HS-MRM acquisition on a Vion IMS QTof results in negative drift time after data processing - WKB115617

SYMPTOMS

• Extracted ion chromatogram of processed data shows negative drift time value
• In example below, the drift time is -1.14 ms 

ENVIRONMENT

• Vion IMS QTof
• UNIFI 1.9.4
• HS-MRM acquisition

CAUSE

An incorrect CCS value was defined for the precursor peak in the acquisition method. The CCS value defined in the method is lower than the actual CCS value. 

FIX or WORKAROUND

Software speculates a drift time window based on the precursor peak and its CCS, which is defined in the acquisition method. An incorrect CCS value for the precursor ion (a CCS value that is lower than the true CCS value) results in a negative drift time that is not highlighted by the software. 

1. Ensure that the CCS value defined in the HS-MRM method is correct.
2. The CCS value can be determined for a precursor by means of other acquisition methods, such as HDMSe, prior to HS-MRM acquisition.  

ADDITIONAL INFORMATION