Facile one-step activated glassy carbon electrode for sensitive tryptophan sensing in yogurt

Activation of glassy carbon electrodes (GCEs) in tailored solution environments introduces oxygenated surface functionalities such as hydroxyl, carboxyl, and quinone groups. These modifications enhance electron‐transfer kinetics and strengthen interactions with target analytes, thereby improving electrochemical sensitivity. In this study, square-wave voltammetry was used, and the most suitable supporting electrolyte for tryptophan (TRP) analysis was a pH 3 Britton–Robinson buffer. The cyclic voltammetry potential range and number of cycles for the Act-GCE were obtained as 0–1.5 V and seven cycles, respectively. The activated electrode exhibited excellent analytical performance, with a linear response for TRP over 0.20–6.28 μM, a detection limit of 0.06 μM, and a quantification limit of 0.20 μM. Its practical applicability was confirmed by recovery tests of yogurt samples, demonstrating accurate and reliable real-sample analysis. Scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy were used for both electrochemical and morphological characterization. For TRP analysis of yogurt samples, the square wave voltammetry results obtained with the Act-GCE showed strong agreement with liquid chromatography-mass spectrometry data, and a statistical evaluation confirmed no significant difference between the two methods (p = 0.17). Moreover, the electrode material was used reliably to determine TRP in a yogurt sample with excellent recovery.