Principles and Practice of Chromatography - The Control of Chromatographically Available Stationary Phase (V<sub>s</sub>) > Stationary Phase Limitation by Chiral Selectivity. > Page 40

Courtesy of ASTEC Inc.

Figure 18 The Separation of Warfarin Isomers on a CYCLOBOND Column

The cyclodextrins are produced by the partial degradation of starch followed by the enzymatic coupling of the glucose units into crystalline, homogeneous toroidal structures of different molecular sizes. Three of the most widely characterized are alpha, beta and gamma cyclodextrins which contain 6, 7 and 8 glucose units respectively. Cyclodextrins are chiral structures and the beta- cyclodextrin has 35 stereogenic centers. CYCLOBOND is a trade name used to describe a series of cyclodextrins chemically bonded to spherical silica gel. The separation of the isomers of Warfarin is shown in figure 18. The column was 25 cm long and 4.6 mm in diameter packed with 5 micron CYCLOBOND 1. The mobile phase was approximately 90%v/v acetonitrile, 10%v/v methanol, 0.2 %v/v glacial acetic acid and 0.2%v/v triethylamine. It is seen that an excellent separation has been achieved with the two isomers completely resolved.