Abstract
Green tea leaves collected from 20 prefectures in Japan were analyzed for their zinc content in two laboratories (Lab. A, Lab. B) by atomic absorption spectrophotometry. Of 77 samples, 10 were analyzed in Lab. A, 62 in Lab. B and 5 in both, in order to estimate the degree of interlaboratory variation. Tea infusion was also analyzed for its zinc content. 1. The difference between the two mean values obtained. from the two laboratories for the same 5 samples was significant, but it was less than 5% of the mean. The variation derived from repetition of measurement in Lab. B was around 4%. 2. Zinc content in the 77 samples of green tea leaves was 34.6±8.8 (mean±standard deviatian) μg/g, the value being comparable with those mentioned in the literature. 3. Infusion rate (the rate of zinc transferred from tea leaves to infusion) increased from 20% to 30% to 40%, as the infusion time was increased from 60 sec to 90 sec to 180 sec.
