Chromatography Forum

Hello all

I'ld like to throw a question out there for the group. Is anyone aware of a chiral column that can also act as a reversed phase column?

The reason I am asking is that we are trying to develop a separation between our API, its chiral epimer, and the other deg products. Since the epimer is a diasteromer of the API it is theoretically possible to do this with a standard reversed phase column, however in practise it is somewhat difficult.

So I was thinking that if there is a chiral column that could also be used as a reversed phase column this might give a little more separation (for something like a diastereomer).

Just to clarify, I don’t just mean that we would run it in "reversed phase mode" (a term often used in the chiral world to mean that we're running it with reversed phase type solvents), I mean where the column is actually giving a reversed phase mechanism of separation. I took a quick look at all the different types of chiral columns that exist and I thought the antibiotic columns might be the best bet. But I'm not at all sure.

Any suggestions would be much appreciated.

Thank You

You can get some reversed-phase properties on chiral columns like Pirkle type, or even with the amilose/cellulose-based columns (modified by hydrophobic isocyanates). The main issue with sugar-based one is that ligand needs to be physically attached to the surface. Also chiral resolution will probably go down in a lot of cases, because you switched to a different mode (non-aqueous to aqueous)

amilose/cellulose-based columns (modified by hydrophobic isocyanates)

- Any idea who sells something like that?

The old Cyclobond columns (cyclodextrin covalently attached to silica) exhibit some reversed-phase properties. I discussed this in the paper that introduced the HILIC mode (J. Chromatogr. 499 (1990) 177). The cyclodextrin forms an alpha helix with the hydroxyl groups on the outside. The core of a helix is a lot more hydrophobic. At low levels of organic solvent, analytes partition into the core and separations are in order of increasing hydrophobic character in addition to chirality. At high levels of organic solvent, analytes interact with the hydroxyl- groups on the outside of the helices and separation is in order of increasing hydrophilic character; an inversion in elution order.

amilose/cellulose-based columns (modified by hydrophobic isocyanates)

- Any idea who sells something like that?

Chiral technologies, Phenomemenx, Supelco...I think that i all modern sugar based column ligand is attached to the silica gel:
http://www.phenomenex.com/Products/Detail/Lux

Perhaps you could try http://www.analytics-shop.com/gb/hplc-c ... rator.html .On this site is a column configurator, so you don´t have to check every single producer.

This tech note shows some separations using a variety of reversed phase conditions with a polysaccharide column. The retention of compounds generally increases with increasing hydrophobicity.

https://phenomenex.blob.core.windows.ne ... ace876.pdf

Hi

I would suggest you to check the Chirobiotic columns from Sigma-Aldrich. They are are based on covalently bonding macrocyclic glycoproteins to a high purity 5 micron silica gel. They separate on ionic, H-bond, π-π, dipole, hydrophobic, and steric interactions.

You can work with Reversed-phase (RP) - methanol or acetonitrile/20 mM ammonium acetate, pH 5 (30:70). And optimize by changing % or type of organic modifier, adjust pH, buffer type, ionic strength.


http://www.sigmaaldrich.com/analytical- ... iotic.html

Please get in touch with local representative. They will surely help you. If you are based @ USA, you can use their Chiral screening facilty at Bellefonte, Pennsylvania