Chromatography Forum

Ran the positive mass calibration using thermos's Peirce positive calibrant, but it failed due to not finding the MRFA peak at m/z 524.265.

I initially thought I could be the calibrants as they were old, so we bought new calibrant. No change.

I then thought I could be a dirt ion source etc. So, I cleaned the ion source housing, sweep cone, and ion transfer tube. Then flushed the system with 98% H2O + 0.1% formic acid (FA) and 2% MeOH + 0.1% FA for about half a day. No change.

Then flushed the system with 50:50, H2O + 0.1% FA:MeOH + 0.1% FA, for a whole day almost. No change.

My colleague suggested a system reset, which was performed....still no change.

-My worry is there may be some contamination deep inside the MS, that is breaking down MRFA as it is traveling through the system.

Does anyone have any ideas on what we could do next?

Ran the positive mass calibration using thermos's Peirce positive calibrant, but it failed due to not finding the MRFA peak at m/z 524.265.

I initially thought I could be the calibrants as they were old, so we bought new calibrant. No change.

I then thought I could be a dirt ion source etc. So, I cleaned the ion source housing, sweep cone, and ion transfer tube. Then flushed the system with 98% H2O + 0.1% formic acid (FA) and 2% MeOH + 0.1% FA for about half a day. No change.

Then flushed the system with 50:50, H2O + 0.1% FA:MeOH + 0.1% FA, for a whole day almost. No change.

My colleague suggested a system reset, which was performed....still no change.

-My worry is there may be some contamination deep inside the MS, that is breaking down MRFA as it is traveling through the system.

Does anyone have any ideas on what we could do next?

An ex-Thermo FSE taught me this, so it may be worth a shot. While infusing a standard and observing its peaks, enabling and disabling either the skimmer offset or source collision may show a shift in signal. If it does, all optics before the quad need to be cleaned.

I'd clean everything again up to and including the skimmer. Do you have alumina powder or Bar Keeper's Friend? Both are great for cleaning and polishing the optics. After I clean/polish them with either of those, I rinse them in ultra-pure water and then sonicate them in a dilute acid. I like to use dilute nitric for everything BUT the tube lens. It will discolor and ruin in nitric, so for it I use a 50:25:25 water:MeOH:IPA solution.

What instrument are you using? I ran and maintained a QE-HFX for a few years, and found the injection flatapole exit lens took on a lot of contamination (depending on samples anyway). If that was dirty, it really hurt sensitivity, and I'd lose MRFA peak too. Once that was cleaned performance would typically return. And as I've told folks I've trained, when cleaning MS ion optics, doing your best effort may not be enough, it needs to be done almost perfectly. I say that not to discourage, but to encourage people to be thorough, be careful, ask a second opinion, and don't be afraid to try again.

If I recall, the user manuals only discuss cleaning through the exit lens of the ion funnel (or S-lens on some models). I have some slides showing how to clean further in, though I never went beyond the inj. flatapole exit lens myself. A cage comes out that holds the inj. flat. and it's exit lens. The FSE's would come out to clean any further than that during a PM. My understanding is the HF-X is an incredible instrument (great sensitivity) but not robust (high ion flux = fast contamination), and required frequent front end cleaning, and labs that couldn't DIY the front end cleaning had too much downtime & service calls to be happy. It was a 1 year instrument for a reason.