[Fluoride contents in tea and Sakura-shrimp in relation to other inorganic constituents].

The purpose of this study is to determine the fluoride contents of shrimp and of tea samples obtained from Shizuoka prefecture which is famous for tea products area and fishery market and to examine the relations between fluoride and other mineral contents, such as calcium, magunesium and phosphorus. Fluoride contents in tea produced in this area have been reported by Matsuura and Kokubu and other investigators, but more recent data are scarce. Samples were taken from a kind of shrimp known as Sakura-shrimp and from 4 kinds of commercial tea (coarse tea, 2 kinds of green tea and refined green tea). After having been dried and powdered, 1g of each sample was reduced to ashes at 550 degrees C for 10 hours with Ca(OH)2 as a fluoride fixative. Fluoride was distilled from each ash sample at about 140 degrees C with HClO4, and about 200 ml of distillate was collected from each sample. Fluoride contents were determined by means of ion-specific electrode. Calcium and magnesium contents were determined by atomic absorption spectrophotometry, and phosphorus contents were determined by Chen, Toribara and Warner's method. Total fluoride contents of the samples were as follows: 61.73ppm in shrimp, 180.16ppm in coarse tea, 72.62ppm and 89.02ppm in the 2 kinds of green tea, and 71.11ppm in refined green tea. More than 99% of the total fluoride was obtained from 150ml distillate of each sample. Calcium contents were extremely high in shrimp (21,822ppm) and 2,106-2,693ppm in tea samples. Magnesium contents were highest in shrimp (3,088ppm) and lowest in coarse tea (1,333ppm).(ABSTRACT TRUNCATED AT 250 WORDS)