Electrodeposition of Au nanoparticles on activated glassy carbon electrode and its electrochemical application for L-tryptophan

In our study, a new sensor was designed for the electrochemical determination of tryptophan (Trp). For this purpose, the glassy carbon electrode (GCE), used as the working electrode, was first activated using cyclic voltammetry in a 0.1 M phosphate buffer solution with a pH of 7. Subsequently, gold (Au) nanoparticles were electrochemically deposited onto the activated GCE (AGCE) electrode. The resulting Au@AGCE was used for the detection of Trp. After optimizing the conditions for the best sensor response, performance factors such as linear detection range, limit of detection (LOD), repeatability, reproducibility, and storage stability for Trp were evaluated. The sensor exhibited two linear detection ranges for Trp. The first range, with a sensitivity of 2280.79 μA μM⁻¹ cm⁻², was found to be between 0.4–75.8 μM, and the second range, with a sensitivity of 260.1 μA μM⁻¹ cm⁻², was observed between 75.8–175 μM. For sensor repeatability, three different Trp concentrations were tested with the same electrode, and the relative standard deviation (RSD) values were found to be in the range of 0.29–5.26%. For reproducibility, three different Trp concentrations were tested using five different electrodes, and the RSD values ranged from 3.43 to 6.03%. Additionally, Trp tablets were used to determine Trp as the real sample. The results demonstrated that the sensor exhibited satisfactory performance factors.