DETERMINATION OF LEAD IN INDIUM METAL AND INDIUM SALTS BY ANODIC-STRIPPING VOLTAMMETRY WITH ADDITION OF SURFACTANT TO SUPPRESS THE INDIUM PEAK

The determination of trace lead in indium and indium salts by d.c. anodic stripping voltammetry without preliminary separation is described. The electrochemical activity of indium, which usually interferes in the determination of lead, is inhibited by using Sulforokanol L-3 (oxyethylated lauryl alcohol sodium sulphate salt) as a surfactant. In 0.5 M tartrate solution at pH 4.4 as a supporting electrolyte without the surfactant present, trace levels of lead (1 x 10(-8) M) can be determined accurately if the molar ratio of indium to lead is not higher than 3, but if the electrolyte also contains 0.1% Sulforokanol L-3, indium can be tolerated at concentrations up to 0.05 M and the height of the lead peak is unaffected. It is therefore possible to determine 1 x 10(-8) M Pb(II) in the presence of 0.05 M In(III), i.e., lead at the 3.6 x 10(-5)% level in indium. The accuracy and precision of the determination are satisfactory (relative standard deviation 2.4-8.8%). Lead has been determined in indium metal and indium salts of various degrees of purity.