DETERMINATION OF TRACES OF HERBICIDE MIXTURES IN WATER BY ONLINE SOLID-PHASE EXTRACTION FOLLOWED BY LIQUID-CHROMATOGRAPHY WITH DIODE-ARRAY DETECTION AND MULTIVARIATE SELF-MODELING CURVE RESOLUTION

Multivariate self-modelling curve resolution was applied to the determination of co-eluted alachlor and metolachlor mixtures. Mixture analysis of these two pesticides in the presence of other interferents in real water mixtures was achieved using automated on-line solid-phase extraction coupled with liquid chromatography and diode-array detection (DAD) followed by a recently developed multivariate self-modelling curve resolution method. Two different kinds of water samples were analysed (Milli-Q-purified water and surface river water) using two different analytical columns (Merck and Waters). The proposed approach permitted an improvement in the resolution of the co-eluted herbicides after preconcentration of 100 mi of water samples spiked at the 1.5 mu g/l concentration level and also allowed their simultaneous determination independently of the water matrix. Recommendations about further incorporation of the proposed method in liquid chromatographic-diode-array detection methods are given.