Application of poly(2-aminobenzenesulfonic acid- co -aniline) for modification of graphite paste electrode for analytical measurement

In this work, we introduce a novel poly(2-aminobenzenesulfonic acid-co-aniline)-modified graphite paste electrode (MGPE) designed for the first time for simultaneous electrochemical determination of caffeine (CA), xanthine (XA), uric acid (UA), and dopamine (DA). The copolymer provides a unique nanostructured surface—comprising nanosheets and nanorolls—that significantly enhances electron transfer, sensitivity, and peak resolution compared with bare GPE. This structural advantage leads to four well-separated oxidation peaks in the potential range of 0.4–1.4 V at pH 2, enabling reliable, interference-free detection of all analytes in a single run. The MGPE demonstrates high electrocatalytic activity and improved conductivity, as confirmed by EIS (Rct reduction from 22.5 kΩ to 3.19 kΩ), resulting in low detection limits of 1.52, 0.40, 0.75, and 0.41 μM for CA, XA, UA, and DA, respectively. Calibration curves show wide linear ranges suitable for biological samples. Importantly, the proposed sensor exhibits excellent performance in human serum and urine, demonstrating high recovery values and confirming its potential for practical clinical and biochemical analysis. The novelty of this study lies in the first-ever application of this copolymer-modified GPE for simultaneous detection of these four biologically important molecules, offering a simple, low-cost, and highly sensitive platform for real-sample analysis.