INFICON 3000 Micro GC Gas Analyzer Operating Manual - Manual (Page 241)

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3000 Micro GC Operating Manual
9.2.1.2 Retention Time Symptoms
9.2.1.2.1 Retention Time Drift
Retention time drift is a steady increase or decrease of retention times in a series
of successive runs. Erratic times (both directions) are discussed later as retention
time wander.
Retention times suddenly increase significantly
 Decreased carrier flow or reduced column temperature; check the pressure
and temperature set points
 The carrier gas tank may be nearly empty
Retention times suddenly decrease significantly
 Increased carrier flow or increased column temperature; check the pressure
and temperature set points
9.2.1.2.2 Retention Time Wander (Reproducibility)
Reproducibility is erratic for successive runs of similar composition
 Temperature or pressure variations within the runs. May indicate possible
detector or control failure
 Radical differences in sample component concentrations alter retention time
Reproducibility is acceptable later in the run but not for early eluting peaks
When the earliest peaks elute very rapidly, they may not achieve chromatographic
equilibrium with the stationary phase. They act as solvent peaks and are carried
straight through the column.
Lower the column temperature.
NOTE: A 30°C drop approximately doubles the retention time.
Retention time changes with large sample concentrations
When there is more sample than the column can handle, peaks will be deformed
and will shift to earlier retention times. Dilute the sample or shorten Inject Time.