Chemistry 4110 – Experiment 3 Page 1 of 2
GAS CHROMATOGRAPHY USING A FLAME IONIZATION DETECTOR
In all chromatographic experiments, the components of a mixture are separated in time
from one another by differences in their partition between a moving phase (in this case a
gas) and a stationary phase (a solid or a bonded liquid). Substances for which the
partition favours the stationary phase spend less time in the moving phase and hence
move down the column slowly. Components in a mixture are therefore separated in the
time they take to travel through the chromatographic column. The column temperature is
often varied during a separation since the partition is strongly temperature dependent.
In this procedure, a Thermo Ultra GC is used with helium as the carrier gas at a flow rate
of approximately 1 mL/min through the capillary column. Since the detectors were
initially designed for the use with larger packed columns, this low flow is too small for
efficient detector operation. Hence, there is also a make- up flow of nitrogen to the
detector to bring the flow rate up to the order of 30 mL/min. The column used is a 30-
meter fused silica capillary column containing a bonded poly(phenylmethyldimethyl)
siloxane (5% phenyl) (Equity™-5; relatively nonpolar) stationary phase (0.25 µm thick).
The instrument is equipped with an isothermal (300 °C) split/splitless heated injector
used in the splitless mode with the split vent opening at 1.0 min after injection. This
injection mode onto a cool column with an, initial temperature of 65 °C (less than the
boiling point of the solvent), gives some focusing of the sample at the front of the column
along with eliminating solvent peak tailing. Components eluding the column are detected
using a flame ionization detector (FID) fueled by compressed air and hydrogen
maintained at 300°C.
Students must have a Chemistry server username and password to logon to the GC
computer. (Contact David Murphy, C-4017, before the scheduled lab if account
information is required.)
Operation of the GC and Chromquest software
Detailed instructions provided during the lab period.
1) Three standards and two unknown polyaromatic hydrocarbon (PAH) mixtures are
provided for analysis using the method file 4110PAH.met. An autosample r will be used
to load the mixtures onto the GC column – instructions for setting up the autosampler
will be provided during the lab period.
2) Run one of the standards under isothermal conditions. Compare this chromatogram to
the chromatogram run using the temperature-programmed 4110PAH method.
Chemistry 4110 – Experiment 3 Page 2 of 2
Data analysis (to be completed during the lab period)
From the known identity and concentrations of the PAHs in the standard solutions (given
below), the identity and concentration of the PAHs in the unknown mixtures can be
determined. The PAH peaks in the unknown mixtures are identified by comparing the
unknown peak retention times to that of the standards. The concentrations of the PAHs in
the two unknown mixture are determined by four calibration methods– area percent,
internal standard, external standard and percent normalization. The Chromquest software
is used for the data analysis - detailed instructions provided during the lab period.
PAH Standard Solutions
Concentration (mg/mL) in hexane
Compound Standard 1 Standard 2 Standard 3
Naphthalene* 100 100 100
2-chloronaphthalene 100 60 80
2,3-dimethylnaphthalene 40 60 80
Acenaphthene 50 70 90
Fluorene 40 60 80
Phenanthrene 50 70 90
* Internal Standard
1) Include all chromatograms and data reports. Label all peaks. Provide summary data
tables for the standards. 
2) In a table, list the identity and concentration of the PAHs in the unknowns as
determined by the four methods of quantification. 
3) Explain, based on the results, which method of quantification is more likely to be the
most accurate. 
4) Compare and explain the chromatographic profile differences between the isothermal
run and the temperature-programmed run.