LockSpray setup failure in negative ion mode - WKB3445

SYMPTOMS

• Negative ion mode LockSpray setup fails
• IntelliStart reports failure due to insufficient intensity, but LockMass peak is intense in the tune page
• LockMass peaks visibly shift to incorrect mass position during setup

ENVIRONMENT

• Xevo G2 Tof
• Xevo G2 QTof
• MassLynx 4.1 SCN 802
• SCN 862

CAUSE

The software is incorrectly using the Positive Ion-specific Veff value in Negative Ion mode for the intensity check.

FIX or WORKAROUND

1. Ensure that the Veff values in Positive Ion and Negative Ion modes are set correctly.
2. Ensure that the LockMass peak is sufficiently intense.
3. Confirm that the LockMass peak in Negative Ion mode is within 2 Da of the correct position during the LockSpray Setup intensity check.
4. The correct mass is displayed in the Detected Mass column of the LockSpray Setup Report.

ADDITIONAL INFORMATION

There is no fix to the problem of the positive ion Veff value being used in negative ion LockSpray setup, but the effect can be minimized by following the steps above.

To set Veff:

1. The Tune page should be in System view.
2. In the menu bar, go to System > Acquisition settings.
3. Specify the reference mass and the observed mass of the reference compound (e.g., leucine enkephalin).
4. Click "calculate".
5. Click "update".