Low sensitivity on Xevo TQ-XS using UniSpray - WKB76652

SYMPTOMS

• Sensitivity decreases significantly when using UniSpray as source enclosure
• Response is as expected when using ESI as source enclosure
• Impactor pin is visibly dirty

ENVIRONMENT

• Xevo TQ-S micro
• Xevo TQ-XS

CAUSE

Very dirty impactor pin. The shape is no longer circular

FIX or WORKAROUND

Clean the impactor pin as described in WKB83167.

If the impactor pin is still dirty, proceed as follow:

1. Ultrasonicate the impactor pin for 20 minutes in a beaker with water + approximately 5% formic acid.
2. Flush the impactor pin with water to remove the acid.
3. Ultrasonicate impactor pin for 20 minutes in a beaker with water.
4. Ultrasonicate impactor pin for 20 minutes in a beaker with methanol.
5. Blow dry the impactor pin with Nitrogen gas.
6. If the issue still remains after cleaning, replace impactor pin (p/n 700011196)

ADDITIONAL INFORMATION

If there is a gap or damage in the impactor pin in the stagnation area in which ionization takes place, ionization efficacy will be lower. 

In this case there was no gap in the pin but a lot of dirt sticking to the outside of the pin, making it noncircular. That can also cause lower sensitivity. 

If the method includes mobile phases containing inorganic salts, in order to prevent accumulation of material on the impactor pin and increase its life-time, divert the UPLC flow to waste at the beginning and at the end of the chromatography (WKB12652).