Twelve chemical ingredients commonly used to formulate detergents were tested to determine their interferences with measurement of calcium in milk by atomic absorption spectrophotometry. For concentrations of 0.01, 0.1, and 1.0% milk, the mean amounts of calcium measured for all ingredients were 0.20, 1.85, and 15.89 mg/1, respectively. Statistical analysis showed that milk accounted for 97.3% of the variation in spectrophotometric response with temperature and concentration of ingredient being of little practical importance. However, increasing the temperature caused the instrument to indicate increased amounts of calcium in solutions containing sodium metasilicate (anhydrous), EDTA plus sodium hydroxide, sodium gluconate, and phosphoric acid. Changing the concentration of ingredient did not interfere substantially with the amount of calcium measured except for sodium metasilicate (anhydrous) where an increase in concentration reduced the amount of calcium measured. From the data it can be concluded that an atomic absorption spectrophotometer shows considerable promise for use in monitoring removal of residue from a milk contact surface.

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Author notes

1Contribution from the University of Missouri Experiment Station. Journal Series No. 6739.

2Trade names and names of commercial companies are used in this publication solely to provide specific information. Mention of a trade name or manufacturer does not constitute a guarantee or warrenty of the product by the U.S. Department of Agriculture or an endorsement by the Department over other products not mentioned.

3Agricultural Engineer, NCR, ARS, USDA.

4Department of Agricultural Engineering.

5Central Luzon State University.

6Department of Food Science and Nutrition.