A Study on the Retention Behavior of Some Imidazole Antimycotic Drugs in Acetonitrile-Water Binary Mixtures

Abstract

Objective: In this study, the thermodynamic protonation constant ( 𝑝𝐾 𝑎 𝑠 𝑠) of antifungal azole derivative miconazole and tioconazole were investigated by the reversed-phase liquid chromatography (RPLC) method. Although classical stationary phases are the most commonly used column-packed materials in the analyses of these compounds by the RPLC method, the determination of the pKa value of miconazole and tioconazole with a cyano-based column has not been reported so far.Material and Method: Chromatographic behavior of the selected compounds was determined with Ultra Cyano column (Restek ® , 150×3.0 mm I.D, 3µm) which is compatible with hydrophobic compounds. The dependence of the retention times on the acetonitrile content of the mobile phase and the effect of the mobile phase pH on the chromatographic retention was determined for each compound by changing the pH in the range of 3.0-7.50. Result and Discussion: The 𝑝𝐾 𝑎 𝑠 𝑠 values were determined by a nonlinear regression program. The thermodynamic aqueous pKa ( 𝑝𝐾 𝑎 𝑤 𝑤 ) value of the studied compounds was calculated from the 𝑝𝐾 𝑎 𝑠 𝑠 value by using the macroscopic parameters (dielectric constant and mole fraction) that play an important role in the solvent properties. The calculated 𝑝𝐾 𝑎 𝑤 𝑤 values were compared with literature values.

Determination of protonation constant value of thiabendazole in ethanol-water binary mixtures by green RPLC method

“…The potentiometric titrations and spectrophotometric analyses used for the determination of this physicochemical parameter can be problematic if the compound is not pure, poorly soluble in water, has no distinct chromophore group, and is low in amount. Determination of pKa values by the RPLC method, which overcomes such disadvantages, is preferred [13][14][15].…”