Chromatography Forum

Hi all,

Our team has been watching some quite intense diference of sensitivity over months, down to 50% or even 30% in some cases.

Cone cleaning, new column and XEVO calibration did not result in any improvement in sensitivity.

We are not sure this is about the detector, but suspecion is incresing heavily since we are all watching it with several compounds.

Can anyone share what is your typical sensitivity flotuations in such an equipment?

Can it be solved or is it normal has the equipment gets older?

I have seen very similar fluctuations on the Xevo TQ-S that I use and the issue was with the mass analyzer (quads & collision cell). When the engineer opened up the analyzer, there were visible ion burns on Q1 and faint ion burns on Q2. They ended up replacing the entire analyzer - thank goodness for service contracts!!

But, before you go changing the Mass Analyzer, could these sensitivity changes simply be a result of changing sample matrix? Perhaps you are observing ion suppression/enhancement and it is perfectly normal.

Overall, I would say that as long as your signal-to-noise ratio is met, calibration passes set criteria (i.e. r>0.995), and resolution is good the system is fine. However, if your application is for trace analysis you need to ensure that your detection limit is met as well - can't have a changing detection limit for a trace analysis!