Method validation of an inductively coupled plasma mass spectrometry (ICP-MS) assay for the analysis of magnesium, copper and zinc in red blood cells

Background: Laboratory measurements of trace elements such as magnesium (Mg), copper (Cu), and zinc (Zn) in red blood cells (RBCs) are essential for assessing nutritional status and diagnosing metal toxicity. The purpose of this study was to develop and validate an ICP-MS method for quantifying these elements in RBCs. Methods: Packed RBCs were aliquoted and diluted in an alkaline diluent solution containing internal standards, 0.1 % Triton X-100, 0.1 % EDTA, and 1 % ammonium hydroxide. The resulting diluted specimen was analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to quantitatively determine the levels of Mg, Cu, and Zn. The method underwent validation for accuracy, precision, method comparison, linearity, analytical sensitivity, and carryover. Additionally, retrospective data were analyzed, and non-parametric reference intervals were calculated. Results: Accuracy and linearity fell within the expected range of <+/- 15 % for all analytes. Within-run, betweenrun, and total imprecision were <15 % coefficient of variation. All other validation experiments met the established acceptance criteria. Retrospective data analysis was conducted on patient samples using the method. The application of Tukey's HSD test for multiple comparisons revealed statistically significant mean differences (p < 0.05) in Mg, Cu, and Zn concentrations between all pairwise groups of age and sex, except for the mean Cu concentration in adult males versus females and the mean Mg concentrations in adult versus minor males. Conclusions: The presented method was successfully validated and met the criteria for clinical use. Retrospective data analysis of patient results demonstrated the method's suitability for assessing nutritional deficiency and toxicity.