column stability in acetic acid?

[skunked_once]

I'm running an analysis once a day at a different location using a Nova-Pak C-18 column and a mobile phase of methanol/water (30:60) with one percent acetic acid. There isn't time to flush the mobile phase each day and replace it with methanol/water. Is it safe to just shut off the flow when I'm not analyzing and leave the column in the acetic acid mobile phase?

[H2Oh]

I run almost the same mobile phase and have instruments idle for a couple of days every few weeks. I haven't seen any detrimental effects. As long as the sample components have eluted completely, you probably don't need to worry. I replace my columns every 6 months as a preventative measure but that's after 7000+ samples.

[Consumer Products Guy]

We oftentimes leave mobile phase with 0.4% acetic acid in the aqueous phase in the columns for weeks or longer. No issues.

[zokitano]

When I am using the same mobile phase every day, at the end of the day I flush the column with pure solvents. For example, if i'm using metanol/water with one percent acetic acid, at the end of the day I would flush the column with the same ratio of metanol and water (but pure,without acetic acid).
I think that kind of column care can prolong the column lifetime, although acetic acid does not make problems at the moment.

Best regards
Zoran

[Consumer Products Guy]

We only flush if we have dissolved solid modifiers in the mobile phase. That's one reason we only use such solid modifiers 10% of the time (only when really needed).

[skunked_once]

Thanks for the replies. You've set my mind at ease and saved me a lot of extra work. Usually I do flush out the columns after the analysis is complete but in this case it would be very inconvenient to do so. Isn't this forum great?