Simultaneous determination of rosiglitazone and metformin in plasma by gradient liquid chromatography with UV detection.

A novel, fast and simple liquid chromatographic method was developed and validated for the simultaneous determination of rosiglitazone and metformin in human plasma. The analysis was performed on a phenyl column (250mmx4.6mm i.d., 5mum) using a gradient method starting with mobile phase composed of acetonitrile:5mM acetate buffer pH 5.5 (75:25, v/v). The flow rate was 1mLmin(-1). UV detection was performed at 245nm and verapamil was used as internal standard. The total run time was less than 10min. Sample preparation included a simple protein precipitation step with acetonitrile. Validation experiments were performed to demonstrate stability, specificity, sensitivity, linearity, accuracy, precision and robustness. The limit of quantification was 100ngmL(-1) for rosiglitazone and 250ngmL(-1) for metformin. The extraction recoveries were 100.02-105.0% for rosiglitazone and 105.64-103.88% for metformin. The method was applied with success to plasma samples obtained from diabetic patients undergoing treatment with rosiglitazone and metformin.