AMBERLITE XAD RESIN SOLID-PHASE EXTRACTION COUPLED ONLINE TO A FLOW-INJECTION APPROACH FOR THE RAPID ENRICHMENT AND DETERMINATION OF PHENOLS IN WATER AND WASTE-WATERS

A novel and expeditious approach for direct determination of phenols i n water and waste waters based on solid-phase extraction coupled on-li ne to a flow injection analysis (FIA) manifold is described. The metho d employs on-line preconcentration of the phenols in an acidified samp le (pH = 2.0) onto a 3 cm x 3 mm column packed with Amberlite XAD-4 re sin. The phenols are subsequently eluted from the resin into a flowing system with an alkaline solution (pH = 13) by actuating a switching v alve; the eluted analytes were then quantified spectrophotometrically as the products of reaction with 4-aminoantipyrine (4-AAP) and potassi um ferricyanide on passing through the flow-cell of a detector. The pr oposed method has a linear calibration range 0.01-1 mu g ml(-1) of phe nol, with a detection limit of 0.004 mu g ml(-1) (S/N = 3) and a sampl e throughput of 12 h(-1), investigated with a 4.4 mi sample volume. Th e relative standard deviation is 2.4% for 0.2 mu g ml(-1) of the analy te. The sensitivity offered by the procedure was higher by a factor of 13 than that provided by a conventional flow injection analysis metho d. The analytical scheme of the proposed system is much simpler than i ts conventional manual counterpart due to the fact that it combines tr ace enrichment, sample clean-up, derivation and detection in one analy tical set-up. The high speed, ease of use and automation, selectivity, and relative freedom from random contamination by sample handling mak e this method ideal for the phenols monitoring in water and waste wate rs. (C) 1997 Elsevier Science B.V.