This Application Bulletin discusses the automated determination of calcium and magnesium in commercially available finished milk products. Calcium and magnesium in milk can be rapidly and easily titrated thermometrically using a standard solution of Na4EDTA as titrant.
The milk sample is first treated with a trichloroacetic acid solution to coagulate protein and fat and liberate calcium and magnesium as dissociated ions. The serum containing the calcium and magnesium is separated by filtration or centrifugation. An aliquot of milk serum is treated with acetylacetone to enhance the separation of the calcium and magnesium endpoints. The solution is then buffered with NH3/NH4Cl solution before titration. Thermometric titrations are conducted under conditions of constant titrant addition rate. Results are reported as mg Ca and Mg/100 mL.