Isotopic tracer aided studies of fenvalerate residues in stored rice grains
1987
Varca, L.M. | Sanchez, T.E. | Magallona, E.D. (Philippines Univ., Los Banos, College, Laguna (Philippines). National Crop Protection Center)
Fenvalerate was applied to milled rice and paddy prior to storage at a concentration of 0.4 mg/kg. The levels of surface residues, methanol-extractable residues and bound residues were determined in milled rice, brown rice and rice husk stored for nine months. Surface residues of both milled and paddy rice decreased with length of storage period. Extractable residues likewise decreased with storage time. Paddy contained less extractable residues than milled rice, with the bulk found in the husk. After two months, one third of the applied dose was present in milled rice. In paddy, it took six to nine months of storage for the applied dose to decrease to one third of the original dose. Bound residues in both milled and paddy rice also decreased with length of storage and accounted for 75% and 40% of the total residue, respectively after six months. Cooking reduced the insecticide residues in milled rice by 33-40% and by 58% in paddy.
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