Cannot save the calibration in UNIFI because of a high confidence interval - WKB7760

SYMPTOMS

• RMS error and mass difference results look great (0.3 ppm and 0.3 mDa).
• Confidence interval was 250.

ENVIRONMENT

• UNIFI
• Xevo QTof 
• Calibration

CAUSE

One of the calibration points had picked the incorrect, more intense ion.

FIX or WORKAROUND

1. Find the mass or masses that have a much larger mass difference than the typical mass difference for the other ions.
2. Zoom in and find that it had picked the incorrect, more intense ion.
3. Select the reference ion by right-clicking it, and then select the correct experimental ion. It should now be highlighted in red (and not blue).
4. Once all of the masses are corrected, select the Create Calibration button and see that the confidence interval is much smaller now and you can save the calibration. 

ADDITIONAL INFORMATION