Determination of Catechol in Water by Electrochemiluminescence Sensor Based on Modified Electrode with g-C₃N₄-UiO-66 Composite

An electrochemiluminescence sensor for the determination of catechol pollutant in water was constructed based on modified electrode with g-C₃N₄-UiO-66 composite by heterojunction structure formed with zirconium metal-organic frameworks (UiO-66) and semiconductor graphite phase carbon nitride (g-C₃N₄). The g-C₃N₄ and UiO-66 were synthesized, and after the matericals were fully ground and calcined, g-C₃N₄-UiO-66 composite was obtained. The 1.0 g·L^-1 g-C₃N₄-UiO-66 dispersion was prepared with N,N-dimethylformamide as solvent, and an aliquot (3.0 μL) was dripped onto the surface of pretreated glassy carbon electrode (GCE). After natural drying, the modified GCE with g-C₃N₄-UiO-66 (g-C₃N₄-UiO-66@GCE) was obtained. The three-electrode system with g-C₃N₄-UiO-66@GCE as the working electrode, platinum wire as the auxiliary electrode and Ag/AgCl as the reference electrode was placed into the phosphate buffer solution (pH 7.5) containing 50 mmol·L^-1 K₂S₂O₈, and the difference of electrochemiluminescence intensity of the system (quenching value) was recorded before and after adding catechol by cyclic voltammetry in the range of -1.6-0 V at scanning speed of 0.1 V ·s^-1. As shown by the results, there was a linear relationship between the quenching value of electrochemiluminescence intensity and the logarithm of catechol concentration, and the linear range was 1.0 ×10^-5-5.0 ×10^-2 μmol·L^-1, with detection limit of 9.0×10^-12mol·L^-1. The six g-C₃N₄-UiO-66@GCE was used for reproducibility test, and RSD of the six determined values was 3.3%. According to the test conditions, 31 cycles were continuously scanned in the range of -1.6-0 V, which showed that RSDs of the determined values were less than 4.0% before and after adding catechol. The sensor had good anti-interference ability to the interfering substances, including hydroquinone, resorcin, glucose, Na⁺ and K⁺. The tap water sample was analyzed with the electrochemiluminescence sensor, and the test for recovery was made by standard addition. The results showed that catechol was not detected, and the recovery was 98.4%, with RSD (n=5) of the determined values of 3.8%.