Oxygen-flask combustion of accumulated organophosphorus pesticides for monitoring water pollution

Hydrolytic degradation and oxygen combustion methods of decomposition were compared for the organophosphorus pesticides, malathion, parathion and phosalone. The pesticides were decomposed to orthophosphoric acid prior to spectrophotometric determination as phosphomolybdenum blue. Pesticide adsorption on Amberlite XAD-4 resin prior to combustion increased the sensitivity of the method, while eliminating both inorganic phosphates and some non-pesticide organophosphorus compounds. A tandem approach involving the determination of total organophosphorus pesticides and a test for cholinesterase inhibitors was recommended for differentiating between various sources of phosphorus; an increased phosphorus content and a positive cholinesterase inhibition test would clearly indicate the presence of organophosphorus pesticides in surface waters.