Determination of tributyltin in marine sediment:: Comite Consultatif pour la Quantite de Matiere (CCQM) pilot study P-18 international intercomparison

The capabilities of National Metrology Institutes (NMIs-those which are members of the Comite Consultatif pour la Quantite de Matiere (CCQM)of the CIPM) and selected outside 'expert' laboratories to quantitate (C4H9)(3)Sn+ (TBT) in a prepared marine sediment were assessed. This exercise was sanctioned by the 7th CCQM meeting, April 4-6, 2001, as an activity of the Inorganic Analysis Working Group and was jointly piloted by the Institute for National Measurement Standards of the National Research Council of Canada (NRC) and the Laboratory of the Government Chemist (LGC), UK. A total of 11 laboratories submitted results (7 NMIs, and 4 external labs). Two external laboratories utilized a standard calibration approach based on a natural abundance TBT standard, whereas all NMIs relied upon isotope dilution mass spectrometry for quantitation. For this purpose, a species specific Sn-117-enriched TBT standard was supplied by the LGC. No sample preparation methodology was prescribed by the piloting laboratories and, by 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 (with GC and HPLC sample introduction), GC-MS, GC-AED and GC-FPD. Recovery of TBT from a control standard (NRCC CRM PACS-2 marine sediment) averaged 93.5+/-2.4% (n=14). Results for the pilot material averaged 0.680+/-0.015 mumol kg(-1) (n=14; 80.7+/-1.8 mug kg(-1)) with a median value of 0.676 mumol kg(-1). Overall, performance was substantially better than state-of-the-art expectations and the satisfactory agreement amongst participants permitted scheduling of a follow-up Key comparison for TBT (K-28), a Pilot intercomparison for DBT (P-43), and certification of the test sediment for TBT content and its release as a new Certified Reference Material (HIPA-1) with a TBT content of 0.679+/-0.089 mumol kg(-1) (expanded uncertainty, k=2, as Sn) (80.5+/-10.6 mug kg(-1)).