ACERC
Abstracts - 1993 |
ACERC
Abstracts - 1993 |
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Thrust Area 3: Pollutant Formation/Control and Waste Incineration |
Boardman, R.D. and Smoot,
L.D.
Chapter 6, Fundamentals of Coal Combustion: For Clean and Efficient Use,
(L.D. Smoot, ed.), Elsevier Science Publishers, The Netherlands, 1993. Funded
by ACERC.
By far the most striking problem associated with human consumption of fossil fuels is the control of air pollutants. The inexorable trend for increasing power demand, both by industrially established countries and developing nations, will inevitably lead to increased production and utilization of fossil fuels. The combustion of fossil fuels produces both primary and secondary pollutants. Primary pollutants include all species in the combustor exhaust gases that are considered contaminants to the environment. The major primary pollutants include CO, hydrocarbons, sulfur-containing compounds, nitrogen oxides, particulate materials, various trace metals, and even CO2 that reached pollutant status with increasing concern for global atmospheric warming or the "greenhouse" effect. Secondary pollutants are defined as environmentally detrimental species that are formed in the atmosphere as a consequence of precursor combustion emissions. The list of secondary pollutants includes particulate matter and aerosols that accumulate in the size range of 0.1-10 µm diameter, NO2, O3, and other photochemical oxidants, and acid vapors. The connection between combustion-generated pollutants and airborne toxins, acid rain, visibility degradation, the greenhouse effect, and stratospheric ozone depletion is well established. The detrimental impact of these contaminants on ecosystems in the biosphere and stratosphere has been the impetus of stricter standards around the world. This chapter emphasizes the formation and control of nitrogen oxides (referred to as NOx pollutants) and sulfur-containing pollutants (referred to as SO pollutants) in which temperature stationary combustors. The focus is on the formation of nitrogen oxides since they can be effectively controlled in the combustion chamber. An understanding of nitrogen chemistry and furnace fluid dynamics is imperative to optimizing in-situ nitrogen oxide control schemes. A brief review on the development of mathematical tools used to predict nitrogen and sulfur oxide formation during combustion of fossil fuels will also be presented, In addition, an overview and comparison of NOx and sulfur pollutant abatement strategies is given.
McClennen, W.H.; Lighty,
J.S.; Summit, G.D.; Gallagher, B. and Hillary, J.M.
Combustion Science & Technology, 1993 (in press). (Presented at the Third
International Congress on Toxic Combustion Byproducts, Cambridge, MA, June
1993.) Funded by Kodak, Presidential Young Investigators and ACERC.
Incineration is an important disposal method for the large volumes of sludge produced by industrial and municipal wastewater treatment. This paper describes analytical methods developed for examining industrial sludge incineration processes and the dependence of potential products of incomplete combustion (PICs) on the sludge composition. A surrogate sludge was developed from peat, calcium and iron salts, and a waste water-treatment polymer suspension to simulate incineration characteristics of the real sludge while allowing for controlled variation of its composition. Experiments were conduced under both oxidative and pyrolysis conditions, in reactor systems ranging from microscale up to bench scale with on-line analytical instrumentation. The organic products emitted from the surrogate were quite similar to those of the sludge, with the exception of products from certain synthetic polymers. Significant quantities of aromatic hydrocarbons were emitted from the combustion of cellulosic and lignin fractions of the material even without the presence of those specific compounds in the original waste. The presence of the metal salts and the additional water they retained significantly affected the peak hydrocarbon concentration by delaying the onset of emissions and lengthening their duration. The amount of polystyrene and polymethylmethacrylate in the real sludge made their decomposition products important potential PICs, which would need further combustion.
Smoot, L.D.; Boardman, R.D.;
Brewster, B.S.; Hill, S.C. and Foli, A.K.
Energy & Fuels, 7 (6):786-795, 1993. Funded by ACERC.
Control of emissions of sulfur (SO2, SO3, H2S) and nitrogen (NO, NO2, N2O, HCN, NH3) pollutants from fossil-fuel-fired furnaces and gasifiers remains a vital worldwide requirement as the utilization of fossil fuels continues to increase. Development and refinement of a predictive model for these acid rain precursors (MARP) has reached the point where this technology can contribute to acid rain control. In this paper, model foundations and recent developments are summarized, including formation of thermal and fuel NOx and sorbent capture of sulfur oxides. The method includes global formation, capture, and destruction processes in turbulent, reacting, particle-laden flows. This submodel has been combined with comprehensive, generalized combustion models (PCGC-2, PCGC-3) that provide the required local properties for the combustion or gasification processes. The submodel has been applied to NOx formation in a full-scale (85 MWe), corner-fired utility boiler, where recent in situ NOx measurements were made, with variations in coal feedstock quality (including fuel N percentage) load-level and percentage excess air. Predictions are also made for in situ sorbent capture of sulfur pollutants in both combustion (fuel-lean, SO2), and gasification (fuel-rich, H2S) laboratory-scale reactors. Limitations of MARP are identified and work to improve the submodel is outlined.
Gao, D. and Silcox, G.D.
JAWMA 43:1004-1005, July 1993. Funded by Gas Research Institute and ACERC.
Determining the fate of metals during hazardous waste incineration is important because of environmental concerns. Such a determination requires an analysis of the waste ash. At high temperatures, metals are frequently immobilized by reactions with silicates or by encapsulation with silicates. In order to determine the metal retention levels in waste ash, a digestion method that insures total metal recovery is necessary. This study compares two digestion techniques and uses each to look at the effect of the incinerator's temperature on the apparent fraction of metal retained in the waste ash. Four metals on a diatomaceous earth matrix were studied: Cr, Cd, Pb, and Ni. An HF-based digestion yielded fractional metal retentions of about 1.0 while an HNO3-based digestion yielded apparent retention levels that decrease from 1 to 0.2 as the reactor temperature was increased from 25 to 870ºC.
A commonly used HNO3-based digestion procedures is EPA SW-846, Method 3050. It is successful at extracting those metal compounds that are soluble at conditions that characterize natural leaching and biological processes. However, Method 3050 was not designed to digest metals immobilized by silicates.
Rink, K.K.; Larsen, F.S.;
Kozinski, J.A.; Lighty, J.S.; Silcox, G.D. and Pershing, D.W.
Energy & Fuels, 7 (6):803-814, 1993. Funded by ACERC.
Large volumes of sludge are produced by a wide variety of industrial processes and by municipal wastewater treatment. Interest in incinerating these sludges, either alone, or co-fired with other fuels, is increasing. The issues surrounding sludge incineration in rotary kilns and fluidized beds were identified through a series of pilot-scale tests using two slightly different paper mill sludges. The specific issues examined include hydrocarbon emissions, NOx emissions, and bottom and fly ash properties. A 61-cm i.d. X 61-cm long, 130-kW pilot-scale rotary kiln simulator (RKS) and a 23-cm i.d., 300-kW circulating fluidized bed combustor (CFB) were maintained at a nominal temperature of 1100 K and a stoichiometric ratio of 1.5. The rotary kiln was fed in a batch mode in order to simulate the passage of solids through a kiln. The fluidized bed was fed in both batch and continuous modes. Samples were removed from the kiln (bottom ash) and transition section (fly ash). Samples of the fluidized bed materials were removed from the bed (bottom ash) and after the cyclone (fly ash). The exhaust gases were analyzed continuous for hydrocarbons, CO, O2, NO, and CO2. This paper presents data on these analyses as well as NO conversion and ash properties. The production of NO in the RKS was dependent on the supply of nitrogen (in the sludge) and oxygen (in the gas phase), in the reactor. The availability of oxygen to the sludge was affected by the particle diameter of the sludge, the charge size, and whether a solids bed was present at the time of the incineration. In the CFB, the nitrogen-containing compounds were oxidized primarily downstream of the feedboard region, resulting in elevated levels of NO in the transition and cyclone regions. Carbon monoxide concentrations were high immediately above the bed, which led to the reduction of NO inside the freeboard zone. In both the CFB and RKS tests little unburned hydrocarbons were present in the exhaust gas streams. Formation of fly ash particles was dependent on types of incinerated material (sludge; mixture of sludge and silica sand). Bottom ash material resembled randomly organized skeletons (or cenospheric skeletons), the structure of which was independent of the type of sludge or reactor. Smaller fly ash and bottom ash particles were formed during CFB incineration experiments.
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.
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.
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.
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.
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.
Gopalakrishnan, R.; Stafford,
P.R.; Davidson, J.E.; Hecker, W.C. and Bartholomew, C.H.
Applied Catalysis B: Environmental, 2: 165, 1993. (Presented at the Seventh
Annual Symposium of the Western States Catalysis Club, Albuquerque, NM,
March 1992; at the American Institute of Chemical Engineers Annual Meeting,
Miami Beach, FL, November 1992 and at the 13th North American Meeting of
the Catalysis Society, Pittsburgh, PA, May 1993). Funded by Shell, Brigham
Young University and Winco.
Selective catalytic reduction of NO with propane and oxygen was investigated on Cu-exchanged ZSM-5, mordenite, X-type and Y-type zeolites at temperatures in the range of 200 to 600º C. Catalytic activities of Cu-X and Cu-Y are negligible, activity of Cu-mordenite moderate, and that of Cu-ZSM-5 very high, converting >90% of NO to N2 at 400ºC and a space velocity of 102,300/hr. Effects of space velocity, NO concentration, C3H8/NO ratio, oxygen concentration, and water vapor on the activities of Cu-ZSM-5 and Cu-mordenite were investigated. NO conversion decreases with increasing space velocity, decreasing propane and NO concentrations, and decreasing propane/NO ratio. Water vapor decreases the activity significantly at all temperatures. At temperatures above 400ºC, propane oxidation by oxygen is a significant competing reaction in decreasing the selectivity for NO reduction. The results indicate that Cu-ZSM-5 is a promising catalyst for SCR of NO by hydrocarbons.
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.
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.
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.
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.
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.
Boardman, R.D.; Eatough,
C.N.; Germane, G.J. and Smoot, L.D.
Combustion Science and Technology, 20: 1-18, 1993. (Previously presented
at the First International Conference on Combustion Technologies For a Clean
Environment, Vilamoura, Portugal, September 1991). Funded by Morgantown
Energy Technology Center.
A combined thermal and fuel nitric oxide submodel has recently been added to a generalized, 2-dimensional pulverized coal gasification and combustion model (PCGC-2). This model is applicable to reacting and non-reacting gaseous and particle-laden flows. The thermal NO model is based on the extended Zel'dovich mechanism. To perform an evaluation of the NOx submodel, combustion measurements of gas velocities, temperatures, and species concentrations were made in a laboratory-scale, experimental reactor with a 150 kW natural gas flame at an equivalence ratio of 1.05 and a secondary-air swirl number of 1.5. Combustion measurements of velocities and major species concentrations show generally good agreement with predicted values. Gas temperature measurements closely match predictions in the recovery region but fail to show predicted high temperature in the annular region. This study provides an evaluation of a comprehensive combustion model and the NOx submodel that can be useful as a design tool to provide pollutant formation trends in applied systems as combustion parameters are varied.
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.
Meuzelaar, H.L.C.
International Symposium Field Screening Methods for Hazardous Wastes and
Toxic Chemicals, 1:35-54, Pittsburgh, PA, 1993. (also presented at the International
Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals,
Las Vegas, NV, June 1993. Funded by Hewlett Packard, US Department of Defense
and ACERC.
Simultaneous advances in miniaturized mass spectrometry (MS) equipment and in field-portable gas chromatography (GC) devices have brought development of man portable GC/MS instruments within reach. Among the various levels of man portability, viz. "luggable," "wearable" or "hand-portable," the latter category is likely to remain an elusive target for GC/MS for the remainder of this millennium. Since hand-portables are unlikely to become feasible soon and "luggables" obviously leave much to be desired, "wearable" GC/MS systems would appear to constitute a logical development benchmark for the immediate future.
Our laboratory has described a wearable, GC/MS system for air monitoring applications based on the integration of a fully automated, repetitive air sampling inlet, a short isothermal capillary GC column, a low power quadruple mass filter (modified HP MSD), a hybrid (bulk getter/ion getter) vacuum system and a PC notebook computer. The system weights 60 lbs, consumes 90 W of battery power and should run 2-3 hrs on high-density disposable batteries. Other man portable GC/MS prototype systems scheduled for completion in the near future are under development at Jet Propulsion Laboratory and at Lawrence Livermore National Laboratory. Major remaining challenges include the need for: further weight reduction; 102-103 times higher sensitivity; and improved man/machine interfaces. Possible future directions are likely to include: drone-portables; use of neural network processors; and, eventually hand-portable GC/MS systems.
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.
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