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Pressure issue with acetonitrile gradient

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

3 posts Page 1 of 1
Hi everyone. I've experienced an issue when using a gradient elution up to 100 % acetonitrile a few times during the last year now and I thought I'd check with you what the reason for this could be.

Today, I washed one of our columns with a gradient washing method going from 5 % acetonitrile to 100 % acetonitril in 60 min (5 % holding for 20 min, ramping up during 20 min, holding 100 % for 20 min). When at ~90% acetonitrile the pressure became unstable and I'm not sure what the reason for this is. The column was a Supelco Ascentis C18, previos run was using 90:10 phosphate buffer:acetonitrile. The 20 min of 5 % acetonitrile should have flushed out all phosphates so that should not have been the issue here. I was running this on a Shimadzu LC-20 system with quartenary pumps.

Any ideas would be very welcome.
Thank you!
... When at ~90% acetonitrile the pressure became unstable and I'm not sure what the reason for this is ...
Issues with check valves when ACN concentration riches 100% ? (I see it was only 90%, but ...)
Perhaps, that was in my mind aswell. But could there be any other reasons?
3 posts Page 1 of 1

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