A Simple Method for the Speciation of Organotin Compounds in Water Samples Using Ethylation and GC-QFAAS

 A simple method for the extraction of organotin compounds from water samples was developed in which both the instrumental parameters and the extraction/derivatization step were optimized. Organotin compounds (butyl-, phenyl- and octyl-) in tap water samples were ethylated with the addition of 2.5 ml of 0.4% w/v NaBEt₄ at pH 5.00 and subsequently extracted two times, for 10 min, with 3 and 2 ml of hexane. The combined extracts were analyzed with on-column capillary GC-QFAAS. The recoveries were quantitative for di- and tri- alkyltin compounds, whereas between 67 and 86% of the monoalkyltin compounds were recovered. The detection limits obtained ranged from 110 pg for monobutyltin to 500 pg for triphenyltin, as sensitivities were found to be compound dependent. The preparation of ethylated standards was also optimized. It was found that two subsequent extractions, with 1.0 and 0.5 ml of hexane were necessary for the quantitative recovery of the ethylated organotin compounds.