8
Contents
Chapter 3 Troubleshooting the MSD
General symptoms, 68
GC does not turn on, 68
MSD does not turn on, 68
Foreline pump is not operating, 68
Fan for the high vacuum pump is not operating, 69
MSD is on but the status LEDs are all blinking, 69
MSD turns on but then the foreline pump shuts off, 69
Chromatographic symptoms, 70
No peaks, 70
Passes tune, 70
Does not pass tune, 71
Peaks are tailing, 71
Peaks are fronting, 71
Peaks have flat tops, 72
Peaks have split tops, 72
Baseline is rising, 72
Baseline is high, 72
Baseline is falling, 72
Baseline wanders, 73
Retention times for all peaks drift – shorter, 73
Retention times for all peaks drift – longer, 73
Poor sensitivity, 74
Poor Repeatability, 74
Mass spectral symptoms, 75
Isotopes are missing or isotope ratios are incorrect, 75
High background, 75
High abundances at m/z 18, 28, 32, and 44 or at m/z 14 and 16, 75
Mass assignments are incorrect, 76
Peaks have precursors, 76
Peak widths are inconsistent, 76
Relative abundance of m/z 502 is less than 3%, 77
Spectra look different from those acquired with other HP MSDs, 77
High mass sensitivity is poor, 78
Pressure symptoms, 79
Foreline pressure is too high, 79
Vacuum manifold pressure is too high, 79
Foreline pressure is too low, 80
Vacuum manifold pressure is too low, 80
Gauge controller displays 9.9+9 and then goes blank, 80
Power indicator on the gauge controller does not light, 81
To Next Page
Loading...
