Determination of Chlorpyrifos (Diethyl-3,5,6-trichloropyridyl phosphorothioate) in Cured Tobacco

A method for determining chlorpyrifos in cured tobacco by gas-Iiquid chromatography, using electron capture and thermionic detection, is described. Ground, cured tobacco, mixed with Florisil, is Soxhlet extracted with acetone for eight hours. The extract is evaporated to dryness, redissolved in a small amount of petroleum ether, and eluted through a silica gel column using first petroleum ether and then 5 % ether in petroleum ether. The volumes of the eluates are adjusted and their chlorpyrifos content determined by gas-liquid chromatography, using an electron capture detector and, for confirmation, a thermionic detector. Recoveries from spiked samples are good, and results are reproducible