Assessment of wheat straw and corn cob-derived biochar in the design of a novel electrochemical sensor for the determination of carbendazim

During the development of quick, inexpensive, and environmentally friendly analytical techniques like voltammetric methods, two distinct waste resources, wheat straw (WBC) and corn cob (CBC), were utilized to synthesize biochars (BCs) at two pyrolysis temperatures (400 °C and 700 °C), which were used as electrocatalytic materials in carbon paste electrodes (CPEs). Scanning electron microscopy and Fourier transform infrared spectroscopy revealed the properties of the synthesized BCs. Cyclic voltammetric (CV) and electrochemical impedance spectroscopic (EIS) measurements showed better conductivity of the electrode WBC700-CPE compared to unmodified CPE, CBC400-CPE, CBC700-CPE, and WBC400-CPE. WBC700-CPE was chosen for the analysis of a persistent organic pollutant, carbendazim (CBZ). According to CV studies, the electrochemical oxidation reaction of CBZ is irreversible and adsorption-controlled. Different variables were tuned, such as the pH of the supporting electrolyte, electrode composition, and the square-wave adsorptive stripping voltammetric (SW-AdSV) parameters. This entails adsorption of CBZ on the electrode surface at the optimized accumulation potential (<i>E</i>_acc = -0.2 V) and accumulation time (<i>t</i>_acc = 60 s) with the obtained linear concentration range of 1.25 to 50.0 ng mL^-1 with a limit of detection of 0.38 ng mL^-1 CBZ, and a relative standard deviation of 1.2% at pH 6.0. The selectivity of WBC700-CPE was confirmed since the investigated interfering substances did not affect the voltammetric signal of CBZ. During the analysis of surface water and wastewater spiked with CBZ, the applied voltammetric method gave good recovery and reproducibility, demonstrating that WBC700-CPE provides reliable results for determining pesticides in contaminated water.