Warfarin Warfarin or Coumadin is a very strong anti-coagulant which functions by inhibiting vitamin K-dependent coagulation factors. It was originally used as a rat poison but has also found use in medicine in very dilute form as an anticoagulant for thrombosis, pulmonary embolism and cardiac valve repleacement. Chemically it is 3-(-acetonylbenzyl)-4-hydroxycoumarin and is supplied as a racemic mixture of the R and S-enantiomers. The Warfarin enantiomers can be separated and quantitatively determined by liquid chromatography using a 25 cm long 4.6 mm I.D. packed with a cyclodextrin stationary phase (CYCLOBOND 1) 5 micron particle size. The mobile phase is 90%v/v acetonitrile, 10 %v/v methanol 0.2%v/v acetic acid and 0.2%v/v triethylamine. Base-line separation is obtained for the two enantiomers.

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Author: RPW Scott Book:Principles and Practice of Chromatography
Section:Principles   Available-Stationary-Phase   Chiral

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

Principles   Available-Stationary-Phase   Chiral

Author: RPW Scott Book:Preparative Chromatography
Section:Preparative   Recycle-Development

of cycles, as significant peak dispersion can occur each time it passes through the pump. Nevertheless, there is a substantial net gain in resolution on each cycle. This procedure can be very time consuming if long retention times are involved, but has the great advantage of solvent economy. The recycling procedure, in effect, artificially increases the column length and actually trades in time for solvent economy.  An example of the recycling process is demonstrated in the separation of the Warfarin enantiomers shown in figure 20. The separation was carried out on a CYCLOBOND 1 2000 column, 25 cm long, 1 in, I.D., using a mobile phase consisting of methanol/acetic acid/triethylamine : 100/0.3/0.2 v/v/v, at a flow rate of 12 ml/min.   Courtesy of ASTEC Inc.   Figure 20 The Separation of the Warfarin Enantiomers by Recycling

Preparative   Recycle-Development