Reduction of insecticide residues in grain dust by treatment with alkali

A series of laboratory and pilot scale experiments was performed to reduce residues of dichlorvos and malathion in grain dust to levels below the maximum permitted for stock feed. Processing such as steaming or pelleting did not reduce pesticide residues sufficiently, but mixing grain dust with three alkaline materials, sodium hydroxide, sodium carbonate or ammonia, reduced residues considerably and this reduction was increased by subsequent processing. Reduction of residues was greater from use of liquid rather than solid alkalis, from use of the stronger (sodium hydroxide) rather than from the weaker (sodium carbonate) base and was proportional to the amount of liquid sodium hydroxide or ammonia that was used. Alkaline materials reduced pesticide residues in possible stock feed combinations of grain dust plus straw and grain dust plus lucerne meal. As these results are consistent with general base-catalyzed hydrolysis of organophosphorus esters, there is probably scope for considerable variations in procedure by use of different alkalis and different exposure times to alkali. In commercial applications amounts of base required (2 per cent w/w) were less than those used to increase the food value of low-grade animal feed.