Assessment of transport routes of triphenyltin used in potato culture in the Netherlands

Abstract

Organotin compounds (OTs) were analyzed after derivatization using a methyl Grignard reagent with gas chromatography with ion trap detection (GC-ITD) for detection. GC-ITD allows full scan mass spectrometry at trace levels and thus allows good verification of the presence of the OTs. With the described methods all currently used OT biocides can be determined in water, sediment and suspended matter: tributyltin (TBT), triphenyltin (TPT), tricyclohexyltin (TCT) and fenbutatin oxide (hexakis-(2-methyl-2-phenylpropyl)-distannoxane, FBTO). Additionally in water also some degradation products of the above mentioned biocides can be determined: dibutyltin (DBT), monobutyltin (MBT), diphenyltin (DPT), monophenyltin (MPT) and dicyclohexyltin (DCT). Detection limits are 1–40 ng/l (as tin) for water samples and 2–10 ng/g (as tin) for suspended matter and sediment samples. Transport routes of triphenyltin acetate (TPT) used in potato culture in the Flevoland polder in the Netherlands were studied. TPT levels were detected in freshwater and suspended matter and the sorption coefficient ( K d) was calculated. On the basis of concentrations in water and suspended matter it was calculated that only a negligible portion of TPT used is pumped out of the polder by the pumping-engines. Evaporation of TPT is probably a much more important transport route. Therefore a first attempt was made to investigate concentration of OTs in rainwater. The results show that at distances of over 20 km from potato fields, TPT in rainwater is around the proposed general quality objective for freshwater of 10 ng/l (as tin). These observations support the modelling study by Baart and Diederen, indicating that evaporation of TPT is one of the transport routes of TPT.