Determination of “Heavy” Organotin Pollution of Water and Shellfish by a Modified Hydride Atomic Absorption Procedure

Abstract

Tin speciation in aquatic environment is very complex. To the natural Sn^IV and methylated compounds, human activities add mainly butylated, octylated, phenylated or even methylated derivatives. The most environmentally significant, due to their high toxicity and direct introduction in water through biocidal use, are the trisubstituted ones. Several sophisticated speciation procedures have been proposed, they are not susceptible of common use. We propose a simple and fast procedure allowing routine global distinction of “heavy” tin species that are most susceptible of exerting harmful effects. This AA method use the differences in volatility of stannanes generated by reduction with NaBH₄. Sn^IV and the methylated species have very close response coefficients whereas “heavy” compounds respond very slightly at room temperature and are eliminated in a -40°C cold trap. “Heavy” tin determination in water is thus obtained by the difference between two hydride AA experiments, one performed on the untreated sample (“light tin”) and the other on a UV mineralised subsample (total tin). (The mineralisation of organotins is realised by UV irradiation–2 hours–in a quartz container–yields 95–100%.) The analysis of shellfish tissue relies also on two experiments. Total tin is measured on a mineralised sample and “light tin” is obtained on a subsample “solubilised” with an Ultra Turrax homogeneizer in a diluted HCl solution.