Lead and cadmium in California raw milk

An atomic absorption procedure for the simultaneous measurement of lead and cadmium in raw whole milk has been developed and tested. A 100 g sample is dry ashed at a temperature not exceeding 425 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 lead and cadmium. After the ammonium pyrrolidino carbo dithioate complexes are extracted in isoamylacetate, the lead and cadmium are measured in the extract by atomic absorption. Mean recoveries of lead and cadmium added to raw whole milk were 92.1 +/- 2.9% and 97.5 +/- 2.5%. A statewide survey showed that the mean concentration of lead in 350 raw milk samples was 91 mug/kg; 222 of the samples were below 100 mug/kg. The mean concentration of cadmium in 315 raw milk samples was 6.0 mug/kg; 40 samples had 1.0 mug/kg or less, and 255 of the samples were below 10.0 mug/kg.