Chiral in Mass Spec

[MS_chrom]

I know enanatiomers and diastereomers will have similar parent mass and daughters. Is there any other way to differentiate them, such as labelling with chiral reference?

Can anyone share their experience to differentiate chiral compounds in Mass Spec? TIA

[lmh]

true chirals are very difficult. I did see, somewhere, a reference that idenitifed the chirality of amino acids by their ability to form cluster ions with other amino acids of known chirality. Sorry, I can't remember where it was, and it was such a weird concept I don't seem to have kept it in my mass spec references folder.

[thohry]

It's better to pay effort on the analytical column. There are chiral columns available.

[chemstation]

As you mentioned in your first line, there is the option of Chiral derivatising reagents, (if your compound will derivatise).

http://www.sigmaaldrich.com/analytical- ... ge=9657462

So you don't need to swap out an GC, or if you used a chiral column as well as the chiral reagent, the retention time difference, theoretically, should be even greater.

Alex

[HW Mueller]

Chemstation, what is the "theory" behind getting better separation when using chiral derivatization reagents + chiral columns?

[chemstation]

Hi HW Mueller,
my theoretical reasoning, is based on the following premise, (ignoring racemix products) that the function group that gets derivatised, is attached to the chiral centre, so that new stereo structure of the compound will interact with different affinity with the stationary phase.
eg if for the two new structures, one is "ball shape" and the other "flatter" then the amount interaction with the station phase, whether it be polar or otherwise, will be different, it is this difference that may affect the enthalpy enough, so as to be visible as a different elution time.

another REMOTE and unlikely possiblity could be that if the function group that gets derivatised, is NOT attached to the chiral centre, then the natural stereo structure that forms (cluster), due to the electrostatic attractions and repulsions being greater that the rotational energy the bonds are receiving from the heat of the GC , Whilst eluting down the column, though I doubt this very much.

Alex

[HW Mueller]

What does anything of this, even if viable, have to do with the chirality of a column?