The potentiometric determination of insecticides: Part I. Organophosphorus insecticides inhibiting cholinesterase |
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Authors: | WN Dahl ÅMR Holm KH Schrøder |
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Institution: | University of Trondheim, Kjemisk institutt NLHT, N-7000 TrondheimNorway |
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Abstract: | A potentiometric method for the determination of organophosphorus insecticides based on the inhibition of cholinesterase is presented. The acetic acid formed by hydrolysis of acetylcholine is sensed by a glass electrode in a weakly buffered system. The insecticide is incubated with cholinesterase for 1 h at 25°C or 37°C before addition to the substrate. The effects of incubation time and temperature are discussed. The method is applied to the insecticides bromophos and dichlorvos. The detection limits are 2 × 10-5 M (7 ppb) for bromophos and 1 × 10-7 M (22 ppb) for dichlorvos. The initial rates of hydrolysis decrease linearly up to 2 × 10-7 M and 1 × 10-6 M, respectively. |
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