Chromatography Forum

Greetings fellow chromatographers,

Currently, I utilize two ESA 582 solvent delivery modules as part of an HPLC-ED setup. Today, I decided I would clean out my 3.0 x 50mm XTerra MS C18 column which I use for amino acid analysis of microdialysate. I reversed the column, pumped through 10 column volumes of mobile phase, 10 column volumes of ultra pure water, and 10 column volumes of %100 methanol purging my system in between each change.

After finishing with methanol, I purged my system with %100 acetonitrile, and went to pump the solvent through my column. While the pressure initially began to rise, within a five minutes it began to decrease down to zero at which point I noticed that no fluid was being drawn through system in spite of the fact that the pump was running and making its normal humming noises. When I attempted to purge the system, the pump reved up like it usually does and proceeded to run, but no fluid was removed to the waste line. I utilize a bubble trap on my pump, and it was completely full of solvent. No air bubbles were present.

Perplexed, I disconnected my check valves and sonnicated them in acetonitrile as well as isopropanol for about an hour total. In spite of this, my pump is still not interested in drawing up any liquid!

With a sudden flash of insight, I decided to move my column and acetonitrile to my second ESA 582 pump and finish my column cleaning there. Much to my chagrin, the problem duplicated itself on this machine as well, and is now not providing any suction when the pump is on and the cams are rotating! I have run %100 acetonitrile through these machines in the past without any kind of issue, and I'm quite perplexed as to why this is happening now.

A final piece of the puzzle: This same problem arose about a month ago on a friday afternoon. Annoyed at the system, I left it over the weekend. When I returned on Monday, the system worked again, but I was never able to give my column the cleaning it deserved.

Any idea what could be causing this? The check valves are of an undetermined age and could stand to be replaced, but is it really possible that this affecting both pumps at the same time on the same day?

I'm sure you've checked this, but just in case - how are your solvent inlet filters?

I replaced the solvent inlet filter this morning and did not have any suction immediately before or after I changed the filter. However, about an hour after changing it, I was able to get enough suction to purge the machine. I can't help but notice that my pressure is fluctuating within an eight bar range. I realized I did not degass my acetonitrile before I used employed it yesterday. Is it possible that whatever gas within the acetonitrile was responsible for my issue?

Given that my issue affected both of my setups, and acetonitrile was the only constant, I would say that the issues mentioned about check valves in this article were the most likely culprit of my issue.

http://www.chromatographyonline.com/lcg ... ail/524647

No more %100 acetonitrile for me when I clean my columns...

I have heard this problem from several sources : acetonitrile over methanol = checkvalve problem.
This is not faced in every methanol and acetonitrile but with certain brands.

I recommend making ultrasonic cleaning the checkvalves with acetone , then with water.
This will most probably solve the problem.

For the cleaning of columns , use 50:50 methanol + water first , then acetonitrile.
I think , this will prevent checkvalve sticking.

Good luck.