Simultaneous and direct determination of tryptophan and tyrosine at boron-doped diamond electrode

A facile method for the simultaneous measurement of tryptophan (Trp) and tyrosine (Tyr) was firstly exploited at unmodified boron-doped diamond (BDD) electrode. The experimental results indicated that by using differential pulse voltammetry, the oxidative peaks of these two kinds of amino acids could be completely separated at BDD electrode. The peak separation of Trp and Tyr was developed to be 0.64 V when Na₂PO₄/NaOH buffer solution with the optimized pH 11.2 was employed. The detection limit of Trp was obtained to be 1 × 10^-5 M, while that of Tyr was achieved to be 1 × 10^-6 M. The present method was also evidenced to be available to the determination of real samples of amino acids.