ESTABLISHING AN SI-TRACEABLE COPPER CONCENTRATION IN THE CANDIDATE REFERENCE MATERIAL MURST ISS A1 ANTARCTIC SEDIMENT USING ISOTOPE-DILUTION APPLIED AS A PRIMARY METHOD OF MEASUREMENT

Traceability is a term that is heavily debated world-wide in the analy tical chemistry community. This paper describes an attempt to obtain a n SI-traceable value for the Cu concentration in the Candidate Referen ce Material MURST-ISS A1 Antarctic Sediment. This material was collect ed by the Institute Superiore di Sanita (ISS, Rome, Italy) and was pro cessed at the Institute for Reference Materials and Measurements (IRMM , Geel, Belgium) into a homogeneous and dried powder. The analytical m ethod used was isotope dilution (ID) combined with inductively coupled plasma mass spectrometry (ICP-MS). Microwave pressurised digestion an d separation of Cu by ion-exchange chromatography were used. The Inter national Vocabulary of Basic and General Terms in Metrology (VIM) defi nition of traceability requires 'stated uncertainties'. Because a prim ary method of measurement (ID) is used, an attempt was made to make th ese 'stated uncertainties' as detailed as possible, thereby using the International Organisation for Standardization (ISO)/Bureau Internatio nal des Poids et Measures (BIPM) guide and taking into account all pos sible sources of uncertainty (Type A and Type B). The established valu e for the Co concentration is 86.7 nmol g(-1) with an expanded uncerta inty of 4.9 nmol g(-1) (coverage factor k=2).