Chromatography Forum

I have been trying to revive a waters 2695 separation module that has not been used for over a year. I could only withdraw very little solvent with a syringe when I first started to DRY PRIME and no liquid coming out of the waste line when I pressed to continue DRY PRIME. Similarly, nothing came out of waste line when WET PRIME. Any suggestions as to where to start to unclog the lines?

Try changing the check valves. When mine got clogged I had the same symptoms - I couldn't pull solvent out at all. Once changed, I was able to get it primed easily.

Are you getting any solvent up to the gradient prop. valve? If so, disconnect the line into the inlet check valve and verify flow there. You need to break it down into small pieces and verify flow at each point. If you are getting flow to the inlet check valve, are you getting flow out of the head? If not, the check valve sugestion is probably the first thing to do. When they are left sitting, the ball in the CV tends to stick to the seat. sometimes, hitting them sharply with a wrench will loosen them, but it is probably better to change them out or sonicate them to clean as well as possible. Follow the flow path and check flow at each point. You may also take the frits off the ends of the solvent lines to ensure they are not plugged too. Good luck.

Lube Chemist & lcguy1:
You are absolutely right. Check valves were bad. I cleaned them out and now this HPLC flows well.

Had another problem though. The system psi fluctuated quite a bit (usually in hundreds) but the baseline of the chromatogram seemed to be good and flat. Does this mean there is still bubbles trapped in lines or is it normal?

could be bubbles, or a leaking seal.
Try wet priming with methanol (7.5ml/min for 3min).
If not solved, you could take a look at the outlet of your sealwash, if this is moving while pumping (and not only when the sealwash is flushed), you probably have a seal problem.

Ace

So, did you clean the CV's or replace them. Sounds like one, or both, of them are still not working corectly. Probably should just get new ones and replace them. Make sure they are oriented correctly when you put them back in.