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DETERMINATION OF PESTICIDES IN COMPOSITE DIETARY SAMPLES BY GAS CHROMATOGRAPHY/MASS SPECTROMETRY IN THE SELECTED ION MONITORING MODE USING A TEMPERATURE PROGRAMMABLE LARGE VOLUME INJECTOR WITH PRE-SEPARATION COLUMN
Citation:
Rosenblum, L, T Hieber, AND J N. Morgan. DETERMINATION OF PESTICIDES IN COMPOSITE DIETARY SAMPLES BY GAS CHROMATOGRAPHY/MASS SPECTROMETRY IN THE SELECTED ION MONITORING MODE USING A TEMPERATURE PROGRAMMABLE LARGE VOLUME INJECTOR WITH PRE-SEPARATION COLUMN. JOURNAL OF AOAC INTERNATIONAL 84(3):891-900, (2001).
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:
Use of a temperature-programmable pre-separation column in the gas chromatographic injection port permits determination of a wide range of semi-volatile pesticides including organochlorines, organophosphates, triazines, and anilines in fatty composite dietary samples while reducing sample preparation time and solvent consumption. Dietary samples are mixed with diatomaceous earth and Soxhlet extracted with an azeotropic solution of hexane and acetone. Sample preparation uses liquid-liquid partitioning over diatomaceous earth followed by normal phase chromatography over partially deactivated alumina. The final clean-up step occurs in a pre-separation column in the GC injector, which is able to perform splitless transfer of the analytes to the analytical column and purge 99% of the high molecular weight residue. 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 24 of 35 pesticides studied, with recovery between 70 and 125% for 27 pesticides in samples fortified at 10 ng/g. Recovery was not dependent on fat content when measured in laboratory fortified samples containing 1%, 5%, and 10% fat by weight. Precision over multiple injections was acceptable with a relative standard deviation of 2.6-15% for 25 analytes.