▎ 摘　　要

NOVELTY - Preparing manganese oxide/graphene modified electrode comprises (a) cleaning the surface of the solid electrode and (b) uniformly mixing potassium permanganate, potassium chloride, graphite and ultrapure water to obtain a mixed solution, inserting the solid electrode, reference electrode and counter electrode into the mixed solution, performing electrodeposition treatment by cyclic voltammetry, setting the potential range of the cyclic voltammetry to -1.5V to 1.5V, where the voltage scanning speed is 0.05-0.2V/s, continuous scanning is 30-100 cycles, taking out the solid electrode, rinsing with ultrapure water and drying to obtain manganese oxide/graphene modified electrode, where the concentration of potassium permanganate in the mixed solution is 0.1-0.5 mol/l, the concentration of potassium chloride in the mixed solution is 0.1-0.5 mol/l and the concentration of graphite in the mixed solution is 5-10 mg/ml. USE - The method is useful for preparing manganese oxide/graphene modified electrode. ADVANTAGE - The method: detects the concentration of salicylic acid in plant tissues, as the lower detection limit can be as low as 2 mu mol/l; has high test sensitivity and accuracy and economical is beneficial to civilian use. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for detecting salicylic acid in plant tissues comprising (a) configuring N first salicylic acid mixtures with different pH, connecting the working electrode, reference electrode and counter electrode to the electrochemical workstation, inserting them into each first salicylic acid mixture respectively, using differential pulse voltammetry method, obtaining the voltage-current curve of N first salicylic acid mixtures, taking the pH value corresponding to the maximum intensity current in N voltage-current curves as X, where N is 6-10, and the configuration method of each first salicylic acid mixed solution is: mixing the phosphate buffer solution with salicylic acid, (b) configuring M second salicylic acid mixed solutions with pH X, M=10-30, where the concentration of salicylic acid in each second salicylic acid mixed solution is Ci, i=1 to M, and Cmax is maximum concentration of salicylic acid in the second salicylic acid mixture, Cmin is the minimum value of the concentration of salicylic acid in the M second salicylic acid mixture, connecting the working electrode, reference electrode and counter electrode with electrochemistry workstation, inserting into each second salicylic acid mixture separately, testing the M second salicylic acid mixtures by differential pulse voltammetry to obtain the current-voltage curves of the M second salicylic acid mixtures, obtaining the salicylic acid response characteristic peak corresponding to each salicylic acid concentration Ci through the current-voltage curve of the M second salicylic acid mixtures, using the current Ii corresponding to the salicylic acid response characteristic peak and salicylic acid concentration Ci is the horizontal and vertical coordinates, drawing a curve, fitting, obtaining the working curve and the linear regression equation of the working curve, where a and b are constants, and the configuration method of the second salicylic acid mixture is: mixing the phosphate buffer solution with salicylic acid, (c) obtaining the coefficient K, using the coefficient K to correct the linear regression equation by as given in the specification, connecting the working electrode, the reference electrode and the counter electrode to the electrochemical workstation, inserting them into the calibration substance respectively, obtaining the open circuit of the calibration substance by the method of open circuit potential-time curve voltage, based on the open circuit voltage, the resistance is obtained by measuring the AC impedance, dividing the resistance of the liquid of the corrected plant tissue after juice extraction by the resistance of the corrected plant tissue to obtain the coefficient K and (d) connecting the working electrode, reference electrode and counter electrode to the electrochemical workstation, inserting into the test plant tissue to obtain the DPV curve of the test plant tissue, where the current value corresponding to the peak of the DPV curve is I test.