PEG contamination in HPLC - How to clean?

Question

Hi Community, 
 We work with an HPLC-QTOF and we have observed, after an exhaustive cleaning procedure, contamination by PEG (spectra with clusters of 44). We have had this issue other times, and cleaning with a solution of 25% ACN, 25% MeOH, 25% water and 25% IPA + 0.2% formic acid has been solved. However, after cleaning all the system, with injections all night, and rinse it properly -including nebulizers-, problem is still there. It is in the HPLC because column is not in the system. Do you know a specfic way to solvent this problem? 
 Thank you so much!

philebel · Answer

Hi InmaCIDAF , 
 
 I recommend you start by evaluating where the contamination is coming from. Even if your clean your system all night, if you are running contaminated solvent to the MS, you will still see PEG's. 
 PEG's can come from glassware that were put in the dishwasher, from pipettes tips, from vials, caps, etc. 
 First, go in the tune context of Masshunter and turn on your calibrant solution. Do you see any PEG's. If not, at least this means the MS is not contaminated. 
 PEG's contamination usually comes from the mobile phase or the additives. You can take your mobile phase, and if you have a syringe and a motor, you will be able to infuse directly in the MS. If you see PEG's, you just found your issue. 
 If you replace the mobile phase for a new bottle or lot, I would also recommend you do the same for any additives/reactive you are using (formic acid, ammonium formate, etc.). 
 I hope this helps. 
 Regards,