Two very similar substances: need column advice

[LCFlo]

Dear all,

I have two substances, that are very similar: Estriol and 9,11-Didehydroestriol (see picture).

What type/method (RP-mode only) would you recommend for the separation of these two substances?

Thank you very much for any hint.

Regards

Florian

[Consumer Products Guy]

Not exactly what you asked, but personally I'd try capillary GC after trimethylsilyl derivatization.

[tom jupille]

The extra hydrogen on 9 is obviously a typo.

If those are the only two compounds to be separated, then a phenyl column might give a bit better selectivity than a C18 for the presence/absence of that double bond. If there are other compounds in the sample as well, then it's a toss-up.

[Alex Buske]

Hi,
separating Estriol and 9,11-Didehydroestriol by HPLC isn't very complicated. Most C18-Columns (150mm, 3µm) will do. Some will also separate 9,11-Didehydroestriol and 6-Didehydroestriol.

Alex

[LCFlo]

Hello,¨

DawnRazor: you are right: the H-atom at position 9 is wrong as noticed by Tom Jupille.

Alex: your statement sounds as you might be experienced in this kind of separation. Do you have an application or similar?

Thank you very much to all responders.

Regards

Florian

[cody84]

Kinetex PFP! I just was at the presentation for Kinetex columns.

[unmgvar]

I would try two possibilities
both from cosmosil for exactly those types of molecules

I would start by the Cholester type. I know of an application for vitamin D2 and D3 where the column helps splendid and the separation is super simple with MeOH Water

another possibility is Pi-NAP to try and do separation on the pi-pi in the molecules but this column uses naphtylethyl group which gives better solution then a phenyl column

the advantages of these columns in these applications is the use of simpler mobile phases with less modifiers

[XL]

A related separation can be found in the 2nd chromatogram in the following link: http://www.dionex.com/en-us/products/co ... 87227.html. The column is Acclaim Phenyl-1, 3-um column.

[Alex Buske]

Florian,

I don't have a recent method on Estriol. If I had, it would be IP of my employer anyway. I would go with a C18 or C8 and try methanol and ACN as organic additives. Small pore size materials can have advantages.

Alex