Primary Reference Procedure for Measuring the Mass Fraction and Molar Concentration of Copper and Zinc in Biological Materials by Isotope Dilution Mass Spectrometry

This study describes the process of developing a primary reference procedure for measuring the mass fraction and molar concentration of copper and zinc in biological materials by isotope dilution mass spectrometry (ID-ICP-MS). In order to improve the measurement accuracy, optimal conditions for sample preparation and measurement were determined. Uncertainty sources were examined, with each source assessed in terms of its contribution to the uncertainty budget. The measurement range of copper and zinc mass fraction and molar concentration comprised from 1·10–6 to 1.5·10–3% and from 2 to 20 μmol/dm3, respectively. The relative expanded measurement uncertainties of copper mass fraction, zinc mass fraction, copper molar concentration, and zinc molar concentration were found to be equal to 7.1–7.5%, 8.9–9.2%, 8.8%, and 8.6%, respectively. The developed procedure can be used to establish metrological characteristics of reference materials (RMs) for the composition of lyophilized blood serum and reconstituted lyophilized blood serum, to control the accuracy of measurement results obtained using other measurement techniques of similar quantities, and to carry out high-precision measurements of copper and zinc mass fraction and molar concentration for arbitration purposes in lyophilized blood serum and reconstituted lyophilized blood serum.