▎ 摘　　要

A highly sensitive electrochemical biosensor has been developed for the determination of methyl parathion (MP), which was based on acetylcholinesterase (AChE) immobilized onto graphene-Fe3O4 nanocomposite film modified glassy carbon electrode. The nanocomposite not only provided a biocompatible microenvironment to keep the bioactivity of AChE, but also exhibited a strong synergetic effect on improving the sensing properties of MP. The combination of graphene and Fe3O4 nanoparticles greatly catalyzed the oxidation of the enzymatically generated thiocholine product, thus increasing the detection sensitivity. The electrochemical behavior of MP at the sensor was investigated by cyclic voltamnnetry and differential pulse voltammetry. On the basis of the inhibition of MP on the enzymatic activity of AChE, some experimental conditions for MP detection were optimized. The inhibition percentage of MP was proportional to its concentration in the range of 2.5 x 10(-9) similar to 2.5 x 10(-6) g mL(-1) with a linear coefficient of 0.9973. The detection limit was 3.0 x 10(-10) g mL(-1) (S/N = 3). Moreover, the proposed biosensor showed good reproducibility and acceptable stability.