Relative Abundance Of M/Z 502 Is Less Than 3; Spectra Look Different From Those Acquired With Other Hp Msds - HP 5973 Hardware Manual

Troubleshooting the MSD
3
Mass spectral symptoms

Relative abundance of m/z 502 is less than 3%

Autotune should give an m/z 502 relative abundance greater than 3%. The rela-
tive abundance of m/z 502 can, however, vary a great deal depending on column
flow, ion source temperature, and other variables. As long as relative abundance
is above 3%, the stability of the relative abundance is more important than the
absolute value. If you observe significant changes in the relative abundance of
m/z 502 for a fixed set of operating parameters, there may be a problem. The
charts in the MSD ChemStation software are useful for identifying changes. Select
View Tunes from the Qualify menu in the Instrument Control view.
Low relative abundance of m/z 502 should not be confused with low absolute
abundances at high masses. Sensitivity at high masses can be excellent even if the
relative abundance of m/z 502 is near 3%. If your MSD produces low absolute
abundances at high masses, refer to the symptom High mass sensitivity is poor.
Tune programs other than autotune have different relative abundance targets. The
DFTPP and BFB target tune programs tune the HP 5973 MSD to achieve about a
0.8% ratio of m/z 502/69.
• Tune program/tune file has a different relative abundance target
(3% only applies to Autotune)
• Not enough time for the MSD to warm up and pump down
• Vacuum manifold pressure is too high
• Ion source temperature is too high
• Column (carrier gas) flow is too high
• Poor filament operation
• Dirty ion source
• Air leak
• Incorrect dc polarity on the quadrupole mass filter

Spectra look different from those acquired with other HP MSDs

Ion ratios are different from those in older HP MSDs. This is due to the HED detec-
tor, and is normal. To get spectra similar to older MSDs, use ,
Standard Spectra Tune
available in the Manual Tune view.
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