Automated headspace-solid-phase micro extraction-retention time locked-isotope dilution gas chromatography-mass spectrometry for the analysis of organotin compounds in water and sediment samples

An automated method for the simultaneous determination of six important organotin compounds namely monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), diphenyltin (DPhT) and triphenyltin (TPhT) in water and sediment samples is described. The method is based on derivatization with sodium tetraethylborate followed by automated headspace-solid-phase micro extraction (SPME) combined with GC-MS under retention time locked (RTL) conditions. Home-synthesized deuterated organotin analogues were used as internal standards. Two high abundant fragment ions corresponding to the main tin isotopes Sn118 and Sn120 were chosen; one for quantification and one as qualifier ion. The method was validated and excellent figures of merit were obtained. Limits of quantification (LOQs) are from 1.3 to 15 ng l−1 (ppt) for water samples and from 1.0 to 6.3 μg kg−1 (ppb) for sediment samples. Accuracy for sediment samples was tested on spiked real-life sediment samples and on a reference PACS-2 marine harbor sediment. The developed method was used in a case-study at the harbor of Antwerp where sediment samples in different areas were taken and subsequently screened for TBT contamination. Concentrations ranged from 15 μg kg−1 in the port of Antwerp up to 43 mg kg−1 near a ship repair unit.