OFF-LINE AND ONLINE SOLID-PHASE EXTRACTION FOLLOWED BY LIQUID-CHROMATOGRAPHY FOR THE DETERMINATION OF PRIORITY PHENOLS IN NATURAL-WATERS

Two analytical methods have been developed for the determination in wa ter of 18 priority phenolics listed in US EPA method 604 and on EEC li st 76/464. A solid-phase extraction system using eight different sorbe nts packed in a precolumn was coupled on-line with a liquid chromatogr aph with UV detection. The ensuing method uses 50-100 mL of ground wat er; its performance was compared with that of an off-line method using Empore extraction disks and 1 L water samples. Phenol recoveries vari ed from < 20 to 100% for concentrations in the range 0.1-10 mu g/L at an acid pH. The presence of the phenols in water was confirmed by usin g thermospray LC-mass spectrometry in the negative ion mode. The stabi lity of the phenols in water was studied at a 10 mu g/l level in groun d and estuarine water at acid pH (2.5-3) and at 4 degrees C for 1 mont h. The system was validated by various interlaboratory exercises with samples containing 2,4,6-trichlorophenol and pentachlorophenol at conc entrations from 0.1 to 0.5 mu g/L.