Chromatography Forum

Hi all

Looks like Merck has discontinued their Lichrospher diol phase- maybe I'm the only one using it now! but I'm wondering where to go next, either I stick with Lichrospher and try a CN phase or I head out & look for someone else's diol phase - there aren't many out there.... Is it better to stick with the same silica (i.e. lichrospher, while it lasts) and a slightly different phase (CN or NH2) or try to keep the same bonded phase (diol) even if the silica specs may be totally different ???

p.s. we're using the diol in normal phase to separate complex mixtures of membrane lipids = phospholipids, glycolipids etc. etc. the diol gives us a nice 'class' separation based on headgroups, not the fatty acid chain length.

thanks, Helen

Either way, you are unlikely to find a "plug and play" solution; you will probably have to modify the mobile phase. The direction depends on how you interpret the interaction between the stationary phase and your analytes.

In many "normal phase" separations, the actual stationary phase is a layer of the polar component from the mobile phase sticking to the support. In that case, the selectivity is based primarily on relative solubility between that phase and your bulk mobile phase, and matching the pore size distribution / surface area may be the most important constraint, which would mean that staying with LiChropher is the best approach.

On the other hand: if you suspect that some more specific interactions with the hydroxyls (hydrogen bonding, perhaps?) are responsible for your class separation, then you need to stay with a diol phase.

If it were my problem, I'd get one of each. Columns are cheap; time is valuable!

Agree with tom, but also check with Merck as to why they are discontinuing, and whether any of their global sites have stock you can purchase.

Reasons for discontinuing can be:-
- lack of sales.
- production/consistency issues.
- replacement by an improved version/product.

I'd also look to purchase from a supplier who has a record of long production of specific products ( eg Waters ). I have a Phenomenex Diol ( Spherex ) that disappeared about one year after I purchased it. It's fine for my purposes, but would be a pain if it was used for long-term research.

Please keep having fun,

Bruce Hamilton

thanks for your suggestions guys, I just ordered a lichrospher cyano column, the retention order may be a little different but it doesn't really matter if we're using MS detection, so long as we get some retention!

Helen