INFICON Explorer Portable Gas Chromatograph - Manual (Page 324)

Assay 2 User Notes
322
These calibration times are based on an extended measurement of peak
area drift of a generic compound (isobutylene) following instrument warm-
up. A Explorer which has been off for an extended period is turned on and
set to auto sample and analyze isobutylene on Column B. Isobutylene is a
volatile compound. The observed peak area drift is an indication of detector
drift only. The resulting area drift over a period of 400 minutes is shown in
Figure 34. The change in peak area over this time period was 5%.
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 2 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 petrochemical 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.
0.8
0.9
1
1.1
1.2
0 100 200 300 400 500
Elapsed Time [min]
Figure 34 Peak Area Stability for Repetitive Sampling for 100 ppm Isobutylene