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Kinetic study of adsorption of some biocompounds at the oil/water interface

100%

Tomoaia G., Tomoaia-Cotisel A., Tomoaia-Cotisel M., Mocanu A.

Open Chemistry

2005

vol. 3

issue 2

347-360

The adsorption kinetics of some local anesthetics, like dibucaine and tetracaine, and of stearic acid from bulk solutions at the oil/water interface was studied by using the pendent drop and ring methods. The anesthetics were dissolved in aqueous solutions (pH 2), and the fatty acid was dissolved in benzene, each biocompound at several different concentrations in bulk solutions. Kinetic equations for Langmuir mechanism of adsorption at oil/water interface were tested. The kinetic analysis shows that Langmuir kinetic approach describes the dynamic interfacial pressures within the limits of the experimental errors over a wide range of time and for different surfactant concentrations in bulk solutions. It is also concluded that this approach allows the calculation of the ratio of the adsorption and desorption rate constants of these biocompounds at the oil/water interface. Obtained results are in substantial agreement with earlier reported data for the surfactant adsorption as, well as with their molecular structure.

Surface properties of some carotenoids spread in monolayers at the air/water interface. Experimental and computational approach

76%

Horovitz O., Tomoaia G., Racz C., Mocanu A., Bobos L.-D., Tomoaia-Cotisel M.

Open Chemistry

2006

vol. 4

issue 3

489-501

The surface pressure versus molecular area isotherms of some carotenoids: β,β-carotene-4-one (echinenone, ECH), β,β-carotene-4,4′-dione (canthaxanthin, CAN) and 4,4′-diapo-ω,ω-carotene-4,4′-dial (APO), spread at the air/water interface, are reported. A van der Waals type state equation is used to describe the high molecular area portions of the compression isotherms and interaction parameters within monolayers are derived. Quantum chemical semi-empirical SCF MO calculations (AM1 and PM3) are performed for the optimized geometries of molecules and dipole moments are calculated. Similar theoretical magnitudes are obtained by both methods. Surface properties, like collapse pressure, surface compressional modulus and interaction parameters are discussed in terms of dipole-dipole interactions, and correlations with the calculated quantities for the carotenoid molecules are analyzed. The orientation of the different carotenoid molecules in the monolayer is discussed.

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2 Open Chemistry

1 2006

1 2005

2 Mocanu A.

2 Tomoaia G.

2 Tomoaia-Cotisel M.

1 Bobos L.-D.

1 Horovitz O.

1 Racz C.

1 Tomoaia-Cotisel A.

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Kinetic study of adsorption of some biocompounds at the oil/water interface

Surface properties of some carotenoids spread in monolayers at the air/water interface. Experimental and computational approach