Determination of glutathione and glutathione disulfide in hepatocytes by liquid chromatography with an electrode modified with functionalized carbon nanotubes.

Glutathione (GSH) and glutathione disulfide (GSSG) are important thiols, which provide defence against oxidative stress by scavenging free radicals or causing the reduction of hydrogen peroxide. The ratio GSH/GSSG is often used as a sensitive index of oxidative stress in vivo. In this paper, a direct electrochemical method using an electrode modified with functionalized carbon nanotubes as electrochemical detector (ED) for liquid chromatography (LC) was described. The electrochemical behaviors of GSH and GSSG on this modified electrode were investigated by cyclic voltammetry and it was found that the functionalized carbon nanotubes exhibited efficiently electrocatalysis on the current responses of GSH and GSSG. In LC-ED, both of the analytes showed good and stable current responses. The detection limit of GSH was 0.2 pmol on column and that of GSSG was 1.2 pmol on column, which were low enough for the analysis of real small samples. The method was sensitive enough to detect difference in concentration of GSH and GSSG in hepatocytes from animals with and without introduction of oxidation stress by glucose or hydrogenperoxide.

Liquid chromatography with amperometric detection using functionalized multi-wall carbon nanotube modified electrode for the determination of monoamine neurotransmitters and their metabolites.

The fabrication and application of a novel electrochemical detection (ED) method with the functionalized multi-wall carbon nanotubes (MWNTs) chemically modified electrode (CME) for liquid chromatography (LC) were described. The electrochemical behaviors of dopamine (DA) and other monoamine neurotransmitters at the CME were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results indicated that the CME exhibited efficient electrocatalytic effects on the current responses of monoamine neurotransmitters and their metabolites with high sensitivity, high stability and long-life activity. In LC-ED, DA, norepinephrine (NE), 3-methoxy-4-hydroxyphenylglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) had good and stable current responses at the CME. The linear ranges of seven analytes were over four orders of magnitude and the detection limits were 2.5 x 10(-10) mol/l for DA, 2.5 x 10(-10) mol/l for NE, 5.0 x 10(-10) mol/l for MHPG, 3.0 x 10(-10) mol/l for DOPAC, 3.5 x 10(-10) mol/l for 5-HT, 6.0 x 10(-10) mol/l for 5-HIAA, 1.25 x 10(-9) mol/l for HVA. The application of this method coupled with microdialysis sampling for the determination of monoamine neurotransmitters and their metabolites in Parkinsonian patients' cerebrospinal fluid was satisfactory.