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Separation of diastereomers
Posted: Wed Jan 23, 2008 4:53 pm
by kaha37
Hello
I am working on a method to separate a pair of diasteromers with a view to using the method on a semi-prep scale and am struggling to obtain a separation. The diastereomers are eluted (as a single peak) right at the top of my scouting gradient (100% organic) with both MeOH and MeCN as the organic eluent and on both a C18 and C8 column. I do see some resolution running at Aqueous:Organic 1:1 but it takes about 40 minutes and the peaks are nowhere near well enough resolved. Is there something else I can try to improve things or do I need to use normal phase or a totally different column? Any advice would be very much appreciated.
Thanks.
Posted: Thu Jan 24, 2008 8:48 am
by blackdrum
If you don't have any chiral preparative column, you should start from normal phase column(silica, cyano) and non-polar mobile phase, for diasteromers separation, silica column sometimes gives good resolution.
Posted: Thu Jan 24, 2008 2:00 pm
by Mattias
Diasteromers are usually not possible to separate by changing gradient or buffer (as you may have noticed). It is a matter of finding the right column!
I don't think it is possible to predict the behaviours of different columns, so it is an trial-and-error practise. I have had some luck in the past when using Hypercarb columns for this application, could be worth a try.
Anyone used additives in the mobile phase? I know cyclodextrines are sometimes used in CE.
Posted: Thu Jan 24, 2008 9:20 pm
by tom jupille
The Hypercarb column as suggested by Mattias would probably be my first trial-and-error choice. Another possibility is the Cyclobond (cyclodextrin) column. This is normally sold for chiral, but can have good isomer and diastereomer selectivity as well.
Posted: Thu Jan 24, 2008 11:44 pm
by banala_b
Hi,
Trial on chiral columns works out for most of diastereomers,I would suggest to try on chiral AG-P column,it worked out previously for me.
Primesep-D has lots os applications in separating positional isomers(diastereomers).Hope u can try on both columns.
Good luck
Posted: Fri Jan 25, 2008 10:53 am
by AdrianF
Another possibility is the Luna PFP (PentaFlourylPhenyl) phase which can separate many isomers.
Posted: Mon Jan 28, 2008 12:02 pm
by sfe-co2
Just to throw in another suggestion: Carbon-clad Zirconia columns. The company is Zirchrom if my memory didn't fail me. Or look up Peter Carr's papers in the literature.
Good luck.
Posted: Fri Feb 01, 2008 4:32 am
by Kelly Johnson
We have been very successful with diastereomers and other closely related products on our ZirChrom-CARB product. I would be happy to supply more information directly. Please feel free to contact me directly with any questions.
Kelly Johnson
support@zirchrom.com
Posted: Sun Feb 10, 2008 11:34 pm
by adam
There are some companies out there that make C30 phases. I have heard that these can also show good shape selectivity: allowing for separation of things like diastereomers.
Kelly: Have you ever done any comparison of how your ZirChrom-CARB works in comparison to these phases.
Anyone: Have any experience using C30 columns to separate compounds with very similar structures.