Pirimiphos-methyl, fenitrothion and chlorpyrifos-methyl residues in milled fractions of paddy
1988
Ong, S.H. (Malaysian Agricultural Research and Development Inst., Kuala Lumpur (Malaysia). Pest Science Unit)
Paddy grain admixturely treated with 3 aqueous insecticide mixture combinations were sampled over the first 24 weeks of concrete silo storage for dehusking and milling in a stake machine. Their organophosphate residue levels in polished rice, bran and husks were determined. The three aqueous insecticide combinations and the concentration of each active ingredient used were pirimiphos-methyl + permethrin (at 12.0 and 1.0 mg/kg; fenitrothion + fenvalerate + piperonylbutoxide) at 20.0, 0.5 and 8.0 mg/kg); and chlorpyrifos-methyl + carbaryl (at 10.0 and 8.0 mg/kg). Results demonstrated that milling reduced organophosphate residues significantly, leaving only a trace amount of 0.13 mg/kg polished rice. These values represent a removal of 97.04-99.6% of total residues that were present on paddy grain. Most of the residues remained on husks (72.0-95.68%) while the rest in bran (3.99-26.33%). The percentage distribution of organophosphates in various fractions were calculated from pre-determined recovery values of 66.87% for polished rice, 10.95% for bran and 22.17% for husks. Values of percentages of residues milled fractions were estimated using analytical and estimated residue levels obtained. Variations between the two calculations are discussed.
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