Analysis of Atorvastatin as per USP Monograph Utilizing Alliance™ iS HPLC System

Atorvastatin, a widely prescribed statin drug, is used to lower cholesterol levels and reduce the risk of cardiovascular diseases.1,2 To ensure the safety and efficacy of this drug, it is essential to analyze atorvastatin and related compounds using techniques such as High-Performance Liquid Chromatography (HPLC).3,4 The USP monograph for atorvastatin assay analysis using HPLC requires careful control of all aspects of the method, including mobile phase and sample preparation.5 The monograph's conditions make it difficult to meet the system suitability criteria. The volatile components in the sample and mobile phase can evaporate during the analysis, causing changes in the peak areas and retention times. This can lead to the method failing system suitability even if the column and instrument are functioning properly. The specific conditions that pose a challenge include the use of a highly volatile sample diluent (1:1:2 acetonitrile: tetrahydrofuran (THF): water), a volatile component in the mobile phase (THF at 12%), and a long analysis time (two hours).

Previously, a thorough investigation was conducted to assess the influence of these conditions on meeting the system suitability criteria.6 The study revealed that the effects of sample preparation and mobile phase composition can be effectively controlled by implementing two measures. Firstly, instead of utilizing a single vial, multiple vials should be employed for the replicate injections. Secondly, employing low vapor reservoir caps for the mobile phase reservoirs proves beneficial. These measures help mitigate the impact of sample preparation and mobile phase composition, contributing to improved control and reproducibility of the analysis. This study will demonstrate the analysis of atorvastatin according to the USP monograph using the Alliance iS HPLC System.