Chromatography Forum

I walked into the lab this morning to be greated by a large puddle in the room. I had ran a very long sequence the night before and was popping in to top up the MP.

I looked at the chromatography of what had run and it was poor.

The check valves were leaking, so i cleaned them up and re-tightened.

Now the pressure keeps jumpping from 1300ish psi to 2000+psi and back and forth. I have primed it for ages and there are no air pockets so it seems. I am a bit clueless as to why the pressure keeps jumping high and back down. Could it be that ive doen the check valves too tight? i had to do them quite tight else they leaked. Or is it somthing to do with the column? (ie buggered).

Im sorry I am fairly new to all of this so there might be an obvious answer, would really appreciate some advise from people with more experiance

Cheers James

Being that your issue seems to stem from your leaking check valves, I would say it has to be a priming issue. You might want to try priming with something viscous, like isopropanol, to try to force any residual air out of your system. If you have a restriction capillary, I would put that in place of the column so you have some back-pressure on the pump while you're trying to force the air out.

It is possible to deform check valves by overtightening (ask me how I learned that! ). Check valves should be tightened to the manufacturer's specified value using a torque wrench. I would try bisnettrj2's suggestion first. If that doesn't work, try loosening and re-torquing the check valves. If *that* doesn't work, replace them.