LIQUID-CHROMATOGRAPHIC DETERMINATION OF SULFONYLUREA HERBICIDES IN NATURAL-WATERS AFTER AUTOMATED SAMPLE PRETREATMENT USING SUPPORTED LIQUID MEMBRANES

Sample pretreatment for the determination of sulfonylurea herbicides i n natural water samples is investigated. Both supported liquid membran e (SLM) extraction and solid-phase extraction (SPE) are used for enric hment of spiked samples. The liquid membrane technique is used on-line with liquid chromatography. The liquid chromatographic detection is b y UV absorption at 240 nm. Enrichment with SLM gives a more selective extraction than SPE, resulting in much cleaner chromatograms. The dete ction limits for enrichment of 250-ml samples are 50-100 ng/l for SLM and around 1 mu g/l for SPE.