A Quantitative Spectrographic Method for the Determination of Tin, Copper, Iron, and Lead in Milk and Milk Products. The Effect of Storage on the Concentration of these Metals in Evaporated Milk

Abstract

A rapid, reliable, and accurate spectrographic method was developed for the simultaneous quantitative determination of tin, Cu, Fe, and Pb in milk and evaporated milk. The concentration of tin in evaporated milk was found to increase rapidly when stored at either 37[degree]C or room temperature. As received, the average concentration of tin was 20 ppm,and 97.4 ppm after 50 days of storage at 37[degree]C in electrolytic cans, after 340 days the concentration was 215 ppm. The Fe content increased with storage from 6.5 ppm (0-50 days) to 16.5 ppm (340 days). No significant increase in content of Cu or Pb was found on storage. The mean values were 0.68 ppm for Cu, and 0.35 ppm for Pb. Darkening and fat separation of the milk were evident after 81 days at 37[degree]C, and corrosion occurred in all cans held at 37[degree]C. Only the tin-iron alloy remained after 300 days.