EVALUATION OF A MAGNETIC PARTICLE-BASED ELISA FOR THE DETERMINATION OF CHLORPYRIFOS-ETHYL IN NATURAL-WATERS AND SOIL SAMPLES

A magnetic particle-based ELISA for chlorpyrifos-ethyl was investigate d in estuarine water matrices, and the results obtained were correlate d with automated on-line solid phase extraction (Prospekt) followed by liquid chromatography/diode array detection. The ELISA test was evalu ated before and after filtration of the particulate matter present in estuarine water with and without prior acidification. The ELISA assay was used as a first screening method for determining chlorpyrifos-ethy l in a highly contaminated soil spiked at common termicidal applicatio n rate (similar to 1000 mg/kg). The ELISA assay permitted us to distin guish soil contamination of chlorpyrifos-ethyl at 50 mg/kg in conjunct ion with Soxhlet extraction. Substantial saving time was achieved when compared to conventional methods, which require a cleanup step prior to chromatographic determinations.