Simultaneous determination of mono-, di-, and tributyltin in sediments by isotope dilution analysis using gas chromatograpby-ICPMS

A mixed spike containing Sn-119-enriched monobutyltin (MRT), dibutyltin (DBT), and tributyltin (TBT) was prepared by direct butylation of Sn-119-enriched tin metal using a 1:3 molar excess of butyl chloride with iodide and triethylamine as catalysts. The isotopic composition of the different tin species in the spike solution was determined by gas chromatography-ICPMS after aqueous ethylation using sodium tetraethylborate. Reverse isotope dilution analysis was used for the characterization of the spike by means of natural MET, DBT, and TBT standards. No species transformation was evident during derivatization from the reverse isotope dilution experiments based on the measured isotope ratios both before and after spiking. The mixed spike was applied to the simultaneous analysis of MET, DBT, and TBT in certified reference materials, PACS-2 and CRM 646, with satisfactory results.