Determination of sodium, potassium, calcium and magnesium cations by capillary electrophoresis compared with ion chromatography

Capillary ion analysis (CIA) is a young analytical methodology adapted to analysis for inorganic ions, and has some remarkable advantages over ion chromatography (IC). In this paper a CIA method used for analysis for K+, Ca2+, Na+ and Mg2+ in water samples is presented, and the factors affecting the separation — such as electrolyte ion, complexing or chelating agents — are discussed. Also the repeatabilities of the method, linearities and the detection limits are compared with those obtained by IC. Sufficient separation of the four ions is achieved with an electrolyte solution of 5 mM imidazole/6.5 mM α-hydroxyisobutyric acid/2 mM 18-crown-6 ether, pH 4.1. Detection is by ‘reverse’ absorbance measurements.