Reactive extraction is a promising bioseparation method to enhance antibiotic partitioning by using specific extractant (or carrier) dissolved in non-polar solvent. In this study, the reactive extraction system of a liquid anion exchanger, trioctyl-methyl-ammonium chloride (TOMAC) in kerosene was used to extract the antibiotics, teicoplanin and rifampicin, from a dilute solution. Both antibiotics were favourably extracted into TOMAC/kerosene solution through ion exchange reaction under optimised experimental condition. The extraction equilibrium constant and the partition coefficient were found to increase with an increase in pH. In addition, a simple extraction equilibrium model was used to predict the separation behaviour in which TOMAC reacts with the anionic form of antibiotic according to the stoichiometric ratio determined by the ionic valency. A monovalent anion model for low pH and a divalent anion model for high pH were developed in order to describe the extraction equilibrium of teicoplanin whilst the monovalent anion model alone was adequate for rifampicin extraction.