Collaborative study of effect of light on cadmium and lead leaching from ceramic glazes.

A limited interlaboratory study was carried out to determine the effect of lighting conditions on the release of cadmium from ceramic glazes by 4% acetic acid. Cadmium release increased with increased exposure to light. Further interlaboratory study on plates manufactured under controlled conditions showed that if temperature, intensity of illumination, and time of exposure are specified, reproducible results for leaching of both lead and cadmium can be obtained. A modification of the official AOAC method, 25.031-25.034, to increase sensitivity was collaboratively studied by 8 laboratories. Each received 6 solutions of lead in 4% acetic acid (3 sets of blind duplicates at the 0.1, 0.5, and 0.8 mug/ml levels) plus a reagent blank. Average recoveries were 0.1006, 0.5056, and 0.8194 mug/ml, respectively, with coefficients of variation of 11.4, 3.3, and 2.8%, respectively. The proposed modification has been adopted as official first action, and a parameter for exposure to light during extraction has been included in the method.