A novel and simple capillary zone electrophoresis method was developed and validated for the simultaneous determination of rosiglitazone and metformin in pharmaceutical preparations. The optimum separation for these analytes was achieved in < 9 min at 25 degrees C with a fused-silica capillary column (80.5 cm x 75 mu m i.d., effective length 72.0 cm) and a running buffer containing 25 mM acetate buffer at pH 4.0. The samples were injected hydrodynamically for 3 s at 50 mbar and the applied voltage was +25.0 kV. Detection wavelength was set at 203 nm. Verapamil was used as internal standard. The method was suitably validated with respect to specificity, linearity, limit of detection and quantitation, accuracy, precision, and robustness. The limits of detection and quantitation were 0.5 and 1.0 mu g mL(-1) for rosiglitazone and metformin, respectively. The method developed was successfully applied to the simultaneous determination of rosiglitazone and metformin in pharmaceutical preparations. The results were compared to a liquid chromatographic method reported in the literature and no significant difference was found statistically. (c) 2005 Elsevier B.V. All rights reserved.