Coupling of NiO Nanoparticles and Room Temperature Ionic Liquid for Fabrication of Highly Sensitive Voltammetric Sensor in Tryptophan Analysis

A NiO nanoparticle (NiO/NPs) ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) modified carbon paste electrode (NiO/NPs/HMIHP/CPE) was developed for the analysis of tryptophan. The electrochemical behavior of tryptophan was investigated using cyclic voltammetry, chronoamperometry and square wave voltammetry (SWV). NiO nanoparticles synthesized by direct chemical precipitation method and characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. These studies revealed that the oxidation of tryptophan is facilitated at NiO/NPs/HMIHP/CPE. Using SWV, the method allowed determination of tryptophan in the linear working range of 0.08-350 μM with detection limit of 0.04 μM (S/N=3). The NiO/NPs/HMIHP/CPE was used for the determination of tryptophan in urine and water samples.