Chromatography Forum

Dear Members,
Our lab will take more than a week vacation.
What is the best way to store the LC system? Keep the organic solvent in the system or drain it out and let the system dry?

Best regards,
Siswanto Tanuatmojo

Leave it in 100% acetonitrile.

Thank you. Next wednesday I can take the trip without hesitate...

Do not leave it in 100% ACN, if you do you will quite probably be replacing the check valves the morning you return. I would (and do) leave it in 1:1 Methanol water.

Dear Syx,

You do not want to leave your instrument in a solvent that could evaporate anywhere. You want to leave it in something compatible with the MPs you normally use, a solvent that is clean, not easily evaporated, and that has some lubricating effect in all parts. Also, make sure the detector cell is well flushed and that there is a conecting line between inyector and detector (not necesarily a column).

I have succesfully "stored" LCs for weeks at a time leaving all the lines flushed with isopropanol HPLC grade. The solvent meets all the conditions listed above and is compatible with aqueous solvents. As an added precaution I always plug or cap the detector outlet, and leave the reservoirs tightly closed.

Good Luck,

josebenjamin

Some of our Agilent HPLCs sit idle for three weeks or more, just because of scheduling. We do nothing special to prepare them, or to start up, except to do a purge of each channel.

ACN 100%, do or don't... I need any explanation about each option asap (before vacation).

We all agree that you do not want to be in salt. Acetonitrile has been suggested, but the input by AA suggests that this may depend on the instrument that you are using. A protic solvent like methanol or IPA might be a better generic solution.

Back when I was an undergraduate, I had to take a class in quantum physics. In one semnar the teaching assistant mentioned that, four billion years from now, the sun was likely to evolve into a red giant and annihilate all life on earth. One of my classmates sitting in the back of the lecture hall had been dozing off, but suddenly sat upright and asked the TA to repeat what he had just said.
"In four billion years, the sun will annihilate all life on earth".
"Oh, what a relief!" said my classmate. "I thought I you said four million".

It probably doesn't matter a whole lot. There has in the past been some evidence of corrosion to stainless steel in protic solvents like alcohols, but I rather suspect that the difference is as relevant as my classmate's misunderstanding of astronomical time scales.

Well, syx, if you can´t decide what to do, just let it run (aren´t you the one who uses 1000 gallon mobile phase reservoirs?).
This is an answer from someone who never gave the subject too much thought other than not wanting to crust up the system with salt. How many years have you contacted what on your apparatus?

AA-please elaborate on your comments about storing the system in acetonitrile.

I seem to remember reading somewhere on this site that pure ACN can clog check valves with polymeric material (??) but this can be removed with hot water......

I have found no issues with any combination of MeOH or ACN with water being left in a system for several weeks, so I just leave it in whatever I cleaned it with at the end of the last run. If it didn't leak a lot during the last run or post-run clean out, don't worry about evaporation. If you didn't have problems between too high a ACN concentration and a check valve during your last run, you probably won't after your vacation.

My experience covers anything from 20-90% organic (MeOH, IPA, or ACN) in water, No Salts, No TFA, TEA or any other modifiers.

If this is your biggest worry before going on vacation, you should have a very nice vacation...

Well, syx, if you can´t decide what to do, just let it run (aren´t you the one who uses 1000 gallon mobile phase reservoirs?).
This is an answer from someone who never gave the subject too much thought other than not wanting to crust up the system with salt. How many years have you contacted what on your apparatus?

Not me but my colleague... My biggest containers are 1000 mL bottles. Last years we drained out the solvent from the degasser and gradient mixer after salt removal. But I think it is wasting time and very risky due bubble formation by trapped air in the mixer.

Yes, air (gas) can be exremely pesky.

Hello, I'm back!
I decided to use 100%ACN and today I found no trouble in the system.