rule, it can be assumed that the solubility of an ionic compound in an organic solvent
decreases as the charge on the ions increases.
2.3 Analyte–Stationary Phase Interactions
in Chromatography Separation
In general, small differences in the interactions between the stationary phase and
every single compound lead to the desired separation effect of a compound mixture
by chromatographic methods. A variety of weak interactions is known and actively
applied to substance-specific retention in chromatographic separation. For a more
in-depth insight into these comprehensive interactions in modern chromatographic
systems, we refer to recent general reviews (Cecchi 2011; Guo and Gaiki 2011; Jian
et al. 2011; Buszewski and Noga 2012; Sherma 2013; Shi et al. 2015; Ciura et al.
2017; Jandera and Janas 2017; McCalley 2017; Jandera and Hajek 2018; Taraji et al.
2018) and to modern standard text book on advanced organic chromatographic
separation.
For chiral compounds, however, due to the special stereoselective structural
character of these groups of compounds, William Pirkle established a general rule
for an optimised chromatographic separation (Hu and Ziffer 1991; Caccamese 1993;
Forjan et al. 2007; Badaloni et al. 2010), the so-called three-point rule:
Chiral recognition during chromatographic separation processes requires a minimum of
three simultaneous but independent compound-stationary phase (SP) interactions for enantiomer selective separation and at least one of the enantiomers with at least one of the
interactions being enantiomer selective.
The following interactions are known to be important for a chromatographic
separation:
• Hydrogen bonds
• π–π interactions.
• Dipole–dipole interactions
• Van der Waals interactions
• Acid–base–ionic interactions.
This simple principle of chromatographic interaction rules the general development of chromatographic methods, the selectivity and sensitivity as important prerequisites for the optimisation of new chiral stationary phases.
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2 Criteria for the Selection of a Proper Enantiomer-Selective Analytical Method
decreases as the charge on the ions increases.
2.3 Analyte–Stationary Phase Interactions
in Chromatography Separation
In general, small differences in the interactions between the stationary phase and
every single compound lead to the desired separation effect of a compound mixture
by chromatographic methods. A variety of weak interactions is known and actively
applied to substance-specific retention in chromatographic separation. For a more
in-depth insight into these comprehensive interactions in modern chromatographic
systems, we refer to recent general reviews (Cecchi 2011; Guo and Gaiki 2011; Jian
et al. 2011; Buszewski and Noga 2012; Sherma 2013; Shi et al. 2015; Ciura et al.
2017; Jandera and Janas 2017; McCalley 2017; Jandera and Hajek 2018; Taraji et al.
2018) and to modern standard text book on advanced organic chromatographic
separation.
For chiral compounds, however, due to the special stereoselective structural
character of these groups of compounds, William Pirkle established a general rule
for an optimised chromatographic separation (Hu and Ziffer 1991; Caccamese 1993;
Forjan et al. 2007; Badaloni et al. 2010), the so-called three-point rule:
Chiral recognition during chromatographic separation processes requires a minimum of
three simultaneous but independent compound-stationary phase (SP) interactions for enantiomer selective separation and at least one of the enantiomers with at least one of the
interactions being enantiomer selective.
The following interactions are known to be important for a chromatographic
separation:
• Hydrogen bonds
• π–π interactions.
• Dipole–dipole interactions
• Van der Waals interactions
• Acid–base–ionic interactions.
This simple principle of chromatographic interaction rules the general development of chromatographic methods, the selectivity and sensitivity as important prerequisites for the optimisation of new chiral stationary phases.
22
2 Criteria for the Selection of a Proper Enantiomer-Selective Analytical Method