<p>This study proposes an efficient method for the internal-state separation of enantiomers in an open system. Under large detuning conditions, by introducing balanced gain and dissipation into the cyclic three-level systems of chiral molecules, we reduce the systems to effective parity-time (PT)-symmetric two-level systems. Both enantiomers are initially prepared in the ground state. When parameters confine them within the PT-symmetric phase, their ground- and excited-state populations exhibit periodic oscillations with distinct periods. Through parameter modulation, left-handed enantiomers stay in the PT-symmetric phase with populations oscillating periodically, while right-handed ones enter the PT-broken phase with populations growing exponentially. Efficient internal-state separation can be achieved in both scenarios by optimizing parameters such that distinct enantiomers occupy different energy levels at a specific evolution time.</p>