▎ 摘　　要

Biosensor based on enzyme inhibition for the determination of organophosphate pesticides residue was developed and fabricated, which explored to modify screen-printed electrode (SPE) with acetylcholinesterase (AChE) and a composite membrane of magnetic nanoparticle (Fe3O4) and graphene (GR). Due to the large specific surface area and high electron transfer of graphene and the strong absorbability and affinity of Fe3O4 for the phosphoric group, the nanocomposite film provided much active site and suitable microenvironment to improve the combination with AChE and maintain the enzymatic activity. The AChE/Fe3O4/GR/SPE was characterized by different methods including cyclic voltammetry and differential pulse voltammetry, indicating the biosensor had some excellent properties, such as high sensitivity, reproducibility and repeatability. Under optimum conditions, the inhibition rates of AChE were proportional to the concentrations of chlorpyrifos in the range from 0.05 mu g/L to 100 mu g/L with the coefficients of 0.981 and the detection limits were found to be 0.02 mu g/L (S/N=3). This proposed biosensor exhibited high accuracy, reproducibility and regeneration, which was suitable for trace detection of chlorpyrifos residue in vegetable.