Chiral separation

[okara]

. HI,
please help me out i am new in chiral separation what is the different between chiral and a chiral compound separation and what is the main point we should need to consider when we are development a method on hplc
thanks
okara

[Cliff Mitchell]

Okara, could you clarify your question? I can probably give you some advice but I don't understand what you mean by "the different between chiral and a chiral compound separation".


Regards,
Cliff

[okara]

Hi Cliff,
Thanks for your response, actually my mean is what is the theory behind the separation of chiral compound when we developing a method in HPLC.
doest it work same like non chiral method development or there are some other roles, please explain or tell me some good website where i can find the detail of chiral separation theory.
Thanks

[Cliff Mitchell]

Okara

The theory is well described in a number of places. I recommend a book by Thomas E. Beesley called Chiral Chromatography. There are chapters on theory as well as method development.

http://www.registech.com/chiral/chiralreview.pdf

This link is to a review of chirality and there is some info on chiral separations and an emphasis of the Regis/Pirkle column technology.

You are right in that developing a chiral method in HPLC is similar to regular method development. The best strategy is to get adequate retention (retention factor of 3-7) on a CSP (chiral stationary phase) and see if there is a separation of enantiomers, a partial separation, or no separation. If there is no separation with adequate retention, it is probably best to try another mode of operation on that stationary phase or try another stationary phase.

If you have a partial separation, you may be able to optimize the conditions to get a baseline separation. Switching the identity of the modifiers in your mobile phase often produces the greatest changes in your separation. Switch from methanol/water to acetonitrile water or THF/water. Add acids or bases to change the ionization of you analyte (if possible). If you are doing a normal phase method, you can make similar changes to the mobile phase.

Best of Luck
Cliff

[ConstantinS]

In fact, series of Chiralcel columns can separate about 80% of racemates. If you have enough money, just buy Chiralcel OD and Chiralcel AD and use hexane-2-propanol. You'll find, that a separation could be carried out without knowing of any theory.
But, frankly speaking, there is no any good theory is chiral chromatography. There are some assumtions and experimental facts, that may help in some situations. Sometimes, it is more useful to look through application guides for the most well-known CSPs.

[Ben Buglio]

Beesley's book would be a good background for chiral chromatography as would seminars and courses in that field. As a practical solultion for a specific problem I would send a sample of the racemic mix to a chiral column manufacturer having a technical service dept. Often they will run your sample through their library of columns and provide you w a working system. Two companies which you might approach are Astec and Daicel.