Analyses of Permanent Gases, Light Hydrocarbons, and Light Polar Compounds, Using Packed Column GC

     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

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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