Hi Ben,
Some of this may be confusing to others so let's define our terms a bit. I propose the following:
Ben Hanson originally used the term "offset" MAN backgrounds to mean the interpolated off-peak intensities calculated from the hi and lo off-peak positions as measured in the MAN standards by acquiring them as off-peak standards. These *interpolated* off-peak intensities would then be applied to the MAN background calibration intensities by simply setting the interpolated on-peak intensity to the calculated (interpolated) off-peak intensity.
This is opposed to the existing practice of just using the measured *on-peak* intensities from off-peak measurements on the standards used in the MAN calibration (and ignoring the off-peak measurements altogether). That is using the Analytical | Use Off-Peak Elements for MAN Fit menu option as discussed here:
http://probesoftware.com/smf/index.php?topic=4.msg2255#msg2255Therefore I think it is less confusing to use the term *interpolated* off-peak intensities to describe this idea of Ben Hanson's which avoids the problem he mentioned where an MAN standard may have a trace amount of the element present (at the peak position).
Instead I would like to propose that the term *offset* MAN backgrounds refer to the "stranger" suggestion I made here:
http://probesoftware.com/smf/index.php?topic=987.msg6444#msg6444where one might "detune" the on-peak position for standards utilized in the MAN calibration (to a slightly offset peak position) so that one might avoid trace contamination that might be present in one's MAN standards. Of course this idea of mine has it's issues (you can't use the same standard as an MAN standard and also as a primary standard, and one has to modify the peak positions to be different for these MAN standards), but this "stranger" idea has the benefit of not requiring any code changes!
So let's call Ben Hanson most excellent idea the *interpolated* off-peak MAN method. In code, this basically consists of setting the on-peak intensity of the MAN standards (acquired using the normal off-peak acquisition method), to the *interpolated* (that is calculated) off-peak intensity from the measured off-peak intensities.
So to respond to your points here:
I concur...this is a great idea as I run into this sometimes as well. It would be great if there was a check box somewhere next to the standards list somewhere to let it know which ones to use the off peak interpolation for.
If I understand you correctly, there is really is no need for this as the software will automatically figure out which MAN standards to perform this interpolation for.
As you say you would have to be careful that you don't have to go miles out to measure interference free background positions where the continuum might be quite different.
I assume you are referring to my "stranger" idea of offsetting the on-peak position to avoid trace (on-peak) contamination. Yes, if we were to utilize this method you'd want to not go too far from the on-peak position so that the continuum intensity is close to the intensity underneath the peak at the on-peak position.
But in the end, I would again suggest that it would probably be preferable to just get pure standards for use with the MAN calibrations!