Simultaneous determination of tyrosine and tryptophan by mesoporous silica nanoparticles modified carbon paste electrode using H-point standard addition method.

A simple, selective and sensitive sensor based on mesoporous silica nanoparticles modified carbon paste electrode (MSNs/CPE) is introduced for electrochemical determination of tyrosine (Tyr) and tryptophan (Trp). Compared with the unmodified electrode and commercial SiO2 modified electrode (SiO2/CPE), the oxidation peak current significantly improved for both amino acids. Under optimized experimental conditions, the oxidation peak current of Trp was linear over a concentration range of 5.0 × 10(-8) to 4.0 × 10(-4) M with a detection limit of 3.4 × 10(-8) M. The oxidation peak current of Tyr was linear over a concentration range from 5.0 × 10(-7) to 6.0 × 10(-4) M with a detection limit of 1.5 × 10(-7) M. For simultaneous determination Trp and Tyr, H-point standard addition method was applied to resolve the overlapping of differential pulse voltammetric peaks of Trp and Tyr. The results showed that the method was successfully applied to the simultaneous determination of Trp and Tyr in some synthetic samples. Moreover, the applicability of the method was demonstrated by the recovery tests of Trp and Tyr in artificial urine.