Study on Dissociation Equilibria of Eberconazole Nitrate in Micellar Media by Spectrophotometry

Marothu Vamsi Krishna,D Gowri Sankar,Salah Ali Mahgoub Idris,B Jalachandra Reddy,M Sowhardhra,G Madhavi

doi:10.11648/j.ijpc.20190505.11

Marothu Vamsi Krishna, D Gowri Sankar + Show 4 more

Open Access

https://doi.org/10.11648/j.ijpc.20190505.11

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Abstract

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.

Highlights

Dissociation constants are important parameters to indicate the extent of ionization of molecules in solution at different pH values [1]
The concentration of the surfactants of 0.01 M chosen in order to examine their effects on pKa value of Eberconazole nitrate (EBZ) was well above critical micelle concentration and the changes in cmc due to the solute could be neglected
The results showed that surfactant micellar media can affect the dissociation equilibria of EBZ

Summary

Introduction

Dissociation constants are important parameters to indicate the extent of ionization of molecules in solution at different pH values [1]. The acidity constants of organic reagents play a fundamental role in many analytical procedures such as acid-base titration, solvent extraction, complex formation, and ion transport. It has been shown that the acid-base properties affect the toxicity, chromatographic retention behavior, and pharmaceutical properties of organic acids and bases [2]. Potentiometric titration [4] and spectrophotometric determination [5] are the most useful and widely used methods. Drugs may be classified into three categories according to their physical behavior in aqueous solution: (1) they may exist entirely as ions, such as K+, Cl−, or NH+4 (strong electrolytes); (2) they may be undissociated, as with the steroids and the sugars (non electrolytes); or (3) they may be partially dissociated and exist in both an ionic and a molecular form, the relative concentrations of which will

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