Determination of Major Cations in Milk by Atomic Absorption Spectrophotometry

Abstract

Milk samples analyzed for major cations by atomic absorption spectrophotometry showed standard deviations for various elements, as follows: Ca, 0.019 g/l or 1.6%; Mg, 0.002 kA or 1.6%; K 0.029 g/l, or 1.9%; andNa, 0.010 g/l, or 2.4%. Recoveries of added Ca, Mg, K, and Na in milk were quantitative, and reproduciblllty of analytical results was satisfactory. Comparison of results obtained with this method and those obtained by flame photometry, direct titration of milk with EDTA, and oxalate-permanganate titration indicated that Ca was significantly higher at [alpha] =0.05. Analysis of data by separation means, however, revealed that the Ca content in whole milk did not vary significantly between methods, whereas for akimmilk, 2 at the 4 samples showed higher results with atomic absorption spectrophotometry. Measured values were within the required accuracy. Determination of Mg by this method was particularly satisfactory, and results were more reliable than those obtained by direct titration of milk; results for K and Na were comparable to those obtained by flame photometry.