INFICON 3000 Micro GC Gas Analyzer Operating Manual - Manual (Page 246)

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3000 Micro GC Operating Manual
9.2.2 Method Problems
This section describes how to troubleshoot a method and solve problems that arise
from incorrect instrument parameter settings, wrong peak identification windows,
and inappropriate peak detection parameters. These conditions cause an
erroneous calculation of the mole percent composition of samples.
Troubleshoot the method if the following symptoms are observed in the reports and
chromatograms when running a calibration standard:
 Zero mole percent composition for components known to be present
 Peaks are not being integrated, or are being integrated incorrectly
 Unusually high or low mole percent composition
 Samples with unnormalized totals outside the 95 to 105% range
First, clean the system as instructed in section 9.2.2.1, Column and Detector
Bakeout .
9.2.2.1 Column and Detector Bakeout
This procedure cleans the column and detector of carryover residue (i.e., high
molecular weight components) from previous samples that may interfere in
subsequent analyses. Over time, small amounts of contaminants accumulate,
especially in the column, and cause peak tailing and retention time shifts.
Perform a bakeout as instructed in section 8.1.1, System Bakeout, on page 8-1 .
9.2.2.2 Correcting Instrument Parameter Settings
9.2.2.2.1 Adjusting Column Head Pressure
Column head pressure controls flow through the column, and directly affects the
retention time of all peaks in the run.
1 Determine the retention time for the start of the unretained peak (first peak) for
all channels in the calibration standard.
2 Adjust column head pressure so that all peaks elute within method defined
peak windows.
3 Save the method in EZ IQ (click File >> Method >> Save).
9.2.2.2.2 Recalibrating
Changes to column head pressure and/or column temperature may cause peak
retention times to shift requiring adjustment to peak retention times and peak
windows. Recalibrate as instructed in
section 7.12, Calibration, on page 7-36 .