STUDY ON THE EXTRACTION OF ORGANOPHOSPHORUS INSECTICIDES FROM SOIL BYSUPERCRITICAL-FLUID METHOD

Recovery of organophosphorus insecticides, quinalphos, chlorpyrifos an d methidathion from soil were examined by extracting with carbon dioxi de under supercritical state. Extraction conditions were designed at 1 00, 150, 200, 250 and 300 atm and under 40, 50 or 60 degrees C. The be tter recovery was obtained by amending 2 mi of methanol into soil samp le before extraction. The best extraction condition was found to be at 300 atm and under 50 degrees C, at 200 atm and under 60 degrees C, an d at 100 atm and under 60 degrees C for quinalphos, chlorpyrifos and m ethidathion, respectively.