SOLID-PHASE EXTRACTION OF ORGANOPHOSPHORUS, TRIAZINE, AND TRIAZOLE-DERIVED PESTICIDES FROM WATER SAMPLES - A CRITICAL-STUDY

A critical study using C18 SPE columns for the determination of organo phosphorus, triazine, and triazole-derived pesticides, napropamide, an d amitraz is presented. The type of sorbent, sorbent mass, now rate in the extraction process, sample concentration of the different compoun ds, sample volume, pH, and ionic strength were evaluated. Special emph asis was placed on the evaporation step of eluates prior to GC determi nations and on prefiltration of sample waters. Pesticide recovery is l inear over a wide range of concentrations for most of compounds under study. Under general extraction conditions losses can be expected for amitraz, prometryn, prometon, dimethoate, penconazole, and propiconazo le. At 100 ng L-1, enhanced responses are produced for mevinphos, sima zine, malathion, triadimefon, methidathion, and phosmet, which can be attributed to matrix effects. At basic pH, recovery of prometon, prome tryn, and penconazole are improved. Low flow rates and high ionic stre ngth enhance the recovery of prometon and prometryn. For phosmet, the influence of sample volume was established. Likewise, the influence of sorbent quantity was established for phosmet and dimethoate, Losses d uring the evaporation step were observed for mevinphos, dimethoate (> 50%), penconazole, propiconazole, and prometon (30%). Prefiltration of sample waters did not cause significant variations in the whole proce ss of extraction. Impurities arising from the sorbent materials were n ot detected.