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Summary. An isocratic ion-pair reversed phase high-performance liquid chromatography-ultraviolet (RP-HPLC-UV) method for analysis of eberconazole nitrate in bulk and in pharmaceutical dosage forms has been developed and validated. Best separation was achieved on Lichrospher C18 column (250 mm × 4.6 mm, 5 μm) using a mobile phase of 10 mM potassium dihydrogen phosphate containing 10 mM tetra-butyl ammonium hydroxide (pH adjusted to 2.8 with ortho phosphoric acid) and methanol (75:25, v/v) at a flow rate of 1.0 mL min −1 . UV detection was performed at 220 nm. The method was validated for specificity, linearity, precision, accuracy, limit of detection, limit of quantification, robustness, and solution stability. The calibration plot was linear over the concentration range of 10-80 μg mL −1 (r 2 = 0.999) and the limits of detection and quantification were 0.3 and 0.9 µg mL −1 , respectively. Intra-day and inter-day precisions were 1.13% and 1.67%, respectively. Experimental design was employed to optimize the method. The method was successfully used for analysis of eberconazole nitrate in commercially available cream (Ebernet).

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The equilibrium dissociation constant (K D ) is the basic parameter to evaluate the binding property of the chemical structure of compounds. Thus, a variety of analytical methods have been established to determine the K D values, including radioligand binding assay, surface plasmon resonance method, fluorescence energy resonance transfer method, affinity chromatography, and isothermal titration calorimetry. Here we present a detailed overview of the dissociation equilibria of Eberconazole nitrate (EBZ) in homogeneous and heterogeneous systems, focusing primarily on methods that are based on spectrophotometrically of the dissociation reaction. The Dissociation equilibria of Eberconazole nitrate (EBZ) in homogeneous and heterogeneous systems were studied spectrophotometrically in Britton-Robinson's (BR) buffer at 25°C. Acidity constant of EBZ in BR buffer was found to be 9.5. The effect of anionic, cationic and non-ionic surfactants applied in the concentration exceeding critical micellar concentration (cmc) on acid -base properties of EBZ were also examined. The results revealed a shift of pKa values in micellar media comparing to the values obtained in BR buffer. These shifts in pKa values are more in cationic and anionic micellar media compared with that of non-ionic. The observed differences in pKa values between micellar media and BR buffer solution ranged between -6.0 to -2.0 units. The micellar-mediated pKa shifts can be attributed to the differences between the mean intrinsic solvent properties of the interfacial and bulk phases, with an additional contribution from the electrostatic micellar surface potential in the case of the charged aqueous micellar solutions.

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