The likelihood of sources of error in the determination of TBT was well illustrated in the present interlaboratory study. The first intention was to certify TBT in this candidate reference material of harbour sediment but the high discrepancies in the results did not encourage the Measurements and Testing Programme to recommend this material as CRM. This material contains high amounts of organic matter (total organic carbon content of ca. 40 mg/g) and a very low TBT mass fraction. The techniques involving derivatization and AAS as final detection experienced great analytical difficulties. It was considered that these techniques, in particular involving hydride generation, could not be used for the analysis of this complicated matrix at such mass fraction level. This RM represents an extreme case and should therefore be reserved for laboratories using techniques such as GC/FPD or GC/MS for the evaluation of the performances of difficult analyses.
The group of experts participating in this interlaboratory study recognised that this material will be very useful as a research material providing that sufficient care is taken in the interpretation of results, i.e. keeping in mind that this materials is not certified.
Whereas inorganic tin species such as Sn(II) chloride, oxide or sulphate do not seem to be toxic or cancerogenic, organotin species are highly toxic. Of all organic tin species the tri-aryl compounds are most dangerous. TBT is mainly used in antifouling paints, wood preserving fungicides, desinfectants and molluscicides, whereas TBT plays a role in agriculture, (e.g. fungicides), other organotin species (e.g. dialkyl compounds) are used as stabiliser for PVC, industrial catalysts or precursors for SnO2-films or glass. The production worldwide of organotin compounds was some 35 000 tons in 1980 of which 8 000 tons were triorganotin compounds for biocidal use; 3 000 tons were produced for antifouling paints, 1 000 tons for wood preservatives, 3 000 tons for agrochemicals and 1 000 tons for disinfectants. Especially the application of TBT in antifouling paints has caused concern. Ship hulls with a TBT containing paint will not be covered under water by mussels and sea weed and therefore allow faster sailing. Also fishing nets have been treated with TBT. However, the TBT leached from the paint by water acts as a strong poison to larvae of oysters, mussels and fish. Therefore France and the UK have already legislation on the use of TBT in ship paints, Ireland announced in April 1987 that legislation on the use of organotins as antifouling agents would be banned. The objective of the project is essentially to develop, through collaborative work of expert laboratories, the methodology to obtain accurate results in the determination of the most important organic tin compounds. It is also intended to certify sediment and mussel samples.
Second intercomparison concluded. Certification of TBT in CRM 424 (harbour sediment) to be concluded by June 1992. Certification of butyltins in coastal sediment (candidate CRM 462) to be concluded by the end of 1992. Certification of organotins in mussel (candidate CRM 477) to be concluded by the end of 1993.
Funding SchemeCSC - Cost-sharing contracts
UB8 3PJ Uxbridge