Chiral separations with Lux and Chirex are dependent on the nature of the aromatic groups in the chiral compounds of interest and the distance between the aromatic functionality and chiral center in the analyte. 

Generally, the closer the aromatic group is to the chiral center in a chiral compound the easier it is to separate its enantiomers and separations of chiral compounds where the chiral center is 4 or more atoms away from the aromatic ring are uncommon if not impossible. Stationary phases are most effective when the distances between the aromatic group and chiral center are the same in the chiral compound of interest. 

If the aromatic group of the compound has electron withdrawing groups like halogens or oxygen containing functionality, it will be more electron deficient and will interact more effectively with electron rich aromatic groups in the stationary phase (generally unsubstituted or with electron donating alkyl groups).