Determination of cadmium and lead in raw milk by graphite furnace atomic absorption spectrophotometer.

A simple, uncontaminated method was described for graphite furnace atomic absorption spectrophotometry used for determination of Cd and Pb in milk serum prepared by spontaneous souring. Samples of raw milk were collected from the bulk holding tanks of 107 dairy farms in six counties in Taiwan. Raw milk samples were placed at room temperature (28 degrees C) for 48 h, to allow the pH to decrease below 4.6 and the casein and fat to precipitate. Milk serum was filtered and then directly injected into a graphite tube. The standard addition method was employed, and .1% phosphoric acid was the matrix modifier. During ashing, a 15-s oxygen influx prevented charcoal accumulation on the graphite tube. The mean recoveries of Cd and Pb from three added concentrations were 93.7% and 94.5%, respectively. The analyzed Cd and Pb concentrations in milk powder using this method were close to the certified values. The mean Cd and Pb contents obtained from 107 samples were .044 ng/ml, ranging from .021 to .173, and 2.03 ng/ml, ranging from .98 to 4.45, respectively. There were no significant differences among the six counties.