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

The establishment and control of the metrological characteristics of the determination of trace elements in biological materials is an urgent task due to the wide application of these measurements in medical laboratory diagnostics. In the course of the research, 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 is presented. The optimal conditions for sample preparation and measurements by isotope dilution and mass spectrometry with inductively coupled plasma are determined in order to increase the accuracy. The sources of uncertainty are studied; the contribution of each source to the uncertainty budget is estimated. During the certification of the developed measurement procedure, the following metrological characteristics were determined: the measurement range of the mass fraction of copper and zinc is from 1 ∙ 10–6 to 1,5 ∙ 10–3 %, the measurement range of the molar concentration of copper and zinc is from 2 to 20 µmol/dm3, the relative expanded measurement uncertainty of the mass fraction of copper is (7.1–7.5) %, the relative expanded uncertainty of the mass fraction of zinc is (8.9–9.2) %, the relative expanded uncertainty of the molar concentration of copper is 8.8 %, the relative expanded uncertainty of the molar concentration of zinc is 8.6 %.The developed procedure is intended to establish the metrological characteristics of reference materials for the composition of lyophilized blood serum and reconstituted lyophilized blood serum, control the accuracy of the measurement results obtained using other procedures (methods) of measuring similar values, perform high-precision measurements of mass fractions and molar concentrations of copper and zinc in lyophilized blood serum and reconstituted lyophilized blood serum for referee purposes.