Inficon Micro GC Fusion 2-Module, Operating Manual

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INFICON Troubleshooting | 11
074-594-P1H Micro GC Fusion Operating Manual 293 / 319
11.2.1.2 Retention Time Symptoms
11.2.1.2.1 Retention Time Drift
Retention time drift is a steady increase or decrease of retention times in a series of
successive runs.
Erratic retention times are discussed in Retention Time Wander (Reproducibility)
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If a backflush injector is configured, verify that the Backflush Time set point is
optimized for that GC module. If the Backflush Time is set improperly, undesired
components can enter the column, resulting in retention time drift.
Retention times suddenly increase significantly due to:
• Decreased carrier flow or reduced column temperature. In the System Status
window, ensure the actual pressures and temperatures match their set points
• Low carrier gas pressure. The carrier gas tank may be empty. Replace if
necessary
Retention time suddenly decreased significantly due to:
• Increased carrier flow or increased column temperature. In the System Status
window, ensure the actual pressures and temperatures match their set points
If the actual pressures and temperatures do not match the set points, power Micro GC
Fusion off, restart, and download the method again. If this does not solve the problem,
contact INFICON.
11.2.1.2.2 Retention Time Wander (Reproducibility)
Reproducibility is erratic for successive runs of similar composition.
• Temperature or pressure variations within the run may be the cause. This may
indicate possible heater or pressure control failure
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
• If peaks were separated, but are no longer baseline resolved, lower the column
temperature to achieve better separation
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. Reduce the Inject (ms) time.