COMPARISON OF SUPERCRITICAL-FLUID EXTRACTION AND LIQUID-LIQUID-EXTRACTION FOR ISOLATION OF SELECTED PESTICIDES STORED IN FREEZE-DRIED WATERSAMPLES

The stability of freeze-dried water samples spiked with eight agrochem icals (atrazine, simazine, linuron, carbaryl, propanil, fenitrothion, parathion and fenamiphos) were examined to evaluate their suitability as candidate reference materials for their determination in water samp les. In addition, two different extraction procedures, liquid-liquid a nd supercritical fluid extraction, were compared for the isolation and trace enrichment of target analytes from freeze-dried water samples. Final analytical determinations were by gas chromatography-nitrogen ph osphorus detection and electronic impact mass spectrometry, and by liq uid chromatography-diode array detection. The whole methodology develo ped in this paper permitted the determination of pesticides spiked in water at levels varying from 0.03 to 6.9 mu g L(-1).