INTERLABORATORY STUDIES FOR THE ANALYSIS OF METAL-IONS IN SOLUTION BYISOTOPE-DILUTION ICP-MS

In order to establish international traceability in chemical measureme nts, the Comite Consultatif pour la Quantite de Matiere (CCQM) has sta rted interlaboratory studies involving ICP-MS or thermal ionization MS using isotope dilution mass spectrometry (ID/MS) as the reference met hod for the analysis of simple aqueous solutions containing metal ions . National metrology laboratories participated in these studies. The t arget level of the relative accuracy for measurements was set at +1%. In CCQM's 1st study concerning the analysis of six elements in solutio ns, neither the inherent trueness nor the precision of the ID/MS was a chieved by most of the laboratories. In CCQM's 2nd study for the analy sis of ph in a solution, in which a measurement protocol was designed for the ID/MS method, the results were significantly improved, with mo st participants achieving the target value. The calibration of the mas s bias factor with isotopic standard solutions at regular intervals an d optimization of the amount of a spike solution added to a sample sol ution are important for highly accurate analysis using ID/MS.