Flow injection spectrophotometric determination of lead using 1,5-diphenylthiocarbazone in aqueous micellar

A simple flow injection colorimetric procedure for determining lead was established. It is based on the reaction of lead in sulfuric acid with 1,5-diphenylthiocarbazone and sodium dodecyl sulfate, resulting in an intense red-blue complex with a suitable absorption at 500 nm. A standard or sample solution was injected into the sulfuric acid stream (flow rate of 2.0 ml min(-1)), which was then merged with sodium dodecyl sulfate stream (flow rate of 2.0 ml min(-1)) and 1,5-diphenylthiocarbazone stream (flow rate of 1.5 ml min(-1)). Optimum conditions for determining lead were investigated by univariate method. Under the optimum conditions, a linear calibration graph was obtained over the range 1.0-12.0 microg ml(-1) and the detection limit was 0.027 microg ml(-1) (s/n=3). The relative standard deviation of the proposed method calculated from 12 replicate injections of 4.0 and 8.0 microg ml(-1) of lead was 0.42% and 0.38%, respectively. The sample throughput was 80 h(-1). The proposed method has been satisfactorily applied to the determination of lead in water samples.