Rapid Determination of Phosphorus and Calcium in Milk Powder

Sample of milk powder was digested with conc.HNO3 under pressure at 120 ℃ for 4 h,and the solution obtained was diluted to 50 mL in a volumetric flask used for determination of phosphorus and calcium.An aliquot of the sample solution was taken and mixed with an appropriate amount of activated carbon to remove its color.After separation of activated carbon by filtration,phosphours was determined in the filtrate by the phosphovanadomolybdate-photometric method.Another aliquot of the sample solution was taken for determination of calcium by FAAS.Six portions of a same sample were analyzed for P and Ca contents to test for precision of the method.Values of RSD′s found were 1.2% for phosphorus,and 0.6% for calcium.Values of recovery found for phosphorus and calcium by standard addition method were in the ranges of 88.9%-92.7% and 96.6%-103.0% respectively.