A multiresidue analysis for trifluralin, simazine, atrazine, propazine, diazinon, parathion-methyl, alachlor, malathion, parathion, chlorpyrifos, pendimethalin, methidathion, and DEF in water that utilizes liquid-solid extraction (LSE) with octadecyl-bonded silica cartridges (C18BSCs) followed by gas chromatography/mass spectrometric analysis was developed. Recoveries of most pesticides were greater than 80% with C18BSCs from fortified water at concentration levels from about 1 to 500 ppb. Recoveries with C18BSCs, from an optically adjusted humic acid solution (10 ppm dissolved organic carbon) made to simulate a natural water with a high dissolved organic content, ranged from 29 to 153% and in general were lower than recoveries obtained from pure water. 14C-Labeled diazinon and parathion were recovered from the humic acid solution at levels of 57 and 68%, respectively, with C18BSCs; the remainder of the labeled pesticides was found in the cartridge eluents. Partition coefficients with human acid were calculated based on recovery of 14C-labeled pesticides from the C18BSCs.
The toxic herbicide impurity 2,3,7,8-tetrachlorodibenzo-p-dioxin and its homologs decomposed rapidly in alcohol solution under artificial light and natural sunlight, the rate of decomposition depending upon the degree of chlorination. However, photodecomposition was negligible in aqueous suspensions and on wet or dry soil.
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