Development of a novel sensor with high sensitivity for electroanalytical determination of bisphenol A based on chitosan-3-mercaptopropyl trimethoxysilane modified glassy carbon electrode

Abstract

In a facile synthesis process, a novel functionalized composite material was synthesized as precursors to the chitosan and 3-mercaptopropyl trimethoxysilane (CHMTS). The materials, chitosan (CH) and CHMTS were characterized using Fourier-transform infra-red, scanning electron microscope/energy dispersive X-rays, transmission electron microscopy, and Brunauer-Emmett-Teller surface area analyser techniques. The cyclic voltammetry (CV) studies showed that a 6-fold increase in oxidative peak current was recorded in CHTMS/GCE compared to bare GCE and 3-fold increase in peak current compared to CH/GCE. Similarly, EIS Nyquist plots showed a significant decrease in a semicircle for the CHMTS/GCE compared to the bare GCE and CH/GCE with the Rct value of 10814.0 Ω, 2639.0 Ω, and 663.7 Ω, respectively for the CHMTS/GCE, CH/GCE, and GCE. Further, the electrochemical behaviour of bisphenol A (BPA) showed an irreversible 2-electron process. Moreover, the differential anodic stripping voltammetry is found sensitive and selective for the trace detection of BPA under optimized experimental parameters such as pH 10.0, deposition potential 0.2 V (vs. Ag/AgCl), and deposition time 180 sec. The determination of BPA showed good linearity with BPA concentration against the oxidation peak current, within the studied concentration range of 140.0 µg/L to 200.0 µg/L, and the calculated limit of detection is 5.61 µg/L. The 10-fold increase in several co-existing ions not affect the detection of BPA, indicating the selectivity and sensitivity of the CHTMS/GCE toward BPA. The fabricated electrode showed reasonably good reproducibility with an RSD value of 0.35%. Furthermore, CHTMS/GCE showed long-term stability since the peak current was retained at 99.42% even after 48 hrs of repeated use. Real water samples using spring water and river water revealed the recovery percentage of Ca. 100% in the detection of BPA, which showed the practical applicability of the fabricated electrode.