Copper metal organic framework based electrochemical sensor for dimethyl phthalate in bottled water samples

An electrochemical sensor for dimethyl phthalate (DMP) on electrochemically transformed copper benzene tricarboxylate (Cu-BTC) metal-organic framework (MOF) was developed. The MOF has been electrochemically activated by cycling on glassy carbon electrode (GCE) surface in presence of graphene oxide (GO) to yield Cu(OH)₂@Cu-BTC-rGO and utilised for sensing of DMP. Physiochemical characterization has been carried out to understand the nature of the composite and electrochemical transformation of Cu-BTC has been investigated in various electrolytes with respect to sensing performance. Sensing behaviour of Cu(OH)₂@Cu-BTC-rGO towards DMP in polyethylene terephthalate (PET) bottled water was analysed using cyclic voltammetry and differential pulse voltammetry. Ex-situ analysis such as NMR, UV-Vis and EPR spectroscopy analyses confirmed that DMP detection was due to the cation-π interaction between Cu¹⁺/Cu²⁺ ions present in composite and the benzene ring of DMP. This interaction resulted in the change in current with respect to DMP concentration in the range of 1 µM to 500 µM with a detection limit of 0.17 µM (R² 0.9870), well below the threshold range (10.3 µM) provided by U.S. Environmental Protection Agency (EPA). The results from electrochemical method employed to quantify the DMP in real environment were validated with conventional HPLC analysis.