| Popis: |
The sorption isotherms of several drugs (progesterone, testosterone, hydrocortisone, amobarbital, barbital, butobarbital (sodium salt), pilocarpine hydrochloride) on C alumina particles as a function of surfactant concentration (Triton X-100) were constructed. It was found that the adsorption of the drugs is considerably enhanced by the nonionic surfactant above a concentration threshold of the order of 5 × 10 −5 mol/l, although Triton X-100 itself is poorly adsorbed on the alumina particles. The maximum increase in drug adsorption due to the surfactant is found to occur close to the critical micelle concentration (CMC); the increase is by a factor of 10 for all compounds studied. Due to the poor adsorption ability of Triton X-100, the drug mole fraction at the particle surface is above 0.8 for all compounds except for pilocarpine. The sorption isotherms were of two types: the more hydrophobic compounds displayed a plateau adsorption above the CMC; for the most hydrophilic compounds and the ionic drugs, the adsorption decreased from its maximum at the CMC to almost zero at higher surfactant concentration. The above phenomena seem to be the consequence of surface particle modifications induced by the surfactant monomers rather than an adsolubilization effect. |
