Chromatography Forum

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

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.

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.

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

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.

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.

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.