On-line preconcentration for the ion chromatographic determination of chlorophenolic and phenolic compounds in environmental samples using electrochemical detection

An on-line preconcentration technique based on 5 ml sample or standard solution injection onto a preconcentration column has been developed for the ion chromatographic (IC) determination of 14 chlorophenolic and phenolic compounds at the picomolar levels. A suitable gradient program using 10 mM sulphuric acid and variable concentrations of acetonitrile (36¯65% (v/v), details given) was applied at the constant flow rate of 1.0 ml min-1. For the detection of 14 phenolic compounds, dc amperometric detection with a glassy carbon working electrode at the potential of +1.2 V versus Ag/AgCl reference electrode was used. The overall repeatability (n=5) for retention times was better than 0.6% and the repeatability (n=5) for the peak areas ranged from 0.5% (resorcinol) to 3.2% (3,5-dichlorophenol) at 50¯ 250 nM concentration levels. LODs (3 S/N) of 200¯500 pM except for 2,6- and 3,5dichlorophenol and 2,3,5,6-tetrachlorophenol (1, 5 and 1 nM, respectively) were obtained. The method has been applied to determine some of the decomposition products of UVirradiated fungicide tecnazene (1,2,4,5-tetrachloro-3-nitrobenzene) solution and phenolic pollutants in drinking water. Due to the high selectivity of the amperometric detection, the only compounds that can be determined are the ones that can be oxidised and therefore possible interferences (e.g. from nitro-compounds) are bypassed.