Abstract
Residual γ-BHC in rice grains and straws were determined by a bioassay method with the use of Adzuki-bean weevil, Callosobruchus chinensis L. The samples were taken from some paddy fields where BHC granules and/or fine dusts had been applied in the irrigation water at the rates of 1.2-8.7kg in ingredient per ha (1.07-7.7lbs. per acre) for controlling rice stem borer. The samples were extracted with n-hexane and the separation of the extracts were carried out by column chromatographic procedure. Under this procedure, 2μg of γ-BHC could successfully be separated from the extract corresponding to 100g of polished grains and 1.6-1.7μg could be separated from 2μg with the extract corresponding to 10g of the bran. The amounts of γ-BHC detected in the polished grains, brans, unpolished grains, hulls and the straws were 0.002-0.051, 0.05-0.53, 0.013-0.081, 0.01-0.18, and 0.1-1.8ppm respectively. It has been ascertained that the large amount of the residual γ-BHC in the rice plant remains in the straws but a little amount of it translocates into the grains, and that the residue in the grains is particularly concentrated in the part of the bran.
