o-Dianisidine: a new reagent for selective spectrophotometric, flow injection determination of chlorine

A flow injection analysis (FIA) procedure for the determination of free chl orine in industrial formulations and water samples is proposed. The manifol d is provided with a gas-diffusion unit which permits the removal of interf ering species and also the preconcentration of chlorine. The determination of chlorine is performed on the basis of the oxidation by o-dianisidine as a chromogenic reagent to a coloured product which can be monitored at 445 n m. The method (for a preconcentration step of 60 s) is linear over the rang e 0.04-1.00 mg l(-1) of chlorine, the limit of detection is 0.04 mg l(-1), the reproducibility of the procedure (as RSD of the slope) is 3.7% for a se ries of four independent calibrations, the precision (as RSD of a series of 30 continuous FIA peaks of 0.56 mg l(-1) of chlorine) is 1.4% and the samp le throughput is 40 h(-1). A detailed comparative study of the analytical c haracteristics of a single mono-channel reverse FIA assembly and the same s ystem but provided with a Fluoropore membrane filter of 0.5 mum pore size w as performed to check the advantages of the new approach in terms of sensit ivity, selectivity and limit of detection.