TFA modifier on C18- how much washing to remove?

[Jack Silver]

When I use a column with 0.1% TFA, how much do I need to wash toh column to remove all of it?

I like to do a "wash" run (no sample, no TFA), I was told that may not be enough.

Thanks in advance!

[tom jupille]

There is no guarantee that you will ever be able to remove *all* of it. A good rule of thumb is that it takes about ten column volumes to get complete "physical" washout of a column. Any additional time for an additive will depend on how tightly that additive sticks to the stationary phase and how effectively it is displaced by your solvent.

If it's a case of getting back to starting conditions, once you can get reproducible retention, that's good enough, so I would start with the 10 column volumes and experiment from there. If it's a case of getting the column clean for an entirely different method, my philosophy is to not bother; simply dedicate the column ("Columns are cheap; your time is valuable!").

[Jack Silver]

Tom-

That's about what I thought. Thanks for the reply. It's nice to have confirmation.