Electrochemical Quantification of Tyrosine in the Presence of Analogous Amino Acids

Abstract

Amnio acids are essential for body life, and thus, introducing novel simples/sensitive techniques/catalyst for detecting their low levels, especially in real samples and mixtures, is a great issue in analytical/bioanalytical chemistry. Thus, NiO nanoparticles were synthesized and used for the modification of a carbon paste electrode (CPE) for the square wave voltammetric (SqW) determination of tyrosine (Tyr) in the presence of tryptophan (Tryp), phenylalanine (PhA), and cysteine (Cis) amino acids (AA), all having the À CH 2 À CH(NH 2 )À COOH functional group. The calibration sensitivity was increased in interfering AA species which caused the decreased detection (for example, detection limit (DL) 1.32 μM to 0.88 μM Tyr) and quantification limits. For different concentrations of interfering AA species, the linear range (LR) was decreased that was more intense with an increase in AA amount. For example, the LR of 5-1800 μM Tyr in the absence of other AA species was changed to 80-800, 90-850, and 70 À 1000 μM Tyr in the presence of 20 mM Tyr, Csy, and PhA, respectively. A g-value of 0.487 < g 0.05,6,5 = 0.5875 confirmed the long-term stability of the electrode for 4 months. The electrode showed good selectivity towards Tyr in the presence of some amino acids and inorganic salts. Recovery experiments also confirmed the good capability of the electrode in Tyr quantification in a complex matrix such as six human serums used.