Abstract: Electroanalytical techniques could be a reliable and promising alternative to classical and sophisticated methods because of their simplicity(small and portable), easy use, the ability to deliver fast response with high sensitivity and selectivity. A square wave voltammetric method was developed for the assessment of organophosphorus(OPs) compound impact on acetylcholinesterase(AChE) of Pheretima with 2,6-dimethyl-p-benzoquinone(2,6- DMBQ) as a redox indicator. The substrate of acetylthiocholine is hydrolyzed by AChE and the produced thiocholine reacts with 2,6-DMBQ to give an obvious shift of electrochemical signal. The reduction peak of 2,6-DMBQ is located at around -0.18 V which is far away from the oxidation potential of possible interference components often present in biosample. The decreased rate of reduction current was related with the activity of AChE. The inhibition of parathion-methyl on AChE was assessed. The inhibiton rate of OPs on AChE activity increased quickly during the first 10 min inhibition, and after that the value of inhibition rate approached to be constant. AChE lost almost 29.3% of acti- vity after 10 min incubation with 1 mg/mL parathion-methyl and 67.5% of activity with 10 mg/mL parathion-methyl, while the activity that corresponds to 40 mg/mL parathion-methyl was nearly completely inhibited(94.9%). Compared to cyclic voltammetry and amperometry, Square wave voltammetry(SWV) method is a high sensitive electroanalysis with fast scan-rate(only several seconds for one signal value) which is useful to prevent the electrodes from possible fouling or passivation. This method can be employed to assess the inhibition of organophosphate on AChE and investigate OPs impact on environmental animals.

Key words: 2,6-Dimethyl-p-benzoquinone, Pheretima, Organophosphorous compound, Square wave voltammetry, Acetylcholinesterase