Geology Reference
In-Depth Information
Figure 8.1.7. Whole air standard used for calibration on the VOC system.
Modifying
A
second method of quality control is human oversight of the computer software
s identification of compounds as
peaks on a chromatogram. This technique is called modifying and is very labor intensive but necessary for high-
quality data. This process involves an individual reviewing every peak quantified. The computer assigns peaks
based on known standard retention times and if a systematic retention time shift occurs the peak is usually missed
or incorrectly assigned by the computer software. This human oversight is vital to high-quality data and illuminates
the intuitive limitations inherent in extremely advanced scientific instruments and computer software.
'
Important Terms
background concentrations
modifying
catalyst
nonmethane hydrocarbon intercomparison experiment
chromatogram
quadrupole mass spectrometer detector
Chromeleon chromatography software
stainless steel canisters
CO/CO
2
system
standards
columns
thermal conductivity detector
electron capture detector
VOC system
flame ionization detector
volatile organic compound
gas chromatography
methane system
References
Colman, J.J., Swanson, A.L., Meinardi, S., Sive, B.C., Blake, D.R., Rowland, F.S., 2001. Description of the
analysis of a wide range of volatile organic compounds in whole air samples collected during PEM-Tropics A
and B. Anal. Chem. 73 (15), 3723
-
3731, http://pubs.acs.org/cgi-bin/abstract.cgi/ancham/2001/73/i15/abs/
ac010027g.html
