1989 Volume 38 Issue 11 Pages 655-658
The simultaneous quantitation of total Mg and total Ca in milk was made by ion chromatography. Total Mg and total Ca were extracted from milk as EDTA complexes. The extract was injected following ultra- or membranefiltration. Non-suppresser type ion chromatography was performed on a Shim-pack IC-Cl cation exchange column (5 mm i. d. × 150 mmL) using 4 mM tartaric acid + 2 mM ethylenediamine (pH 3.41) as the mobile phase. It was found that the coexistance of EDTA·2Na with two equivalents of phosphoric acid disrupted EDTA-Mg (Ca) complexation. If sample pH is ≤10, and total Mg (Ca) in the EDTA complex does not exceed 1 μg, the dissociation of the EDTA complex to detectable Me2+ (Ca2+) cations is mobile phase pH-dependent. Typical milk samples (n=4) yielded 112.5 115.7 ppm total Mg, and 1151.5 1190.6 ppm total Ca. Comparison with values obtained from AAS (=100%) showed 106% and 103% for Mg and Ca, respectively.
