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Title: Determination of volatile organic compounds in ambient air with gas chromatograph-flame ionization and ion trap detection

Abstract

Two new techniques are utilized to integrate the following three equipments: an Entech 2000 automated air concentrator, a Hewlett Packard gas chromatograph (GC) with flame ionization detector (FID) and an ion trap mass spectrometer detector (ITD). This combined analytical system is used to determine low ppb level volatile organic compounds (VOC) in ambient air. The first technique is to configure the inlet system of the GC, so that the pressure regulated flow control system of the GC injection port is used to control the flow of both the desorb gas of the automated air concentrator and the carrier gas of the GC column. The injection port still can be used to inject gas and liquid samples directly. The second technique is to split the effluent of GC column at a 1:1 ratio to the ITD and the FID. In this way, both FID and ITD data can be obtained for each analysis. For ambient air non-methane hydrocarbons monitoring, the FID detector is widely used. Oxygen containing and halogenated organic compounds cannot be differentiated by FID detector and would be quantified as coeluting hydrocarbons. However, volatile organic compounds other than target hydrocarbons can be identified by ITD. This analytical system ismore » very valuable research tool for non-methane hydrocarbons and urban air toxic monitoring. The performances of this developed system have been presented.« less

Authors:
; ; ; ;  [1]
  1. Univ. of Connecticut, Storrs, CT (United States). Environmental Research Inst.
Publication Date:
OSTI Identifier:
197447
Report Number(s):
CONF-9405167-
TRN: IM9612%%221
Resource Type:
Book
Resource Relation:
Conference: Measurement of toxic and related air pollutants, Durham, NC (United States), 3-6 May 1994; Other Information: PBD: 1994; Related Information: Is Part Of Measurement of toxic and related air pollutants. Proceedings of the 1994 U.S. EPA/A and WMA international symposium; PB: 1075 p.
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ORGANIC COMPOUNDS; AIR POLLUTION MONITORING; CHEMICAL ANALYSIS; AIR SAMPLERS; PERFORMANCE; EXPERIMENTAL DATA; VOLATILE MATTER; GAS CHROMATOGRAPHY; MASS SPECTROSCOPY; EMISSION SPECTROSCOPY

Citation Formats

Liu, S., Carley, R.J., Kang, J., Chen, J., and Stuart, J.D. Determination of volatile organic compounds in ambient air with gas chromatograph-flame ionization and ion trap detection. United States: N. p., 1994. Web.
Liu, S., Carley, R.J., Kang, J., Chen, J., & Stuart, J.D. Determination of volatile organic compounds in ambient air with gas chromatograph-flame ionization and ion trap detection. United States.
Liu, S., Carley, R.J., Kang, J., Chen, J., and Stuart, J.D. 1994. "Determination of volatile organic compounds in ambient air with gas chromatograph-flame ionization and ion trap detection". United States. doi:.
@article{osti_197447,
title = {Determination of volatile organic compounds in ambient air with gas chromatograph-flame ionization and ion trap detection},
author = {Liu, S. and Carley, R.J. and Kang, J. and Chen, J. and Stuart, J.D.},
abstractNote = {Two new techniques are utilized to integrate the following three equipments: an Entech 2000 automated air concentrator, a Hewlett Packard gas chromatograph (GC) with flame ionization detector (FID) and an ion trap mass spectrometer detector (ITD). This combined analytical system is used to determine low ppb level volatile organic compounds (VOC) in ambient air. The first technique is to configure the inlet system of the GC, so that the pressure regulated flow control system of the GC injection port is used to control the flow of both the desorb gas of the automated air concentrator and the carrier gas of the GC column. The injection port still can be used to inject gas and liquid samples directly. The second technique is to split the effluent of GC column at a 1:1 ratio to the ITD and the FID. In this way, both FID and ITD data can be obtained for each analysis. For ambient air non-methane hydrocarbons monitoring, the FID detector is widely used. Oxygen containing and halogenated organic compounds cannot be differentiated by FID detector and would be quantified as coeluting hydrocarbons. However, volatile organic compounds other than target hydrocarbons can be identified by ITD. This analytical system is very valuable research tool for non-methane hydrocarbons and urban air toxic monitoring. The performances of this developed system have been presented.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1994,
month =
}

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  • The current approach to measuring trace levels of volatile organic compounds (VOCs) in ambient air requires cryogenic trapping of the analytes, followed by thermal desorption and low-temperature refocusing onto a column for analysis by capillary gas chromatography/mass spectrometry (GC/MS). The approach has been successfully applied to nonpolar VOCs, but its use for more polar species has been complicated by the problems associated with the ambient water vapor collected with the VOCs. A promising technique for measuring polar VOCs is chemical ionization GC/MS (GC/CI-MS) in the quadrupole ion trap. The approach allows whole air samples to be taken since the watermore » present in the air is used as the CI reagent gas. Water CI leads to appreciable intensities for the proton transfer agent H{sub 3}O{sup +}, which produces intense pseudomolecular ions and class-specific fragmentation patterns for various low molecular weight polar compounds. Standard mixtures of polar species at low concentrations in humidified zero air were analyzed without a membrane dryer, using a cryogenic trap and CI-GC/MS with the ion trap detector in the full scan model.« less
  • Accurate measurements of atmospheric concentration of non-methane organic compounds (NMOC) are necessary in the application of photochemical models that are used by states in developing the control strategies needed to achieve compliance with ambient air-quality standards for ozone. NMOC measurements obtained with available continuous NMOC analyzers have often been of inadequate quality. Speciated gas-chromatographic measurements, though adequate, are excessively difficult and expensive where speciated data are not needed. A simplified cryogenic preconcentration, direct flame ionization detection (PDFID) method that is sensitive and provides accurate measurements of ambient NMOC concentrations has been developed and standardized sufficiently to be recommended for usemore » by state and local air pollution control agencies in the development of their ozone control plans. Recent refinements to the method are discussed, an automatic remote sampling system is described, and the performance (precision and accuracy) of the method is characterized, based on results from utilization of the method for NMOC analysis of 1375 air samples collected from 22 sites during the summer of 1984. A complete description of the method is also provided in an appendix.« less
  • The results of this study which successfully demonstrated the analysis of gaseous nonmethane organic compounds (NMOC) using cryogenic trapping to both preconcentrate NMOC and separate NMOC from CH/sub 4/ are discussed. The analysis system is essentially a combination of the preconcentration technique used with the gas chromatographic procedure and a standard, commercial hydrocarbon analyzer modified to maintain a stable flame in the FID under the conditions used in the new analytical system. The method can be used either for direct, in situ ambient measurements or for analysis of integrated samples from a sample bag or canister. The method provides amore » simple and cost-effective means of acquiring the data base necessary as input to the simple photochemical dispersion models. 7 references, 3 figures, 2 tables.« less
  • A gas chromatographic system is described for the determination of toxic organic compounds in ambient air. These compounds include all those specified within the US EPA Compendium Method TO14 and some polar additional analytes under consideration for the proposed TO15 Method. The system supports both on-line and off-line (passivated canisters and adsorption tubes) methods for sampling air--providing a fully automated analysis. A key feature of the system is that liquid cryogen is not required for either the analyte preconcentration or the subsequent chromatographic separation. Water management is achieved by dry-purging an adsorbent trap upon which the sample analytes have beenmore » retained. The performance of the system is demonstrated with conventional detection systems (electron capture and flame ionization) and with a mass spectrometer.« less
  • The relative performance of two commercial automated gas chromatography (Auto-GC) systems for ambient air monitoring is discussed. Both systems have proven their ability to quantify most of the C{sub 2}--C{sub 10} compounds targeted in the US EPA`s enhanced monitoring program, at or below the requisite 1.0 part per billion carbon detection level. Neither cryogenic cooling of adsorption trap material nor low temperature ({minus}180 C) refocusing prior to sample injection were found to be necessary for satisfactory separation of these compounds. However, the permeation-style dryer utilized by both systems removes many polar and/or oxygenated species of interest. In addition to obtainingmore » the technical expertise to operate Auto-GC systems, organizations involved in enhanced monitoring need to reevaluate their data handling resources. Raw data from these GC`s must be backed-up, telemetered and quickly assessed in order to efficiently utilize resources and minimize lost data. Because existing data logging and telemetering systems are structured for relatively low data flows, the large quantity of raw data from a single GC (> 1.5 Megabytes/day) can easily overwhelm such systems. Data management and assessment may well prove to be the most labor intensive activity associated with the enhanced monitoring program.« less