A β-CD/MWCNT-modified-microelectrode array for rapid determination of imidacloprid in vegetables

This work introduces a beta-cyclodextrin/multi-walled carbon nanotube (beta-CD/MWCNT)-modified microelectrode array (MEA) for rapid determination of imidacloprid in vegetables. The MEA, fabricated on a silicon wafer, contains 20 parallel-connected working electrodes, a counter electrode and a reference electrode. The MWCNT is drop-casted onto the working electrode area, and beta-CD is decorated onto the MWCNT layer with electropolymerization. Electrochemical behaviors of the as-fabricated sensor are investigated with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Obtained results validate that the proposed sensor has a large electroactive area, great electrical conductivity, and high sensitivity. During preparation and application of the sensor, 0.5 mg mL(-1) MWCNT suspension and phosphate-buffered solution (0.1 mol L-1, pH = 7) are found to optimize experimental conditions. Under optimized conditions, a wide linear range as 5 to 100 mu mol L-1 is obtained for target imidacloprid, and the limit of detection (LOD, S/N = 3) is well defined as 0.629 mu mol L-1. The sensor is used for sensing imidacloprid in cabbage, cucumber, and tomato. The results from this method are in accordance with high-performance liquid chromatography-mass spectrometry (HPLC-MS) data.