Pirimiphos, fenitrothion and chlorpyrifos residues in milled fractions of paddy
1989
Ong Seng Hack (Malaysian Research and Development Inst., Serdang, Selangor (Malaysia))
Paddy grain admixturely treated with three aqueous insecticide mixture combinations were sampled over the first 24 weeks of concrete silo storage for dehusking and milling. 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 and 1 mg/kg); fenitrothion + fenvalerate + piperonyl butoxide (at 20, 0.5 and 8 mg/kg); and chlorpyrifos-methyl + carbaryl 1 (at 10 and 8 mg/kg). Results demonstrated that milling reduced organophosphate residues very 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 (72-95.68%) while the rest in bran (3.99-26.33%). The percentage distribution of organophosphate in the various fractions were calculated from predetermined recovery values of 66.87% for polished rice, 10.95% for bran and 22.17% for husks. Values of percentages of residues in milled fractions were estimated using analytical and estimated residue levels obtained.
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