INFICON 3000 Micro GC Gas Analyzer Operating Manual - Manual (Page 244)

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3000 Micro GC Operating Manual
9.2.1.4 Deformed peaks
The ideal chromatography peak is a pure Gaussian shape. In reality, some
asymmetry is always present, particularly near the baseline. Some common types
of deformed peaks are described.
9.2.1.4.1 Peak Fronting
The peak rises normally, then drops sharply to baseline
Figure 9-1 Fronting
Fronting is usually caused by column overloading. Try diluting the sample by a
factor of ten or, if the channel has a variable volume injector, reduce the sample
Inject Time by a factor of ten.
Fronting could also be two (or more) closely merged (unresolved) peaks.
Decrease the Column Temperature by 30°C and repeat the analysis. If peaks
separate at the lower temperature, the fronting was caused by merged peaks.
9.2.1.4.2 Peak Tailing
The peak rises sharply and then falls normally to baseline.
Figure 9-2 Tailing
Tailing is usually caused by column overloading. Try diluting the sample by a
factor of ten or, if the channel has a variable volume injector, reduce the sample
Inject Time by a factor of ten.
This could also be two (or more) closely merged (unresolved) peaks. Decrease
the Column Temperature by 30°C and repeat the analysis. If peaks separate
at the lower temperature, the tailing was caused by merged peaks.
Tailing can also be caused by a low Inlet Temperature. Increase the Inlet
Temperature and repeat the analysis.