Nonsuppressed ion chromatographic determination of total calcium in milk.

A novel approach for measuring calcium in milk by the use of high performance nonsuppressed ion chromatography is proposed. Total calcium as well as the calcium present in the colloidal and salt state in milk can be quantified. Because the presence of citrate in the milk serum interferes with the measurement of calcium by the conductivity detector, the free and chelated calcium can also be distinguished. By using a sample preparation procedure using Amberlite resin (Fluka, Steinheim, Germany), the amount of soluble calcium in milk can be determined. Because the quantification of calcium in milk and milk derivatives is becoming increasingly important in order to understand the functionality of the milk proteins, better methods need to be developed to determine, with a high level of accuracy, the amount of calcium present in milk in various forms.