Lead and Cadmium in California Raw Milk

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Abstract
An atomic absorption procedure for the simultaneous measurement of Pb and Cd in raw whole milk was developed and tested. A 100 g sample is dry ashed at a temperature not exceeding 425.degree. C. The ash then is dissolved in hydrochloric acid and neutralized with ammonium hydroxide to pH 8.5 in the presence of ammonium citrate. Potassium cyanide is added to complex interfering ions followed by addition of ammonium pyrrolidino carbo dithioate to complex Pb and Cd. After the ammonium pyrrolidino carbo dithioate complexes are extracted in isoamylacetate, the Pb and Cd are measured in the extract by atomic absorption. Mean recoveries of Pb and Cd added to raw whole milk were 92.1 .+-. 2.9% and 97.5 .+-. 2.5%. A statewide survey showed that the mean concentration of Pb in 350 raw milk samples was 91 .mu.g/kg; 222 of the samples were below 100 .mu.g/kg. The mean concentration of Cd in 315 raw milk samples was 6.0 .mu.g/kg; 40 samples had 1.0 .mu.g/kg or less, and 255 of the samples were below 10.0 .mu.g/kg.

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