Incorporation of thermally activated zeolite into carbon paste electrodes for voltammetric detection of carbendazim traces in milk samples

A simple, inexpensive, yet highly sensitive, and selective novel electrochemical method was developed to quantify traces of carbendazim (MBC) in soy milk and cow milk samples using previously thermally activated zeolite incorporated into carbon paste electrodes. Fourier-transformed infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used to examine the structure of untreated and thermally activated zeolite, unmodified carbon paste electrodes, and zeolite-modified carbon paste electrodes (ZMCPEs). The electrodes were electrochemically characterized using cyclic voltammetry, square-wave voltammetry, and electrochemical impedance spectroscopy. The following electrochemical variables were measured: electrode area, number of transferred electrons, electron transfer coefficient, standard rate constant of the electrode reaction, and capacitance of the electrical double layer. The electrocatalytic properties of zeolite were demonstrated by its strong influence on these variables when incorporated into carbon paste in both untreated and thermally activated forms. The electrochemical procedure applied to MBC was developed using ZMCPEs under optimal conditions. MBC oxidation currents exhibited linear concentration in the 12.9-777.7 nmol L-1 range, with a limit of detection of 1.5 nmol L-1. The proposed electrochemical method was employed to quantify MBC in soy milk and cow milk samples. Recovery rates were in the 98.6-99.8 % range, indicating that the method is applicable for quantifying MBC in such samples.