Stability Study of Pravastatin under Hydrolytic Conditions Assessed by Hplc

In this work an HPLC stability-indicating method was developed and applied to study the hydrolytic behavior of pravastatin in different pHs and temperatures. From the system suitability test, the selected chromatographic conditions were a C-18 column, acetonitrile-30 mmol L-1 phosphate buffer solution pH 2 (28:72) as mobile phase, 40oC temperature column, a flux of 1 mL/min and 239 nm as wavelength detection. The developed method exhibited an adequate repeatability and reproducibility (CV 0.11% and 0.49%, respectively) and a recovery higher than 98%. Furthermore, the detection and quantitation limits were 3.4×10-7 mol L-1 and 3.7×10-6 mol L-1. The kinetic degradation of pravastatin fits to a pseudo-first order kinetic. The degradation was pH-dependent: alkaline pH < acid pH and the generation of degradation products was dependent of the media tested (one product in alkaline medium and 4 products in acid medium). Activation energy, kinetic rate constants at different temperatures, t1/2 and t90 values are also reported.