Interaction of cephalexin monohydrate with surfactants in aqueous and sodium chloride solution at variable temperatures: Conductivity and spectroscopic measurements

Abstract

Cephalexin monohydrate (CLM) is a well-known antibiotic applied for prohibiting bacterial growth. Herein, the mode of interaction of CLM with both ionic (cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS)), and nonionic (triton X-100 (TX-100)) surfactants, was investigated using the conductivity measurement and UV–Visible spectroscopic techniques in H2O and NaCl + H2O media at numerous temperatures ranging from 293.15 to 328.15 K. In the current study, the critical micelle concentration (CMC) of CLM + CTAB and CLM + SDS mixed systems was estimated from a sudden and clear breakpoint of specific conductivity (κ) versus the concentration of surfactant plot. A single CMC was found for both CLM + CTAB and CLM + SDS systems in entirely experimental cases studied. The value of CMC of surfactants undergoes a drop in presence of CLM in an aqueous phase and hence, the drug causes an enhancement of the extent of micellization of surfactants. Also, the CMC values of CLM + CTAB and CLM + SDS mixed systems were found to reduce in NaCl + H2O medium and the CMC values were observed to experience a further reduction with increasing concentration of NaCl salt. A negative standard free energy change (∆Gmo) of micellization discloses that the CLM + ionic surfactant micellization is spontaneous. The different thermodynamic parameters of transfer and the enthalpy-entropy compensation parameters of micelle formation were also measured and demonstrated appropriately. The binding constant (Kb) of the CLM + TX-100 mixture has been evaluated from the Benesi-Hildebrand equation and the values were found to be dependent on CLM concentration and temperature. The ∆Hbo and∆Sbo values of CLM + TX-100 mixture reveal the survival of the electrostatic force of interaction along with the presence of hydrophobic interaction developed between the CLM drug and TX-100 surfactant.