Chromatography Forum

Greetings

I have come across a 1979 article that uses a 250x4mm column packed with Merckosorb Si60 (5um) with ethyl acetate as mobile phase, but it gives good separation of two compounds we have so far been able to resolve.

What would a more modern equivalent of this column be? I happen to have a Kromasil silica 100A, 250x4.6mm, 5um available. Would this be suitable? Also, would there be a more suitable mobile phase than ethyl acetate? Maybe an IPA:hexane mix? The problem is that the analytes require methanol to dissolve.

Thanks!

That would be a 60Ã… pore-size silica. That's a small-pore material by today's standards. I'd check with Merck to see if it's still available.

If the mobile phase was indeed pure ethyl acetate, you should be able to duplicate the strength with an appropriate mixture of IPA in hexane (it wouldn't take much IPA!), but you might not get the same selectivity. No way to tell except to try. If memory serves, methanol and ethyl acetate are at least somewhat miscible, so injection in methanol should be feasible if the volume is small enough.

Cheers Tom. We'll give this a shot.

Normal phase chromatography,

maybe you can stay clear of it.

have you tried to use a hilic column?
depending on the nature of your compounds, several companies aslo have c-18 column that better retain polar compounds away from the front of reversed phase applications.

it is worth trying before you go to normal phase.

anyway i know of this type of merck column:
LiChroCART® 250-4 Superspher® Si 60 PN: 1160090001

i know that there is also a LiChrosorb Si 60 but i cannot find the part number right now. you will need to ask your local merck rep

Unmgvar, haven't tried a HILIC column. Unfortunately, I do not have one in my collection. I have tried a number of C18 columns but haven't had any luck in separating the two analytes, which are anomers of a nucleoside. Not entirely sure what kind of column would be best suited for these kinds of analytes so advice would be most welcome.

I think there is a bug in the Column Name

possibly its
Licrosorb (Merck)
or
Microsorb (Varian) wich is avalilble with 60A ( I dont know this for Licrosorb)

Both are on the market for a long time


best regards
Chris

I'm not sure that HILIC would be a viable option in this situation. While HILIC is "normal phase" in terms of polarity, it is essentially based on liquid-liquid partition as a mechanism. Silica columns used in "classical" normal-phase chromatography are arguably based on adsorption as a mechanism and (I would guess) considerably more selective for isomerism.

Chris0000, this is a paper from 1979. Maybe in those days the stationary phase was called Merckosorb. I am not surprised it does not exist anymore. Thanks all for the feedback. We'll do some tests with the Si100 which we happen to have in house for starters.