Determination of l-tryptophan in the presence of ascorbic acid and dopamine using poly(sulfosalicylic acid) modified glassy carbon electrode

In this work, a glassy carbon electrode modified with poly-sulfosalicylic acid (PSA/GCE) was prepared using electropolymerization method and applied for the determination of l-tryptophan (l-Trp) in the presence of ascorbic acid and dopamine. The morphologies and interface properties of PSA film were examined by scanning electron microscopy and electrochemical impedance spectroscopy. The electrocatalytic oxidation of l-Trp on the PSA/GCE from potentially interfering species, e.g. ascorbic acid (AA) and dopamine (DA) was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under optimum conditions, the proposed method exhibited wide linear dynamic range of 5 × 10−8 to 1 × 10−5 M with a detection limit (S/N = 3) of 6.8 × 10−9 M. Moreover, the modified electrode exhibited good reproducibility and high selectivity, demonstrating its feasibility for the analytical purpose.