An electrochemical sensor based on copper-based metal-organic frameworks-graphene composites for determination of dihydroxybenzene isomers in water.

A highly and simply sensitive electrochemical sensor was presented for the simultaneous determination of hydroquinone (HQ) and catechol (CT) in the water based on copper centered metal-organic framework-graphene composites (Cu-MOF-GN) [Cu-MOF = Cu3 (BTC)2 (BTC = 1, 3, 5-benzenetricarboxylicacid)] modified glassy carbon electrode (Cu-MOF-GN/GCE). The modification procedure was carried out through casting metal-organic framework-graphene oxide composites (Cu-MOF-GO) on the bare glassy carbon electrode and followed by the transformation of Cu-MOF-GO to Cu-MOF-GN by an electrochemical reduction. The electrochemical behavior of HQ and CT at Cu-MOF-GN/GCE was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under the optimized conditions, the modified electrode had excellent electrocatalytic activity and high selectivity toward HQ and CT. The electrochemical sensor exhibited a linear response in the same range of 1.0 × 10-6 to 1.0 × 10-3 M with the detection limits of 5.9 × 10-7 M for HQ and 3.3 × 10-7 M for CT (S/N = 3). Four samples of tap water spiked with different concentrations of HQ and CT were considered. The method has been applied to the analysis of these isomers in spiked tap water with recoveries from 99.0 ~ 102.9% and relative standard deviations (RSDs) for 5 successive measurements less than 5% were also acceptable. This method was successfully applied to detect target analytes in the real samples with satisfying results. The MOFs-based sensors in the field of electrochemical sensing held a great promise for routine sensing applications.