Electroanalysis for organotin in natural waters including sea-water by cathodic stripping voltammetry

Abstract

A simple procedure was developed to determine total organotin in natural waters including sea-water. The method entails adsorptive cathodic stripping voltammetry of the 2-hydroxycyclohepta-2,4,6-trienone(tropolone) complex of tin for the determination of organotin after its conversion into inorganic tin by ultraviolet irradiation. The method is free from interference by organic surface-active compounds, as these are decomposed during the irradiation stage. The concentration measured has to be corrected for the inorganic tin originally present in the sample by analysis of a sample from which organotin has been removed. Organotins are removed by passing the acidified sample through a C₁₈ column (Sep-Pak), which adsorbs all organotin from the sample, leaving inorganic tin in solution. The limit of detection for total organotin is approximately 10 pmol dm^–3(with a deposition time of 10 min), but this increases with the amount of inorganic tin present in the sample (typically up to 100 pmol dm^–3).