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The equilibrium dissociation constant (KD) 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 KD 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.

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 (r2 = 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 metho...

An isocratic RP-HPLC–UV method for the analysis of voriconazole in skin diffusate samples has been developed and validated. Experimental design was employed to optimize the method. The method was validated as per ICH guidelines. Linearity was observed over the concentration range of 2–100 μg mL−1 (r2 = 0.999). Limits of detection and quantification were 0.6 and 2 μg mL−1, respectively. Intra-day and inter-day precision (% RSD) was within the ICH limits (⩽2%). The method was successfully used to analyze skin diffusate samples, and the effectiveness of different permeation enhancers was compared with respect to flux and permeability coefficient.

Stability of eberconazole nitrate (EBZ) was investigated using a stability indicating HPLC method. Quality by Design (QbD) approach was used to facilitate method development. EBZ was exposed to different stress conditions, including hydrolytic (acid, base, neutral), oxidative, thermal and photolytic. Relevant degradation was found to take place in all the conditions. The degradation of EBZ followed (pseudo) first-order kinetics under experimental conditions. The kinetic parameters (rate constant, t1/2, and t90) of the degradation of EBZ were calculated.