normal-phase and polar organic modes. The enantioselectivity is usually different in
each mode (Hui et al. 2001; Staroverov et al. 2006; Berthod 2009).
Armstrong and co-workers point out that the principle of complementary separations is a very useful concept when developing methods with glycopeptide-based
chiral stationary phases (Ekborg-Ott et al. 1998). Vancomycin and teicoplanin are
similar, closely related chiral selectors. They can exhibit similar but different
enantioselectivities. Consequently, if a partial separation is obtained on one chiral
stationary phase, in many cases chromatographers can take the related column and
obtain a baseline separation using identical or very similar conditions.
• Type 6: The CSP is a protein and the solute/CSP complexes are based upon
combinations of hydrophobic and polar interactions. This group may be regarded
as a major subdivision of Type 5, as a globular protein is certainly a high
molecular mass polymer offering opportunities for inclusion. Type 6 HPLC
phases belong to the most attractive types of chiral stationary phases for pharmaceutical applications. Although early examples of this class of CSP, based on
either bovine serum albumin (Andrisano et al. 1997; Haginaka and Kanasugi
1997; Nakamura et al. 1998; Andrisano et al. 2000; Mallik and Hage 2008) or
acid glycoprotein (Fitos et al. 1992; Bunton and Walker 1995; Yehl et al. 2000),
suffered from a lack of reproducibility and a tendency to deteriorate in use, the
more recent commercial examples, such as the second-generation silica-bound
α1-acid glycoprotein (Krstulovic 1989; Krstulovic and Vende 1989), appear to be
more reliable and popular, although still fairly expensive. Further details can be
inferred from recent literature (Krstulovic 1988; Gyimesi-Forras et al. 2003;
Barbato et al. 2007).
3.6 Other Selection Strategies for Enantioselective Liquid
Chromatography
As already stated, selective CSPs in chromatographic separation are often costly and
associated with a restricted application time. Furthermore, for multi-compound
separation, often many CSPs must be applied in sequence or in parallel, which
again add to the overall costs for the performed separation. Therefore, enantiomerselective sample preparation methods maybe of advantage by applying selective
adsorption, diffusion processes, or dialysis on enantiomer-selective surfaces or
transport through enantiomer-selective membranes (Piacentini et al. 2017; Yuan
et al. 2017).
3.6 Other Selection Strategies for Enantioselective Liquid Chromatography
43
each mode (Hui et al. 2001; Staroverov et al. 2006; Berthod 2009).
Armstrong and co-workers point out that the principle of complementary separations is a very useful concept when developing methods with glycopeptide-based
chiral stationary phases (Ekborg-Ott et al. 1998). Vancomycin and teicoplanin are
similar, closely related chiral selectors. They can exhibit similar but different
enantioselectivities. Consequently, if a partial separation is obtained on one chiral
stationary phase, in many cases chromatographers can take the related column and
obtain a baseline separation using identical or very similar conditions.
• Type 6: The CSP is a protein and the solute/CSP complexes are based upon
combinations of hydrophobic and polar interactions. This group may be regarded
as a major subdivision of Type 5, as a globular protein is certainly a high
molecular mass polymer offering opportunities for inclusion. Type 6 HPLC
phases belong to the most attractive types of chiral stationary phases for pharmaceutical applications. Although early examples of this class of CSP, based on
either bovine serum albumin (Andrisano et al. 1997; Haginaka and Kanasugi
1997; Nakamura et al. 1998; Andrisano et al. 2000; Mallik and Hage 2008) or
acid glycoprotein (Fitos et al. 1992; Bunton and Walker 1995; Yehl et al. 2000),
suffered from a lack of reproducibility and a tendency to deteriorate in use, the
more recent commercial examples, such as the second-generation silica-bound
α1-acid glycoprotein (Krstulovic 1989; Krstulovic and Vende 1989), appear to be
more reliable and popular, although still fairly expensive. Further details can be
inferred from recent literature (Krstulovic 1988; Gyimesi-Forras et al. 2003;
Barbato et al. 2007).
3.6 Other Selection Strategies for Enantioselective Liquid
Chromatography
As already stated, selective CSPs in chromatographic separation are often costly and
associated with a restricted application time. Furthermore, for multi-compound
separation, often many CSPs must be applied in sequence or in parallel, which
again add to the overall costs for the performed separation. Therefore, enantiomerselective sample preparation methods maybe of advantage by applying selective
adsorption, diffusion processes, or dialysis on enantiomer-selective surfaces or
transport through enantiomer-selective membranes (Piacentini et al. 2017; Yuan
et al. 2017).
3.6 Other Selection Strategies for Enantioselective Liquid Chromatography
43