Determination of Butyltin Compounds in Aqueous Samples by Gas Chromatography with Flame Photometric Detector and Headspace Solid-Phase Microextraction after in-situ Hydride Derivatization

A method for the extraction and determination of butyltin species in aqueous samples by solid-phase microextraction (SPME) combined with a capillary gas chromatography—flame photometric detector (GC-FPD) is described. The butyltin species was converted to its hydride form by sodium tetrahydroborate (NaBH4) in a closed headspace vial prior to extraction. A laboratory-assembled SPME device including a fused-silica fiber and a modified microsyringe protection part was used throughout the experiment. The extraction was an equilibrium process that depended on the butyltin species partitioning between the liquid phase and the fiber. When the equilibrium was reached, the fiber was directly transferred to a GC column under the protection of a microsyringe, where the analyte was thermally desorbed inside the heated injector and subsequently, separated in a HP-1 capillary column and detected by a laboratory-made flame photometric detector using quartz surface-induced tin emission. The detection limits based on the signal equal to 3 times of the base-line noise were 0.2 ¼g/L, 0.2 ¼g/L, 0.1 ¼g/L and 0.02 ¼g/L for monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT) and tetrabutyltin (TeBT), respectively. The recovery ranged from 85% to 117%. The proposed method has been applied to determination of butyltin species in various aqueous samples.