Voltammetric determination of thallium(I) at a mechanically renewed Bi-graphite electrode

A composite of high-purity grade carbon powder and an epoxy resin is used to in situ obtain a bismuth-film electrode. The surface of the indicator electrode is renewed by cutting a thin surface layer before each determination. The in situ obtained Bi-film electrode is virtually no different from an Hg-film electrode in sensitivity, reproducibility, and the ability to separate signals from Tl, Cd, and Pb. The calibration graph is linear in the range of thallium concentrations from 0.01 to 1 mg/L (RSD varies from 4 to 2%). A significant excess of Pb(II), Sn(II), and Cd(II) does not interfere with the determination of thallium. A procedure for determining down to 5 × 10^?6% thallium in lithium carbonate is developed.