DETERMINATION OF CARBARYL AND SOME ORGANOPHOSPHORUS PESTICIDES IN DRINKING-WATER USING ONLINE LIQUID-CHROMATOGRAPHIC PRECONCENTRATION TECHNIQUES

Reversed-phase high-performance liquid chromatography (HPLC) was adapted for the determination of trace concentrations of carbaryl and seven organophosphorus pesticides in drinking water. Between 100 and 300 ml of water sample is passed through a 1.5-cm precolumn, packed with C18-bonded silica or styrene-divinylbenzene copolymer (PRP-1) sorbent at a flow-rate of 3 ml/min. The HPLC system is then switched to an acetonitrile-water gradient elution programme. The analytes that have been concentrated on the precolumn are eluted and separated on a 15-cm C18 analytical column and are determined by measuring their UV absorption at 254 nm. This wavelength was selected as the optimum for the simultaneous determination of these pesticides. The preconcentration yields of the examined solutes obtained with the two types of precolumn are almost identical. Band broadening is avoided by a suitable choice of the C18 precolumn and the analytical column. With 200 ml of tap water, the recoveries for most of the examined pesticides were ca. 90%, except for carbaryl (54%). The detection limits are in the range 0.03-0.2 mug/l.