Electrochemical determination of aspirin using a poly(alizarin red S) modified glassy carbon electrode in pharmaceutical formulations

Aspirin (acetylsalicylic acid, ASA) is extensively used in the management of pain, inflammation, and cardiovascular diseases, making its accurate determination in pharmaceutical formulations essential for quality control and patient safety. Conventional analytical methods, including chromatography and spectrophotometry, are often expensive, time-consuming, and require complex sample preparation. Electrochemical techniques offer a rapid, sensitive, and cost-effective alternative; however, bare glassy carbon electrodes (GCEs) exhibit limited sensitivity and selectivity toward ASA, necessitating electrode surface modification. In this work, a poly(alizarin red S) modified glassy carbon electrode (poly(ARS)/GCE) was fabricated by potentiodynamic electropolymerization and characterized using cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical response of ASA was investigated under optimized conditions, and its quantitative determination was achieved using square wave voltammetry. The method was successfully applied to commercial aspirin tablets and validated through calibration, recovery, interference, and stability studies. The poly(ARS)/GCE showed markedly enhanced electrocatalytic activity toward ASA oxidation, providing a five-fold increase in effective surface area and a significant decrease in charge-transfer resistance compared with the bare GCE. Under optimal conditions (pH 6.0 PBS), the sensor exhibited a wide linear range of 0.05–300.0 μM, with a low detection limit of 2.1 nM and a quantification limit of 7.1 nM. High precision (%RSD < 4.0%), excellent selectivity against common interferents, and stable performance over ten days were achieved. Analysis of tablet samples yielded recoveries of 96.05–99.65% of labeled contents, while spike recoveries ranged from 98.60% to 99.83%. Overall, the poly(ARS)/GCE-based voltammetric sensor provides a simple, sensitive, and reliable method for aspirin determination in pharmaceutical formulations. Its superior performance is attributed to the improved surface area, conductivity, and electrocatalytic properties of the polymer film. The method is recommended for routine quality control analysis and may be extended to biological samples and other clinically important drugs using similar polymer-modified electrodes.