Spectrophotometric determination of lead in traditional Chinese medicines with dibromop-methyl-acethylsulfonazo

A new highly sensitive and selective chromogenic reagent dibromo-p-methyl-acethylsulfonazo (DBMASA) has been synthesized and purified. A method has been proposed for the spectrophotometric determination of lead with DBMASA in traditional Chinese medicines. The content of lead in the samples was low, so we used sulfhydryl cotton fiber (SCF) to separate and enrich trace Pb(II), which lead to a satisfactory result. In 0.25 M phosphoric acid medium, which greatly increased the selectivity, lead reacted with DBMASA to form a 1: 2 blue complex, having an intense absorption peak at 640 nm. Under the optimal conditions, Beer's law is obeyed over the range 0.01-1.0 A mu g/mL of Pb(II) and the apparent molar absorptivity is 1.06 x 10(5) L/mol cm. The detection limit and variation coefficient are found to be 2.1 ng/mL and 1.3%, respectively. The method has been applied to the determination of lead in traditional Chinese medicines with satisfactory results.