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Chiralm selective chromatography. D. Kozma ed. Handbook of Optical Resolutions via Diastereomeric Salt Formation. CRC Handbooks, 2001. Z Juvancz, G. Seres Appendix. Definition of chirality. Chiral molecules are asymmetric.
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Chiralm selective chromatography D. Kozma ed. Handbook of Optical Resolutions via Diastereomeric Salt Formation. CRC Handbooks, 2001. Z Juvancz, G. Seres Appendix
Definition of chirality • Chiral molecules are asymmetric. • Enantiomers or optical isomers are mirror image of each others, but they are not same. • Diastereomeric molecules are not • mirror images, but they have same constitutions. Central chirality with for different substituents.
Enantiomers DNS molecules Kajtár M., Változatok négy elemre, Gondolat, 1984.
Application of chiral selective analysis Checking the chiral selective synthesis: Pharmaceutical, pesticide industry Metabolite research: (pl. Warfarin, Ibuprofen, pheromonos) Adulteration, bacterial infectiouns: ( pl. wine, essential oils) Racemisation: (pl. heat treatment, age determination)
Three point interaction is necessary for the chiral recognation I. V.R. Meyer, M. Rais, Chirality 1 (1989) 167.
Two point interactions are not enough II. V.R. Meyer, M. Rais, Chirality 1 (1989) 167.
Certain rigidity is necessary for chiral recognition V.R. Meyer, M. Rais, Chirality 1 (1989) 167.
Interaction points can be surface or axis π acid - π base, and h_bridge are the key interactions.
Working theory of chiral stationer phase, (CSP) C. Welch et al., Review of Stereochemistry
Working theory of chiral mobile phase addtitive (CMA) C. Welch et al., Review of Stereochemistry
Rigid structure offers high selectivity. Flexible structure offer broad selectivity range. Most of the separation bases on three point interaction. Functional groups close to asymmetric center improves the resolution. Repulsion interactions havea big role. Low analysis temperature improves the separations. General rules of chiral selective chromatography
Temeperature dependence of chiral chromatography ln α = S+- (S0sm)/R - H+- (H0sm)/RT +- : difference between the two isomers (+and -) • sm: difference between two phases (stationary and mobile). Generally the low analysis temperature improve the separation. Using high efficiency stationaryphase, 0,1kJ/mol (α: 1,01) energy difference is enough between the enantiomers for Rs 1.5 resolution value.
Shape of derivatized a CD The direction and length of bonds are differents..
Reason of good chiral recognation properties of cyclodextrins • There are several chiral center in a CD • The surrounding of chiral centers are of uniform in a glucose unit. • The shape of glucose units are different • Substituted derivates are bunch of isomers • The chiral recognition depends on the type of substituents • The selectivity can depend on the ionized state • Cyclodextrins have flexible structure (induce fit)
Cyclodextrins can separate even the functionless hydrocarbons enantiomers
Selecticvity vs. Concetration of chiral selector The acharial silicone matrix offers a good efficiency.
Separation of enetiomers of essential aminoacids with Chirasil-Val Orginal CSP ImprovedCSP
Key interaction of polysaccharide CSps H-bridge ands π- π interactions
Chiral separation in CE Neutral selector can not separate neutral molecules. The oppositely charged selector and sample offer high resolution. Separation has maximum value in the function of the selector concentration.
High selectivity with oppositelly charged sample and selector
Chiral separation with β-HDMACD 0,5 mMol concentration of selectror is enough for baseline separation.
Chiral selective separation of γ-PhoCD reversed migration orders TRIMEB
50 mM acetic acid / TRIS; pH 5.0 mAU 30 20 10 0 -10 -20 2 4 6 8 10 12 14 min 50 mM acetic acid / TRIS; pH 5.0 mAU + 1 mM MAbCD 30 20 10 Kass : 100 – 370 M-1 0 -10 -20 2 4 6 8 10 12 14 min 50 mM acetic acid / TRIS; pH 5.0 mAU + 10 mM PMMAbCD 30 20 10 Kass : 1.3 – 70 M-1 0 mAU -10 20 -20 4MePPA 15 + 1 mM MAbCD + 10 mM PMMAbCD 2 4 6 8 10 12 14 min 50 mM acetic acid / TRIS; pH 5.0 10 5 Fenoprop 0 PPA - 5 - 10 5 10 15 20 25 min mecoprop, 2,4-DP, 3ClPPA Dual CD seletor system R. Iványi et al.
The selectivity of ionizable CDs depend on their ionized states
Partially filling technique No EOF (acrylamide coated column). The sample and selector migrate in opposite directions. The selector nigrates away, when the sample reaches the detector windows.
Chips chiral separation EKC Designed for Martian space rockett
Chiral CEC Monolit CSP selector