In Vivo Determination of Tetrahydrobiop- terin and Monoamine Neurotransmitters in Rat Brain by Liquid Chromatography with a Nano Crystalline Mn-Doped Lead Dioxide Film Modified Electrode

Abstract

The fabrication and application of a novel electrochemical detector (ED) with nano crystalline Mn-doped lead dioxide film chemically modified electrode (CME) for liquid chromatography (LC) were described. The Mn-doped PbO₂ film was characterized by scanning tunnel microscope. The electrochemical behaviors of tetrahydrobiopterin, monoamine neurotransmitters and their metabolites at the CME were investigated by cyclic voltammetry and differential pulse voltammetry. It was found that the CME exhibited efficiently electrocatalytic effect on the current response of the seven analytes and the linear ranges of them were over three orders of magnitude with the detection limits being 5.0 × 10⁻¹⁰ mol L⁻¹ for tetrahydrobiopterin, 2.5 × 10⁻¹⁰ mol L⁻¹ for dopamine, 2.0 × 10⁻¹⁰ mol L⁻¹ for norepinephrine, 5.0 × 10⁻¹⁰ mol L⁻¹ for serotonin, 4.0 × 10⁻¹⁰ mol L⁻¹ for 3,4-dihydroxyphenylacetic acid, 2.0 × 10⁻⁹ mol L⁻¹ for homovanillic acid, 1.0 × 10⁻⁹ mol L⁻¹ for 5-hydroxyindoleacetic acid. For its stability, sensitivity, convenience in preparing and long-life of activity, the Mn-doped PbO₂ electrode is therefore suitable for determination of real samples. Coupled with microdialysis sampling, the application of this method for the analysis of tetrahydrobiopterin, monoamine neurotransmitters and their metablites in rat brain was satisfactory.