J have a steroid and I'm not able to separate the two forms, one with the -OH in position Alpha (or S) and the other with the -OH in position Beta (or R).
I tested columns C8, C18, normal, microbore, long, short, 5 µm, 3.5 µm and associations of them. I use Acetonitril and Water because they are the best. I already tested THF, IPA and MeOH also.
He (she) who help me.....is a genius!
Thank you!

Have you try using chiral columns? chiralcel OD-R for reversed phase or chiralcel OD for normal phase.

Generally speaking, reverse-phase is not very selective for differences in the arrangement of polar functional groups, because the primary interaction is solvophobicity (secondary interactions are another matter). Normal-phase is often a better choice for this type of separation.
You might look at a cyano bonded-phase column used with a non-polar eluant (methylene chloride/hexane, or iPrOH/methylene chloride.

Another possibility is the use of a porous graphite carbon (Hypercarb comes to mind, but maybe Tim Brady will chime in here with additional choices). This column uses a reversed-phase mechanism (with typical ACN/H2O mobile phases) but seems to give exceptional selectivity for shape differences.

A third approach might be the use of cyclodextrin bonded-phase columns. These are normally thought of mainly for enantiomer separations, but they are also selective for shape differences which will affect how the analytes fit in the cyclodextrin cavity.

Good luck (and let us all know what finally works!)

-- Tom Jupille / LC Resources

As Tom mentioned above, there is the Hypersil
Hypercarb and two additional sources of graphitized carbon columns on the market.
They are...

TSKgel Carbon-500
ZirChrom CARB 300

The Hypersil Hypercarb has a stereo-selective surface ideal for resolving isomeric and closely related compounds. The Hypercarb is available from...Alltech, Bodman, Hypersil, Keystone,
Metachem, Phenomenex and Western Analytical.

According to the manufacturer, Chiral Technologies

The Chiralcel OD is designed for Beta blockers, compounds with similar functionality, and steroids; Examples: alprenolol, atenolol, flavanone, metoprodol, oxprenolol, pindolol

The Chiralcel OD-R is reversed phase type of CHIRALCEL OD. It can be used with neutral, acidic and basic compounds, including verapamil, propranolol, pindolol, diphenylethylamine, and other compounds separated in normal phase on CHIRALCEL OD

If you want to do a little more research on the subject, please visit www.chromatography.net and use the following for temporary access..

Username-lcgc
password-columns

Hope this helps

All of the preceding suggestions are good and one of them will probably work. Normal-phase separation is most isomer-specific when silica is used (rather than a bonded-phase, e.g., cyano column), with a less-polar B-solvent. If you continue to have difficulty, I suggest a few exploratory TLC separations on silica, using hexane-methylene chloride or methyene-chloride MTBE mobile phases. If TLC works, then a silica column in NPC will probably also work, although with the experimental problems usually found with silica columns (need for water control, slow column equilibration, etc.)

Hi

You may want to try the polymeric YMC C30 column. It has become known as the "carotenoid" column as it was developed specifically to separate the many isomeric carotenoids, both polar and non-polar.
Available from YMC Inc, Wilmington, NC, USA. I've used it for cis/trans separations that failed on all C18 columns.