Amperometric determination of organophosphorus pesticide by silver electrode using an acetylcholinesterase inhibition method

Abstract

An amperometric method for the detection of organophosphorus pesticide based on acetylcholinesterase inhibition is reported. A silver electrode is used and shows an inherent advantage in determination of pesticides, which can monitor the activity of the enzyme in real time by electrochemical oxidization of thiocholine at low potential. Cyclic voltammetry and amperometry were used to evaluate the performance of silver electrode for thiocholine detection. Spectrophotometry was conducted to optimize the parameters for the enzymatic reaction. Cyclic voltammetry shows the advantages of silver over others (platinum, glassy carbon and gold) electrodes, when detecting thiocholine at low potentials. The silver electrode could linearly respond to thiocholine in the range from 5.2 × 10⁻⁷ to 2.6 × 10⁻⁵ M at 0.08 V. The measurement displayed a detection limit of 6.2 ppb. The analytical feasibility was investigated further via determination of paraoxon in Chinese cabbages and Fuji apples, which shows recovery rates of 92.05% and 106.11%, respectively. The results indicate the capability of the proposed method for pesticides monitoring in real samples.