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Stability study of simvastatin and pravastatin sodiumunder acidic hydrolytic conditions assessed by high performance liquid chromatography

Hayam M.Lotfy, Hoda F.El Sanabary, Zeinab A.El-Sherif, Mohammad G.El-Bardicy

In this work, a liquid chromatography stability indicating method was developed and applied to study the hydrolytic behavior of simvastatin (I) and pravastatin sodium (II) in acid medium of different normalities at different temperatures. The developed chromatographic conditions were Zorbax C8 (10µm,150mm ï‚´ 4.6mm, i.d..)with particle size of 5 µm column, with a mobile phase consisting ofmethanol : de-ionized water (80 :20, v/v) ;and flow rate 1.5 ml / min. The method showed high sensitivity with good linearity over the concentration range of 2 to 25 µg / ml of both. The method is successfully applied to the analysis of pharmaceutical formulations containing (I) and (II) with excellent recovery. The kinetics investigation of the acidic hydrolysis of (I) and (II) are carried out in hydrochloric acid solutions of 1.0, 2.0 N and 4.0 N by monitoring the parent compound itself. The reaction order of (I) and (II) followed pseudo-first order kinetics. The activation energy could be estimated from the Arrhenius plot and it was found to be 11.82 and 11.22 Kcal/ mol. for simvastatin (I) and pravastatin sodium (II) respectively.