Ion chromatography as potential reference methodology for the determination of total sodium and potassium in human serum.

The potential of ion chromatography to serve as a new reference method principle for the determination of total sodium and potassium in human serum was investigated. Sample pretreatment consisted of acidic dilution and filtration and detection was based on conductivity. Methods for the separate and simultaneous determination of both analytes were investigated. Further, the influence of calibration (using either a single-point calibration or a standard curve) on method imprecision, inaccuracy and analysis time was examined. The best method performance was achieved by separate analysis using single-point calibration with bracketing analysis scheme. For this variant, the mean total coefficient of variation for sodium and potassium was 1.0% and the mean method bias was -0.2% for sodium and 2% for potassium, as determined with three control materials from the National Institute of Standards and Technology. Our results are comparable to those of reference methods based on flame atomic emission spectrometry. Therefore, we consider ion chromatography as a valuable reference methodology for the determination of total sodium potassium in human serum.