Treating column with EDTA prior to use on LC/QTOF

Question

We have confirmed that some our proteins are binding to active sites on our SEC column used on our MS. We need this specific column material and pore size so we cannot switch to bioinert. 
 The column vendor recommended running 40 mM EDTA disodium hydrate through the column prior to use. I've used EDTA for scrubbing metals from an LC but never with a QTOF attached. I would obviously bypass the MS until the EDTA had flushed out completely but I'm concerned that it might contaminate the system with sodium and lead to increased Na+ adducts in our spectra. 
 I've seen some non disodium based solutions but it's hard to tell whether there is Na/K present and non are MS-grade. 
 Any suggestions? 
 Thanks for your help!

BrianRivera · Accepted Answer

So haven't ever really run into specific issues with native MS with SEC methods, though I will assume that the ammonium acetate that you are using is low metal content, so even ACS reagent grade may not be sufficient to ensure no adduct formation. Otherwise, if you have run into this issue and still see trace sodium and potassium, I would suggest flushing the LC front end with 0.1% formic acid and some ACN (5-10%); this should displace most trace metals in the flowpath. Otherwise, avoiding glassware, using high quality vials and such, this is critical as well. 
 You can use EDTA in the mobile phase eve, though you don't need a lot, 1-5 &micro;M or so might suffice if it's still an issue. 
 Also, note the aforementioned recommendations are typically what I recommend for oligos (ion pair reversed phase). Different application I know, but a lot of the same challenges. That is, the real issue with non-RPLC methods and LC-MS is that, in most RPLC methods, you're basically running formic acid so you are displacing trace metals while running your method. However, with Native MS (or whatever you are using for your SEC-MS method), you are running likely at pH neutral conditions, so effectively you are not"passively passivating" using formate to complex heavy metals, so it's going to cause problems when working with analytes that are prone to adduct formation. 
 Hope this is useful!

Treating column with EDTA prior to use on LC/QTOF

Top Replies