Quantitation of oxidized and reduced glutathione in plasma by micellar electrokinetic capillary electrophoresis

A method for the separation of reduced (GSH) and oxidized (GSSG) glutathione was optimized in terms of buffer concentration, sodium dodecyl sulfate concentration, buffer pH, detection wavelength, run voltage and injection volume. The method demonstrated good linearity (r2 > 0.999) and reproducibility (internal standard corrected peak area RSD < 2.3%) in the range of interest (16-81 microM GSH and 8-40 microM GSSG). A detection limit of less than 1 microM GSH and GSSG was obtained using a high sensitivity flow cell. When the optimized method was applied to plasma samples, concentrations of 1.6 microM GSH and 0.8 microM GSSG were easily detected without the need for derivatization. The on-capillary detection was calculated to be 38.6 fmol of GSH and 18.3 fmol of GSSG.