Solid-phase extraction, clean-up and liquid chromatography for routine multiresidue analysis of neutral and acidic pesticides in natural waters in one run

Solid-phase extraction using C-18 silica cartridges, liquid chromatography analysis and UV diode array detection were investigated for the routine trace-level determination of neutral pesticides over a wide range of polarity. Detection limits below the 0.1 mu g/l range were easily obtained in drinking water. Lf neutral and acidic pesticides over a wide range of polarity have to be determined in the same run, samples have to be acidified to obtain good recoveries of extraction. The effect of the sample matrix was studied and detection limits in the 0.1 mu g/l range were obtained in drinking water except for the more polar ones which are in the interfering peak of humic and fulvic acids. For surface water, a clean-up step using a Florisil cartridge has to be included in the procedure that allows detection limits in the range 0.05-0.3 mu g/l.