Determination of Tributyltin and Triphenyltin Fungicides in Synthetic Resin Emulsion Paints

Abstract

A method is described for the determination of tributyltin and triphenyltin fungicides in synthetic resin emulsion paints by flameless atomic absorption spectrophotometry and two-dimensional thin-layer chromatography (TLC). Tributyltin and triphenyltin compounds can be extracted from paints with methanol containing 1.7% of hydrogen chloride. The methanol extract is diluted to 4-fold volume with phosphate-citrate buffer solution (pH 2.0), and both tributyltin and triphenyltin are extracted with hexane. Hexane is carefully evaporated, and the residue is re-dissolved in dichloromethane. This solution is passed through an alumina column to remove dibutyltin and diphenyltin compounds which might disturb the determination of tributyltin and triphenyltin. After evaporation of dichloromethane from the eluate, the residue is heated with concentrated nitric acid and its tin concentration is determined by flameless atomic absorption spectrophotometry. Detection limit as metal tin is 0.2 μg/g. Average recovery (five experiments) from 1 g of the paint added with 10 μg of tributyltin or triphenyltin, was in the range of 87.1-90.1% (tributyltin) and 74.7-82.1% (triphenyltin), depending on the type of the paint. The presence of tributyltin or triphenyltin in the paint is confirmed by two-dimensional TLC, using dichloromethane and hexane-acetone-acetic acid (16 : 3.5 : 0.5) as developing solvents and 0.1% dithizone solution in acetone as a spraying reagent. Tributyltin and triphenyltin compounds in 14 commercial emulsion paints were determined.