Evaluation of liquid-solid extraction with a new sorbent and liquid-liquid extraction for multiresidue pesticides. Determination in raw and finished drinking waters

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.