DETERMINATION OF PHENOLIC-COMPOUNDS IN WATER SAMPLES BY ONLINE SOLID-PHASE EXTRACTION - SUPERCRITICAL-FLUID CHROMATOGRAPHY WITH DIODE-ARRAYDETECTION

The eleven Environmental Protection Agency (EPA) priority phenolic com pounds have been determined by solid-phase extraction (SPE) coupled on -line to supercritical-fluid chromatography (SFC) with diodearray dete ction. The variables affecting chromatographic separation were optimiz ed and the analytes were separated at 40 degrees C in two diol columns connected in series; a gradient of methanol, as modifier, and CO2 was used as mobile phase. Under these conditions, all the compounds studi ed were separated to baseline in less than 13 min. PLRP-S and LiChrolu t EN were tested as sorbents in a 10 x 3 mm i.d. laboratory-packed pre column for solid-phase extraction. An ion-pair reagent, tetrabutylammo nium bromide (TEA), was used in the extraction process to increase bre ak-through volumes. The performance of the method was checked with tap and river waters and the pre-concentration of 20 mL of sample in a PL RP-S pre-column enabled phenolic compounds to be determined at low mu g L-1 levels with limits of detection ranging between 0.4 and 2 mu g L -1, The repeatability and reproducibility between days (n = 3) for rea l samples spiked at 10 mu g L-1 were lower than 10 %.