NEW SPECTROPHOTOMETRIC METHOD FOR THE ANALYSIS OF COMMERCIAL MALATHION FORMULATION AND ITS RESIDUES ON SOME CROP PRODUCES AND ENVIRONMENTAL SAMPLES

Abstract

Malathion is the most widely used insecticide globally. Because of the toxicity of this insecticide its presence in residues in crop produces, drinking water and environmental samples is of serious health and environmental concern thus necessitating its analysis in these substrates. The analysis of its marketed formulations is equally important to obtain reliable residue data and also in curbing adulteration problems. A new simple and rapid spectrophotometric method based on the reaction of dimethyl dithiophosphate formed from the alkaline hydrolysis of malathion with chloranil in 4:1 molar ratio to form yellowish brown colored dichlorodithiophosphato-1,4-benzoquinone complex has been developed for the purpose. The color showed λmax at 420 nm and was stable for at least 60 min. The stoichiometry of the color reaction has been well supported by potentiometric and photometric titrations. Malathion solution obeyed the Beers law in the range 2.4-66.0 μg mL-1. The method has successfully been applied to the analysis of malathion in residues on some grains, apple and water samples with high recoveries in the range 80.3-99.0% with low relative standard deviation in the range 0.55-2.29%. The method has also been applied for the assessment of its risk of ground water contamination.