The Thermodynamics of Chromatography - Other Thermodynamic Methods that are Used for Studying Chromatographic Systems > Optimum Operating Conditions for Chiral Separations in Liquid Chromatography > Page 66
As an example of the application of the opimizing equations the retention data reported by Beesley and Scott (15) for the two enantiomers, (S) and (R) 4-benzyl-2-oxazolidinone will be employed. The column that was used was 25 cm long, 4.6 mm I.D., packed with 5 mm silica particles bonded with the stationary phase Vancomycin (Chirobiotic V, Advanced Separations Technology Inc., Whippany New Jersey). Vancomycin is a macrocyclic glycopeptide thaving a molecular weight of 1449.22, and containing 18 chiral centers surrounding three 'cavities' bridged by five aromatic rings.
The column was operated in the normal phase mode using mixtures of n-hexane and ethanol as the mobile phase. As the interactive character of the solvent mixture was highly dispersive, the mechanism of retention, and the chiral selectivity, would be dominated by polar interactions between the solute and the bonded Vancomycin
Table 4 Retention Data for (R)–4-Benzyl-2-Oxazolidinone
Ethanol v/v | V'_{A} (5˚C) | V'_{A} (15˚C) | V'_{A} (25˚C) | V'_{A} (35˚C) | V'_{A} (45˚C) |
10 % | 62.57 ml | 50.58 ml | 40.78 ml | 35.06 ml | 29.18 ml |
20 % | 28.34 ml | 22.79 ml | 18.28 ml | 15.18 ml | 12.72 ml |
30 % | 16.88 ml | 13.74 ml | 11.48 ml | 9.37 ml | 7.82 ml |
40 % | 12.34 ml | 9.48 ml | 7.85 ml | 6.37 ml | 5.27 ml |
50 % | 8.05 ml | 6.73 ml | 5.27 ml | 4.75 ml | 3.88 ml |