2.4 Rotation Energy
One type of chirality demands additional considerations concerning chromatographic separations. As already described in the introduction, atropisomers gain
their chirality by a rotation hindrance between two cyclic molecule substructures
with different substitution patterns (Perez-Fernandez et al. 2012; Dai et al. 2017; Li
et al. 2018). Only if the substituents are of a certain size, the rotation barrier can be
preserved (LaPlante et al. 2011; Glunz 2018). Today, it is possible to calculate the
energy of the rotation barrier and the temperature limit below with chromatographic
separation (gas or liquid chromatographic methods) (Ghosn and Wolf 2011; Yan
et al. 2015). Furthermore, theoretical calculations may also be applied to determine
the temperature-dependent stability of atropisomers (Hesek et al. 2001; Casarini
et al. 2005; Callear et al. 2015; Buevich 2016). One of the predominant environmental pollution groups featuring atropisomers in environmental pollution research
is the group of polychlorinated biphenyls (PCBs). PCBs will be introduced later in
the group-specific chapters (Warner et al. 2009; Lu et al. 2013).
Based on the careful application of the above-described interactions to chromatography in combination with sensitive detectors, analytical chemists have developed a multitude of selective and sensitive methods for the chromatographic
separation of environmentally relevant chiral trace compounds into their respective
enantiomers. However, based on modern ultra-high-resolution mass spectrometry,
new methods based on enantiomer-selective mass-selective separation focussing on
enantiomer selectivity in ion mobility and MALDI are currently under development.
These methods are considered as a new promising enantiomer-selective detection
method also for low-level environmental applications (Awad and El-Aneed 2013;
Jurcek et al. 2015; Nachtigall et al. 2018; Li et al. 2019).
References
Adhikari S, Kang JS, Lee W (2016) A convenient and validated enantiomer separation of chiral
aliphatic amines as nitrobenzoxadiazole derivatives on polysaccharide-derived chiral stationary
phases under simultaneous ultraviolet and fluorescence detection. Chirality 28(12):789–794
Ali I, Aboul-Enein HY, Sanagi MM, Wan-ibrahim WA (2012) Chirality and its role in environmental toxicology. In: Luch A (ed) Molecular, clinical and environmental toxicology, vol
3. Springer, Heidelberg, pp 413–436
Awad H, El-Aneed A (2013) Enantioselectivity of mass spectrometry: challenges and promises.
Mass Spectrom Rev 32(6):466–483
Badaloni E, Cabri W, Ciogli A, D'Acquarica I, Deias R, Gasparrini F, Giorgi F, Kotoni D, Villani C
(2010) Extending the use of “inverted chirality columns approach” for enantiomeric excess
determination in absence of reference samples: application to a water-soluble camptothecin
derivative. J Chromatogr A 1217(7):1024–1032
Basheer AA (2017) Chemical chiral pollution: impact on the society and science and need of the
regulations in the 21(st) century. Chirality 30(4):402–406
Berthod A (2010) Chiral recognition in separation methods: mechanisms and applications.
Springer, Heidelberg; New York
References
23
One type of chirality demands additional considerations concerning chromatographic separations. As already described in the introduction, atropisomers gain
their chirality by a rotation hindrance between two cyclic molecule substructures
with different substitution patterns (Perez-Fernandez et al. 2012; Dai et al. 2017; Li
et al. 2018). Only if the substituents are of a certain size, the rotation barrier can be
preserved (LaPlante et al. 2011; Glunz 2018). Today, it is possible to calculate the
energy of the rotation barrier and the temperature limit below with chromatographic
separation (gas or liquid chromatographic methods) (Ghosn and Wolf 2011; Yan
et al. 2015). Furthermore, theoretical calculations may also be applied to determine
the temperature-dependent stability of atropisomers (Hesek et al. 2001; Casarini
et al. 2005; Callear et al. 2015; Buevich 2016). One of the predominant environmental pollution groups featuring atropisomers in environmental pollution research
is the group of polychlorinated biphenyls (PCBs). PCBs will be introduced later in
the group-specific chapters (Warner et al. 2009; Lu et al. 2013).
Based on the careful application of the above-described interactions to chromatography in combination with sensitive detectors, analytical chemists have developed a multitude of selective and sensitive methods for the chromatographic
separation of environmentally relevant chiral trace compounds into their respective
enantiomers. However, based on modern ultra-high-resolution mass spectrometry,
new methods based on enantiomer-selective mass-selective separation focussing on
enantiomer selectivity in ion mobility and MALDI are currently under development.
These methods are considered as a new promising enantiomer-selective detection
method also for low-level environmental applications (Awad and El-Aneed 2013;
Jurcek et al. 2015; Nachtigall et al. 2018; Li et al. 2019).
References
Adhikari S, Kang JS, Lee W (2016) A convenient and validated enantiomer separation of chiral
aliphatic amines as nitrobenzoxadiazole derivatives on polysaccharide-derived chiral stationary
phases under simultaneous ultraviolet and fluorescence detection. Chirality 28(12):789–794
Ali I, Aboul-Enein HY, Sanagi MM, Wan-ibrahim WA (2012) Chirality and its role in environmental toxicology. In: Luch A (ed) Molecular, clinical and environmental toxicology, vol
3. Springer, Heidelberg, pp 413–436
Awad H, El-Aneed A (2013) Enantioselectivity of mass spectrometry: challenges and promises.
Mass Spectrom Rev 32(6):466–483
Badaloni E, Cabri W, Ciogli A, D'Acquarica I, Deias R, Gasparrini F, Giorgi F, Kotoni D, Villani C
(2010) Extending the use of “inverted chirality columns approach” for enantiomeric excess
determination in absence of reference samples: application to a water-soluble camptothecin
derivative. J Chromatogr A 1217(7):1024–1032
Basheer AA (2017) Chemical chiral pollution: impact on the society and science and need of the
regulations in the 21(st) century. Chirality 30(4):402–406
Berthod A (2010) Chiral recognition in separation methods: mechanisms and applications.
Springer, Heidelberg; New York
References
23