ANYL 42 |
| Synthetic pyrethroid usage has escalated since the ban of organochlorines in the 1970's due to their lower toxicity to humans and relatively shorter half lives in the environment. With their widespread popularity resulting in virtually all individuals being exposed, there is increased interest regarding both acute and chronic toxicity of these pesticides, how long they persist in the environment, and how bioavailable they are. As a consequence to their widespread usage, these pesticides are almost certain to be found in soil. Therefore, soil is an indicative matrix to assess pesticide exposure. Soil is also an inexpensive-to-obtain and accessible matrix and consequently used for many pesticide exposure analyses. This study analyzes various clean-up methods for pesticides in soil in order to identify a robust, efficient and inclusive (multi-residue screen) extraction method. A single, pressurized-fluid extraction method (Dionex ASEŽ) was developed for quantifying seven organophosphates, seven pyrethroids and five organochlorines in soil. Three additional clean-up methods of the extract were evaluated to enhance analyte selectivity and exclude any interfering compounds. The pressurized fluid extraction clean up was followed by either solid-phase extraction, liquid-liquid extraction, or liquid-liquid extraction utilizing sorbent-immobilized cartridges and then analyzed using positive electron ionization gas chromatography-mass spectrometry. Several aspects of the extraction and clean-up system were analyzed to achieve the most precise, accurate and robust method. First, overall extraction efficiencies of the pressurized fluid extraction step were investigated with various solvent systems in addition to pressure, temperature and static cycles. Secondly, multiple parameters for the additional clean-up steps were evaluated such as: solvent selection, cartridge selection, cartridge rinse selection, and volume of solvent use. The results of these investigations indicate that it is possible to develop a robust method capable of analyzing this large multi-class group of pesticides with excellent recovery, sensitivity, and precision. |
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General Papers
7:00 PM-9:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster
Division of Analytical Chemistry |