線状抽出型オブンによる弗素の微量測定とその応用

Abstract

A linear wash-out type oven was developed for micro determination of fluoride. The procedures are similar to the Weisz's ring oven technique but with higher sensitivity in detection and with more convenient operations. Organic substances were ashed with an oxygen combustion flask, and the fluoride was detected with alminium chromazrol S complex as the color regent following the recovery from coexisting interferences by the diffusion method. Concentration range from 0.08 to 4×105 ppm can be successfully quantitated with 90 per cent recovery, and the standard deviation relative to the expected amount of four repetitive measurements was less than 30 per cent. The method was applied to the fluoride determination in rice crops harvested in localities within 10 kilometers from an alminium refinery firm in Japan. Analytical results showed that the highest concentration was found in bran powder as up to 122 ppm, up to 32 ppm in full grains, and 2.91 ppm as average in cleared grains which is higher than 1.20 ppm as average in the rationed rice grains cleared Clear relations among fluoride concentration in crops and the distance of the harvested location from the alminium refinery discharging hydrogen fluoride were mentioned by the author with 16 rice samples surveyed in 2 years. Fuoride in cleared grain can easily be dissolved in water, and be vaporized and removed from grain on cooking. Average 240 μg of fluoride would be taken into human subject if 1500 g of the polluted rice was served in 3 meals a day, and yet the amount does not exceed the average intake of 180s240μg among normal adults in rural districts of Japan from rice 3 times a day, daily intake from total diet being estimated as approximately 1.6 to 2.1 mg.