Citation:

Morgan, J N., P Kauffman, T E. Hieber, AND J. Brisbin. PESTICIDE ANALYTICAL METHODS TO SUPPORT DUPLICATE-DIET HUMAN EXPOSURE MEASUREMENTS. Presented at 5th European Pesticide Residue Workshop, Stockholm, Sweden, June 13-16, 2004.

Impact/Purpose:

The overall objective of the MCEARD dietary exposure research program 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 conducted under this task provides the tools needed to analyze composite food and beverage samples for the presence of pesticides, starting with pyrethroids. The specific objectives of this task are to develop and improve analytical methods for contaminants in composite food and beverage samples collected in dietary measurements studies and to analyze small numbers of samples in support of these studies. A series of analytical methods and/or journal articles are anticipated through FY07.

Description:

Historically, analytical methods for determination of pesticides in foods have been developed in support of regulatory programs and are specific to food items or food groups. Most of the available methods have been developed, tested and validated for relatively few analytes and food items. Method performance for composited duplicate diet samples, as collected in USEPA residential-based exposure monitoring programs, is largely unknown.
Several considerations impact development of methods to support duplicate diet human exposure measurements. The methods must generate useful dietary exposure data. Consequently, they must be sufficiently sensitive to detect pesticides in composite diet samples collected from the general population and they must be both accurate and precise. Detection limits should be comparable to those for other media collected in a total exposure monitoring program. Additionally, the methods should be as simple and cost effective as possible to minimize the costs associated with analysis of large numbers of samples.
A multi-class, multi-residue method utilizing a temperature-programmable pre-separation column in the gas chromatographic injection port for determination of a wide range of semi-volatile pesticides has been developed. Detection is performed by gas chromatography/mass spectrometry in the selected ion monitoring mode. Method detection limits are at or below 2 ng/g for most pesticides studied, with recovery between 70 and 125%. Sample preparation time and solvent consumption are reduced using this technique. Various extraction techniques have also been evaluated in conjunction with this method.
An organophosphate pesticide method has been developed which utilizes pressurized fluid extraction (PFE), diatomaceous earth and C18 clean-up and detection by gas chromatography with flame photometric detection. Detection limits for most analytes are in the low part per billion range with recoveries typically between 70 and 130%. Pulsed flame photometric and atomic emission detection have been evaluated in conjunction with this method. Additionally, PFE with in-line clean-up has been studied.
An overview of recent method development efforts, as summarized above, will be presented. Current research which focuses on determination of synthetic pyrethroids at sub-ppb levels by gas chromatography tandem mass spectrometry will also be discussed.

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