Residues of 14C- chlorpyrifos in coconut by radiotracer techniques
1992
Tejada, A.W. | Calumpang, S.M.F. | Magallona, E.D. (Philippines Univ., Los Banos, College, Laguna (Philippines))
A coconut tree was root-infused with 5g a.i. chlorpyrifos (Lorsban) plus 1.4 uCi of 14C-chlorpyrifos. Coconut samples both young and mature, were taken 24h up to 60 days after root infusion. Analysis of the meat and water was done. The maximum uptake of chlorpyrifos equivalents was on the 13th day after root infusion both in mature and young fruit. The residue in water reached the peak on the 20th day after infusion and declined thereafter. A preharvest interval (PHI) of more than sixty days may be recommended for safe consumption. The usual practice of storing copra in treated warehouses until it is processed into oil was simulated in the laboratory to determine the residues absorbed on the meat. Forty kg of copra with moisture content of 7-12% were stored in an improvised warehouse, i.e. 1m x 1.5m x 1m wooden box, which was treated with 100 ml 1% a.i. Lorsban 50 WP plus 100 uCi 14C-chlorpyrifos for protection against insects. Analysis showed that 14C-chlorpyrifos equivalents ranged from 22.6 mg/kg on the 30th day to 8.2 mg/kg on the 90th day with a 63.7% reduction in residues. Bound residues were detected on samples stored for 60-90 days, with levels of 1.0 to 0.2 ug/g 14C-chlorpyrifos equivalents. This is within the Maximum Residue Limit of 2mg/kg set by FAO/WHO for chlorpyrifos in most agricultural commodities. Chlorpyrifos residues were also determined at various stages of refining and processing of crude coconut oil. It was subjected to alkali refining, bleaching and finally steaming. The residues were reduced by as much as 32.7%
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