Determination of Benzoic Acid in Carbonated Beverage with Modified Glassy Carbon Electrode of Bis-Schiff Base Copper Complex

Bis-Schiff base copper complex (M) was prepared by solution synthesis method, then M was deposited on the surface of glassy carbon electrode (GCE) by electrodeposition to prepared modified electrode of M (M/GCE). M/GCE was developed for determination of the content of benzoic acid in carbonated beverage. Elemental analysis and infrared spectroscopy showed that M was successfully prepared in the experiment; the curves of cyclic voltammetry (CV) of the electrodeposition process showed that M had been deposited on the GCE surface; scanning electron microscope (SEM) results showed that a polymer film had been formed on the surface of M/GCE. In the CV analysis for determination of the content of the benzoic acid, the three-electrode system was selected with M/GCE as working electrode, saturated calomel electrode as reference electrode, platinum wire electrode as auxiliary electrode and 0.1 mol·L^-1 KCl solution as the supporting electrolyte at the scan rate of 50 mV·s^-1. It was shown by results that the oxidation peak potential and reduction peak potential of benzoic acid on M/GCE were ca. -0.007, -0.359 V, respectively. The electrode reaction was reversible and controlled by diffusion. Linear relationship between concentrations and their respective oxidation peak current of benzoic acid found was in the range of 0.001 0-2.000 0 mmol·L^-1, with detection limit (3S/N) of 0.27 μmol·L^-1. After placing the electrode at 4℃ for 7 d, the oxidation peak current of benzoic acid decreased by 4.8%. A sprite sample was used as a matrix to made a spiked recovery test, giving recoveries of 97.6%-102%; and RSD (n=5) of the measured value found was 1.2%.