Micellar electrokinetic chromatography method development for determination of impurities in Ritonavir

Ritonavir is a synthetic peptidomimetic human immunodeficiency virus (HIV) protease inhibitor employed in the treatment of AIDS since 1996. Synthetic precursors are potential impurities in the final product. In the present work a micellar electrokinetic chromatography (MEKC) method for the separation of Ritonavir from three available synthetic precursors was developed. The optimized separation is performed in a background electrolyte composed of sodium tetraborate (pH 9.6; 15 mM) containing sodium dodecylsulfate (30 mM) and acetonitrile (18%, v/v). Mass spectrometry was used to confirm the identity of the tested substances. Good repeatability was observed for migration time (RSD about 0.4%) and peak area (RSD about 0.8%). The limits of detection (LOD) obtained allow the determination of two of the impurities at levels as low as 0.005% m/m, and one at a level of 0.3% m/m.