Development of a semi-automated high-performance liquid chromatographic diode array detection system for screening pesticides at trace levels in aquatic systems of the Axios River basin

A semi-automated HPLC-diode array detection (HPLC-DAD) system associated with an on-line sample enrichment device was developed for the analysis of a wide range of pesticides in water samples of the Aries River basin. The system was optimised with respect to the analytical column, the on-line trace enrichment device, the mobile-phase composition and gradient duration, the sample volume and pH, and the chromatographic profile of the background dissolved organic material. The system developed was applied for the tentative identification and quantitation of 46 target analytes including parent pesticides and major conversion products in field water samples. The limit of detection (LOD) for the majority of the compounds was in the range 0.10-0.02 mu g/l level; the LOD for three target analytes, the aliphatic carbamate esters aldicarb sulfone, oxamyl and methomyl, was in the range of 1.0-0.5 mu g/l. In addition, stability studies of all analytes in field water samples stored either under ambient or refrigerated conditions were conducted to optimise field water transport and sample storage conditions. Monitoring residue data derived from the HPLC-DAD system were validated with off-line solid-phase extraction (SPE) of field water samples and analysis of extracts by independent GC-NPD-ECD and GC-MS systems.