Date of Award
Master of Science (MS)
Christopher T. Rhodes
The uptake of each of eleven structurally related solutes from pH 1 donor solution by an invariant liquid membrane formulation was investigated. The presence of polyamino surfactants in liquid membrane formulation significantly altered the partition of solutes between aqueous phase and oil phase. Benzoic acid and salicylic acid followed monoexponentiai kinetics while the uptake of other solutes followed biexponential processes, except p-aminobenzoic acid which was not transported at all. Both benzoic acid and salicylic acid were removed with a much faster rate compared to other solutes. Approximately, 90% of these solutes were removed in two and half minutes from the donor solution. It is proposed that the presence of a phenolic group allowed salicylic acid to be transported with a significantly high rate as it can form intramolecular hydrogen bonding which increases its solubility in non-polar solvents. This is supported by the fact that meta and para-hydroxybenzoic acids were removed at a much slower rate. As expected, p-amino benzoic acid was not transported through liquid membrane from an acidic donor solution probably because of the ionized amino group. In presence of methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, acetaminophen and salicylamide rupture of the liquid membrane was apparent. This is possibly due to the formation of alcohols in the internal aqueous phase when these esters react with the encapsulated buffer. From the data obtained, it appears that the apparent leakage follows zero order kinetics. A new and more sophisticated kinetic model is proposed in an attempt to rationalize the basic mechanisms behind the solute uptake by the liquid membranes. The data for benzoic acid, salicylic acid and acetylsalicylic acid were analyzed by this model. Benzoic acid was not fit by this model. The lack of success to fit the data for benzoic acid is probably due to the dimerization of benzoic acid in the liquid membrane. For salicylic acid, which followed monoexponential kinetics, micro-rate constant k1 is significantly higher than k2 and k3 while k1 is significantly smaller than k2 and k3 for acetylsalicylic acid which followed biexponential kinetics. Hence, it is possible that depending en the magnitude of these micro-rate constants the uptake process may follow either mono or biexponential kinetics.
Chilamkurti, Rao Nagamasthan, "STUDIES ON EFFECT OF MOLECULAB STRUCTURE OF SOME AROMATIC COMPOUNDS ON THEIR UPTAKE RATES BY A LIQUID MEMBRANE SYSTEM" (1979). Open Access Master's Theses. Paper 187.