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COMPARISON OF GC-FPD AND GC/AED FOR DETERMINATION OF ORGANOPHOSPHATE PESTICIDES IN COMPOSITE DIET SAMPLES
Citation:
Morgan, J N. AND P Kauffman. COMPARISON OF GC-FPD AND GC/AED FOR DETERMINATION OF ORGANOPHOSPHATE PESTICIDES IN COMPOSITE DIET SAMPLES. Presented at Eastern Analytical Symposium, Atlantic City, NJ, October 29-November 3, 2000.
Impact/Purpose:
The overall objective of this research is to support NERL's human exposure measurement and exposure modeling efforts by reducing the amount of uncertainty in the dietary measurements critically needed for improved risk assessment. Specifically, the research provides the tools needed to collect and analyze food samples and to design and understand dietary measurements. The current specific objectives are:
1. to investigate more efficient methods for characterizing population exposures in dietary measurements studies (short-term subtask initiated in FY00; extramural);
2. to develop and improve analytical methods for contaminants in composite food samples collected in dietary measurements studies (long-term subtask; in-house);
3. to improve the model and food database system used in measurements studies for estimating dietary exposure and identifying sources (long-term subtask; extramural).
Description:
In order to assess an individual's total exposure to contaminants in the environment, it is essential that the contribution of dietary exposure be quantified. As a result, USEPA's National Exposure Research Laboratory has initiated a program to develop methods to measure chemical pollutants in dietary samples collected from individuals. Methods developed previously utilizing GC/MS-SIM for pesticides in composite diets are unsuitable for many organophosphorus pesticides. Consequently the present study was undertaken to evaluate the suitability of GC/FPD and GC/AED for determination of organophosphorus pesticides in composite diets. Composite diet samples containing three levels of fat (1, 5 and 10%) and fortified with 37 organophosphorus pesticides were extracted with a methylene chloride-acetone solvent mixture using accelerated solvent extraction and cleaned up using diatomaceous earth and C18 reversed phase chromatography. Pesticides were quantitated by capillary GC using a DB-17 column with both flame photometric detection (phosphorous mode) and atomic emission detection. Recovery of fortified pesticides, precision (% relative standard deviation) and method detection limits were determined using both GC/FPD and GC/AED. Recoveries ranged from 30-93% for 37 pesticides studied. Recoveries from high fat composite diets were greater than 70% for 30 of 37 pesticides. RSDs were generally below 15%. Recoveries were poor for naled, methamidophos, acephate, chlorethoxyfos, dichlorvos, and disulfoton. In general GC/FPD was more snesitive than GC/AED for most analytes tested. Specific results will be presented along with a discussion of advantages and disadvantages of each technique.