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RECOVERY OF SEMI-VOLATILE ORGANIC COMPOUNDS DURING SAMPLE PREPARATION: IMPLICATIONS FOR CHARACTERIZATION OF AIRBORNE PARTICULATE MATTER
Citation:
Swartz, E, L Stockburger, AND L. A. Gundel. RECOVERY OF SEMI-VOLATILE ORGANIC COMPOUNDS DURING SAMPLE PREPARATION: IMPLICATIONS FOR CHARACTERIZATION OF AIRBORNE PARTICULATE MATTER. ENVIRONMENTAL SCIENCE & TECHNOLOGY 37(3):597-605, (2002).
Impact/Purpose:
Develop and evaluate methods for the sampling and analysis of PM in ambient air, with emphasis on FRM/FEM for PMc, measurement of carbonaceous aerosols, measurement of biogenic aerosols, comparisons measurements from the STN and IMPROVE monitoring networks, and continuous methods for PM mass and its chemical components.
Description:
Semi-volatile compounds present special analytical challenges not met by conventional methods for analysis of ambient particulate matter (PM). Accurate quantification of PM-associated organic compounds requires validation of the laboratory procedures for recovery over a wide volatility and polarity range. To meet these challenges, solutions of n-alkanes (nC12 to nC40) and polycyclic aromatic hydrocarbons PAHs (naphthalene to benzo[ghi]perylene) were reduced in volume from a solvent mixture (equal volumes of hexane, dichloromethane and methanol), to examine recovery after reduction in volume. When the extract solution volume reached 0.5 mL the solvent was entirely methanol, and the recovery averaged 60% for n-alkanes nC12 to nC25 and PAHs from naphthalene to chrysene. Recovery of higher MW compounds decreased with MW, because of their insolubility in methanol. When the walls of the flasks were washed with 1 mL of equal parts hexane and dichloromethane (to reconstruct the original solvent composition), the recovery of nC18 and higher MW compounds increased dramatically, up to 100% for nC22 - nC32 and then slowly decreasing with MW due to insolubility. To examine recovery during extraction of the components of the High Capacity Integrated Gas and Particle Sampler, the same standards were used to spike its denuders and filters. For XAD-4 coated denuders and filters, normalized recovery was > 95% after two extractions. Recovery from spiked quartz filters matched the recovery from the coated surfaces for alkanes nC18 and larger, and for fluoranthene and larger PAHs. Lower MW compounds evaporated from the quartz filter with the spiking solvent. This careful approach allowed quantification of organics by correcting for volatility- and solubility-related sample preparation losses. This method is illustrated for an ambient sample collected with this sampler during the Texas Air Quality Study 2000.
The United States Environmental Protection Agency through its Office of Research and Development partially funded and collaborated in the research described here under Interagency Agreement DW-898164-01 to E.O. Lawrence Berkeley National Laboratory (LBNL), through the U.S. Department of Energy, under Contract DE-AC03-76SF00098. The project was also supported by the University of Texas under an intergovernmental personal act and a contract with LBNL. It has been subjected to Agency Review and approval for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.