tuning question - mass gain vs AMU gain

[tangaloomaflyer]

Can anyone tell me what is the difference between mass gain and mass offset versus AMU gain and AMU offset?

[jerole]

Amu gain and offset are parameters that affect the mass peak width, while mass gain and offset are parameters that affect the mass axis calibration.

[James_Ball]

Amu gain and offset are parameters that affect the mass peak width, while mass gain and offset are parameters that affect the mass axis calibration.

I believe the Gain changes the high mass faster than the low mass and the Offset changes them at equal amounts. Of course I could have that backwards but that is the difference between gain and offset.

[tangaloomaflyer]

Thanks for the replies.

I understand the difference between gain and offset - as James stated, on the Mathieu stability diagram, gain increases the slope of the scan line and offset increases the y-axis intercept.

I see how this affects peak width and resolution, but I'm not sure what the mass axis calibration is all about

[jerole]

The mass axis calibration converts your experimentally measured intensity-time signal into intensity-m/z plot in order to obtain an accurate mass determination of the ions in the mass spec.

[James_Ball]

Thanks for the replies.

I understand the difference between gain and offset - as James stated, on the Mathieu stability diagram, gain increases the slope of the scan line and offset increases the y-axis intercept.

I see how this affects peak width and resolution, but I'm not sure what the mass axis calibration is all about

It makes an ion at 218.6m/z move to 219.0 m/z to correct the mass assignment.

[tangaloomaflyer]

Thanks James and Jerole - I think I get it now

So increasing the gain of the mass axis calibration will 'stretch' the m/z axis to fit the time axis optimally, and offset will shunt it along.