The determination of malathion in formulations by a method based on cleavage by alkali

Abstract

A method for the determination of malathion in formulations is described. The malathion dissolved in methanol is hydrolysed at room temperature by sodium hydroxide in the presence of phenol to give OO-dimethylphosphorodithioic acid. The latter is converted into its yellow copper complex by reaction with copper(II) sulphate in acetate buffer solution, and the complex extracted with chloroform. The copper(II) sulphate remaining in the aqueous layer is then determined iodimetrically. The free OO-dimethylphosphorodithioic acid in the sample, and other materials that are likely to interfere, are accounted for in a parallel determination, which omits the hydrolysis stage. Hence the amount of malathion in the sample can be calculated.