Abstract—
Capillary zone electrophoresis (CZE) was employed to quantify major cations (K+, Na+, Ca2+, Mg2+) and anions (Cl−, \({\text{SO}}_{4}^{{2 - }}\) , \({\text{PO}}_{4}^{{3 - }}\) , lactate, citrate) in blood serum samples obtained from 40 healthy donors aged from 20 to 85 years. Ammonium concentration (µmol/L) was additionally measured in capillary blood, as this cation was not reliably detectable in deproteinized serum using CZE due to its methodological limitations. Statistical analysis revealed sex-based differences only for ammonium (p = 0.001), with higher levels observed in men compared to women (median 97.5 µmol/L vs. 89 µmol/L, respectively). Statistically significant age-related differences were observed for phosphate (p = 0.04), ionized calcium (p = 0.008), as well as Na/K (p = 0.01) and Mg/Ca (p = 0.003) ratios. Ionized calcium levels in older donors (65–85 years) were lower than in younger groups and fell below reference ranges. Lactate concentrations in young and middle-aged donors slightly exceeded literature reference values. This study established reference intervals in blood serum for all the analytes studied, including sulfate and citrate ions, for which there is almost no information in the literature about the normal concentrations of these ions. Correlation analysis revealed statistically significant positive correlations between chloride and lactate, potassium and sodium, chloride and sulfate, and magnesium and ionized calcium in serum (p < 0.05). These results support the applicability of CZE for ion determination in blood serum and provide valuable reference data for clinical practice.
