Comparison of partial digestion procedures for determination of Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P, and Zn in milk by inductively coupled plasma-optical emission spectrometry.

A fast procedure was developed for determination of Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P, and Zn in milk samples. This procedure consisted of a partial digestion with hydrochloric acid on a hot plate. The results obtained were compared with 3 other digestion procedures (dry ashing and 2 microwave digestions). All the procedures showed similar precision levels, with coefficients of variation <10% for most analyzed elements. Accuracy was evaluated by using certified reference materials, and the values obtained were within the confidence intervals for these products. The results obtained were not considered statistically different. The partial digestion on a hot plate with HCl can be very practical for laboratories with relatively large numbers of sample analyses.