A new process has been developed to separate phenylsuccinic acid (H(2)A) enantiomers, based on the oppositely preferential recognition of hydrophobic and hydrophilic chiral selectors in organic and aqueous phases, respectively, which is named as biphasic recognition chiral extraction (BRCE). BRCE system is established by adding hydrophobic L-iso-butyl tartrate in organic phase and hydrophilic beta-cyclodextrin (beta-CD) derivative in aqueous phase, which preferentially recognize S-H(2)A and R-H(2)A, respectively. The studies performed involve two enantioselective extractions in a biphasic system, where H(2)A enantiomers form four complexes with beta-CD derivative in aqueous phase and L-iso-butyl tartrate in organic phase, respectively. Here it is shown that the efficiency of the extraction depends, often strongly, on a number of process variables, including the types of organic solvents and beta-CD derivatives, iso-butyl tartrate configurations, the concentrations of the extractants and H(2)A enantiomers, pH and temperature. Phase-equilibria in BRCE systems is governed by the complex chemical equilibria in both the organic and aqueous phases. By changing the monophasic recognition chiral extraction (MRCE) system into BRCE system, the enantio-selectivity increases from 1.501 to 2.862. The maximum enantioselectivity for H(2)A enantiomers is obtained at pH <= 2.5 and the ratio of 2:1 of [L-(+)-iso-butyl tartrate] to [HP-beta-CD]. The experimental results show that BRCE is of much stronger chiral separation ability than MRCE, which is due to utilization of the separation abilities of both tartrate and beta-CD derivative. It may be very helpful to optimize the extraction systems and realize the large-scale production of pure enantiomers. (C) 2009 Elsevier Ltd. All rights reserved.