BACKGROUNDOur previous study indicated that monophasic recognition enantioseparation based on an aqueous two-phase system (ATPS) is restricted because of its relatively low enantioselectivity. To improve the enantioselectivity, biphasic chiral selectors could be introduced into the ATPS. This work has focused on ATPS technology utilizing cooperation of L-tartaric acid (L-TA) with hydroxypropyl--cyclodextrin (HP--CD), for the biphasic recognition enantioseparation of ofloxacin (OFLX) enantiomers. RESULTSUnder the optimum conditions, namely PEG2000 mass fraction of 40% (w/w), ammonium sulfate mass fraction 25% (w/w), pH value 4, HP--CD concentration 0.02 mol L-1, L-TA concentration 0.05 mol L-1, separation factor () reached 1.32 after just one-step extraction. Furthermore, for the purpose of explaining the extraction behavior, a reasonable enantioselective extraction mechanism was also proposed. CONCLUSIONThe novel biphasic recognition extraction based on ATPS presented in this work has the ability for good enantioseparation of OFLX enantiomers. (c) 2014 Society of Chemical Industry