• For preparative applications, the chiral additive must be removed from the
enantiomeric solutes prior to compound characterisation.
• The detection mode may limit the choice of additives as well.
For these reasons, many recent reports conclude that the current trend is to use
rather robust and long-lasting chiral stationary phases, whenever HPLC/UHPLC is
considered for enantiomeric separations (Toda 2004; Subramanian 2007;
Mangelings and Vander Heyden 2008; Schurig and Ciogli 2013; Scriba 2013).
3.5 The Evolution of Chiral Stationary Phases for Liquid
Chromatography
The earliest reviews on chiral stationary phases for HPLC applications were
published already in the late 1970s and the 1980s (Hare and Gil-Av 1979; Krstulovic
1988; Meyer 1989). The history of CSPs is comprehenisively described in a comprehensive review (Hühnerfuss and Shah 2009).
However, already in 1952, long before HPLC had emerged as the powerful
instrumental separation method familiar to us now, Dalgliesh was studying the
separation of amino acid enantiomers by paper chromatography (Dalgliesh 1952).
Although not the first to observe such separations (Swanson et al. 1945; Bickel and
Peaslee 1948; Baldwin and Berg 1949), he correctly attributed them to
enantioselective adsorption by the optically active cellulose molecules of the paper
and proposed tentative requirements for such process as follows:
• Three points of attachment are required for stereochemical specificity in
adsorption.
• Within the amino acid analyte to be resolved, the amino group, the carboxylic
acid group, and a structural component of the side chain (such as the
hydroxyphenyl group of tyrosine) should all participate in the molecular interactions, envisaged to be due to hydrogen bonding or steric repulsion.
Pirkle later refined the above structural considerations and established the wellknown Pirkle three-point rule (Pirkle et al. 1984): “Chiral recognition requires a
minimum of three simultaneous interactions between analyte and the CSP and at
least one specific of the enantiomers, with at least one of these interactions being
stereochemically dependent” (see below, and Fig. 3.1). This means, at least one of
the interactions will be absent by replacing one enantiomer with its antipode.
These early experiments were continuously followed and expanded by new
CSPs, during which the types of materials used for CSPs were extended until
today with substrates like amylose derivatives (Sousa et al. 2004; Cirilli et al.
2006; Wang et al. 2008a, b; Jin et al. 2009; Peluso et al. 2009), cellulose acetate
containing CSPs (Rudaz and Veuthey 1999; Aboul-Enein et al. 2000; Kubota et al.
2004; Peluso et al. 2009), chiral-modified zeolites (Jirapongphan et al. 2007a, b;
Beeram et al. 2017) and surface-coated silica gel (Wang et al. 2017b; Xu et al. 2017)
3.5 The Evolution of Chiral Stationary Phases for Liquid Chromatography
37
enantiomeric solutes prior to compound characterisation.
• The detection mode may limit the choice of additives as well.
For these reasons, many recent reports conclude that the current trend is to use
rather robust and long-lasting chiral stationary phases, whenever HPLC/UHPLC is
considered for enantiomeric separations (Toda 2004; Subramanian 2007;
Mangelings and Vander Heyden 2008; Schurig and Ciogli 2013; Scriba 2013).
3.5 The Evolution of Chiral Stationary Phases for Liquid
Chromatography
The earliest reviews on chiral stationary phases for HPLC applications were
published already in the late 1970s and the 1980s (Hare and Gil-Av 1979; Krstulovic
1988; Meyer 1989). The history of CSPs is comprehenisively described in a comprehensive review (Hühnerfuss and Shah 2009).
However, already in 1952, long before HPLC had emerged as the powerful
instrumental separation method familiar to us now, Dalgliesh was studying the
separation of amino acid enantiomers by paper chromatography (Dalgliesh 1952).
Although not the first to observe such separations (Swanson et al. 1945; Bickel and
Peaslee 1948; Baldwin and Berg 1949), he correctly attributed them to
enantioselective adsorption by the optically active cellulose molecules of the paper
and proposed tentative requirements for such process as follows:
• Three points of attachment are required for stereochemical specificity in
adsorption.
• Within the amino acid analyte to be resolved, the amino group, the carboxylic
acid group, and a structural component of the side chain (such as the
hydroxyphenyl group of tyrosine) should all participate in the molecular interactions, envisaged to be due to hydrogen bonding or steric repulsion.
Pirkle later refined the above structural considerations and established the wellknown Pirkle three-point rule (Pirkle et al. 1984): “Chiral recognition requires a
minimum of three simultaneous interactions between analyte and the CSP and at
least one specific of the enantiomers, with at least one of these interactions being
stereochemically dependent” (see below, and Fig. 3.1). This means, at least one of
the interactions will be absent by replacing one enantiomer with its antipode.
These early experiments were continuously followed and expanded by new
CSPs, during which the types of materials used for CSPs were extended until
today with substrates like amylose derivatives (Sousa et al. 2004; Cirilli et al.
2006; Wang et al. 2008a, b; Jin et al. 2009; Peluso et al. 2009), cellulose acetate
containing CSPs (Rudaz and Veuthey 1999; Aboul-Enein et al. 2000; Kubota et al.
2004; Peluso et al. 2009), chiral-modified zeolites (Jirapongphan et al. 2007a, b;
Beeram et al. 2017) and surface-coated silica gel (Wang et al. 2017b; Xu et al. 2017)
3.5 The Evolution of Chiral Stationary Phases for Liquid Chromatography
37