Determination of major inorganic ions in blood serum and urine by capillary electrophoresis with contactless conductivity detection

Potassium, sodium, calcium, and magnesium cations as well as the chloride anion were determined in human serum samples and the same species plus ammonium, nitrate and sulfate ions were also successfully measured in urine. The high molar excess of sodium and chloride in these samples required the optimization of the buffer solutions. Complete separation of all ions was achieved in 6.5 mM maleic acid/7.5 mM L-arginine and in 13 mM maleic acid/15 mM L-arginine at pH 5.5 for the determination of cations and anions, respectively. The quantitative results achieved by capillary electrophoresis with contactless conductivity detection were compared with reference values obtained by standard methods and a good correlation was found between these results. The inclusion of internal standards assured a precision of better than 1% in all cases.