Gas-chromatographic speciation of methylstannanes in the Chesapeake Bay using purge and trap sampling with a tin-selective detector

Abstract

A method was developed permitting detection and speciation of both volatile and non-volatile organotin compounds in aqueous media. The method employed a commercial gas chromatograph (GC) with a flame photometric detector (FPD) optimized for tin-selective detection. Solvated organotins were volatilized with sodium borohydride during the purge cycle of a commercial automatic purge and trap sampler (P/T). Purged volatiles and species volatilized by hydridization were concentrated on a Tenax-GC filled trap at ambient temperature. Tetramethyltin (Me4SN) present in the sample is unaffected by the reduction process. The P/T-GC-FPD method was used to analyze water samples collected from the Chesapeake Bay and Baltimore Harbor. Varying amounts of methyltin compounds, including tetramethyltin and methyltin hydrides, were detected in polluted sites in Baltimore Harbor. In vitro studies using GC-MS confirmed earlier reports of microbial methylation of inorganic Sn(IV) by a strain of Pseudomonas species isolated from the Chesapeake Bay. Consequently, biogenic origins are suspected for the methylstannanes (Me(n)SnH(4-n) n = 2,3) found in the Chesapeake Bay. (Author)