Simultaneous gas chromatographic determination of four organophosphorus insecticides

Abstract

Of organophosphorus insecticides, parathion, methyl parathion, EPN and methyl demeton are legal items to be determined in industrial wastes. The former three were possible to be determined simultaneously by gas chromatography or colorimetry after extracted. into n-hexane. but methyl demeton had to be determined with another colorimetric method after extracted into chloroform. The authors have developed a method for simultaneous determination of the four insecticides as follows. The four insecticides in a 200 ml of sample solution, which was previously adjusted to pH lower than 4 with hydrochloric acid, were extracted into n-hexane containing 10% chloroform. The organic phase, after dried with dehydrated sodium sulfate, was concentrated to 5 ml with a Kuderna-Dannish distillator. To remove contaminants, such as oil, dyestuff, etc., the concentrate was applied on a column of florisil activated at 130°C for 12 hours. Elution was carried out with n-hexane containing 2% acetone for the former three, and then with a mixture of one part of acetone and two parts of n-hexane for methyl demeton. Both effluents were combined and concentrated. An aliquot was injected into a gas chromatograph equipped with a flame photometric detector. The lower limit of determination was 0.001 ppm, and the recoveries, after column chromatography with a sample size of 200 ml of water or 10 to 20 g of solid, were 85 to 95% for the former three and 55 to 60% for methyl demeton. © 1976, The Japan Society for Analytical Chemistry. All rights reserved.