Zinc , Copper , Lead and Cadmium Contents in Japanese Green Tea

There has been a remarkable increase in the interest shown to trace metal contents in various foodstuffs, since various heavy metals have been shown to be invariably present in environment and in the foodstuffs with the development of analytical methods and techniques. Lead and cadmium have been recognized as important environmental pollutants with toxic effects on human at relatively low levels. On the other hand zinc and copper have been shown to be essential to plants and animals. There has been a few reports on the trace metal contents in green tea and tea plants. Takeo showed the seasonal changes in manganese and copper in tea roots and also showed the contents of manganese and copper in both green and black teas by the method of neutron activation analysis'>. As this method is not easy to use generally, the author has used the atomic absorption spectrophotometry combined with the method of extraction by means of iodide-methyl isobutyl ketone (MIBK)'). This paper reports the results of analyses for zinc, copper, lead and cadmium contents in 139 samples of green teas presented at the National Tea Contest in 1974 at Kagoshima. In addition, changes in the content of these four metals in tea leaves during the growth and development are shown. The cause of lead contamination in some samples is also discussed briefly. Iodide-MIBK extraction method combined with atomic absorption spectrophotometry