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.
Highlights
Atorvastatin calcium (ATC) is chemically [R-(R,R)]-2 (4fluorophenyl)-β,δ-dihydroxy-5(1-methylethyl)-3-phenyl-4(phenylamino)]-1H-pyrrole-1-heptonoic acid, calcium salt (2:1) with molar mass 1115.36 g/mol whereas pitavastatin calcium (PTC) is monocalcium (3R,5S,6E)-7-[2-cyclopropyl-4-(4-fluorophenyl)-3quinolinyl]-3,5-dihydroxy-6-heptenoic acid with molar mass 880.98 g/mol
Dimethyl sulfoxide (DMSO), N, N-dimethyl formamide (DMF) and acetonitrile were of spectroscopy grade solvents purchased from Merck, India
The different colored ionpair complexes showed maximum absorbance at 637 nm for both ATC: bromothymol blue (BTB) and PTC: BTB, 606 nm for ATC: bromocresol purple (BCP), 601 nm for PTC: BCP, 631 nm for both ATC: bromocresol green (BCG) and PTC: BCG, which was shown in the fig
Summary
Atorvastatin calcium (ATC) is chemically [R-(R,R)]-2 (4fluorophenyl)-β,δ-dihydroxy-5(1-methylethyl)-3-phenyl-4(phenylamino)]-1H-pyrrole-1-heptonoic acid, calcium salt (2:1) with molar mass 1115.36 g/mol whereas pitavastatin calcium (PTC) is monocalcium (3R,5S,6E)-7-[2-cyclopropyl-4-(4-fluorophenyl)-3quinolinyl]-3,5-dihydroxy-6-heptenoic acid with molar mass 880.98 g/mol. The chemical structures of them are shown in the fig. They are the statin drugs and are a potent inhibitor of 3-hydroxy-3methylglutaryl coenzyme A (HMG-CoA) reductase. They are used to reduce serum levels of LDL-cholesterol; apolipoprotein B and triglycerides and to increase serum levels of HDL-cholesterol in the treatment of hyperlipidemias and prevent of cardiovascular diseases in patients with multiple risk factors [1]. ATC is official in USP 34, IP [2, 3].
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