Selective on-line immunoextraction coupled to liquid chromatography for the trace determination of benzidine, congeners and related azo dyes in surface water and industrial effluents.

A new extraction immunosorbent involving antigen-antibody interactions was coupled on-line to liquid chromatography for the selective extraction in aqueous samples of benzidine and congeners, widely used as intermediate compounds in the manufacturing of dyes and pigments. Due to the cross-reactivity of the antibodies for analytes with chemical structures closely related to that of the analyte used for immunization, the immunoextraction sorbent was shown to be able to extract aminoazobenzene and related azo dyes with good recoveries. The on-line coupling was optimized for the trace determination of benzidine, dichlorobenzidine, aminoazobenzene and some azo dyes with detection limits in the range 0.1 to 1 microgram/l. The high selectivity of the immunoextraction was shown by comparing the analysis of an industrial textile effluent obtained using precolumns packed either with a non-selective polymeric sorbent or with the anti-benzidine immunosorbent. In such complex samples, extraction and clean-up are achieved in the same step.