A simple sensor for the quantitation of tryptophan (Trp) has been developed using a glassy carbon electrode (GCE) modified with electro-synthesized carbon dots functionalized with glycine (Gly@CDs). The surface functionalization with an amino acid led to the formation of large clusters of nanostructures. To our knowledge, this is the first study in which a Gly@CDs clusters modified GCE is used for the analysis of Trp. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are the techniques used to study Trp electrochemical behavior in an alkaline solution using such an electrode. A linear concentration range was found for Trp from 5 × 10−6 to 5 × 10−3 mol L−1 with a detection limit (LOD) of 5 × 10−6 mol L−1. The reproducibility and repeatability data were satisfactory in terms of RSD%. Moreover, the stability during the time of the modified electrode was considered, evidencing interesting results. The described sensor was used for the determination of Trp in herbal tea and a dietary supplement, and the results were compared with those obtained with HPLC-ESI-MS in the Selected Ion Recording (SIR) mode as an independent method. The electrochemical sensor presents significant advantages in terms of low cost, portability, ease of handling and not requiring skilled personnel.
