INFICON Explorer Portable Gas Chromatograph - Manual (Page 306)

Assay 1 User Notes
304
0.8
0.9
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1.1
1.2
0 100 200 300 400 500
Elapsed Time [min]
Figure 26 Peak Area Stability for Repetitive Sampling for 100 ppm Isobutylene
This drift characteristic is typical of Explorer’s detector response drift,
following a 20 minute warm-up period. Although this test is performed with
isobutylene, the same approximate, peak area drift can be expected for any
of the Assay 1 compounds.
To ensure a measured concentration (at the calibration concentration) is within
10% of the actual value:
1. Calibrate once when the instrument is turned on.
Allow 30 minutes for the instrument to stabilize before performing the
calibration run(s).
2. Calibrate at 8 hour intervals.
Assuming detector response drift is similar for the Assay 1 compounds, you need to
calibrate once, immediately following instrument warm-up. Measurement of dry,
pure samples at a similar concentration to the calibration concentration should then
give a result accurate to within 10% for an 8 hour working period.
As a measuring instrument, Explorer has a non-linear response for many
compounds. Therefore, in order to make accurate measurements at concentrations
other than the calibration concentration, it is necessary to correct for instrument
non-linearity. This can only be done if a multiple point calibration is performed to
determine the response of the instrument throughout the concentration range of
interest.
If the response curve characteristics are measured in this way, then reasonably
accurate measurements can be made.