Optimization stacking by transient pseudo-isotachophoresis for capillary electrophoresis: example analysis of plasma glutathione

Low concentrations of both reduced form glutathione (GSH) and oxidized form glutathione (GSSG) in diabetic nephropathy (DN) patient’s plasma were measured with transient pseudo-isotachophoresis. The plasma samples were deproteined with acetonitrile and centrifuged. The method was performed at constant voltage of 5 kV using a 300 mM borate buffer (pH 8.0), with a fused-silica capillary of 21 cm×75 μm. The sample length can reach 25% of the efficient length of the capillary, and the sensitivities of GSH and GSSG increased 15–20-fold. The method was also systematically optimized, and the results show that this type of stacking offers good repeatability for routine clinical assay of glutathione in DN plasmas.