DETERMINATION OF PHENOLS IN SEA-WATER BY LIQUID-CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION AFTER ENRICHMENT BY USING SOLID-PHASE EXTRACTION CARTRIDGES AND DISKS

The efficiency and the reproducibility of different solid-phase adsorb ents such as C-18 cartridges, C-18 and poly(styrenedivinylbenzene) (PS -DVB) membrane extraction disks were evaluated for the extraction of p henols from water at mu g l(-1) concentration levels. Liquid chromatog raphy with electrochemical detection (LC-ED) was used for the analysis of the organic extracts. A phosphate buffer-acetonitrile-methanol mix ture as mobile phase and coulometric detection at + 750 mV were used. High recoveries (70-98%) and good reproducibility (relative standard d eviation between 3 and 12%) were obtained using PS-DVB disks, which ca n be recommended for the enrichment of samples with low concentration of phenols (0.5 mu g l(-1)). For more concentrated samples (10 mu g l( -1)), the use of C-18 cartridges was preferred because smaller solvent and sample volumes were used and the analysis time was reduced.