Care for pumps running high conc buffers

[HPLC_chainik]

Somebody told me that I shall not keep high concentration buffers in the HPLC pumps even overnight. I am using mostly 150 mM phosphate pH 7.0 and was not expected to be very corrosive. Flashing it every evening and morning and stabilizing the instrument is going to be rather burdensome. What is a reasonable balance between good care and being overprotective? I am using Shimadzu LC-10 pumps.

[Blazer]

The concern typically is letting the pumps sit idle with the buffer in it. If you have your system switch to a low flow (e.g. 0.1 mL/min) after your sequence is complete can help prevent problem, if flushing the buffer out each night is cumbersome.

[Andy Alpert]

An HPLC system fills the pump head with solvent via a piston pulling back. The piston then pushs forward, forcing the liquid out of the pump head and into the flow path. The piston slides back and forth through a seal which is rather stiff in order to be able to contain the pressurized solvent. Now, if you leave a pump overnight with a solution containing a high concentration of salt, then some of the piston will be sitting outside the pumphead. Its surface will be wetted with that salty solution. Overnight, the water will evaporate, leaving behind crystals of the salt. When you start up the pump in the morning, then the crystals on the piston surface will be carried forward and will encounter the seal. It will hold them in place while the piston moves. Salt crystals can be remarkably hard. Some of them can score a sapphire or ruby piston that's moving against them. Result: a groove in the surface of the piston through which liquid can flow beneath the seal, resulting in a slow leak. Conclusion: Yes, do flush out salts every day before shutting down your system. If you really can't do that, then like Blazer says, run the system overnight at a slow flow rate.

[HPLC_chainik]

I am washing the seals and the part of pistons outside of the pump head with DI water before I start operations in the morning. Would that be sufficient to prevent damage to pistons and seal?

[Andy Alpert]

Maybe.

[lmh]

If you do decide to go for flushing, there are things you can do to automated the process and make your life easier. If you have a solvent-selection valve, then you can have a safe salt-free solvent set up on a spare bottle on the pump, and have a method at the end of your batch that pumps this solvent to wash out the pump heads before stopping. If the safe solvent isn't good for your column, then unfortunately you also need a column selection valve. Shimadzu software also allows batches with a programmed start-time (it's in the batch settings), so if you're feeling really organised, you could set up a start-up batch to re-wash your system back into salty conditions ready for 9 O'clock the following morning.
Or just pump very slowly to keep things moist as Blazer suggested, because Andy is right, salt grinding around in pistons and their seals is going to cost you a lot in leaky pump problems.

[HPLC_chainik]

Thank you all for suggestions. I was thinking about a low pressure selection valve. I will most likely disconnect and plug the column in the end of the day. I think the column itself is compatible with DI water (or aqueous ethanol), but it takes a long time to equilibrate it back. Also, I am a little worried that if there are proteins left on it, they may denature and stick to the stationary phase.
Part of the problem is that I am using Chromeleon and it does not support many Shimadzu components. E.g., I have a FCV-11AL valve, and (I think) the software supports only FCV-10AL.
I will figure something out. The main point is to realize that there is a problem and to admit that something has to be done about it. It is down hill from there

[bunnahabhain]

Looks like FCV-11AL is supported:
http://www.shimadzu.com/an/lc/driver/chromel3.html
Have fun fiddling around

What pump model do you have? Is there a seal wash option available? This would solve all of your potential problems by continuously washing the back side of the seals (where the salt buildup might form). Check it out.

[HPLC_chainik]

Looks like FCV-11AL is supported:
http://www.shimadzu.com/an/lc/driver/chromel3.html
Have fun fiddling around

What pump model do you have? Is there a seal wash option available? This would solve all of your potential problems by continuously washing the back side of the seals (where the salt buildup might form). Check it out.

I use LC-10ADvp pump. Washing the seals continuously is probably even more hassle than to switch solvents in the end of the day. I did wash seals in the morning before starting the pump. I actually started switching solvents by hand, and it turned out to be not that much pain. I just transfer the intake line into a bottle of DI water and purge the pump for 3 min at 10 ml/min. In the morning, I transfer the intake line back into a bottle with the buffer and purge the pump again. It does not seem to affect stabilization time for the system.

You are correct about support of FCV-11AL by Chromeleon. It was the high-pressure valve, FCV-14AH that was not supported, at least by the version I currently have (SR 3, I guess). If both were supported, I could have implemented washing of both the pump and the detector. I will probably install the low pressure valve at some point...