New Application of pH-Mediated Acid Stacking Technique for Amphoteric Compounds in Capillary Electrophoresis: Example Assay of Blood Glutathiones.

Both reduced and oxidized forms of glutathiones were firstly stacked and detected using pH-mediated acid stacking method, in which glutathiones were stacked as cations and separated as anions. Factors, such as injection time, sweeping time, buffer pH, concentration of sodium chloride in sample matrix, that influenced stacking and separation were systematically studied and optimized. Under the optimum condition, the enhancement factors of similar to 20 times for both reduced and oxidized forms of glutathiones could be easily obtained within 20 min with satisfied sensitivities (limit of detections were 0.12 and 0.06 mu mol/L for reduced and oxidized glutathione, respectively, at signal-to-noise ratio, S/N = 3), linearity range (0.3-300.0 and 0.6-300.0 mu mol/L for reduced and oxidized glutathione, respectively), recoveries (> 98%) and reproducibilities (relative standard deviation < 5.1% for peak height). The proposed method provides an alternation way for assaying of glutathiones, as well as amphoteric compounds, in blood sample.