Acid leaching solvent extraction treatment of sediment samples for organotin speciation

A method is described for leaching of nanogram amounts of monobutylin (MBT), dibutyltin (DBT) and tributyltin (TBT) and monophenyltin (MPT), diphenyltin (DPT) and triphenyltin (TPT) from sediments. The procedure is based on soaking the sediments in water-hydrogen bromide mixture (1:1) with magnetic stirring for 30 min followed by extraction with 0.04% (w/v) tropolone solution in dichloromethane for 2 h. Organotins are determined by gas chromatography with a flame photometric detector (GC-FPD) after cleanup through a Florisil column and derivatization by Grignard pentylation. The method has been applied to the study of water and sediments in different areas of the south-west Spain. Predominant species are butyltins, especially TBT which rise critical levels in waters and sediments of fishering harbours. In this study it has been found a direct relation between organotin levels and distance to potential sources determined by boating activities. In addition, it has been verified the relative occurrence of DBT and MBT together with TBT, possibly as a result of a degradation process, and the influence of sediment grain size and organic matter content on organotins accumulation.