permit the recording of "transfer line" GC/MS profiles. By contrast, the second laser pulse produced <10% of the volatiles observed from the first pulse, thereby demonstrating nearly complete devolatilization of the impregnated particle by a single laser pulse.

Finally, a series of experiments was performed with actual coal particles in the 100-130 mm size range, prepared by careful sieving of two coals from the Argonne National Laboratory Premium Coal Sample bank, namely a Pittsburgh #8 seam (Illinois) coal and a Blind Canyon seam (Utah) coal of comparable rank. From previous studies of Pitt. #8 coal using time-resolved Curie-point pyrolysis, pyrolysis temperatures necessary to produce these phenolic building blocks at heating rates of 105 K/sec are estimated to be ca. 900 K. Of course, kinetic parameters obtained at the much lower heating rates of the Curie-point pyrolysis MS experiment (approx. 102 K/s) may only be extrapolated to the laser pyrolysis experiment if the underlying reaction mechanisms are comparable. Evidence supporting this assumption is presented showing similar C1 and C2-alkyl phenol profiles for the Pitt. #8 coal obtained by Curie-point pyrolysis GC/MS using a 15 m fused silica capillary with temperature programming.

Development of a Mobile Ion Trap Mass Spectrometer for Environmental Monitoring

Meuzelaar, H.L.C.; McClennen, W.H.; Arnold, N.S.; Maswadeh, W.; Reynolds, T.K.; Urban, D.T. and Jones, P.R.
Proc. 37th ASMS Conference on Mass Spectrometry and Allied Topics, Miami Beach, Florida, 1424-1426, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, US Department of Energy, the Department of Defense Chemical Research Development and Engineering Center and Finnigan-MAT Corp.

The objective of the work reported here is to develop a compact, mobile mass spectrometer with EI, CI and MSn capabilities. Moreover, the mobile MS system should be capable of analyzing gases, vapors and aerosols in air at low ppb levels while allowing positive identification of individual components in complex mixtures. In view of the size and weight restrictions inherent in the mobility requirement, a special miniaturized version of the Finnigan MAT Ion Trap Mass Spectrometer (ITMS?) was constructed in close collaboration with the manufacturer. This MINITMASS Miniaturized Ion Trap Mass Spectrometer) system is equipped with automatic gain control, automatic reaction control, selective mass storage and axial modulation options, in addition to the required EI/CI and MSn operating modes. The 2x2x2 ft MINITMASS module is mounted within a 6 ft high mobile rack together with all gas supplies, pumps, inlet controls and a PC 80386 workstation. The entire system requires approx. 1000 W of ac power. A 6x7x8 ft, self-contained mobile laboratory module, which fits on a standard 3/4 ton pick-up truck, enables operation of the MINITMASS in remote locations and rugged terrain. Also, the MINITMASS system can be remotely controlled from a distance up to several miles using a second PC workstation, and Carbon Copy© software. A direct air-sampling inlet enables repetitive collection of 10-50 microliter air samples at 15-60 sec intervals. Use of "transfer line chromatography" provides additional resolution and specificity for complex mixtures. Minimum detectable levels of gases and vapors in air are in the low to medium ppb range without the use of concentration devices. Alternatively, a special automated inlet enables electrostatic precipitation of air particulate matter on a ferromagnetic filament with subsequent analysis by Curie-point pyrolysis (GC)/MSn. The system has been successfully operated in the desert (at temperatures up to 100 F), as well as under a variety of indoor conditions, e.g., for monitoring laboratory-scale combustion reactors.

 

Direct On-Site Vapor Monitoring by Transfer Line GC/MS

Arnold, N.S.; Roberts, K.A.; McClennen, W.H. and Meuzelaar, H.L.C.
Proc. 37th ASMS Conference on Mass Spectrometry and Allied Topics, Miami Beach, Florida, 1424-1426, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, US Department of Energy, the Department of Defense Chemical Research Development and Engineering Center and Finnigan-MAT Corp.

A direct atmospheric vapor sampling inlet has been used for on-line monitoring of vapors in laboratory scale reactors. The inlet consists of three concentric tubes with appropriate flow control plumbing and electronics. This inlet provides for direct introduction of a pulse of air (.5 to 2 s) into a short (1 m) coated fused silica capillary column enclosed in the heated transfer line housing of a Finnigan-MAT ITD. Effluent from the column emerges directly into the ion trap. Data presented here were obtained by sampling from a bed-characterization reactor (for waste disposal studies) using the MINITMASS, a modified mobile Ion Trap Mass Spectrometer. (Alternate sampling environments have included a coal combustor, an open air chemical release, a micro-scale laser pyrolysis chamber, and in-building ambient atmospheres.) Vapor samples were obtained repetitively at 60 s intervals, allowing for an isothermal GC separation of various components. A ~1.5 s vapor sample allowed up to 100 ul (@STP) of reactor atmosphere to enter the transfer line for chromatographic separation. A .18 mm ID transfer line with a .4 um DB-5 coating (J+W Scientific) was operated isothermally at either 25º, 80º or 125ºC. Carrier gas (helium) velocity was -2.7 m/s (at column temp=25ºC and 4400 ft elevation). All analyses were performed using electron impact ionization. Detection limits have been established near the 1 ppb level for various substituted aromatic compounds using this (MINITMASS) system and taking advantage of the Axial Modulation* and Selective Mass Storage* features to improve sensitivity. Estimations of concentration in this presentation are provided from the calibration data obtained on toluene, ethylbenzene, o-, m-, and p-xylene and general sensitivity characteristics of ion trap mass spectrometers for the compounds of interest. In the present analyses, halogen-, nitrogen- and oxygen-substituted aromatics have been detected at <100 ppb. Various column temperatures allowed for analysis of compounds with atmospheric boiling points from 80ºC (benzene) to 350ºC (anthracene) present in reactor vapors. To date, test analyses of high boiling compounds than these have required the reactor be run under nitrogen to prevent rapid column degradation, though compounds as involatile as dibenzanthracenes (bp 550ºC) have been detected under test conditions.

 

A Mobile, Tandem Ion Trap Mass Spectrometer System for Environmental Monitoring of Vapors

Arnold, N.S.; McClennen, W.H.; Maswadeh, W.; Urban, D.T.; Reynolds, T.K.; Jones, P.R. and Meuzelaar, H.L.C.
Proceedings of the 1989 U.S. Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, US Department of Energy, the Department of Defense Chemical Research Development and Engineering Center, Geocenter, Inc. and Finnigan-MAT Corp.

A fieldable, Miniaturized Ion Trap Mass Spectrometer (MINITMASS) was constructed for tandem mass spectrometry of environmental vapors. Furthermore, a vapor sampling inlet for transfer line gas chromatography/mass spectrometry was developed which permits direct on-column introduction of atmospheric vapor samples. The transfer line gas chromatography/tandem mass spectrometry combination provided for direct introduction of complex vapor samples with short overall analysis times for on-line monitoring of changing environmental conditions. Work to date has shown the capability for low ppb analysis of substituted aromatic hydrocarbons, corresponding to subpicogram quantities per compound, in MS as well as MS/MS mode.

 

On-Site Transfer Line GC/MSn Analysis of Environmental Vapors Using a Modified Ion Trap Mass Spectrometer

Arnold, N.S.; McClennen, W.H. and Meuzelaar, H.L.C.
Preprints of Papers Presented at the 198th ACS National Meeting, 29 (2),Miami Beach, Florida, 1989. Funded by ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, US Department of Energy, the Department of Defense Chemical Research Development and Engineering Research Center and Finnigan-MAT Corp.

An air-sampling inlet has been developed for on-column injection of atmospheric vapor samples using transfer line GC/MS analysis. Repetitive sampling at 15 to 60 sec intervals provides for short GC separations of the individual components. On-site GC/MSn analyses have been performed using a modified mobile ion trap mass spectrometer. Sites sampled thus far include a laboratory scale coal combustor, a high temperature soil desorber for hazardous waste disposal studies, an open-air chemical release and in-building ambient atmospheres.

Current detection limits are on the order of 1 ppb for selected compounds. Compounds with boiling points greater than 80ºC (e.g., benzene) can be readily separated with a 1 m DB-5 coated fused silica column. Analyses reported here are primarily aimed at aromatics through benzopyrene including nitrogen-, oxygen- and halogen-substituted compounds.

 

Progress in CB Detection by Transfer Line GC/MSn Using a Miniaturized Ion Trap Mass Spectrometer

Meuzelaar, H.L.C.; Arnold, N.S.; McClennen, W.H. and Snyder, A.P.
Proceedings of the 1989 US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, 1989. Funded by ACERC (National Science Foundation Associates and Affiliates), the State of Utah, US Department of Energy, the Department of Defense Chemical Research Development and Engineering Center and Finnigan-MAT Corp.

A novel direct vapor-sampling inlet has been tested in combination with Transfer line Gas Chromatography/Mass spectrometry (TLGC/MSn) using the MINITMASS (Miniaturized Ion Trap Mass Spectrometer) system developed at the University of Utah. Typically, 0.2-0.5 s wide air pulses are injected into the 1 m long transfer line at 15-60 s intervals. Even with relatively complex mixtures of vapors, e.g., produced by desorption and combustion of model compounds in a laboratory-scale fixed bed reactor, sufficient GC separation may be obtained to allow positive identification of minor reaction products by direct library search and matching procedures. Moreover, the high sensitivity of the MINITMASS allows tandem MS analysis of subpicogram quantities of selected model compounds.

 

Development and Testing of a Mobile Tandem Mass Spectrometer for Monitoring Gases, Vapors, and Aerosols

Meuzelaar, H.L.C.; Arnold, N.S.; McClennen, W.H. and Maswadeh, W.
Conference on Environmental Chemistry, Jeckyll Island, Georgia, 1989. Funded by ACERC (National Science Foundation Associates and Affiliates), the State of Utah, US Department of Energy, the Department of Defense Chemical Research Development and Engineering Center, Geocenter, Inc. and Finnigan-MAT Corp.

Recent advances in Ion Trap/Mass Spectrometry (ITMS) technology now enable the assembly of compact ITMS systems with Chemical Ionization (CI) as well as tandem MS (MSn) capabilities. In combination with the proven high sensitivity (full spectra have been recorded on less than 1 pg of sample) and the favorable vacuum characteristics, ITMS devices appear especially well suited for a variety of environmental monitoring tasks.

Based on these assessments, we undertook the development of a mobile Miniaturized Ion Trap Mass Spectrometer (MINITMASS) equipped with specialized air sampling inlets for gases/vapors as well as for aerosols. Both inlet systems employ the so-called transfer line chromatography (TLGC) approach in order to increase specificity and minimize exposure of transfer line, ion source and electron multiplier to oxygen.

Gases and vapors are sampled as 1-2 sec wide air "pulses" at 15-60 second intervals depending on the degree of chromatographic separation required. Minimum detectable concentration levels were found in the low to medium ppb range. The aerosol inlet uses electrostatic precipitation of aerosol particles (0.5-5 um range) on a ferromagnetic filament. After a preselected collection period (e.g., 1-10 minutes) the filament is automatically inserted into a Curie-point pyrolysis reactor with subsequent production of the pyrolysis GC/MS patterns of the collected aerosol particles.

Thus far, the system has been tested with synthetic polymers, biopolymers and bacterial spores.

Monitoring the Evolution of Organic Compounds from the Thermal Treatment of Contaminated Soil Samples Using Short Column GC/MS

McClennen, W.H.; Arnold, N.S.; Lighty, J.S.; Eddings, E.G.; Lindgren, E.R.; Roberts, K.A. and Meuzelaar, H.L.C.
Preprints of Papers Presented at the 198th ACS National Meeting, 34 (3), Miami Beach, Florida, 1989. Funded by the Gas Research Institute, Dave Linz, Project Manager, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.

Incineration is an effective technology for the remediation of organic chemical contaminated wastes. For solid wastes, such as contaminated soils, processes involving separate stages of a primary desorber and secondary afterburner are particularly useful. The desorption stage is currently being modeled using a particle-characterization reactor (PCR, 0-500 g capacity), a bed-characterization reactor (BCR, 0.5-5 kg), and a rotary kiln simulator (2-15 kg) to study fundamental processes such as mass transfer, heat transfer, and volatilization of contaminants. This paper describes the analytical methods and preliminary results from monitoring the evolution of organic compounds in these and smaller reactors.

The samples are soil contaminated with a broad range of polynuclear aromatic (PNA) hydrocarbons such as those derived from coal tars. The analytical methods primarily involve mass spectrometry (MS) with a variety of sample introduction techniques. The on-going analyses include solvent and thermal extractions of soil before and after various thermal treatments as well as on-line monitoring of vapors during desorption.

Fast, Repetitive GC/MS Analysis of Thermally Desorbed Polycyclic Aromatic Hydrocarbons (PAHs) from Contaminated Soils

McClennen, W.H.; Arnold, N.S.; Roberts, K.A.; Meuzelaar, H.L.C.; Lighty, J.S. and Lindgren, E.R.
1st International Congress on Toxic Combustion, 1989. Funded by Remediation Technologies, the Gas Research Institute, ACERC (National Science Foundation and Associates and Affiliates), the State of Utah, and US Department of Energy.

A system for on-line analysis of organic vapors by short column gas chromatography/mass spectrometry (CG/MS) has been used to monitor products from a thermal soil desorption reactor. The system consists of a unique air-sampling inlet with a 1 meter long capillary column coupled directly to a modified Ion Trap Mass Spectrometer (Finnigan MAT) with demonstrated detection limits for alkylbenzenes in the low ppb range. In this work the mobile instrument is used for repetitive GC/MS and GC/MSn (tandem MS) analysis at 30 to 60 sec intervals of PAH products from coal tar contaminated soils in a bed characterization reactor.

Results for naphthalene through dibenzanthracenes are compared to conventional, more detailed GC/MS analyses of extracts from the soil before and after thermal treatment.