Highly sensitive and selective electrochemical sensor based on ZIF-67-derived Co₃O₄-LaMn_0.5Ni_0.5O_{3/MWCNTs for simultaneous detection of protocatechuic acid and ascorbic acid}

An electrochemical sensor based on ZIF-67 derived Co3O4-LaMn0.5Ni0.5O3/MWCNTs composite for the simul-taneous determination of protocatechuic acid (PCA) and ascorbic acid (AA) was successfully fabricated by using the MOF template method. The results showed that the modified electrode significantly reduced the oxidation peak potential and increased the oxidation peak current of AA and PCA, and had a high electrocatalytic activity for their oxidation. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) plots showed the peak potential difference of PCA and AA was bigger enough to be beneficial to their simultaneous determination by the ZIF-67 derived Co3O4-LaMn0.5Ni0.5O3/MWCNTs modified glassy carbon electrode (GCE). The DPV tests showed that the current responses of PCA and AA were linearly with the concentration with the linear detection range being 9.31-272.28 mu mol L-1, 9.26-210.68 mu mol L-1 and the low detection limits being 8.83 mu mol L(-)1 and 7.35 mu mol L-1, respectively. The optimal ZIF-67 derived Co3O4-LaMn0.5Ni0.5O3/MWCNTs/GCE was successfully employed to the simultaneous determination of PCA and AA in real beverage samples. Moreover, the reaction mechanism of PCA and AA oxidation on the surface of ZIF-67-derived Co3O4-LaMn0.5Ni0.5O3/MWCNTs/GCE was also explored to understand deeply the reaction process.