Carbon paste electrode modified with a binuclear manganese complex as a sensitive voltammetric sensor for tryptophan

We report on a carbon paste electrode that was modified with a binuclear manganese(II) complex by the drop-coating method. A study on the mechanism of the electro-oxidation of tryptophan (Trp) at this electrode indicated that it enables Trp to be determined with good sensitivity and selectivity. Second-order derivative linear sweep voltammetry at pH 4.1 revealed that a sensitive anodic peak appears at 812 mV (vs. SCE) whose current is proportional to the concentration of Trp in the concentration range from 0.1 to 1.0 μmol L−1 and 1.0 to 80 μmol L−1, with a detection limit (S/N = 3) of 0.08 μmol L−1 (60 s of accumulation). The method was applied to the determination of Trp in amino acid injection solutions with satisfactory results.