Elena Ruse

Analytical Applications of Transport Through Bulk Liquid Membranes

ABSTRACT This review discusses the results of research in the use of bulk liquid membranes in separation processes and preconcentration for analytical purposes. It includes some theoretical aspects, definitions, types of liquid membranes, and transport mechanism, as well as advantages of using liquid membranes in laboratory studies. These concepts are necessary to understand fundamental principles of liquid membrane transport. Due to the multiple advantages of liquid membranes several studies present analytical applications of the transport through liquid membranes in separation or preconcentration processes of metallic cations and some organic compounds, such as phenol and phenolic derivatives, organic acids, amino acids, carbohydrates, and drugs. This review presents coupled techniques such as separation through the liquid membrane coupled with flow injection analysis.

Facilitated transport of 5-aminosalicylic acid through bulk liquid membrane

This paper describes the experimental results obtained at the transport of 5-aminosalicylic acid (5ASA) through agitated bulk liquid membrane, using Aliquat 336, as carrier, dissolved in a chloroform membrane. The influence of 5-aminosalicylic acid concentration in the feed source, HCl concentration in the stripping phase and carrier (Aliquat 336) concentration in the membrane were investigated. The optimal pH condition of feed source was established based on the speciation diagram of 5-aminosalicylic acid. The assessment of the transport process was performed by determining the kinetic parameters—mass transfer coefficient and entrance and exist flow in and out of the chloroform membrane.

Transport and separation through bulk liquid membrane of some biologic active compounds

Abstract Transport through liquid membranes of various chemical species is a viable method for different applications in analytical or technological domain. This paper presents the transport and separation results of two compounds of pharmaceutical importance: salicylic acid and aspirin, using bulk liquid membrane technique. We studied the effect of the feed source and receiving phase pH on the transport efficiency of the two compounds throught chloroform membrane. These results were correlated with speciation diagrams of salicylic acid and aspirin. The speciation diagrams shows that in these pH conditions, for aqueous phase of the membrane system, the two compounds are mostly undissociated form and therefore active for transport. In this system it can be achieve separation of the two compounds, salicylic acid and aspirin, using a suitable complexing agent in the feed source such as Fe3+. In this way salicylic acid forms an inactive complex structure for transport while aspirin crosses the membrane and it is recovered in a percentage of 80% in the receiving phase membrane system.

Optimization of the transport of aminic substrates

Abstract A series of aminic substrates were transported and separated by means of a chloroformic liquid membrane. Several system parameters (source phase pH, receiving phase pH, carrier concentration, substrate concentration, stirring rate, transport duration) were investigated in order to determine the best experimental conditions that allow a proper separation of aliphatic and aromatic amines from aqueous mixtures. As the substrate started to be transferred against its concentration gradient, the part played by the carrier became more important. The results were analyzed assuming that the global transport experiment consisted of a series of extraction equilibria taking place simultaneously at the two water–membrane interfaces, and considering that the rate determining process was the diffusion of the neutral substrate, and its association with the carrier through the organic membrane. Aniline could be successfully separated from dimethylaniline, and di-n-butylamine, and cyclohexylamine from morpholine, fact that encouraged the working out of the environmental aspects of our project.

Amine Mixture Separation Assisted by Macrocyclic Ligands

Liquid-liquid extraction and liquid membrane transport were used to separate mixtures of aliphatic and aromatic amines. Experiments showed that it is possible to discriminate between the aliphatic and aromatic amines of a given mixture. Selectivity is a result of a well-chosen aqueous pH in the biphasic system, or a suitable pH gradient in the membrane system. Results suggest that the macrocyclic ligand (18C6, DB18C6, or DCH18C6) associates with the substrate at the source phase-membrane interface, forming an aggregate of relatively low stability, that has a positive effect when transporting aniline, dibutylamine, and cyclohexylamine. Liquid-liquid extraction is very little affected by the presence of these classical compounds.