Commonly used methodologies for inorganic analysis in international key comparisons

Abstract

The Consultative Committee for Amount of Substance – Metrology in Chemistry (Comité Consultatif pour la Quantité de Matière, CCQM) has the task of organizing international key comparisons. The main purpose is to establish a technical basis for mutual recognition of measurement capabilities among national measurement institutes (NMIs) in the field of chemical measurement. More importantly, key comparison results provide an effective means of assessing the degree of equivalence of measurement standards used at different NMIs. Since 1998, the Inorganic Analysis Working Group of CCQM has been identifying and organizing key comparisons for the determination of analytes, such as elements, inorganic compounds and organo-metallic compounds in various matrices. Methodologies, including inorganic mass spectrometry [e.g., isotope dilution mass spectrometry (IDMS) and species-specific IDMS], inductively coupled plasma atomic emission spectrometry, neutron activation analysis, ion chromatography, high performance liquid chromatography, X-ray fluorescence spectrometry, flame atomic absorption spectrometry (AAS) and graphite furnace AAS, have provided satisfactory results in terms of accuracy and precision. Complex sample matrices examined so far include inorganic solutions and water (e.g., calibration solutions and natural water), metal and metal alloys (e.g., steel and aluminum alloy), biological fluids, materials and food (e.g., serum, rice, wine, shellfish, salmon fish, tomato and bovine liver), fuels (e.g., diesel), sediments and soils (e.g., sediments and sewage sludge). The use of IDMS for elemental analysis has attracted considerable attention. In this review, we focus on commonly used methodologies for inorganic analysis in CCQM key comparisons between 1998 and 2007, and we suggest potential areas for strategic research and development.