(1) Preparation of polysulfosalicylic acid-ruthenium terpyridine modified glassy carbon electrode
The glassy carbon electrode was placed in an aqueous solution containing 1.0×10-2mol/L sulfosalicylic acid and 1.0×10-4mol/L ruthenium terpyridine, and electropolymerized by cyclic voltammetry at -1.5~+2.0V Within the potential range of , the scanning speed was 0.1 V/s, scanning for 10 to 30 circles, and the modified electrode was obtained after taking it out to dry.
(2) Drawing of standard curve
The modified electrode prepared in step (1) was used as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum electrode was used as the auxiliary electrode to form a three-electrode system, and 0.1mol/L PBS buffer with pH=10 was used as the blank solution for detection Luminescence intensity, the three-electrode system was placed in different concentrations of allura red (1.0×10-7mol/L, 5.0×10-7mol/L, 1.0×10-6mol/L, 5.0×10-6mol/L, 1.0× 10-5mol/L, 5.0×10-5mol/L and 1.0×104mol/L) pH=10 PBS buffer solution, cyclic voltammetry scanning in the potential range of 0.1V to 1.5V, photomultiplier tube voltage At 800V, under this condition, record the E-ECL curve, and read out the peak luminescence intensity. After statistics, the concentration of allura red is taken as the abscissa, and the luminous intensity difference between the blank solution and allura red is the ordinate, and a standard curve is drawn to obtain the corresponding linear regression equation. The linear range of the above equation is 1.0×10-7~1.0×10-4mol/L, the diameter of the glassy carbon electrode used according to the present invention is 3mm, and the detection limit is 0.6×10-7mol/L.
(3) Detection of samples
Select 1.0 mL of a commercially available watermelon beverage sample and place it in a 100 mL volumetric flask, dilute to 100 mL with 0.1 mol/L PBS buffer solution with pH=10, and take 20 mL of the obtained solution for electrochemiluminescence detection. ) the same electrochemical test method is used to test the sample solution to be tested to obtain the ECL luminescence intensity value and the difference between the luminescence intensity value of the blank solution and the luminescence intensity value of the blank solution. The equation calculates the concentration of allura red in the sample to be tested.