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Anodic stripping voltammetry: sn and pb analysis in archaeometallurgical samples

In most electrolytes the peak potentials of tin and lead are so close together that a voltammetric determination is impossible. Difficulties occur especially if one of the metals is present in excess. The simultaneous anodic stripping voltammetric analyses of lead and tin in ancient archaeometallurgical samples have been studied. Two different electrolytes were used; cetyltrimethylammonium bromide in a mixture of citrate and oxalate buffer, and methylene blue in oxalate buffer. Cetyltrimethylammonium bromide was found to be unsuitable for the determination of tin; the tin peak was asymmetric and often split. Methylene blue was studied at pH values of 1.35, 1.60, 1.80, 2.00, 2.68, 3.00 and 3.15. Differential pulse voltammograms were obtained between −800 mV and −250 mV. It was concluded that as pH was increased the corresponding half-wave potentials, E 1/2, for tin and lead were shifted to more negative values and the sensitivity of the simultaneous determination of tin and lead was decreased. However, tin and lead concentrations could be determined simultaneously in oxalate buffer and in the presence of methylene blue at about pH 1.6.