title: Combined effect of polarity and pH on the chromatographic behavior of some angiotensin II receptor antagonists and optimization of their determination in pharmaceutical dosage forms.
abstract: In the present study, the combined effect of mobile phase polarity and pH on retention behavior of some ARA-IIs (irbesartan, losartan, valsartan and telmisartan) is investigated. The linear relationships established between retention factors of the species and the polarity parameter of the mobile phase has proved to predict accurately retention in LC as a function of the acetonitrile content (50%, 55%, 60%, v/v). The suggested model uses the pH value in the acetonitrile-water mixture as mobile phase instead of pH value in water and takes into account the effect of activity coefficients. Moreover, correlation between retention and the mobile phase pH can be established allowing prediction of the retention behavior as a function of the mobile phase pH. The model can be used to estimate the pKa in an acetonitrile percentage between 50% and 60%, at 30 degrees C. The developed method was successfully applied to both the simultaneous separation of these drug-active compounds and individual determination in their commercial pharmaceutical dosage forms.
authors.affiliation: Department of Chemistry, Faculty of Science and Literature, Süleyman Demirel University, 32260 Isparta, Turkey.
authors.forename: Ebru Cubuk
authors.initials: EC
authors.lastname: Demiralay
authors.forename: Burcu
authors.initials: B
authors.lastname: Cubuk
authors.forename: Sibel A
authors.initials: SA
authors.lastname: Ozkan
authors.forename: Guleren
authors.initials: G
authors.lastname: Alsancak
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D047228:Angiotensin II Type 1 Receptor Blockers / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D013607:Tablets
chemical_list: D000097:Acetonitriles; D047228:Angiotensin II Type 1 Receptor Blockers; D013607:Tablets; C032159:acetonitrile