Detector setup fails with error "Isotope ratio setup could not achieve IPP beam too weak and saturated" - WKB204337

SYMPTOMS

• On running instrument setup, detector setup fails with error "Isotope ratio setup could not achieve LPP beam too weak and saturated"
• Detector setup fails when beam obtained with infusion of 200 pg/µL leucine enkephalin solution and signal height of m/z 556/554 precursor ion is about 4e6 cps in Sensitivity (continuum) mode or 10 fold weaker
• During instrument setup, the beam is visibly saturated with many artifact peaks and the detector is ramped to attempt to achieve higher signal

ENVIRONMENT

• Xevo G2-XS QTof
• waters_connect with UNIFI 
• UNIFI Xevo G2-XS driver 4.0

CAUSE

This is the current design of instrument setup for the Xevo G2-XS driver on waters_connect. The system is looking for 0.5 IPP in TDC peak detect mode. If this threshold is not met, the software increases the detector V in an attempt to meet 0.5 IPP. However, it saturates and will never achieve the intensity in this way. 

FIX or WORKAROUND

1. Tune for sensitivity as normal on the front end using capillary voltage, cone voltage, gas, temperature, and so on. 
2. If necessary, prepare a fresh solution of 200 pg/µL leucine enkephalin. Less than 200 pg/µL will likely not achieve the necessary intensity. 
3. Verify that 0.5 IPP (~3e6) in peak detect TDC mode can be achieved with tuning or fresh solution.

ADDITIONAL INFORMATION

The system is looking for 0.5 IPP in TDC peak detect mode. If the beam intensity is too weak, increasing the detector V as the s/w does will not accomplish this. The way to get more counts is to increase the intensity of the main isotope peak of leucine enkephalin by increasing the capillary voltage, making fresh sample, or making a stronger solution.