Agilent Technologies 5975T LTM GC/MSD, Troubleshooting And Maintenance Manual

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Chromatographic Symptoms
3
Troubleshooting and Maintenance Guide 57
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
Checkout
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 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
• Analyzer chamber 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 MSDs
Ion ratios are different from those in older models MSDs. This is
due to the HED detector, and is normal. To get spectra similar to
older MSDs, use
Standard Spectra Tune
, available in the
Manual
Tune view. Note that this tune takes much longer to complete
than
Autotune.
High mass sensitivity is poor
This refers to a condition where the absolute abundance at the
upper end of the mass range is poor. Absolute abundance
should not be confused with the
relative abundance
(percentage) of m/z 502 to m/z 69. Sensitivity at high masses
can be excellent even if the relative abundance of m/z 502 is low.
• Wrong tune program
• Wrong tune file