Evaluation of Liquid−Solid Extraction with a New Sorbent and Liquid−Liquid Extraction for Multiresidue Pesticides. Determination in Raw and Finished Drinking Waters

Abstract

A comparative study is made of the application of liquid−liquid (LLE) and liquid−solid (LSE) extraction techniques with a new sorbent with trifunctional bonding chemistry (tC 18 ) for environmental sampling and trace enrichment. The experimental conditions of the LLE and LSE methods were evaluated for the determination of 22 organochlorine and 2 organophosphorus pesticides, 2 triazines, and 7 polychlorinated biphenyls (PCBs), which were analyzed by gas chromatography with a capillary column and electron-capture detector (ECD). Mean recovery yields were found to be higher with the LLE method, although LSE for most of the 33 analytes assayed surpassed 70%. The detection limits for both techniques were lower than 5 ng L - 1, except for the pesticides parathion (7 ng L - 1 ), methoxychlor (8 ng L - 1 ), atrazine (35 ng L - 1 ), and simazine (95 ng L - 1 ). The absolute standard deviations and the variation coefficients of both techniques were slightly higher in LSE and ranged from 0.5 to 2.6 ng L - 1 and 7 to 24%, respectively. The method was applied to the analysis of raw and finished drinking water from four towns with different water sources and qualities. Keywords: Liquid−solid extraction; GC/ECD of pesticides in water; pesticide enrichment; tC 18 cartridges