AUTOMATED ONLINE TRACE ENRICHMENT AND DETERMINATION OF PHENOLIC-COMPOUNDS IN ENVIRONMENTAL WATERS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Automated trace enrichment of phenolic compounds on a 10 x 2.0 mm I.D. precolumn packed with PLRP-S was coupled on-line with reversed-phase column liquid chromatography and electrochemical detection. Two differ ent eluents were used owing to the different polarities of the phenoli c compounds and the difficulty of combining gradient elution with elec trochemical detection. In the analysis of real samples (tap and river water), each step of the automatic method was optimized taking into ac count the complexity of the matrix. in tap water, the preconcentration of 4-ml samples allowed phenolic compounds to be determined at the ng l(-1) level and the limits of detection (LODs) were between 1 and 10 ng l(-1) (except for 2,4-dinitrophenol and 2-methyl-4,6-dinitrophenol, for which the LODs were 75 and 50 ng l(-1), respectively). When river water was analyzed, only 1 ml of sample could be preconcentrated beca use of humic and fulvic acid interference and the detection limits wer e about four times higher.