Validation of HPLC method for determination of atorvastatin in tablets and for monitoring stability in solid phase

A rapid high performance liquid chromatographic method was developed and validated for determination of atorvastatin in pharmaceutical dosage forms, and for evaluation of its stability in the solid phase. Separation of atorvastatin was successfully achieved on a C-18 column utilizing water--acetonitrile at the volumetric ratio of 48:52, adjusted to pH 2.0 with 80% ortho-phosphoric acid. The detection wavelength was 245 nm. The method was validated and the response was found to be linear in the drug concentration range of 0.04 mg/mL - 0.4 mg/mL. The mean values +/- RSD of the slope and the correlation coefficient were 8.192 +/- 0.260 and 0.999, respectively. The RSD values for intra- and interday precision were < 1.00% and 0.90%, respectively. The degradation kinetic of atorvastatin at 363 K in a relative humidity of 76.4% was observed to be autocatalytic first order reaction. The kinetic parameters were as follows: k (where k represents the velocity constant; s(-1)) = (1.42 +/- 0.19) 10(-6); t(0.5) (where t(0.5) represents the time needed for a 50% decay of atorvastatin; days) = 32.82 +/- 0.9; t(0.1) (where t(0.1) represents the time needed for a 10% decay of atorvastatin; days) = 13.86 +/- 0.8.