VOLTEC

Chiral Chromatography

Resolve Chiral Molecules
Three Classes of Columns Available
Reasonably Priced

Chiral compounds, or enantiomers, have identical molecular structures but are related as mirror images of one another much like a left hand is related to a right hand. The rapid and accurate stereochemical resolution of enantiomeric molecules is an important issue which touches many areas of the natural sciences. With the realization that the enantiomeric forms of a drug substance can have wildly different pharmacological effects, resolution of pharmaceutical enantiomers took on great significance. The ability to analyze and purify enantiomers was greatly enhanced by the introduction of chiral stationary phases (CSPs) for HPLC. Most chiral HPLC columns contain one form of an enantiomeric compound immobilized to the surface of a silica packing material. For chiral resolution to occur, there must be at least three points of simultaneous interaction between the CSP and one analyte enantiomer, one or more of these interactions being stereochemically dependent. As shown in the schematic above, enantiomers I and II will have differing degrees of interaction with the stationary phase, since enantiomer I has three simultaneous points of interaction, while enantiomer II has only two points of interaction. Therefore, enantiomer I will be more strongly retained than II and will elute after II.

Type I Phases
D-phenylglycine and L-leucine are Type I CSPs and use combinations of p-p interactions, hydrogen bonds, dipole-dipole interactions, and steric interactions to achieve chiral recognition. To be resolved on a Type I column, analyte enantiomers must contain functionality complementary to that of the CSP so that the analyte undergoes essential interactions with the CSP. The sample should ideally contain one of the following functional groups: p-acid or p-base, hydrogen bond donor and/or acceptor, or an amide dipole. Derivatization is sometimes used to add the interactive sites to those compounds lacking them. The most common derivatives involve the formation of amides from amines and carboxylic acids.

Type II Phases
The MetaChiral ODM™ is a type II CSP. The primary mechanisms for the formation of solute-CSP complexes is through attractive interactions, but inclusion complexes also play an important role. Hydrogen bonding, pi-pi, and dipole stacking are important for chiral resolution on the MetaChiral™ ODM. Derivatization is often necessary when the solute molecule does not contain the groups required for solute-column interactions. Derivatization, usually to benzylamides, is also required of some strongly polar molecules like amines and carboxylic acids, which would otherwise interact too strongly with the stationary phase through non-stereo- specific interactions.

Type I	SafeGuard Cartridges $ 175 (3/pkg)	250 x 3.0 $ 439	250 x 4.6 $ 439	250 x 10 $ 1159	250 x 21.2 $ quote
5µ D-Phenylglycine	0515-CS	0515-250X030	0515-250X046	0515-250X100	0515-250X212
Type I	SafeGuard Cartridges $ 175 (3/pkg)	250 x 3.0 $ 579	250 x 4.6 $ 579	250 x 10 $ 1199	250 x 21.2 $ 3800
5µ L-Leucine	0512-CS	0512-250X030	0512-250X046	0512-250X100	0512-250X212
Type II	SafeGuard Cartridges $ 225 (3/pkg)	250 x 3.0 $ 879	250 x 4.6 $ 879	250 x 10 $ 2300	250 x 21.2 $ 6100
5µ MetaChiral ODM	0991-CS	0991-250X030	0991-250X046	0991-250X100	0991-250X212
	Guard Column $ 450	150 x 4.6 $ 1300	250 x 4.6 $ 1550
5µ Ceramospher®	0993-035G046	0993-150X046	0993-250X046