76
3
Troubleshooting the MSD
Mass spectral symptoms
Mass assignments are incorrect
Small shape changes at the top of the mass peaks can cause 0.1 amu shifts in mass
assignments. Shifts greater than 0.2 amu indicate a possible malfunction.
•
MSD has not had enough time to reach thermal equilibrium
•
Large variations in the temperature of the laboratory
•
MSD has not been tuned recently, or at the temperature at which it is operating
•
Incorrect tune file (inappropriate parameters)
Peaks have precursors
The tune report lists the size of the precursors for the tune masses. Small precur-
sors are not unusual. There are no specifications for acceptable or unacceptable
precursor size. If the precursors are unacceptably large for your application, one
of the following may be responsible:
•
Repeller voltage is too high
•
Peaks are too wide
•
Incorrect dc polarity on the quadrupole mass filter
•
Dirty quadrupole mass filter
Peak widths are inconsistent
•
MSD has not had enough time to reach thermal equilibrium
•
Large variations in the temperature of the laboratory
•
Incorrect tuning
•
Calibration vial is empty or almost empty
•
Calibration valve is not working correctly
•
Dirty ion source
•
Electron multiplier is nearing the end of it useful lifetime
•
Ground loop
Summary of Contents for 5973
Page 1: ...H Hardware Manual HP 5973 Mass Selective Detector ...
Page 3: ...HP 5973 Mass Selective Detector Hardware Manual ...
Page 25: ...1 Installing GC Columns To condition a capillary column 25 ...
Page 30: ...30 ...
Page 37: ...2 Operating the MSD To view MSD analyzer temperature and vacuum status 37 ...
Page 39: ...2 Operating the MSD To set monitors for MSD temperature and vacuum status 39 ...
Page 41: ...2 Operating the MSD To set the MSD analyzer temperatures 41 ...
Page 43: ...2 Operating the MSD To set the interface temperature from the ChemStation 43 ...
Page 51: ...2 Operating the MSD To remove the MSD covers 51 Upper cover Lower cover ...
Page 92: ...92 ...
Page 105: ...4 Maintaining the MSD To drain the foreline pump 105 Fill cap Drain plug Pump motor ...
Page 113: ...4 Maintaining the MSD To separate the MSD from the GC 113 ...
Page 121: ...4 Maintaining the MSD To reconnect the MSD to the GC 121 ...
Page 141: ...4 Maintaining the MSD To lubricate the side plate O ring 141 Side plate O ring ...
Page 159: ...4 Maintaining the MSD To remove a filament 159 Filament 2 Filament 1 ...
Page 161: ...4 Maintaining the MSD To reinstall a filament 161 Filament 2 Filament 1 ...
Page 210: ...210 ...
Page 214: ...214 ...
Page 232: ...232 7 Analyzer Analyzer heaters and radiators ...
Page 280: ...280 ...
Page 294: ...294 Index ...
Page 296: ...294 Chapter ...
Page 297: ...H Manual Part Number G1099 90027 Copyright 1998 Hewlett Packard Printed in USA 11 98 ...