Application Note
112
Analyses of Permanent Gases, Light
Hydrocarbons, and Light Polar Compounds,
Using Packed Column GC
GC columns containing Carboxen-1000 packing separate mix-
tures of permanent gases (nitrogen, hydrogen, oxygen/argon,
carbon monoxide, carbon dioxide) and C1-C3 light hydrocar-
bons (methane, acetylene, ethylene, ethane, propyne, propy-
lene, propane). A 15’ x 1/8” column will separate the perma-
nent gases and C1 and C2 hydrocarbons in less than 25 minutes.
A 2’ x 1/8” column provides excellent resolution of the C1-C3
hydrocarbons in the absence of permanent gases. These one-
column analyses are more convenient than the two-column
procedures often used to separate permanent gas/light hydro-
carbon mixtures.
Key Words:
l
permanent gases l light hydrocarbons
l
gas-solid chromatography l formaldehyde
Analysts have used a variety of combinations of packed GC
columns to separate mixtures that include permanent gases
(nitrogen, hydrogen, oxygen/argon, carbon monoxide, carbon
dioxide) and C1-C3 hydrocarbons (acetylene, ethane, ethylene,
methane, propane, propylene, propyne). A one-column proce-
dure, however, is easier to set up and to duplicate than two-column
analyses. Carboxen™-1000, a spherical carbon molecular sieve,
combines analytical capabilities previously requiring two packings
(Carbosieve™ S-II
■ and Carbosieve G). The material efficiently
separates permanent gases, C1-C3 hydrocarbons, and permanent
gas/light hydrocarbon mixtures. In addition, Carboxen-1000 col-
umns can be used for analyses of more polar light compounds,
such as formaldehyde and sulfur dioxide.
Carboxen-1000 particles have a mean pore diameter larger than
that of the Carbosieve packings (70Å, versus 39Å) and a distribu-
tion of macropores (diameter >500Å), mesopores (20-500Å diam-
eter), and micropores (diameter <20Å) optimized to provide
effective kinetics for GSC analyses. This pore size distribution,
combined with a large surface area (more than 1200m2/g, versus
1000m2/g for Carbosieve S-II), ensures the Carboxen-1000 pack-
ing will provide chromatographic analyses with retention times
similar to those for the Carbosieve packings, but with greater
efficiency (Table 1).
A 15' (4.5m) column containing 60/80 mesh Carboxen-1000
packing effectively separates the permanent gases and C2 hydro-
carbons (Figure A). Hydrocarbons separate by degree of
unsaturation, with saturated compounds eluting last. Samples
containing no C2 compounds can be analyzed in only 15 minutes.
Higher concentrations of oxygen relative to nitrogen, as in air
samples, also can be resolved under these conditions. If the
separation of oxygen and nitrogen is unnecessary, a 5' (1.5m)
column containing 45/60 mesh material will separate the C2
hydrocarbons from oxygen/nitrogen, carbon monoxide, carbon
dioxide, and methane. Under the conditions used for Figure A,
argon (approximately 0.9% of an air sample) will not separate from
oxygen. If it is necessary to separate these two gases, much lower
temperatures (-70°C to -80°C) are required.
A 2' (0.6m) column containing 45/60 mesh packing will separate
C1-C3 hydrocarbons that are not admixed with permanent gases
(Figure B). You also can monitor trace hydrocarbons on this short
column (Figure C).
Table 1.
Carboxen-1000 Columns Are
More Efficient Than Carbosieve Columns
Carboxen 1000
Carbosieve S-II
60/80 mesh
100/120 mesh
60/80 mesh
Analyte
plates/foot k’
plates/foot k’
plates/foot k’
CO
2
280
12
280
12
136
11
Ethane
247
13
197
13
66
12
1.
Oxygen
2.
Nitrogen
3.
Carbon monoxide
4.
Methane
5.
Carbon dioxide
6.
Acetylene
7.
Ethylene
8.
Ethane
0
4
8
12
16
20
24
1
2
3
4
5
6
7
8
794-0114
Min
Figure A.
Permanent Gases and
C2 Hydrocarbons Resolved
Column:
60/80 Carboxen-1000, 15' x 1/8" SS (2.1mm ID)
Cat. No.:
12390-U (general configuration)
Oven Temp.:
35°C (5 min) to 225°C at 20°C/min
Carrier:
helium, 30mL/min
Det.:
TCD
Inj.:
0.6mL Scott gas mix (Cat. No. 2-3437) with oxygen added,
1% each analyte, 4-6µg each analyte (except N
2) on column
T396112
©
1996 Sigma-Aldrich Co.
For more information, or current prices, contact your nearest Supelco subsidiary listed below. To obtain further contact information, visit our website (www.sigma-aldrich.com), see the Supelco catalog, or contact
Supelco, Bellefonte, PA 16823-0048 USA.
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H
Supelco is a member of the Sigma-Aldrich family. Supelco products are sold through Sigma-Aldrich, Inc. Sigma-Aldrich warrants that its products conform to the information contained in this and other
Sigma-Aldrich publications. Purchaser must determine the suitability of the product for a particular use. Additional terms and conditions may apply. Please see the reverse side of the invoice or packing slip.
The surface chemistry of Carboxen-1000 particles also makes the
material useful for analyses of more polar compounds, such as
formaldehyde in formalin solutions and sulfur dioxide in air (Figure
D). These analyses previously were performed using Carbosieves S
and B, materials that have been unavailable for years.
Figure D.
Polar Compounds
Column:
45/60 Carboxen-1000, 2' x 1/8" SS (2.1mm ID)
Cat. No.:
12370-U (general configuration)
Oven Temp.:
150°C (formalin) or 190°C (SO
2)
Carrier:
helium, 30mL/min
Det.:
TCD
Inj.:
0.2µL formalin solution or
1µL 1000ppm SO
2 in N2, ~1µg SO2 on column
We recommend Carboxen-1000 columns for efficient, reproduc-
ible analyses and accurate peak quantification in GSC
analyses of permanent gases, light hydrocarbons, or mixtures of
these two classes of compounds. If you currently are using
Carbosieve S-II columns, and wish to continue to use them, packed
columns and packing are still available. Carbosieve G material is
available on special request.
Ordering Information:
Carboxen-1000 in 1/8" (2.1mm ID)
Stainless Steel Columns
Col. Length / Particle Size / Cat. No.
2'/0.6m
5'/1.5m
15'/4.5m
Instrument
45/60 mesh 45/60 mesh 60/80 mesh
General configuration◆
12370
12380
12390-U
Hewlett-Packard 5700-5800
12371
12381
12391
Hewlett-Packard 5880 (9" span) 12372
12382
12392-U
Perkin Elmer 900-3920
12373
12383
12393
Varian 3700
12374
12384
12394
◆Coil diameter 6" (152.4mm), arm length 8" (203.2mm)
For information about custom packed columns, refer to our
catalog, or call our Sales Department.
Trademarks
Carboxen, Carbosieve — Supelco, Inc.
■ German Pat. No. 1935500. Patent holder — Badische Anilin- & Soda-Fabrik
Aktiengesellschaft.
0
2
4
Nitrogen
Sulfur dioxide
0
2
4
Water
Formaldehyde
Methanol
Min
Min
794-0117,0118
Sulfur Dioxide in Air
Formalin Solution
Contact our Technical Service Department
(phone 800-359-3041 or 814-359-3041, FAX 800-359-3044 or
814-359-5468) for expert answers to your questions.
Figure C.
Trace Acetylene in Ethylene
Column:
45/60 Carboxen-1000, 5' x 1/8" SS (2.1mm ID)
Cat. No.:
12380 (general configuration)
Oven Temp.:
160°C
Carrier:
helium, 30mL/min
Det.:
FID
Inj.:
0.5mL ethylene with trace impurities
Ethylene
Methane
Acetylene (14ppm)
0
4
12
8
Min
794-0116
1
2
3
4
5
7
6
1.
Methane
2.
Acetylene
3.
Ethylene
4.
Ethane
5.
Propyne
6.
Propylene
7.
Propane
Figure B.
C1-C3 Hydrocarbons
Column:
45/60 Carboxen-1000, 2' x 1/8" SS (2.1mm ID)
Cat. No.:
12370-U (general configuration)
Oven Temp.:
165°C (1 min) to 220°C at 16°C/min
Carrier:
helium, 60mL/min
Det.:
FID
Inj.:
0.6mL Scott gas mix (Cat. No. 2-3470), 15ppm each analyte,
~10ng each analyte on column
0
2
4
6
794-0115
Min
Note 112
