Organic Chemistry Section
Air Analysis

Section 1910: C2 - C12 Hydrocarbons in Ambient Air

Revision 3.1 (August 1, 2003 - present) Replaces Revision 3.0

1910.1 Scope and Application

This method is appropriate for the analysis of various VOCs in ambient air. The method includes the specific parameters listed below, but may be adapted to similiar compounds.

Compound Report Limit (ppbC)
C2 - C12 Hydrocarbons<10.
ethylene<0.30
acetylene<0.30
ethane<0.30
propene<0.30
propane<0.30
chlorodifluoromethane (freon22)<0.30
isobutane<0.30
isobutene/1-butene<0.30
1,3-butadiene<0.30
n-butane<0.30
t-2-butene<0.30
c-2-butene<0.30
3-methyl-1-butene<0.30
isopentane<0.30
1-pentene<0.30
2-methyl-1-butene<0.30
n-pentane<0.30
isoprene<0.30
t-2-pentene<0.30
c-2-pentene<0.30
2-methyl-2-butene<0.30
1,1,2-trichloro-1,2,2-trifluoroethane (freon113)<0.30
2,2-dimethylbutane<0.30
cyclopentene<0.30
4-methyl-1-pentene<0.30
cyclopentane<0.30
2,3-dimethylbutane<0.30
2-methylpentane<0.30
3-methylpentane<0.30
1-hexene<0.30
n-hexane<0.30
t-2-hexene<0.30
2-methyl-1-pentene<0.30
c-2-hexene<0.30
methylcyclopentane<0.30
2,4-dimethylpentane<0.30
benzene<0.30
cyclohexane<0.30
2-methylhexane<0.30
2,3-dimethylpentane<0.30
3-methylhexane<0.30
2,2,4-trimethylpentane<0.30
n-heptane<0.30
2,4,4-trimethyl-1-pentene (diisobutylene)<0.30
methylcyclohexane<0.30
2,5-dimethylhexane<0.30
2,3,4-trimethylpentane<0.30
toluene<0.30
2-methylheptane<0.30
3-methylheptane<0.30
n-octane<0.30
ethylbenzene<0.30
m\p-xylene<0.30
styrene<0.30
o-xylene<0.30
n-nonane<0.30
isopropylbenzene<0.30
n-propylbenzene<0.30
m-ethyltoluene<0.30
p-ethyltoluene<0.30
1,3,5-trimethylbenzene<0.30
o-ethyltoluene<0.30
1,2,4-trimethylbenzene<0.30
n-decane<0.30
m-diethylbenzene<0.30
p-diethylbenzene<0.30
1,2,3-trimethylbenzene<0.30
undecane<0.30
unidentified C2 - C12 hydrocarbons<10.
hydrocarbons eluting before and including toluene<10.
hydrocarbons eluting after toluene<10.

1910.2 Summary of Method

This method incorporates a two stage concentration process which starts with 400mL of sample being passed through a nafion dryer (to remove water) and then through a liquid nitrogen cooled glass bead cryotrap, which traps the C2 and heavier hydrocarbons, reducing the sample volume to less than one milliliter. The cryotrap is then rapidly heated and the sample is transferred to a guard column attached to the head of the analytical column where it is cryogenically refocused. The cryofocusing further reduces the sample volume to less than one microliter for injection. The guard column is rapidly heated (independently of the analytical column) and the sample is injected onto a gas chromatograph equipped with a DB-1 capillary column and flame ionization detector (FID). The resultant separated components are detected by the FID and quantitated by the HP Chemstation.

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Last updated 11/13/03