Chromatography Forum

My QTOF if showing huge mass deviation, within a run, about 0.05 Da to sometimes 0.5 Da. I learned that QTOF mass measurements depend on temperature stability. The position of our instrument is like this:

https://drive.google.com/file/d/0B4z8B_pxCo0FNlhwcVVZemk4cUk/view?usp=sharing

The exhaust of the nitrogen generator is pointed towards the back side of QTOF and the rough pump is also at the back. I have noticed the temperature in the back of the QTOF is actually different, little warmer than the rest of the room. My question is, is this a valid potential reason for the observed mass deviation?

However, our service engineer is predicting it might be because of some component problem inside the machine.

arnabroy81 wrote:
My QTOF if showing huge mass deviation, within a run, about 0.05 Da to sometimes 0.5 Da. I learned that QTOF mass measurements depend on temperature stability. The position of our instrument is like this:

https://drive.google.com/file/d/0B4z8B_pxCo0FNlhwcVVZemk4cUk/view?usp=sharing

The exhaust of the nitrogen generator is pointed towards the back side of QTOF and the rough pump is also at the back. I have noticed the temperature in the back of the QTOF is actually different, little warmer than the rest of the room. My question is, is this a valid potential reason for the observed mass deviation?

However, our service engineer is predicting it might be because of some component problem inside the machine.

Warmer in that area would not be a problem as long as it is fairly consistent temperature. If the temperature is fluctuating several degrees over a few hours then that could be a problem.

That means I should put the temperature scale near that area and check. Thanks

trust the service engineer on this one; they know what happens to their instruments. A deviation as large as 0.5Da can't just be thermal expansion of the flight tube (even 50mDa is pushing the boundaries of believability).