Forced degradation studies of simvastatin using microemulsion liquid chromatography

Abstract

In this paper, the definition of simvastatin degradation profile by microemulsion liquid chromatography (MELC) is presented. The aim of the study was to investigate simvastatin stability after various stress tests, such as: acid and base hydrolysis, oxidation, and heat. The kinetics of acid and oxidative degradation was also studied. The complex retention mechanism occurring when microemulsion is used as eluent enabled the successful separation of a large number of degradants in prepared stress samples. The existence of a second partitioning site due to microstructural and interfacial characteristics of o/w microemulsion eluent facilitated HPLC separation. All the expected capabilities of MELC method were realized, demonstrating the advantage and value of the MELC method for a wide area of pharmaceutical analysis. For acid degradation the second order rate constant and half-life were calculated. Oxidative decomposition proved to be the first order reaction for which the rate constant and half-life were also determined.