TSQ Vantage - background in negative mode.

[Oxabolone]

Hello all. In last time in negative mode appeared a huge background peak with 169 m/z. What can it be and how to remove it ? I've tried to clean ESi box, wash tubes but without effect.

Thanks!

[Rndirk]

Did you isolate it to the MS only?

[Oxabolone]

Did you isolate it to the MS only?

In case calibration with polythyrosine (direct infusion in mass) or direct conection LC without column - the same strong 169 m/z.

[Rndirk]

What if you just turn on the MS without infusion or column flow?

If it's still there and it's bothering your analysis, i'd advice to take cleaning 1 step further and clean the part behind the transfer tube: the first lens system/ion funnel.

If you don't have experience doing that it's best to ask Thermo.

[Oxabolone]

What if you just turn on the MS without infusion or column flow?

If it's still there and it's bothering your analysis...

I tried to do such way,but peak is still here (.
So i have to clean capillary and ion optics(we can do it without Thermo service).
Thank you so much!

[Oxabolone]

Sorry for confusion. Ii checked out system one more time - contamination with 169 m/z goes from channel of pump with organic phase. Very strange thing - i got excellent tune with polythyrosine in positive and negative modes, but instrumental method in MRM doesn't work properly. MRM in negative - no signal. in positive -everything good.