Spectrophotometric Determination of Atorvastatin Calcium and Pitavastatin Calcium Through Ion-Pair Complex Formation Using Acid Dyes in Pharmaceutical Formulations and Human Urine Samples

Abstract

Objective: The main objective was to develop simple, cost-effective, rapid and selective spectrophotometric methods for the determination of atorvastatin calcium and pitavastatin calcium in pure and pharmaceutical formulations using acid dyes like bromothymol blue, bromocresol purple and bromocresol green and also in human urine samples.
 Methods: The developed methods were based on the formation of ion-pair complexes between statin drugs and acid dyes after studying the optimization conditions. The association constants of the developed ion-pair complexes were evaluated using Benesi–Hildebrand equation. The methods were validated according to ICH guidelines.
 Results: The formed ion-pair complexes showed maximum absorbance which was measured at 637 nm for both methods A and D, 601 nm, 606 nm for methods B and E and 631 nm for both methods C and F respectively with correlation coefficients 0.999. The analytical parameters and their effects in the developed methods were investigated. The ion-pair complexes were stable up to 24 h and showed good linearity. The molar absorptivity, Sandell sensitivity, detection, and quantification limits were also calculated. The stoichiometry ratio in all the cases was 1:2 by using Job’s method of continuous variation. The recovery studies again showed good results because co-formulated substances did not interfere for the determination of ATC and PTC in the developed methods.
 Conclusion: The developed methods were applicable for routine quality control analysis of ATC and PTC in pure and pharmaceutical dosage forms. Good results were obtained when the developed methods were applied in healthy human urine samples.