Method development in liquid chromatography with a charged cyclodextrin additive for chiral resolution of rac-amlodipine utilising a central composite design
✍ Scribed by Paul K. Owens; Anthony F. Fell; Michael W. Coleman; John C. Berridge
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 908 KB
- Volume
- 8
- Category
- Article
- ISSN
- 0899-0042
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✦ Synopsis
A negatively charged derivative of pcyclodextrin, sulphobutyl ether-p-cyclodextrin (SBE-p-CD), was examined as a c h i d mobile phase additive in reversed-phase highperformance liquid chromatography for the enantiomeric resolution of the calcium channel blocker rac-amlodipine. Theoretical and practical aspects are discussed for setting up a central composite design applicable to any analytical method. These include the correct location of factor points for maintaining orthogonality within the design and the augmentation of centrepoint experiments to allow a larger factor space by increasing the distance of axial star points. Optimised separation was achieved using a reverse-phase column with eluent comprising: acetonitrile (ACN)-potassium dihydrogen phosphate (PH 3.93) containing 2.66 mM SBE-p-CD (26.5:73.5% v/v) at a flow rate of 1.0 ml/min. This yielded a Kaiser peak separation index, Pi = 0.96, at tRz = 52 min with satisfactory reproducibility, relative standard deviation values: tR1, 0.39% tR2, 0.47% (n = 5). These experimental results were in excellent agreement with those predicted by the SAS software package for a chromatographic response function model.
Multiple regression analysis in four dimensions, with three response models based on K, Pi, and a function of Pi, produced response surfaces which revealed zones of optimum robustness and illustrated the interactions involved between the key chromatographic factors. Putative proposals for a mechanism involving the interaction of each of the positively charged enantiomers with the negatively charged cyclodextrin are also discussed. These examine the possibility of ion-pairing and inclusion phenomena to account for the excellent resolution observed.