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EVALUATION OF ANALYTICAL METHODS FOR DETERMINING PESTICIDES IN FOODS
Citation:
Chuang, J. C., J. S. Chang, L. E. Bowman, J M. Van Emon, AND A W. Reed. EVALUATION OF ANALYTICAL METHODS FOR DETERMINING PESTICIDES IN FOODS. 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 overall objectives of the task include several components: (1) develop immunochemical methods for compounds difficult to analyze by conventional methodologies; (2) tailor immunochemical methods to support specific human exposure assessment studies; (3) team immunochemical sample preparations with instrumental analysis such as mass spectrometry for in-depth sample characterization; (4) provide methods to support NERL's human exposure and environmental monitoring efforts; (5) provide analytical methods that improve risk assessments by reducing the amount of uncertainity in environmental measurements; (6) provide multimedia analytical methods to support an integrated multimedia approach to assess and characterize risk to human health and the environment; (7) provide sponsorship of annual immunochemistry research meetings as a forum for stimulating interest and discussion on current or emerging bioanalytical methods; (8) develop and incorporate rapid, cost-effective laboratory and field portable immunochemical techniques such as enzyme-linked immunosorbent assay (ELISA) methods into monitoring studies and human exposure field surveys to delineate sub-populations of "highly exposed" individuals for detailed follow-up studies.
Specific method needs have been identified through consultations with client office personnel. This Task strives to fulfill those needs as appropriate. In particular, methods for pyrethroids, e.g., permethrin, cypermethrin, and deltamethrin are being developed and evaluated. Efficient sample preparations are under development for exposure samples using pressurized liquid extraction. Confirmation will be achieved using high performance liquid chromatography (HPLC). A rapid immunoassay approach for the analysis of 2,4-D in urine will be completed and a SOP and report written. Immunoaffinity chromatography sample preparations for the pyrethroids will be developed. Work will continue on the application of antibody replacements such as molecularly imprinted polymers. Additional candidate analytes will be identified for a tiered approach and to guide development of the next Task. Flexibility will be maintained to address methods and measurement issues as they arise during the task period which ends in FY06. The objective of the Task is to develop bioanalytical methods to support exposure monitoring studies during the task period.
Description:
Children can be exposed to pesticides by inhaling contaminated air, ingesting tainted food or non-dietary substances, or absorbing them through the skin from contaminated media. Earlier pilot-scale exposure studies suggest that dietary ingestion is an important pathway for children's exposure to some pesticides. Determinations of pesticides in food are often complicated by the presence of fats, and therefore require multiple cleanup steps before analysis. Cost-effective analytical methods are needed for conducting large-scale exposure studies.
In this presentation, we discuss the investigation of several extraction methods and clean-up procedures for determining target pesticides in baby foods. The extraction techniques examined were supercritical fluid extraction (SFE) and accelerated solvent extraction (ASE). The clean-up procedures evaluated were C18 solid phase extraction (SPE), basic alumina SPE, ENVI-Carb SPE, and tandem SPE column (ENVI-Carb-florisil, ENVI-Carb-amino). The detection techniques used were enzyme-linked immunosorbent assay (ELISA) and gas chromatography/mass spectrometry (GC/MS).
The SFE-GC/MS procedures evaluated did not provide quantitative recoveries (<50%) of the spiked pesticides in fatty baby foods. Using SFE-GC/MS, recoveries of target pesticides were greater than 80% in dried baby food, but 10-60% of the spiked pesticides were lost during the freeze-drying process. The ASE-ELISA method provided a quantitative determination of atrazine in both non-fat and fatty baby food. Several spike recovery tests were carried out to determine target pesticides in baby foods using ASE-GC/MS. These tests resulted in an analytical method for determining target pesticides in baby foods. The method consists of extracting baby food with acetonitrile (ACN) at 80 degrees C under 2000 psi pressure, fractionating the ACN extract with ENVI-Carb SPE, and analyzing the collected fraction using GC/MS. Selected sample extracts were analyzed by ELISA and good agreement was obtained between the ELISA and GC/MS results. Duplicate diet samples from the Total Dietary Study were prepared with the above method and analyzed for four target pesticides: malathion, chlorpyrifos, P,P -DDE, and P,P -DDT. The concentrations of the target pesticides ranged from <0.3 to 110 ppb.
This work has been funded wholly or in part by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for publication. Mention of trade name or commercial products has not constituted endorsement or recommendation for use.