Determination of water-soluble small molecular antioxidants by capillary electrophoresis with electrochemical detection

The water-soluble small molecular antioxidants including glutathione (GSH), uric acid (UA), tryptophan (Try) and eystein (Cys) are very important to human being health and their detection is significant too. Because they are electro-active, electrochemical detection is more effective than ultraviolet detection in their analysis and performs a higher sensitivity. As a powerful separation technique, capillary electrophoresis has some advantages such as cheap instrumentation, low sampling volume and high speed and has been extensive studied and applied in biological analysis in past twenty years. The optimum conditions of determining GSH, UA, Try and Cys by capillary zone electrophoresis with electrochemical detection (CZE-AD) based on metallic copper electrode were studied in detail. The optimum conditions of CZE-AD were separation voltage 15 kV, running buffer 25 mmol/L Na₂B₄O₇-50 mol/L NaH₂PO₄ (pH 7.9), kinetic injection time 30 s and detection potential 0.5 V. The linear ranges of the four analytes were (1.0-5.0) × 10-⁶-5.0 × 10^-4 mol/L and the limits of detection were about 10^-6 mol/L under the optimal experimental conditions. This method performed some advantages in quickness, high sensitivity and simple instrumentation, and satisfactory results were obtained when it was applied to analyzing human plasma samples.