Our source is EI High Efficiency source, I find that the sensity keep droping. The tuning report said :Post Extractor Lens 1 Offset did not respond as expected. The lens may be disconnected or the wrong source installed.
The voltage of ion body is 0.4V which used to be 9.6V.
When I use the fullscan mode to detect samples, the base line is huge I can't see any target peaks.
We normally use MRM to measure samples.
When was the ion source last cleaned? When that was done, were the edges of the lenses cleaned as well? The lenses make contact with the system through the steps on the edge or pressed-in ball bearings, depending on the age of the system.
Step style lens - the red arrow is the step, make sure that outer edge is scrubbed clean while cleaning the source.
The older style lenses had a ball bearing on the edge that should be cleaned.
See: (+) GCMS Ion Source Cleaning - Videos - GC/MS Portal - Agilent Community and (+) How to Clean Your High Efficiency Ion Source - Videos - GC/MS Portal - Agilent Community
Everything that comes out of the column goes into the source. So carrier gas contaminants, sample matrix, solvent and its contaminants, sample peaks, column bleed, and problems caused by a leak will all increase the frequency of cleanings. Cleaning only the ion source parts means that everything else inside still has the residue on it and that residue continuously redistributes onto a freshly installed clean source.
Next time you vent and open the analyzer, take a look at the front of the collision cell. If a brown + sign is visible, like in this picture, it is past time for some remedial cleaning. The collision cell entrance lens should be completely clean stainless steel. That deeper cleaning is outside of most operator's capabilities so contact your local Agilent service to get a quote for it. Contact Us | Agilent
Running in MRM mode means that you are only looking at few ions yet all the rest of the stuff in your sample still enters the source. There could be vast amounts of sample going in with every injection. It is important to do some runs in scan mode once in a while to see how bad that mess is.
It is not uncommon for operators to have to clean the source once a month or more. It's like washing the dishes, a never-ending task.
