Simultaneous Determination of Zidovudine and Lamivudine in Plasma Samples Using Miniaturized Homogenous Liquid-Liquid Extraction and High-Performance Liquid Chromatography

A simple and effective miniaturized homogenous liquid-liquid extraction technique coupled with a gradient HPLC method for the determination of lamivudine and zidovudine in the human plasma samples was developed. Separation of these drugs was performed on a C-18 stationary phase by using a mixture of acetonitrile and water as mobile phase. Extraction of drugs was achieved based on salting-out phenomenon. Variables affecting the extraction efficiency, such as solvent type and its volume, type of salt and its concentration and sample pH have been fully evaluated and optimized. These drugs were successfully extracted by acetonitrile as extracting solvent with sodium sulfate as salting-out agent. Under the optimized experimental conditions calibration curves showed good linearity (r(2) > 0.9938) and precision (RSD < 6.7%) in the working concentration ranges. The limits of detection for lamivudine and zidovudine were 0.006 and 0.003 mu g/mL, respectively. The limits of quantification for lamivudine and zidovudine were 0.02 and 0.01 mu g/mL, respectively. The recoveries were in the range of 88.0-100.0% with RSD values less than 7.5%. The method was successfully applied to extract and determine lamivudine and zidovudine in human plasma.