Abstract. The pilot study CCQM P43 was undertaken to allow the assessment of the current capabilities of interested National Metrology Institutes (NIMs) (those which are members of the CCQM) and selected outside 'expert' laboratories for quantification of (C₄H₉)₂Sn⁺ (DBT) and (C₄H₉)₃Sn⁺ (TBT) in a prepared marine sediment. It was organised in parallel to the key comparison CCQM-K28, in which only NMIs determined TBT.

This exercise was sanctioned by the 8^th CCQM meeting, 18–19 April 2002, as an activity of the Inorganic Analysis Working Group and was jointly coordinated by the Institute for National Measurement Standards of the National Research Council of Canada (NRC) and LGC, UK.

A total of 13 laboratories initially indicated interest (nine NMIs and four external laboratories). Only one external laboratory utilised a standard calibration approach based on natural abundance TBT and DBT standards, whereas all NMIs relied on isotope dilution mass spectrometry for quantitation (one NMI used ID-MS and an internal standard approach for the analysis of DBT). For this purpose, species specific ¹¹⁷Sn-enriched TBT and DBT standards were supplied by LGC. No sample preparation methodology was prescribed by the coordinating laboratories and, as a consequence, a variety of approaches was adopted by the participants, including mechanical shaking, sonication, accelerated solvent extraction, microwave assisted extraction and heating in combination with Grignard derivatization, ethylation and direct sampling. Detection techniques included ICP-MS (coupled to GC or HPLC), GC-MS and GC-AED.

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The final report has been peer-reviewed and approved for publication by the CCQM.