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Method development in liquid chromatography with a charged cyclodextrin additive for chiral resolution of rac ‐amlodipine utilising a central composite design
Author(s) -
Owens Paul K.,
Fell Anthony F.,
Coleman Michael W.,
Berridge John C.
Publication year - 1996
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/(sici)1520-636x(1996)8:7<466::aid-chir2>3.0.co;2-9
Subject(s) - chemistry , enantiomer , chromatography , central composite design , cyclodextrin , theoretical plate , chiral resolution , amlodipine , analytical chemistry (journal) , response surface methodology , stereochemistry , medicine , blood pressure , radiology
A negatively charged derivative of β‐cyclodextrin, sulphobutyl ether‐β‐cyclodextrin (SBE‐β‐CD), was examined as a chiral mobile phase additive in reversed‐phase high‐performance 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 m M SBE‐bgr;‐CD (26.5:73.5% v/v) at a flow rate of 1.0 ml/min. This yielded a Kaiser peak separation index, P i = 0.96, at t R2 = 52 min with satisfactory reproducibility, relative standard deviation values: t R1 , 0.39%; t R2 , 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 R s , P i , and a function of P i , 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. © 1996 Wiley‐Liss, Inc.