A novel portable electrochemical sensor based on post-synthetic modified Cu-MOF for highly sensitive electrochemical detection of pefloxacin in food samples

Developing a reliable detection method with high performance for pefloxacin (PFL) is crucial for environmental protection and food safety. However, this remains a challenge. In this study, a new portable electrochemical sensor with a smartphone readout system based on a modified Cu-MOF was designed for PFL detection. The modified Cu-MOF was prepared using a two-step post-synthetic modification strategy. Firstly, thiourea (Th) was doped into the Cu-MOF framework using a solvothermal method, and then the Th-Cu-MOF was further functionalized with MWCNTs using a self-assembly method. X-ray photoelectron spectroscopy combining with chronocoulometry technique and electrochemical impedance measurements revealed that Th not only increased the Cu-MOF’s affinity to PFL but also acted as a bridge, enhancing the interaction between Cu-MOF and MWCNTs. This led to a MOF-based nanocomposite with significantly improved conductivity and specific catalytic properties for PFL. After optimizing detection conditions, the portable sensor showed wide linearity range (9 nM–2.5 μM), excellent selectivity, good stability and a low detection limit (2.6 nM) surpassed that of HPLC in the detection of PEL by utilizing square wave voltammetry technique. In real sample analysis of pond water, shrimp flesh and pork, the portable sensor showed good recoveries (87.92 %–104.4 %), which were comparable to those of HPLC and an electrochemical sensor with a classical three-electrode configuration. This demonstrates that the sensor holds excellent potential for on-site monitoring of PFL in aquaculture.