Stability-indicating high-performance liquid chromatographic assay of atorvastatin with fluorescence detection

The purpose of this work was to develop a sensitive, selective, and validated stability-indicating high-performance liquid chromatographic (LC) assay of atorvastatin (ATV) in bulk drug and tablet form. ATV was subjected to different stress conditions, including UV light, oxidation, acid-base hydrolysis, and temperature. ATV and its degradation products were analyzed on an Agilent Zorbax XDB C18 column using isocratic elution with acetonitrile-0.02 M sodium acetate, pH 4.2 (45 + 55, v/v) for 25 min. The samples were monitored with fluorescence (FL) detection at 282 nm (excitation)/400 nm (emission). The response ratio of FL to UV detection (at 247 nm) for ATV was 1.66. The method showed good resolution of ATV from its decomposition products. The photodegradation products were separated by silica gel thin-layer chromatography using double development with ethyl acetate-n-hexane-glacial acetic acid-methanol (40 + 55 + 0.5 + 4.5, v/v/v/v) followed by (39 + 55 + 0.5 + 5.5, v/v/v/v), and confirmed by LC-FL analysis. The FL response was linear over the investigated range for ATV. The linear range was 10-1200 ng/injection, and the limit of quantitation was 2.0 ng/injection.