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STORAGE STABILITY OF PESTICIDES IN EXTRACT SOLVENTS AND SAMPLING MEDIA
Citation:
Ortiz, M. M., D. E. Camann, P. W. Geno, A. Y. Yau, W. D. Ellenson, H L. Crist, AND A E. Bond. STORAGE STABILITY OF PESTICIDES IN EXTRACT SOLVENTS AND SAMPLING MEDIA. Presented at ISEA 2000 Exposure Analysis in the 21st Century: Integrating Science, Policy and Quality of Life, Monterey Peninsula, CA, October 24-27, 2000.
Impact/Purpose:
The objective of this task is to develop state-of-the-art methods for measuring xenobiotic compounds, to include the isolation of the analyte from the appropriate matrix (extraction), preconcentration (typically sorbent-based), and analysis via GC/MS and/or LC/MS. Once established, these methods will be applied in small scale pilot studies or demonstration projects. Particular emphasis will be placed on methods which are readily transferable to other laboratories, including those within the Human Exposure and Atmospheric Sciences Division (HEASD), the National Exposure Research Laboratory (NERL), other EPA Laboratories, Program Offices, Regions, and academic institutions.
Specific objectives of this task include the following:
1) Development of GC/MS and LC/MS methods for the measurement of key xenobiotic compounds and their metabolites (to include the pyrethroid pesticides, perfluorinated organic compounds, and the BFRs) in relevant environmental and biological matrices.
2) Development of efficient low cost methods for the extraction and clean up of these compounds collected from relevant matrices.
3) Determination of xenobiotic compound and metabolite concentrations in samples derived from laboratory and field monitoring studies to help assess exposures and evaluate associated risks.
Description:
Demonstrating that pesticides are stable in field media and their extracts over extended storage periods allows operational flexibility and cost efficiency. Stability of the 31 neutral pesticides and 2 acid herbicides of the Agricultural Health Study exposure pilot was evaluated for air samples, wipe samples, and their extracts.
To simulate extracts, 31 pesticides were prepared in diethyl ether/hexane (1:9) at~-0.5 ug/mL, 9 pesticides at ~0.5 mg/mL, and 2 acid herbicides in acetonitrile at both levels. The solutions were stored in vials at -12?8?C. After designated storage intervals, three replicates at each concentration were removed from the freezer and analyzed. None of the pesticides showed significant loss through 238 days of storage, except for captan and folpet at the low concentration and terbufos at the high concentration. Acid herbicide losses were 15-20% through 113 days.
To simulate air samples, cleaned polyurethane foam (PUF) and quartz filter media were spiked with ~0.5 ug each of 31 pesticides or 2 acid herbicides and stored at -12?8?C. After designated storage intervals, three replicates were removed for extraction and analysis. Most pesticides were stable through 120 days of storage. Trifluralin, phorate, dicloran, and terbufos were poorly extracted from PUF and filter. Significant losses were observed for metalaxyl by day 14 and captan and folpet by day 60. Anomalous losses of diazinon, malathion, and fonofos were seen only on day 60. Dicamba was stable through 59 days, but 2,4-D recovery remained ~65% after day 14.
To simulate wipe samples, Sof-wick sponges were wetted with isopropanol, spiked with ~1 ug of 31 pesticides and 2 acid herbicides, and stored at -12?8?C. A problem traced to the extract evaporator prevented a full evaluation. Most pesticides and both acid herbicides were stable through the 48-day storage period. Losses of trifluralin, phorate, dicloran, chlorothalonil, terbufos, captan, and folpet suggested inefficient extraction and/or storage instability.
This work was funded by the U. S. Environmental Protection Agency under contract 68-D5-0049 to ManTech Environmental and its subcontractor Southwest Research Institute. It has been subjected to Agency review and approved for publication