In vivo monitoring of the monoamine neurotransmitters in rat brain using microdialysis sampling with liquid chromatography electrochemical detection

The fabrication and application of a novel electrochemical detector (ED) with the new ion-exchange polymer-overoxidized polypyrrole (OPPy) film chemically modified electrode (CME) for liquid chromatography (LC) are described. The electrochemical behavior of dopamine (DA) and ascorbate (AA) at the OPPy CME is investigated by cyclic voltammetry (CV). It is found that the CME can permselective dopamine cations and exile the ascorbate anions, which could be used to determine the monoamine neurotransmitters and avoid the interference of ascorbate in liquid chromatography. The thickness of the OPPy film has an important effect on the sensitivity and selectivity for dopamine with respect to ascorbate. In liquid chromatography with electrochemical detection (LC-ED), DA, norephinephrine (NE), 5-hydroxytryptamine (5-HT), epinephrine (E) and 3,4-dihydroxyphenylacetic acid (DOPAC) have good and stable current responses at the CME. The linear ranges of five analytes are over three orders of magnitude and the limits of detection are 0.05 pmol for DA, 0.05 pmol for NE, 0.05 pmol E, 0.1 pmol for 5-HT and 1.0 pmol for DOPAC. The applications of this method coupled with microdialysis sampling for the in vivo determination of the monoamine neurotransmitters in the different areas of rat brain is satisfactory. (C) 2001 Elsevier Science B.V.