By MG on Thursday, September 25, 2003 - 09:56 am:
What's the best storage solvent for reverse-phase columns? The manufacurer will often say something like 60/40 ACN / water or 70/30 MeOH / water. Some say acetonitrile is preferred over methanol as the organic. Where I work, I was told by someone more experienced to use around 50/50 organic / water with no buffer or acid, and that was good enough. I've heard some folks on this board say that 100% organic is best. So, what is best and why?
What about for underivitized silica, or polar bonded phases?
By Anonymous on Thursday, September 25, 2003 - 10:15 am:
I think that the best guideline is to store columns in the same solvent that it was shipped in. That information should be on the box or inside.
By Uwe Neue on Thursday, September 25, 2003 - 03:04 pm:
If you store RP columns for extended periods of time in an aqueous solvent, they will hydrolyse. This is why we recommend that you store our columns in acetonitrile. For underivatized silica columns used in normal phase applications, you can store them in the solvent that you use. For silica columns used in HILIC, the recommended storage solvent is acetonitrile. What polar bonded phases are you talking about?
By K.H.W. on Thursday, September 25, 2003 - 10:33 pm:
What is the advantage of ACN over Methanol? We store our columns, which we not use, in Methanol and have not got any problems in the past. Should we be afraid of "methanolysis"?
By Anonymous on Friday, September 26, 2003 - 12:30 am:
Principally Methanol is no problem but it is a protic solvent, ACN is non-protic.
By MG on Friday, September 26, 2003 - 06:17 am:
Uwe: Polar bonded phases like cyano and amino, bonded to silica.
By HW Mueller on Friday, September 26, 2003 - 08:41 am:
Protic solvents are classified as such, because they can dissociate (lyse) a proton. In the case of methanol this leaves a highly reactive MeO- at extremely low concentrations, fortunately. Simply, acetonitrile must, therefore, be regarded less reactive in respect to column chemistry.
We have noticed many times that if columns are not clened very well of proteins that MeOH (therefore, also ACN, though not tested) can cause coagulation (or whatever) of proteins which manifests itself as a rise in backpressure (provided you work with protein samples).
By Uwe Neue on Friday, September 26, 2003 - 03:30 pm:
If these cyano and amino columns are used in normal phase chromatography, the answer is the same as for silica - store them in the mobile phase. For amino column in HILIC, or other applications that require the use of water, acetonitrile is recommended. For CN in reversed-phase, look at what the manufacturer recommends in the care and use manual.
By bill tindall on Saturday, September 27, 2003 - 05:14 am:
a practical reason not to store in methanol is that if the next analysis is at low UV it will take an annoyingly long time to get a low baseline.