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Homochiral metal-organic framework [Zn2(d-Cam)2(4,4′-bpy)]n for high-resolution gas chromatographic separations

Xue X. D, Zhang M., Xie S. M, Yuan L. M

Acta Chromatographica

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2015

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Vol. 27, no. 1

15--26

EN

The metal-organic framework (MOF) is a kind of new type self-assembly porous coordination polymer, which possesses many characteristics such as homologic hole, controllable size of cave, high specific surface area, and good chemical stability. In this study, a three-dimensional framework [Zn2(d-Cam)2(4,4′-bpy)]n with large homochiral channel and the orderly arrangement of left- and right-handed helices was used as chiral stationary phases (CSPs) in gas chromatography (GC). [Zn2(d-Cam)2 (4,4′-bpy)]n-coated open tubular column was prepared by a dynamic coating method for high-resolution GC. Some racemates, isomers, linear alkanes, and alcohols are used as the targets for separation. The column coating properties efficiency, polarity, and selectivity were studied. The experimental results show that the stationary phase has outstanding selectivity and also possesses good recognition ability toward these compounds.

2

Enantioseparation of amino alcohols by reversed-phase high-performance liquid chromatography using cyanuric chloride-based chiral derivatizing reagents having amino acids and their amides as chiral auxiliaries

Bhushan R., Lal M.

Acta Chromatographica

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2014

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Vol. 26, no. 3

413--427

EN

A high-performance liquid chromatographic (HPLC) method was developed for enantioresolution of amino alcohols using an indirect approach. Two sets of chiral derivatizing reagents (CDRs) having amino acids (CDRs 1–4; set A) and their amides (CDRs 5–8; set B) as chiral auxiliaries in cyanuric chloride (CC) moiety were synthesized and characterized. Diastereomers of eight amino alcohols were synthesized, under microwave irradiation, using each of the eight CDRs. The resulting diastereomers were separated by reversed-phase high-performance liquid chromatography (RP-HPLC) using C18 column and eluting mixtures of acetonitrile with aqueous trifluoroacetic acid (aq.TFA) in a linear gradient (45 min) with UV detection at 230 nm. The results (in terms of resolution Rs and retention factor k) obtained for the two sets of diastereomers were compared among themselves and among the two groups. The effects of chiral auxiliaries (in terms of acid and amides variants), constituting CDRs, on separation were also evaluated. The elution order for the diastereomers was determined. The separation method was validated for limit of detection (LOD), linearity, accuracy, precision, and recovery.

3

On ups and downs by analysis of profen drugs. A mini review

Sajewicz M., Kowalska T.

Acta Chromatographica

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2012

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Vol. 24, no. 2

145--161

EN

Drug analysis is among the most sensitive areas of chemical analysis, simply because of its relevance to human health. Profens make the most important group of nonsteroidal anti-inflammatory drugs (NSAIDs), and in many countries some of them are freely sold over the counter. The in vitro liquid chromatographic analysis of profen drugs faces certain not commonly recognized yet acute and often impassable problems, due to the specific physicochemical properties of these compounds. In this mini review, we share our experience on the practical failures with the enantioseparation of profen drugs both by means of chiral planar and column chromatography. By use of such analytical techniques as polarimetry, 1H and 13C NMR spectroscopy, and mass spectrometry, we point out objectively the reasons that make liquid chromatographic enantioseparation of profens an almost impossible task. These compounds have an inherent ability (both in aqueous and nonaqueous solutions) to undergo oscillatory chiral conversion and oscillatory condensation, combined with a highly pronounced gelating ability. In our view, the oscillatory chiral conversion of profens questions the credibility of widespread claims on the superiority of the curative potential with the (+)-profens over that of the respective (−)-antimers (although the rightfulness of such claims cannot be dismissed, as the in vivo and in vitro behavior of many drugs are known to sometimes fundamentally differ). Moreover, it seems highly probable that, due to their highly pronounced gelating property, profen drugs can easily clog the blood vessels and thereby jeopardize living organisms.

4

Direct separation of clopidogrel enantiomers by reverse-phase planar chromatography method using β-cyclodextrin as a chiral mobile phase additive

Antic D., Filipic S, Ivkovic B., Nikolic K, Agbaba D.

Acta Chromatographica

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2011

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Vol. 23, no. 2

235--245

EN

A simple and rapid TLC method using β-cyclodextrin as a chiral mobile phase additive (CMPA) was developed for direct separation of S-clopidogrel and its impurity R-clopidogrel. The influence of different factors (stationary phases, organic modifiers, chiral selectors and their concentrations in the mobile phase, and optimal saturation time of the chamber) on enantioseparation was studied. The best resolution of clopidogrel enantiomers was achieved on Polygram®cel 300 Ac-10% plates using isopropanol-0.5 mM β-cyclodextrin (6:4, υ/υ) as mobile phase in TLC chamber previously equilibrated with the mobile phase for 20 min. The spots were detected under UV light and using iodine vapours. The method enables rapid separation of clopidogrel enantiomers and can be successfully used in control of stereoselective synthesis of clopidogrel and in control of its purity. Finally, the molecular modelling of the inclusion complexes between the analytes and α-, β-, and γ-cyclodextrin was performed to investigate the mechanism of the enantiorecognition.