The MS Workstation includes diagnostics tests for isolating problems associated
with the mass spectrometer. These tests may be used to isolate simple ion trap
problems, e.g., air leaks, burned-out filaments, electronic failures, etc.
A 4000 MS Service directory is included in the MS Workstation
(C:\VarianWS\4000 MS Service). There are service methods in this directory for
internal (4000 MS Int Service.mth) and external (4000 MS Ext Service.mth)
modes. These service methods are designed to be used in Manual Control to
identify common spectrometry issues such as elevated air/water and
hydrocarbon background levels, mass assignment, and resolution.
In certain cases, you may need to separate physically the GC and MS to isolate
an ion-trap problem. In these cases, remove the column from the injector, and
plug its end with a septum. This will minimize the input of air. Maintain the
column and transfer line at ambient temperature to prevent degradation of the
stationary phase. You do not need to vent the MS vacuum system to complete
this procedure.
If you wish to isolate the mass spectrometer further, you must remove the
column from the ion trap by shutting down the system and capping the transfer
line with a no-hole ferrule.
Troubleshooting Problems with Spectra
The following describes the common problems a user may encounter with an ion
trap mass spectrometer.
No Spectrum Appears
If a spectrum fails to appear on the screen when you click on the ion trap icon in
the Manual Control Page, regardless of mass range, you should investigate the
following potential causes:
•
If the method segment is a FIL/MUL Delay segment, ionization is turned
off. When a segment is set up with the ionization off the trap icon is red.
•
The “filament is open (broken).”
•
The turbomolecular pump has stopped.
•
An RF adjustment is required.
•
The instrument parameters are inappropriate.
•
The trap has been incorrectly assembled.
•
There is a problem with the electronics.
•
The system has not finished baking out.
Before you begin troubleshooting, however, be sure that you have baked out the
4000 MS for at least 2 hours. Run Diagnostics to determine if any hardware
problems are present. If you have done this, and the missing-spectrum problem
persists, continue as follows. These steps apply if either air/water or Cal Gas
peaks are missing.
Check for an Open Filament
Diagnostics will determine if one or both filaments are open.
•
If necessary, replace the filaments.
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