Speciation analysis was performed by using a leaching procedure followed by Grignard derivatization and GC-FPD detection for cork samples and by hydride generation, SPME and GC-FPD for wine samples. Measurable concentrations of MBT, DBT and TBT were found in agglomerated cork stoppers but not in one-piece corks. It was shown that measurable amounts of butyltins are released from contaminated stoppers into the wine during bottle storage. The highest concentrations of butyltin compounds found in cork samples reached 13.1 µg Sn/g for MBT and 7.4 µg Sn/g for DBT. The highest concentrations in contaminated wine reached 5.7 µg of Sn/L for MBT, 33.2 µg Sn/L for DBT, and 13.6 µg Sn/L for TBT. Since some liquor samples and some wine samples with metallic caps also contained measurable amounts of organotin compounds, other potential contamination sources have to be taken into account.

Michael Sperling

Original publication:

Gui-Bin Jiang, Ji-Yan Liu, Qun-Fang Zhou, "Search for the Contamination Source of Butyltin Compounds in Wine: Agglomerated Cork Stoppers", Environ. Sci. Technol., 38/16 (2004) 4349-4352.

Many corks undergo microbiological and chemical changes which impair the quality - or even the safety - of wines and spirits, with the danger that natural cork could be progressively replaced by synthetic substitutes. Whether butyltin compounds have been added intentionally to avoid microbial activity or were accidentially brought in is not yet clear. Anyhow, a European research project has patented an innovative new process which looks set to remove such and other threats. The partners therefore studied a new production method which is free of any unwanted ecological, toxic or sensory effects. It was found, that by initially exposing all the raw materials to microwaves effectively kills the micro-organisms. Better still, it substantially reduces chemical contamination.

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