PARTITIONING OF OXYTETRACYCLINE BETWEEN AQUEOUS AND ORGANIC-SOLVENTS - EFFECT OF HYDROGEN-BONDING

Phase equilibrium behavior of antibiotics is important in drug design and for optimization of the recovery process in manufacturing. Aqueous /organic partitioning behavior of a clinically important antibiotic, o xytetracycline is measured. The organic phase includes pure solvent n- hexane, chloroform, diethyl ether and ethyl acetate. In addition, meas urements are also made for mixed organic phase composed of n-hexane+et hyl acetate. Organic-phase partitioning increases with the hydrogen bo nding (H-bonding) tendency of the solvent in the order n-hexane < chlo roform < diethyl ether < ethyl acetate. An activity coefficient model that includes H-bonding, UNIQUAC-HB (Gupta, R.B., Kumar, R., Betageri, G.V., 1997. Ind. Eng. Chem. Res., 36, 3954-3959), is used to model th e partitioning behavior between aqueous and organic phases. Single sol vent-organic-phase data are correlated using the model to obtain the f ree-energy-of-H-bonding parameters for H-bonding between antibiotic an d solvent. Predictions made for mixed-solvent-organic-phase systems ag rees well with the experimental data without using any adjustable para meter. (C) 1998 Elsevier Science B.V. All rights reserved.