Abstract:

The determination of calcium concentration in milk was achieved using microwave digestion and micro-titration. Satisfying results of determining Ca2+ concentration in milk were obtained when a 10.00 mL sample of milk was digested with a mixture consisting of 5 mL of 98% HNO3 and 3 mL of H2O2 fortified with 0.4 mL of triethanolamine for eliminating the interference from Al3+ and Fe3+. The average consumptions of EDTA standard solution for Yili branded pure milk and high calcium milk were 1.616 mL and 1.450 mL with RSDs of 0.16% and 0.32%, respectively. The average spike recovery rate of seven replicate determinations was in the range of 98% to 101.5%. The accuracy and precision of the micro-titration method were both comparable to those of the traditional digestion and titration methods. This method is a simple, rapid, reagent-saving and environmentally friendly.

Key words: calcium, micro-titration, microwave digestion, milk