PERSISTENCE PATTERN OF CHLORPYRIFOS, CYPERMETHIRN AND MONOCROTOPHOS IN OKRA

Persistence of chlorpyrifos, cypermethrin and monocrotophos on okra was studied following application at dose of 100,200,300g a.i.h-1 to work out the safe preharvest waiting period. Samples of okra fruits were collected periodically days at harvest after treatment of the pesticides. A multi-residue extraction procedure was carried out using acetonitrile containing 1% acetic acid and cleaned up with PSA and magnesium sulphate extract analysed by GC-MS. The average initial residues chlorpyrifos, cypermethrin and monocrotophos were in the range of 0.389-0.874, 0.378-0.862 and 0.391-0.898mgkg 1respectively. The residues of pesticides fell below detection in the 15, 17 and 19 days of chlorpyrifos, cypermethrin and monocrotophos, respectively.