A novel label-free hypochlorite amperometric sensor based on target-induced oxidation of benzeneboronic acid pinacol ester

In this work, a novel label-free hypochlorite amperometric sensor based on the direct oxidation of benzeneboronic acid pinacol ester (BAPE) induced by hypochlorite was developed. 4-Aminophenylboronic acid pinacol ester (ABAPE) chemically bonded to functionalized multi-walled carbon nanotubes (f-MWCNTs) was employed to recognize the hypochlorite species. In nearly neutral solutions, the ABAPE probe was able to provide a distinct oxidation signal at approximately 0.65 V vs. Ag/AgCl. When hypochlorite was added, it reacted with ABAPE rapidly to form a stable hydroxyl derivative, resulting in a significant decrease of the current at 0.65 V. Therefore, the hypochlorite target could be detected by recording the reduced oxidation signal of ABAPE. Under optimized conditions, the fabricated sensor offered linear amperometric responses for the target in the concentration ranges of 0.01–0.1 mM and 0.1–1 mM, providing a limit of detection down to 5.3 μM based on S/N = 3. The presence of common anions, including carbonate, sulfate, nitrate, and halide ions, had no obvious effects on the selective determination of hypochlorite. The amperometric sensor also exhibited excellent accuracy and precision in monitoring the hypochlorite level in tap water. These results suggest that the new sensor has great promise for use in various fields such as water pollution control, environmental monitoring, and food safety.