John Siller
Laboratory 2
GC/MS and GC/FID
Introduction
The purpose of this lab was to familiarize and learn the operations of the GC/MS and GC/FID. To
do this we ran a number of hydrocarbon samples and reviewed the spectrum of peaks. The gas
chromatograph separates volatile compounds into its molecular components. Mass spectrometry and
flame ionization detectors are two methods of detecting the components that are separated by the GC.
The GC is a very good instrument to use when attempting to separate and identify a number of analytes
from a mixture. Gas chromatographs are found in a wide variety of laboratory’s including labs that focus
on the analysis of gasoline and its components. There are a variety of detectors for gas chromatographs
each with a different purpose. The detectors for this lab are the mass spectrometer and the flame
ionization detector. The mass spectrometer is useful for a number of anyltes including volatile
hydrocarbons. The flame ionization detector is also useful for a wide range of flammable products. In
this experiment we ran octane, 1-octanol, and t-butyl methyl ether on both gas chromatographs with
different detectors. In addition we prepared different mixtures of these hydrocarbons and ran them to
see separation.
Procedure
Day 1
GC/MS
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Only 1 sample of 1-octanol was run due to the helium running out.
0.1 mL of octanol was diluted with 10 mL of chloroform.
1 μL of this solution was injected into GC with 1 µL of air.
Peaks were observed at 1 minute and 5 minutes.
Day 2
GC/MS
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Multiple samples of octane, 1-octanol, and t-butyl methyl ether were run including mixtures
containing each analyte.
Again 0.1 mL of analyte was diluted with 10 mL of chloroform and 1 μL was injected with 1 µL of
air.
Different peaks were observed for different anyltes.
GC/FID
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Same anyltes as GC/MS were run including mixtures of each.
Similarly 0.1 mL of anylte was diluted with 10 mL of chloroform and then 1 μL was injected with
1 µL of air.
Peaks were observed at different retention times depending on the anylte(s).
Results
All spectra can be found in my lab book. Below is a list of anyltes and there corresponding
retention times for each peak. Normally only one peak was observed per analyte and this peak is used to
identify each peak in the mixture spectra. All analytes are diluted in chloroform solutions as previously
stated.
GC/MS
Analyte
1-Octanol
Retention Time
0.85 min
4.95 min
Octane
0.65 min
1.25 min
1.70 min
3.05 min
T-butyl methyl ether
3.05 min
Mixture
0.75 min
0.95 min
Table 1: GC/MS retention times for analytes completed. Octane’s spectrum was very messy so those are
just the four largest peaks.
GC/FID
Analyte
1-Octanol
Octane
T-butyl methyl ether
1-Octanol and t-butyl methyl ether
n-butanol, decane, and heptane
Retention time
0.75 min
0.80 min
0.85 min
0.80 min†
0.55 min
0.58 min
0.65 min
5.35 min
Table 2: GC/FID retention times for anylates completed.
Analysis and Conclusion
This was our first lab after our two weeks of expert work and as a result it did not go off as
smoothly as we thought it would. Gas chromatographs are great for collecting detailed data but require
a good amount of time per sample. On the first day of our lab, Monday, we only were able to run two
samples of 1-octanol before the helium tank ran out and we were forced to quit for the day. This put us
pretty far behind and we were not able to run as many separations as I would have wanted. We were
also not able to sit down and figure out the best way to analyze our chromatograms as a result of this
time crunch. If it were possible I would have liked to spend at least another week on the gas
chromatographs to finish collecting our data and come up with spectra that we could properly analyze
and interpret. Many of our spectra, especially on the GC/MS, were not as good looking as I hoped, but
running multiple samples of each analyte were simply not possible due to time constraints. If I were to
repeat this lab in the future I would run at least three samples of each analyte to confirm the accuracy of
the spectra. Additionally we were not too sure on the method we selected for the temperature variance
of the chromatogram, and if any future work would be done on them I would like to test to see the
optimal method for separation. Because this was our first lab on a new instrument on our own however,
I am not entirely disappointed with the results. My father used to work with a GC/MS every day in his
lab at ExxonMobil so I know how useful they can be for the analysis and separation of different anyltes.