Enantiomer resolution of d- and l-α-amino acid derivatives by supercritical fluid chromatography on novel chiral diamide phases with carbon dioxide

Dobashi, Akira; Dobashi, Yoshinori; Ono, Tamami; Hara, Shoji; Saito, Muneo; Higashidate, Sakae; Yamauchi, Yoshio

doi:10.1016/s0021-9673(00)94281-x

Cited by 27 publications

(2 citation statements)

References 9 publications

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“…Such an increase in column efficiency can often be obtained by operating under sub- or supercritical fluid conditions rather than under HPLC conditions. Numerous workers − have demonstrated the benefits this efficiency brings to chiral analysis. This increased efficiency does not generally come at the expense of selectivity.…”

mentioning

confidence: 99%

“Entropically Driven” Chiral Separations in Supercritical Fluid Chromatography. Confirmation of Isoelution Temperature and Reversal of Elution Order

Stringham

Blackwell

1996

Anal. Chem.

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Chiral separations depend upon column efficiency and chiral selectivity. Supercritical fluid chromatography (SFC) has been shown to have pronounced advantages in chiral separations due to its enhanced column efficiency at normal flow rates. Examination of factors affecting selectivity in SFC is crucial to systematic chiral method development. Selectivity is a compromise between differences in enantiomeric binding enthalpy and disruptive entropic effects. Increased temperature will decrease the effect of differences in enantiomer binding enthalpy, eventually decreasing selectivity to a point where the enantiomers coelute. Extension of this thermodynamic theory predicts that further increases in temperature lead to selectivity values of less than 1.0, and elution order of the enantiomers reverses. In this region separations are said to be "entropically driven", and selectivity increases (decreases from 1.0) with temperature. Performing separations in this region is attractive because column efficiency is also expected to increase with temperature. Such entropically driven separations have been observed only in gas chromatography. Most data used to support the application of this theory in SFC have been generated at subcritical temperatures, while theory purports to predict behavior above the critical temperature (T(c)). This approach ignores the effects of traversing the critical temperature in SFC, which is known to have a variety of unpredictable consequences. Work presented here shows the effect of temperatures above T(c) on chromatographic behavior. Contrary to theory, capacity factors increase near T(c) and column efficiency declines. Use of pressures well above the critical pressure lessens these effects. In accordance with theory, selectivity does decrease with temperature through T(c) and isoelution temperatures and two instances of elution order reversal are observed here for the first time in SFC.

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confidence: 99%

“Entropically Driven” Chiral Separations in Supercritical Fluid Chromatography. Confirmation of Isoelution Temperature and Reversal of Elution Order

Stringham

Blackwell

1996

Anal. Chem.

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“…Racemic amino acid derivatives have been analyzed by SFC with rapid resolution results [38]. Racemic N −4-nitrobenzoyl amino acid isopropyl esters were separated on chiral valine-diamide phases with methanol as the modifier.…”

Section: Chiral Sfc On Drug Compounds and Intermediatesmentioning

confidence: 99%

Separations of Chiral Compounds by SFC

Wang

2010

Chiral Separation Methods for Pharmaceutical and Biotechnological Products

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Relationship between resolution and analysis time in chiral subcritical fluid chromatography

Stringham

1996

Chirality

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Enantiomer resolution of d- and l-α-amino acid derivatives by supercritical fluid chromatography on novel chiral diamide phases with carbon dioxide

Cited by 27 publications

References 9 publications

“Entropically Driven” Chiral Separations in Supercritical Fluid Chromatography. Confirmation of Isoelution Temperature and Reversal of Elution Order

“Entropically Driven” Chiral Separations in Supercritical Fluid Chromatography. Confirmation of Isoelution Temperature and Reversal of Elution Order

Separations of Chiral Compounds by SFC

Relationship between resolution and analysis time in chiral subcritical fluid chromatography

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