Development of the Spectrophotometric Method for the Determination of Atorvastatin Calcium in Tablets by using Bromophenol Blue

A simple, rapid, and inexpensive spectrophotometric method for the determination of atorvastatin calcium in tablets has been developed. It requires only one reagent (BPB) and suitable for routine pharmaceutical analysis with less sophisticated equipment. The procedure for atorvastatin determination is based on its interaction with bromophenol blue (BPB) in medium of organic solvent. As a result of the reaction, the intensity of the band of the doubly ionized form of the BPB with a maximum at 595 nm increases. The maximum analytical signal is observed in a solution of methanol, chloroform, or acetonitrile, while ethanol and ethyl acetate turned out to be unsuitable. The optimal concentration of BPB is 4.12·10-4 M. To study the stability, the absorbance of the obtained solution was measured under optimal conditions for 45 min. The stoichiometric ratio of components in the resulting associate, determined by the method of continuous variations, is 1:1. The calibration graph is linear in the range from 4.1 to 33 μmol/L. The calculated LOD and LOQ values were 1.36 μmol/L and 4.13 μmol/L, respectively. The systematic error of the method is statistically insignificant in the whole range of calibration graph. The developed method was successfully applied for the determination of atorvastatin in tablets.