Chromatography Forum

I have an Agilent 1100. It is the second time this year that it starts with leaks at the outlet valve. Someone has a suggestion about what is happening?
Thank you.

What pressures are you running at? Does your mobile phase
contain non-volatile additives? Is your mobile phase filtered?

What pressures are you running at? Does your mobile phase
contain non-volatile additives? Is your mobile phase filtered?

We use the 1100 to due benzimidazolcarbamates residues and N-methylcarbamates residues with a pos-column pickering. The solvents are allways filtered with 0,2µm filters and degassified at a sonic bath about 5 minutes. The solvents are a mixture of MeOH+H2HPO4 and HK2PO4 and CH3CN/H2O. The H2O cames from a Simplicity (Milipore). I Think is something with the PO4... The pressures are about 200 bar and we do not use volatile aditives...

You may have a bad fitting or bad threads on the outlet valve?

Is the leak at the top of the valve, or the bottom?

If at the bottom, try replacing the gold seal.

I'm assuming that you know that when solids are dissolved in mobile phase (like your phosphate salts) that you need to keep the mobile phase pumping (even at slow rate) or flush out all the salts before shutting off the pump. Failure to do so can cause salt precipitation and accelerated wear. I'm not sure we've EVER had an issue with an HP/Agilent 1050 or 1100 outlet valve.

I'm assuming that you don't mean the purge valve.

Yeah - pretty much what everyone in here said.

As you know, the problem with phosphates is that if there
is any leak around the pump - the MP evaporates - leaving
residual phosphate crystals in the pump (as well as the autosampler
needle seat).

I'm not familiar with the post column pickering methods, but
if you can reduce the system pressure, you'll have less maintenance
to deal with. We always tried to keep our methods at ~ 120 bar ceiling.
Maybe it's possible to reduce the flow rate?

You may have a bad fitting or bad threads on the outlet valve?

Is the leak at the top of the valve, or the bottom?

If at the bottom, try replacing the gold seal.

The leak is always on the top. Thank you.

I'm assuming that you know that when solids are dissolved in mobile phase (like your phosphate salts) that you need to keep the mobile phase pumping (even at slow rate) or flush out all the salts before shutting off the pump. Failure to do so can cause salt precipitation and accelerated wear. I'm not sure we've EVER had an issue with an HP/Agilent 1050 or 1100 outlet valve.

I'm assuming that you don't mean the purge valve.

After the analysis we run always a method with water (about 40 minutes) and after a run with metanol (10 minutes). I will pay more attention to these solvents.
(I use to change the small filter inside the purge once a year). Thank you!

If the leak is from the top of the valve, then you probably have a bad fitting. There is a small chance that the threads on the outlet valve are damaged, but this is rare. Remove the fitting and visually inspect it. You probably won't see anything, sometimes damage is evident. Try replacing that fitting and tubing with some other tubing, and then buy a replacement if necessary. If you don't have extra tubing, try replacing the outlet valve (or switching them) to see if the problem goes with the valve or not.

Either way, it looks like you will need to order some new parts.

Yeah - pretty much what everyone in here said.

As you know, the problem with phosphates is that if there
is any leak around the pump - the MP evaporates - leaving
residual phosphate crystals in the pump (as well as the autosampler
needle seat).

I'm not familiar with the post column pickering methods, but
if you can reduce the system pressure, you'll have less maintenance
to deal with. We always tried to keep our methods at ~ 120 bar ceiling.
Maybe it's possible to reduce the flow rate?

I can't reduce the flow (0,9 ml/min.). I will pay more attention to the solvents. Thank you.

If the leak is from the top of the valve, then you probably have a bad fitting. There is a small chance that the threads on the outlet valve are damaged, but this is rare. Remove the fitting and visually inspect it. You probably won't see anything, sometimes damage is evident. Try replacing that fitting and tubing with some other tubing, and then buy a replacement if necessary. If you don't have extra tubing, try replacing the outlet valve (or switching them) to see if the problem goes with the valve or not.

Either way, it looks like you will need to order some new parts.

Exactly right. Do be aware though Agilent outlet ball valves do leak when they fail. If you pull the plastic cap off and turn the pump on as pressure builds you may see solvent start to appear around the centre of the valve. With the cap in place this solvent tends to appear at the top thus leading to incorrect diagnosis.
Hope this helps