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 μg ml−1 and the detection limit was 0.027 μg ml−1 (s/n = 3). The relative standard deviation of the proposed method calculated from 12 replicate injections of 4.0 and 8.0 μg 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.