Electrochemical behavior and determination of L-tryptophan on carbon ionic liquid electrode

Abstract

A carbon ionic liquid electrode (CILE) was fabricated by mixing N-butylpyridinium hexafluoro-phosphate (BPPF ₆ ) with graphite powder and further used for the investigation on the electrochemical behavior of L-tryptophan (Trp). The fabricated CILE showed good conductivity, inherent electrocatalytic ability and strong promotion to the electron transfer of Trp. On the CILE, an irreversible oxidation peak appeared at 0.948 V (vs. saturated calomel reference electrode). For 5.0 × 10⁻⁵ M Trp the oxidation peak current increased about 5 times and the oxidation peak potential decreased on 0.092 V compared to carbon paste electrode. The results indicated that an electrocatalytic reaction occurred on CILE. The conditions for the electrochemical detection were optimized and the electrochemical parameters of Trp on CILE were carefully investigated. Under the selected conditions, the oxidation peak current showed linear relationship with Trp concentration in the range of 8.0 × 10⁻⁶ ∼1.0 × 10⁻³ M for cyclic voltammetry and the detection limit was estimated as 4.8 × 10⁻⁶ M (3σ). The interferences of other amino acids or metal ions on the determination were tested and the proposed method was successfully applied to the synthetic sample analysis.