A Green Approach to the Simultaneous Detection of Vitamin C, Paracetamol, and Caffeine Using an Aspartic...

In this study, a waste dry cell battery (WB) electrode was electrochemically modified with aspartic acid (APA) to fabricate the APA-WB electrode for the simultaneous detection of ascorbic acid (AA), paracetamol (PA), and caffeine (CA). The WB electrode was fabricated, cleaned, and polished, its upper surface was insulated with dye, a copper wire attached for electrical contact, and finally modified with APA using voltammetric techniques. Structural and elemental characterizations of the bare and APA-modified WB electrodes were carried out using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FTIR). The results show that the bare WB electrode is mainly graphite-based and that APA modification forms a poly-APA film on its surface. The detection techniques used in this study included cyclic voltammetry (CV), differential pulse voltammetry (DPV), and UV-vis spectroscopy. Of these techniques, DPV was employed for the simultaneous analysis of the analytes. Among various APA-modified electrodes (APA-GC, APA-Pt, APA-PG, and APA-Au), APA-WB exhibited the highest sensitivity and detection capability. The APA-modified electrode demonstrated excellent analytical performance for the three analytes in phosphate buffer (pH 7.0), exhibiting diffusion-controlled behavior and high selectivity with well-resolved peaks for AA, PA, and CA. Limits of detection were 0.20, 0.15, and 0.33 μmol L^-1, with sensitivities of 54.4, 99.9, and 151.7 μA/mM/cm² for AA, PA, and CA, respectively. Interference studies confirmed reliable detection in complex matrices. The UV-vis spectra were able to detect AA, PA, and CA individually; however, they could not simultaneously detect the presence of two or more compounds. The sensor was successfully applied to pharmaceutical and soft drink samples, achieving recoveries of 98-104%. In this work, we report for the first time the application of an APA-modified WB electrode for the simultaneous detection of AA, PA, and CA. This approach transforms hazardous e-waste into a high-performance, low-cost electrochemical sensor, contributing to green chemistry by enabling resource recycling and reduced environmental pollution.