HPLC Chiral Separation by Reversed-Phase

[mjs20323]

I'm working with a neutral drug molecule, containing several amides and N-heterocycle moieties. A chiral method exists for normal phase separation and I would like to try reversed phase. Anyone have experience with chiral separation by reversed phase and could recommend a column(s).

Alternatively, lab staff have noted difficulty in switching over from normal to reversed phase. Anyone have a suggestion/procedure for making the switch.

Thanks for any help you can provide.

[ChemicalBond007]

I am in the same position. I am just now setting up my solvent system, hexane and IPA.

Although I have not tried my compound in NP chiral.


Fortunately I came across a pass-downed chiral column. But I would like to try synthesising a CSP.

[philippem]

Hi,
There is a lot of information on the web and in literature provided by the suppliers of chromatographic chrial columns/ systems.

if you want to use RP for chiral separations one has to use special mobil phase in order to form complexes of your anlytes of interest, these compexes can be separated by means of RP . Or one could use special chiral stationary phaes which can be run in RP mode

regards

philippe

[mbreslav]

I assume that you would like to switch to a polar organic mobile phase, like methanol, ethanol, etc. vs. non-polar organic mobile phase (like hexane/IPA). "Switching protocol" may already exist for your column. What column gave you separation in a "normal phase mode" anyway? Let me know and I will try to help you.
Actually I don't think that we can use "normal phase" or "reversed phase" mode when we are talking about chiral separation. Main characteristics which destinguish "noraml phase" i "reversed phase" modes are not the mobile phases per se, but the dominant mechanisms. With "normal phase" it is predominantly adsorption; with "reversed phase" it is mostly partition. Chiral separation is a specific mode, where all common interactions with the stationary phase (adsorption and/or partition) are responsible for general retention, but not selectivity.
I hope that there will be a revision of some of the terms that people are using in chiral chromatography.

[iSeparate]

Alternatively, lab staff have noted difficulty in switching over from normal to reversed phase. Anyone have a suggestion/procedure for making the switch.Thanks for any help you can provide.

I assume you are talking about polysaccharide based chiral sationary phases (CSPs) here, e.g. AD, OD. These CSPs work best in the normal phase modes. The coated nature of the selector prevented them from being used with solvents of strong solubility, and being swithed back and forth between the normal phase mode and the reversed phase mode, or even the polar organic mode.

To answer your question, Chiral Technologies now have the chemically immobilized version CSPs corresponding to AD OD. (commercially known as IA and IB). These new CSPs can be used in all modes, back and forth. Another choice is the Chirobiotic CSPs from supelco. These CSPs also have broad enantiomeric selectivities, and can be used in all modes. Most importantly, they are good at separating amino acids and peptides. I've known poly peptides different in only one amino acid resiude being separated on Chirobiotic T CSP. The choices are really determined by your budget.

Regards,

Owen.