Second harmonic a.c. anodic stripping voltammetry of metals at trace level: simultaneous determination of lead and thallium, and bismuth and antimony

Pairs of elements with very small differences in their half-wave potentials were determined at trace levels by second harmonic a.c. anodic stripping voltammetry. The simultaneous determination of lead and thallium as well as that of bismuth and antimony in 1M hydrochloric acid as supporting electrolyte was found to be possible in the range of concentration ratios: 7:1 > or = C(Pb):C(Tl) > or = 1:36 and 45:1 > or = C(Sb):C(Bi) > or = 1:35, with <5 % relative error due to mutual interference. The limit of detection was approximately 10(-8)M for all four elements, and the precision and error were 2-3%. The simultaneous determination of these metals in mixtures with concentration ratios outside the quoted ranges is still feasible by the standard-addition technique.