HP 5973 MSD, Hardware Manual

Page: 88 / 122

88
Troubleshooting
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Reagent gas ion ratio is difficult to adjust or unstable
Possible Cause Residual air and water in the MSD or in the reagent gas supply lines.
Action Run the methane pre-tune. Air will appear as a peak at
m/z
32 and excessive water
as a peak at
m/z
19 >
m/z
17. If either of conditions is present, purge the reagent
gas supply lines and bake out the MSD. See page 40. Continued presence of a large
peak at
m/z 32 may indicate an air leak. After correcting the problems, you may
need to clean the ion source.
Possible Cause Air leak.
Action
Run Methane Pre-tune (in PCI). Large peak at m/z 32 indicates air in the system.
Check for and correct any leaks. See the Leaks section at the beginning of this
chapter.
Possible Cause The reagent gas supply is at the wrong pressure.
Action Check the regulator on the reagent gas supply. It should be adjusted to
20 psi (140 kPa).
Possible Cause
A leak in the reagent gas delivery path. This is especially likely if you have set the
methane flow much higher than normal and the ratio is still too low.
Action Check the reagent gas path. Tighten fittings.
Possible Cause
The CI ion source is dirty.
Action
Clean the ion source. See the Maintenance chapter of this manual for more
information.
Possible Cause The interface tip seal is incorrectly placed, damaged, or missing.
Action Inspect the interface tip seal. If necessary, remove and reinstall it to insure a good
seal with the CI ion source. Replace it if it is damaged. Install it if it is missing.