Improving the measurement of butyltin compounds in environmental samples

Abstract

Tributyltin compounds (TBT) are highly toxic pollutants, mainly introduced to the environment as a marine antifouling agent. The main aim of this work was to evaluate the present methods for the measurement of TBT and its breakdown products dibutyltin and monobutyltin in environmental sediments and waters and to improve upon their measurement. For the analysis of sediments, a triple hexane/acetic acid extraction was employed of tropolone complexes of the organotin compounds. Grignard reagent derivatization and measurements by gas chromatography with pulsed flame photometric detection were then employed. The TBT detection limit of 5 ?g Sn/ kg in sediment was below the UK environmental quality target (EQS) value for TBT in sediment (1-2 mg Sn/kg). A pilot investigation was carried out on a small dockyard in Southampton to evaluate if the total amount of tin could be used to predict the presence of TBT. Due to different sources of tin contamination in the studied area no clear overall correlation of TBT with total tin was found. As part of the investigation into the determination of butyltin in sediment, the extraction of TBT from paint particles deposited in sediment during boat refurbishment and the removal of sulphur interferences were investigated. For the extraction of TBT in paint, a pre-treatment procedure was developed based on pre-treatment with dichloromethane (DCM). This treatment improved the extraction of TBT from the paint, but TBT losses can occur during DCM removal by evaporation. Sulphur interferences were successfully removed from the sediment extract by improving the clean-up procedure. This procedure was based on treatment of the hexane extract with activated copper and then passing the hexane extract through a C18 solid phase extraction column. For the determination of butyltins in water a doubly functionalized mesoporous silica was synthesized and used to extract butyltin compounds from water based on a solid phase dispersion technique. Butyltin chlorides were collected from the water on the surface of the HOC18-nanoscavenger, hexylated using a Grignard reagent and quantified by GC-PFPD. Another approach was based on ethylation of tributylin chloride using NaEt4B followed by extraction of the ethylated species on the HOC18-nanoscavenger. TBT detection limits of 1.5 and 3 ng Sn/ L were achieved using the Grignard and NaEt4B approaches respectively and were regarded satisfactory, as they were below or near to the UK EQS for water ( 2 ng/ L). The Grignard approach was more efficient than the NaEt4B approach, but the latter was more precise

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