Oncepts in development of fast, simple, stability indicating HPLC method for analysis of atorvastatin related compounds in tablets

Abstract

New, fast, simple and mild conditioned High Performance Liquid Chromatography (HPLC) method for determination of atorvastatin and its 7 main specified impurities, as well as unspecified impurities that might possibly appear, was developed. Chromatographic runs last between 25 and 40 minutes, with simple stepwise gradient elution. The main accent in our method development strategy was focused on mobile phase, composed of simple binary system composed of phosphate buffer and acetonitrile, at pH 4.1, without use of tetrahydrofuran, ion-pair reagents, trifluoroacetic acid and other modifiers with high Ultraviolet (UV) cut-off like absorptive acetate or formiate buffers or amines. With our concept of mobile phase, different columns from myriad were tested, with different efficiency, dimensions and properties, which resulted in different separation efficiency and run time. The best results, concerning essential critical peak resolution, run time length including column preparation and equilibration and column backpressure, were achieved with: YMC C18 Triart 150mm x 4.6mm, 3µm (YMC America, Inc.), afterwards with Nucleodur 100-3-C18ec 250mm x 4.6mm, 3µm (Macherey-Nagel GmbH & Co., Germany), Waters Symmetry C18 250mm x 4.6mm, 5µm (Waters, USA) and Superspher C18e 125mm x 4mm, 4µm (Merck, Darmstadt, Germany). All this columns achieve excellent results regarding obligated critical resolution between atorvastatin impurity B and atorvastatin (according to European Pharmacopoeia),1 or in some cases between atorvastatin impurity B and atorvastatin impurity C, to be minimum about 1.5, in both cases.