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 analytical chemistry community. This paper describes an attempt to obtain an SI-traceable value for the Cu concentration in the Candidate Reference Material MURST-ISS A1 Antarctic Sediment. This material was collected by the Institute Superiore di Sanita (ISS, Rome, Italy) and was processed at the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) into a homogeneous and dried powder. The analytical method used was isotope dilution (ID) combined with inductively coupled plasma mass spectrometry (ICP-MS). Microwave pressurised digestion and separation of Cu by ion-exchange chromatography were used. The International Vocabulary of Basic and General Terms in Metrology (VIM) definition of traceability requires 'stated uncertainties'. Because a primary method of measurement (ID) is used, an attempt was made to make these 'stated uncertainties' as detailed as possible, thereby using the International Organisation for Standardization (ISO)/Bureau International des Poids et Measures (BIPM) guide and taking into account all possible sources of uncertainty (Type A and Type B). The established value for the Co concentration is 86.7 nmol g(-1) with an expanded uncertainty of 4.9 nmol g(-1) (coverage factor k=2).