Contamination m/z 118.1230 on a LC-QTOF

Hi

Do you see this background when just running mobile phase?

Yes, we see 118.1230 when we only run mobile phase, without sample injection.

What have you used to flush the LC? Have you removed the column? What is your mobile phase?

Our mobile phase is a mix of MTBE, methanol and acetonitrile. I tested all solvant plus water separately by direct infusion via bottle B in tune mode. The 118.1230 is always present. I tested different batch of ammonium formate and old vs new bottle of solvent. I washed capillary and all part of the source that I have access. I changed column.

The contaminant is there since 2019 and present in our two LC-QTOF but the problem of adduct begin to be a struggle in the last month. We think that the problem came maybe from the nitrogen.

You are probably right about the nitrogen. 118.12 can be a contaminant linked to hydrocarbon impurities in Nitrogen. Sometimes it can be seen to build up overtime in tune mix (the bottles are under nitrogen on the instrument). In which case it can interfere with the 1180.863 tune ions. I assume you nitrogen is coming from a nitrogen generator. You could approach your Nitrogen generator vendor / service provider about additional traps for this and see if they thing something like an active carbon trap would work (For example, this product from PEAK Peak's Resource Portal (peakscientific.com). The generators extract nitrogen from the air but don't necessarily have the capability to remove these impurities.

You are probably right about the nitrogen. 118.12 can be a contaminant linked to hydrocarbon impurities in Nitrogen. Sometimes it can be seen to build up overtime in tune mix (the bottles are under nitrogen on the instrument). In which case it can interfere with the 1180.863 tune ions. I assume you nitrogen is coming from a nitrogen generator. You could approach your Nitrogen generator vendor / service provider about additional traps for this and see if they thing something like an active carbon trap would work (For example, this product from PEAK Peak's Resource Portal (peakscientific.com). The generators extract nitrogen from the air but don't necessarily have the capability to remove these impurities.

Yes, we contacted the Peak vendor this morning. We think maybe it comes from the ventilation/air who are recircutated by the nitrogen generator to the LC-QTOF.

Were you able to resolve this?