Can anyone suggest a highly retentive column that that is stable (not prone to C18 chain collapse)in greater than 98% aqueous conditions. I am trying to develop a method that can separate some highly polar compounds (sugar alcohols) along with some relatively nonpolar compounds. I have tried the Phenomenex AQUA ODS column with no success.....Any suggestions?

Dan Ryder

It might not be as retentive as you need, but I use a Micra Scientific SCD-100. It's a "short chain" which obviously won't collapse , so it's stable in 100% AQ. I've heard good things about the "base-deactivated" columns, specifically the HP/MacMod Bonus RP. It's a C16 chain with a polar group bonded between the chain and the silica. It's supposed to eliminate phase collapse and the tailing seen in basic compounds.

Dan,

I searched our column database and came up with the following results. If you visit our application at www.chromatography.net, you will find more details about these columns (part numbers, suppliers, applications, etc.). Finding columns of this nature takes only a couple of seconds using our database.

The following list of HPLC columns are designed for extra polar selectivity. Here are your results...

AquaSep C8
Aquasil C18
Chromegabond PSC
Combiprep ODS-AQ
Combiscreen ODS-AQ
Discovery RP-AmideC16
MetaSil AQC18
MetaSil AQC18
Pinnacle IBD
Platinum Rocket EPS C18
Platinum Rocket EPS C8
Platinum EPS C18
Platinum EPS C18
Platinum EPS C4
Platinum EPS C8
Platinum EPS C8
ProntoSIL 3-C18 AQ
ProntoSIL 3-C18 AQ
ProntoSIL 5-C18 AQ
ProntoSIL 5-C18 AQ
Supelcosil ABZ+Plus
Supelcosil LC-ABZ
SymmetryShield RP18
SymmetryShield RP8
YMC-Pack ODS-AQ
YMC-Pack ODS-AQ
Zorbax Bonus-RP

I hope you find this information helpful.
Tim Brady

Aquasep from ES Industires is the most retentive of the columns we have evaluated for polar hydrophillic compounds. If it doesn't retain your compounds in 100% water its probably not doable by RPLC. MIght try a carbohydrate column, for example one of BioRads.

YMC-Pack ODS-AQ is very good column for polar hydrophilic compounds. The column is very stable in 100% aqueous.

I don't know about your relatively nonpolar compounds, but regarding highly polar compounds such as sugar acids, organic acids, and alcohols, I feel your best bet would be a Resex ROA-Organic Acid column. These can be purchased though Phenomenex. This is a sulfonated styrene-divinyl benzene column. The mobile phase is really simple, 0.005N - 0.01N H2SO4 in water. Adjusting the sulfuric acid concentration and / or operating temperature should have an effect on optimizing your chromatography. Up to 5% organic modifier, i.e., methanol can be used. These columns operate at low flow rates. When you start with a new column, you have to run mobile phase through the column for at least hours to achieve steady base line. Once you do this, from there on in, you should be ready to go with a short equilibration on startup.

Aquasil C18 (Keystone Scientific) was developed for the retention of highly polar solutes under 100% aq. conditions. I have found it to be quite useful for the analysis of small alliphatic acids such as ascorbic acid using 0.05M KH2PO4, pH 2.5 as the mobile phase. It might be worth a try for your application.

Hypersil have a new HyPurity phase - HyPurity Advance.

Its been proved stable ( ie no phase collapse) in 100% water at room temperature for 236 hours plus.

It's a rather good phase since it offers different selectivity to conventional C18 and increased analysis speed.

There was a poster at Pittcon '99 about this phase - I got more info from their Tech Support Chemist.

I've used this phase a lot and it's fantastic for basic drugs - the peak shapes are the best I've ever seen.

We've also had some luck with the Keystone Prism column. It is somewhat of a black box however in that while it is primarily C18, there is some secondary chromatography (ion-exchange ?) going on. Nevertheless, we have found it very retentive for a wide range of analytes.

Peace

You may try also a Resolve C18 column from Waters. It is a not endcapped column having a special selectivity in comparison to other C18 columns, and also it is very retentive.

I am experiencing a problem of fluctuating retention times on a day to day basis when using a simple methanol gradient in a weak ammonium acetate buffer and a Waters symmetry C8 column to separate nucleoside analogues in plasma. The starting condition for the gradient is 0.5%methanol in buffer (gradient goes upto 20% methanol curve#9 over 13min, holds at 20% for 2 min then returns to starting conditions to re-equilibrate). Temp, pH & solvent mixing are all consistent. Is my problem likely to be due to the gradient starting conditions being too aqueous for a symmetry C8 column?

There has been a number of column introduced in recent times to separate very water soluble compounds. I have had a lot of success with the Aquasil C18 from Keystone Scientific, and even better, with the Diazem Alpha C18 column.

The Prism columns from Aquasil, and the Phenomenex Aqua C18 have not been good enough for my needs. Another one which works well initially is the YMC-ODS-AQ, but as many people have found, the columns just dont last very long.

MacMod is introducing a Hydrobond line of columns which is likely to be useful as well.