Determination of thallium in the presence of large excess of lead by anodic stripping voltammetry

The paper is concerned with the determination of traces of thallium, as T1(I), in the presence of very large amounts of lead, by d.c. anodic stripping voltammetry, by adding both a complexing agent and anionic surfactant. The supporting complexing agent was 0.1M solution of EDTA (pH 4.4). The influence of the several surfactants on the signals of lead and thallium was investigated.In 0.1M EDTA at pH 4.4 at the absence of a surfactant, lead does not interfere at concentrations below 10^–4M. When the electrolyte contains also an anionic surfactant, lead can be tolerated at concentrations up to 2 × 10^–3–6 × 10^–3M (depending on the type of the surfactant), and the height of the thallium peak remains unaffected. This makes the determination of 10^–8M T1(I) possible when the molar excess of lead is 2–6 × 10⁵ fold. The method has been tested by determining the thallium content of soil extracts.