Determination of Fluorine in Tea

A simple method is presented for the determination of the fluorine content of tea by using a 0.5–1.0-g sample. Fluorine is fixed by means of calcium oxide during the destruction of organic matter and then converted to soluble fluoride by fusion with sodium hydroxide. The fluoride is determined titrimetrically after steam distillation of fluosilic acid. Analysis of 16 varieties of tea reveals that fluorine concentration increases with the age of tea leaves upon harvest and that commercial teas contain fluorine in the range between 40 and 120 ppm. Large amounts of fluorine-containing compounds in the environment lead to extremely high fluorine values in the leaves of Camellia sinensis, suggesting that it may be used to monitor the extent of pollution.