ASTM D2685-95(1998)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact
ASTM International (www.astm.org) for the latest information.
Designation: D 2685 – 95 (Reapproved 1998)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas
Chromatography
This standard is issued under the fixed designation D 2685; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 5. Apparatus
1.1 This test method covers the determination of air (Note 5.1 Gas Chromatograph, consisting of a sample inlet sys-
1) and carbon tetrafluoride as impurities in sulfur hexafluoride. tem, adsorption column, flow meter, detector, and data han-
dling system. Ensure that the column material of construction
NOTE 1—Nitrogen, oxygen, or any of their mixtures is considered to be
and sample components are compatible. The apparatus must
air. Commercial grade air or nitrogen is used for standardization.
completely separate air, carbon tetrafluoride, and sulfur
1.2 This standard does not purport to address all of the
hexafluoride as indicated by return of the recorded peak to the
safety concerns, if any, associated with its use. It is the
base line between each successive peak. Chromatograms must
responsibility of the user of this standard to establish appro-
be reproducible so that successive runs of a reference standard
priate safety and health practices and determine the applica-
agree on each component peak area or height within 5 %.
bility of regulatory limitations prior to use.
6. Reagents and Materials
2. Referenced Documents
6.1 Cylinder of Helium Gas.
2.1 ASTM Standards:
6.2 Reference Standard Mixture—A gas mixture that con-
D 2472 Specification for Sulfur Hexafluoride
tains known percentages of air and carbon tetrafluoride in
helium or air and carbon tetrafluoride in sulfur hexafluoride is
3. Summary of Test Method
required. The concentration of a component in the reference
3.1 Air and carbon tetrafluoride are separated physically by
sample should not be less than 50 % nor more than 300 % of
gas chromatography and compared to corresponding compo-
the concentration of the corresponding component in the
nents separated under similar conditions from a reference
unknown.
standard mixture of known composition. The individual com-
pounds of air are not separated. The composition of the sample
7. Calibration and Standardization
is calculated from its chromatogram by comparing the area of
7.1 Apparatus Preparation—Prepare the gas chromato-
the peak of each component with the area of the peak of the
graph for use as directed by the manufacturer. The following
corresponding component on the reference standard chromato-
operating conditions have been found satisfactory. However,
gram.
any combination of conditions that result in complete separa-
tions as indicated in the apparatus section will be satisfactory.
4. Significance and Use
Carrier gas helium, 40 to 50 mL/min
4.1 Air and carbon tetrafluoride (CF ) are two contaminants
Column Porapak Q-80/100 mesh or Porapak R 50/80 mesh
of interest in sulfur hexafluoride (SF ). Both of these contami- Column size 6 to 10 Ft (2–3.5 m) by ¼ in. (6.4 mm) nominal
Column temperature 40 to 50°C
nants adversely affect the performance of SF when used as an
Detector temperature 70 to 80°C
electrical insulating gas. Specification for maximum levels of
Sample volume 2 to 5 mL approximately
these contaminants are given in Specification D 2472. Attenuation lowest which will keep peaks on a scale may be varied
during run
4.2 Gas chromatography is used to separate these contami-
Detector thermal conductivity
nants from a sample of SF and to determine their concentra-
tion.
7.2 Example of Chromatography Conditions—Specific con-
ditions used by one laboratory which produces acceptable
chromatograms are as follows:
This test method is under the jurisdiction of ASTM Committee D-27 Electrical Carrier gas helium, 50 mL/min
Insulating Liquids and Gases and is the direct responsibility of Subcommittee Column packing Porapak R 50/80 mesh
D27.03 on Analytical Tests. Column size and material 0.25 in. (6.4 mm) nominal ID,
Current edition approved Sept. 10, 1995. Published November 1995. Originally 10 ft (3.5 m) long, copper
Column temperature 48°C
published as D 2685 – 68. Last previous edition D 2685 – 94.
Detector thermal conductivity
Annual Book of ASTM Standards, Vol 10.03.
NOTICE:¬This¬standard¬has¬either¬been¬superceded¬and¬replaced¬by¬a¬new¬version¬or¬discontinued.¬
Contact¬ASTM¬International¬(www.astm.org)¬for¬the¬latest¬information.¬
D 2685
Detector temperature 75°C
(5 summation of the individual peak areas.
Sample volume 5 mL
9.3 Calculate the concentration of each component in the
7.3 Reference Standard Intr
...