Surface activity and micellization of streptomycin sulfate and diphenhydramine hydrochloride in the presence of alkali and alkaline earth metal chlorides

The study investigated the surface tension of the surface-active drugs streptomycin sulfate and diphenhydramine hydrochloride using three uni-univalent and three bi-univalent electrolytes: NaCl, KCl, and RbCl (0.01 mol.kg⁻¹), and MgCl₂, CaCl₂, and SrCl₂ (0.002 mol.kg⁻¹) over a temperature range of 298.15 to 313.15 K. Surface tension determination has proven instrumental in examining the micellization and surface-active properties of these drugs in the presence of specific electrolytes. The surface tension values of these drugs exhibit a decrease in magnitude with increasing drug concentration, particularly noticeable in streptomycin sulfate. This phenomenon can be elucidated by considering the delicate balance between hydrophobic and hydrophilic forces within the system. Additionally, the impact of the nature of metal halides and temperature on surface tension magnitude has been scrutinised, with interpretations focused on alterations in size. From surface tension values, the interfacial parameters, such as Γmax, Amin, and πCMC were examined. The results indicate a strong affinity between drug-electrolyte molecules that reduces the surface tension values. The CMC relations govern the hydrophobic and hydrophilic interactions in the ternary system of water-drug-electrolyte. The thermodynamics of micellization explains the work done for micellization and illuminates the surface and bulk properties of drugs.