Sensitive Spectrophotometric Determination of Atorvastatin in Pharmaceutical Formulation by Ion Pair Complexation with Pararosaniline Hydrochloride

Objectives: A sensitive visible spectrophotometric method was developed for the determination of atorvastatin in tablet dosage form. Methods: Atorvastatin (ASN) has a free carboxylic moiety in its structure, which when being deprotonated in basic buffered medium facilitates its ion pairing with the cationic pararosaniline dye. Results: The red colored ion pair is easily extractable in organic solvent and exhibits maximum absorption at 547 nm. Different factors affecting the formation of the ion pair and its stability were studied and optimized in order to obtain the best conditions for the experiment. Method validation was done over a concentration range of 1 to 8 µg/mL. The method was proven to be sensitive with limit for quantitation of 0.93 µg/mL and limit of detection of 0.31 µg/mL. Conclusion: The proposed method was easily and successfully applied for the quantitative determination of atorvastatin in commercial tablets without interference from extractable tablet additives. The sensitivity and cheapness of the method will encourage its use in routine quality control of atorvastatin tablets.