CMC determination and thermodynamic changes of the mixture of non-steroidal anti-inflammatory drug (mefenamic acid) with anionic surfactant (SDS), and cationic surfactant (CTAB) in aqueous solution

Surface tension was measured using a platinum plate of the tensiometer for aqueous solutions of non-steroidal anti-inflammatory drugs (NSAIDs) such as mefenamic acid in concentrations of (10-3,10-2,10-10 M) to study the effect of adding surfactants on the drug solubility, which are anionic surfactant    such as   sodium dodecyl sulfate (SDS) and cationic surfactant such as   cetyltriamonium bromide (CTAB) concentrations within range (1x10 -3 -1x10 -1 M). The effect of temperature at (313,303,293,283 K) on these aqueous solutions with Mefenamic acid has also been studied. From the plot of the concentration of aqueous solutions of surfactants with drug versus surface tension (ɣ) were obtained the critical micelle concentration (CMC). As well, the values of the Gibbs surface excess concentration (Γmax), minimum area occupied per molecule (Amin.), surface pressure at CMC (Πcmc) were determined on basis of the standard Gibbs free energy of adsorption (ΔG°ads) and the thermodynamic constants (ΔHm, ΔSm, ΔGm, ΔGads) were found at CMC for aqueous solutions.&nbsp