Abstract
Chiral resolution of DL-alanine-DL-tyrosine and DL-leucine-DL-phenylalanine dipeptides was achieved on AmyCoat-RP column. The mobile phase used for DL-alanine-DL-tyrosine was acetonitrile-ammonium acetate (10 mM, pH 6.0) [50:50, v/v]. It was acetonitrile methanol ammonium acetate (10 mM; pH adjusted to 4.5 with glacial acetic acid) [50:20:30, v/v] for DL-leucine-DL-phenylalanine. The flow rate of the mobile phases was 0.8 mL/min with UV detection at 275 nm. The values of retention factors for LL-, DD-, DL- and LD-stereomers of DL-alanine-DL-tyrosine were 1.71, 2.86, 5.43 and 9.42, respectively. The values of separation and resolution factors were 1.67, 1.90 and 1.73 and 2.88, 6.43 and 7.90, respectively. Similarly, these values for DL-leucine-DL-phenylalanine stereomers were 1.50, 2.88, 3.50 and 4.07 (retention factors), 1.92, 1.22 and 1.62 (separation factors) and 2.67, 1.55 and 2.30 (resolution factors). The limits of detections and quantitation were ranged from 2.03 to 6.40 and 6.79 to 21.30 mu g/mL, respectively. The modeling studies were in agreement with the elution orders. The mechanism of chiral recognition was established by modeling and chromatographic studies. It was observed that hydrogen bondings and pi-pi interactions are the major forces for chiral separation. (C) 2015 Elsevier B.V. All rights reserved.