KB001995: What are the Steps to Perform a Capillary Passivation Procedure? - General LC/MS 

The dielectric capillaries for the LC/MSD systems occasionally exhibit (electrostatic) charging. This causes a loss of low m/z ion abundance. This procedure describes an electrostatic passivation procedure, which creates a silanated, semi-conductive surface in the inner bore of the capillary. This process is analogous to the preparation of GC liners and columns prior to the application of organic silanizing compounds for chemical passivation, but the objective for the LC/MSD capillary is charge dissipation.
1. Prepare ~ 10-20 ml of a 1 M solution of NaOH in water and place in a polypropylene beaker or flask.
2. Place a pipette bulb over the end of the capillary and draw the NaOH solution fully through the capillary and into the bulb.
3. After ~ 1 hr, remove the bulb, drain the capillary and wipe down the exterior with a good tissue paper.
4. Rinse the capillary ONCE ONLY by drawing 100% methanol through the capillary and into a pipette bulb.
Remove the pipette bulb and drain the capillary.
5. Wipe the exterior with a a good tissue paper and allow the capillary to dry for about 10 minutes.
Notes:
* Do NOT rinse the capillary with water. This will create a hydrolyzed surface and rinse away the sodium ions.
* Wear proper eye protection and rubber gloves.
* If the capillary is cleaned with wire and cotton, the passivation procedure will need to be repeated.
The NaOH rinse is an effective cleaning procedure in itself for most contaminants.