probably by using chiral column or by proton NMR or single crystal X-ray

only using chiral columns which are compatible with electrospray ionization

YES we can! You need a chiral column. Otherwise a derivatization with a chiral reagent is necessary (if there is a easy reaction center on the molecule) to get two diastereoisomers, which are separable on a classical column.

In NMR, enantiomers are not differentiated unless you add a chiral reagent or solvent, but a reaction is not necessary (the so called “shift reagents”, i.e. lanthanides complexes soluble in usual NMR solvents, were used when I was young, and chiral ones, like camphorates, were available). There are some in the Sigma Aldrich catalog.

For NMR see (I have the PDF)

http://onlinelibrary.wiley.com/doi/10.1002/chir.10190/pdf

There are different LC columns and eluants dependeing og the class of substances.

Good luck ! J-F 

excuse me my professor, absolutely any separation techniques like HPLC, CE and LcMs can differentiate between R,S enantiomers but you have to use a chiral column which is considered as a chiral selector bounded to a silica stationary phase , Cyclodextrins considered the most common used (CSP),also may be proteins, Crown ether and bulky antibiotics such as zincomycin

there is another way which is using a chiral selector  soluble in your mobile phase such as Hydroxy propyl-beta or gamma - Cyclodextris and recently highly sufated CDs

I agree with most of the statement here. To go to application may need a good analysis of the bibliography.

My dear instructor, Dr. Mohamed:

If by R and S, you mean an enantiomeric pair: then the answer would be no, unless a chiral column is used.

However, if the pair of compounds in question are diastereoisomeric, then there may be a chance if the column and conditions used can/are optimized to resolute the pair from each other.

with best regards,

Refaat

Thanks all. Many papers now contain LC-MS analysis using RP-18 columns. The identified compounds include enantiomers. I was surprised, so I have asked my question

You have two choices, you may use a chiral column to separate isomers or you may use a chiral specific derivative such as Marfey's reagent.  Our lab uses Marfey's reagent for the separation of D&L Methamphetamine.  We chose that route because it is more efficient for us to derivatize a rarely occurring batch rather than making a column and mobile phase switch in the middle of a busy routine production day. See our poster that we presented at MATT last spring.

Thanks a lot Dr. Jones

Yes, we used Marfey's analysis for cyclic peptides (cylicodysidins) after hydrolysis to identify the D and L amino acids building blocks

Profs. Akasaka, Ohtaka, Ohrui and Kenji Mori used normal phase columns to separate derivatives of enantiomers made with fluorescing chiral derivatizing agents.   This was for synthesis of many enantiomers of the New World Screwworm fly sex pheromone in my RG bibliography: There are several recent papers describing this very sophisticated process listed there.    

Article: Determination by HPLC fluorescence analysis of the natural enantiomers of sex pheromones in the New World screwworm fly, Cochliomyia hominivorax.

K Akasaka, D A Carlson, T Ohtaka, H Ohrui, K Mori, D R Berkebile

[Show abstract]

Medical and Veterinary Entomology 07/2009; 23 Suppl 1:126-30. DOI:10.1111/j.1365-2915.2008.00781.x

hmmm. It seems there is some agreement here and that is fine.

1) the MS cannot discriminate between stereoisomers, but the HPLC eventually can.

However, stereoisomers is more than enantiomers: cis/trans, E/Z, diastereomers etc. are all stereoisomers that do not require an enantioselective column, but can in principle be separated by pretty much standard columns.

2) If however the stereoisomers are enantiomers, an enantioselective column or pairing reagent will be needed.