Using 100% aqueous mobile phase with a phenyl colum

[hajdaei]

Quick question: Can you use 100% aqueous mobile phase with a phenyl column.

I know all about the 'phase collapse' or 'pore exclusion' issues that people talk about. But usually those are for C8 or C18. My understanding is that with a phenyl phase having some polarity, it would be more amenable to use in 100% aqueous environment.

For that matter what about cyano?

[Uwe Neue]

Cyano is guaranteed to be fine. For the phenyl column, I would think that most phenyls will work, but it does depend on the details of the design. Try it, and let us know.
Test: run the column in about 50% organic; convert it to a fully aqueous mobile phase, never stopping the flow; inject a standard that is retained in the fully aqueous mobile phase until you get stable retention times, then stop the flow for a minute or a bit more, then start the flow again. If the retention is the same before and after the flow stop, your column does not have a dewetting problem, and you are safe to eternity.

[XL]

To continue Uwe's comments, you need to repeat the cycle of "test and stop flow" several times and monitor the retention time. If you do observe retention drop after "stop flow", no need to worry. Just "re-wet" the column with 100% acetonitrile or acetane at 1 to 2 mL/min (for a 4.6-mm i.d. column) for 30 min and the column will be "normal" again. Make sure the liquid in the column is compatible with pure organic solvent when you do so.

[FSE]

You might want to check Phenomenex' Synergi Polar-RP. This phenyl column should be stable in 100 % aqueous environment. They let you test it kind of for free - you buy and if it does not do the job you can return it for refund - best you contact your sales rep.

[Kwet]

Be carefull that Polar-RP is not a classical phenyl colum. It's an ether linked phenyl with polar endcapping. So the bonding is more polar than classical phenyl columns wath should avoid more easily the column to collapse in 100 % aqueous. You should also take into account that the phenylether group gives a different selectivity than a classical phenyl.

With classical phenyl columns the risk to collapse is low but perhaps exist if a fully apolar encapping is realized.