▎ 摘　　要

An electrochemical sensor based on a palladium (Pd) and graphene (Gr) composite modified glassy carbon electrode (GCE) was fabricated, characterised and used for the simultaneous determination of omethoate (OMT) and dichlorvos (DCV) in grain samples. The Pd/Gr/GCE was characterized by scanning electron microscopy (SEM) and cyclic voltammograms (CV). The modified electrode displayed a greatly improved voltammetric response to OMT and DCV. Square wave voltammetry (SWV) was used for the individual and simultaneous determination of OMT and DCV. Various conditions were optimized, such as the pH of the buffer, the applied sample volume, the accumulation potential, the accumulation time, the square wave frequency and the step potential. Well defined reduction (OMT at C=O, DCV at C=C) peaks were obtained over the potential maximum in an acidic medium in phosphate buffer solution at -0.50 V and -0.80 V for both OMT and DCV. Low current peaks were obtained over the concentration of 3.50 x 10(-8) M with detection limits 2.47 x 10(-10) M and 3.28 x 10(-10) M for OMT and DCV respectively. The composite modified electrode showed good stability and reproducibility. Therefore, the proposed method was successfully applied as an economical and simple sensor with a shorter analysis time.