Solid phase microextraction (SPME): a new procedure for the control of butyl- and phenyltin pollution in the environment by GC-FPD

Abstract

A new alternative to liquid–liquid extraction for the speciation of organotin compounds is proposed using NaBEt₄ ethylation–simultaneous solid phase microextraction (SPME)–GC-FPD. SPME is carried out using a polydimethylsiloxane (PDMS) fibre immersed in 100 ml of solution for an adsorption time of 60 min. The optimisation step confirms the importance of stirring the solution. The higher efficiency of mechanical stirring is also clearly demonstrated. Under these conditions, SPME was applied for the first time to the simultaneous extraction of butyl- and phenyltins and the analytical performances were evaluated. Very low detection limits were reached, in the range 0.006–0.031 ng Sn l⁻¹ for butyltins and 0.2–0.6 ng Sn l⁻¹ for phenyltins. The repeatability is also improved compared with classical liquid–liquid extraction thanks to the small volume of the fibre and the on-line procedure (between 3 and 9% except for triphenyltin). The new method was applied to various environmental samples such as natural aqueous samples, sediment and sewage sludge. The competitive extractions between some organotins and organic matter present in complex matrices are discussed.