Determination of phenolic compounds in water samples by on-line solid-phase extraction - Supercritical-fluid chromatography with diode-array detection

The eleven Environmental Protection Agency (EPA) priority phenolic compounds have been determined by solid-phase extraction (SPE) coupled on-line to supercritical-fluid chromatography (SFC) with diodearray detection. The variables affecting chromatographic separation were optimized 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 studied were separated to baseline in less than 13 min. PLRP-S and LiChrolut EN were tested as sorbents in a 10 x 3 mm i.d. laboratory-packed precolumn for solid-phase extraction. An ion-pair reagent, tetrabutylammonium bromide (TEA), was used in the extraction process to increase break-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 PLRP-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 real samples spiked at 10 mu g L-1 were lower than 10 %.