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 t rifunctional bonding chemistry (tC(18)) for environmental sampling and trace enrichment. The experimental conditions of the LLE and LSE meth ods were evaluated for the determination of 22 organochlorine and 2 or ganophosphorus pesticides, 2 triazines, and 7 polychlorinated biphenyl s (PCBs), which were analyzed by gas chromatography with a capillary c olumn and electron-capture detector (ECD). Mean recovery yields were f ound to be higher with the LLE method, although LSE for most of the 33 analytes assayed surpassed 70%. The detection Limits for both techniq ues 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 sim azine (95 ng L(-1)). The absolute standard deviations and the variatio n coefficients of both techniques were slightly higher in LSE and rang ed 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.