ASTM E1747-95(2000)
(Guide)Standard Guide for Purity of Carbon Dioxide Used in Supercritical Fluid Applications
Standard Guide for Purity of Carbon Dioxide Used in Supercritical Fluid Applications
SCOPE
1.1 This guide defines purity standards for carbon dioxide to ensure the suitability of liquefied carbon dioxide gas for use in SFE and SFC applications (see Guide E1449 for definitions of terms). This guide defines quantitation, labeling, and statistical standards for impurities in carbon dioxide that are necessary for successful SFE or SFC laboratory work, and it suggests methods of analysis for quantifying these impurities.
1.2 This guide is provided for use by specialty gas suppliers who manufacture carbon dioxide specifically for SFE or SFC applications. SFE or SFC CO 2 products offered with a claim of adherence to this guide will meet certain absolute purity and contaminant detectability requirements matched to the needs of current SFE or SFC techniques. The use of this guide allows different SFE or SFC CO 2 product offerings to be compared on an equal purity basis.
1.3 This guide considers contaminants to be those components that either cause detector signals that interfere with those of the target analytes or physically impede the SFE or SFC experiment.
1.4 The values stated in SI units are to be regarded as the standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: E 1747 – 95 (Reapproved 2000)
Standard Guide for
Purity of Carbon Dioxide Used in Supercritical Fluid
Applications
This standard is issued under the fixed designation E1747; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Therapidcommercialdevelopmentofcarbondioxideforuseinsupercriticalfluidextraction(SFE)
and supercritical fluid chromatography (SFC) has hastened the need to establish common purity
standards to be specified by specialty gas suppliers. As a consequence of its isolation from
petrochemical side-streams or as a by-product of fermentation or ammonia synthesis, carbon dioxide
contains a wide range of impurities that can interfere with analytical quantification or instrument
operation.Thisguideisintendedtoserveasaguidetospecialtygassuppliersfortestingthesuitability
of carbon dioxide for use in SFC and SFE applications.
1. Scope 2. Referenced Documents
1.1 Thisguidedefinespuritystandardsforcarbondioxideto 2.1 ASTM Standards:
ensure the suitability of liquefied carbon dioxide gas for use in D2504 Test Method for Noncondensable Gases in C and
SFEandSFCapplications(seeGuideE1449fordefinitionsof Lighter Hydrocarbon Products by Gas Chromatography
terms).This guide defines quantitation, labeling, and statistical D2820 TestMethodforCThroughC Hydrocarbonsinthe
standards for impurities in carbon dioxide that are necessary Atmosphere By Gas Chromatography
for successful SFE or SFC laboratory work, and it suggests D3670 Guide for Determination of Precision and Bias of
methods of analysis for quantifying these impurities. Methods of Committee D-22
1.2 Thisguideisprovidedforusebyspecialtygassuppliers D3686 Practice for Sampling Atmospheres to Collect Or-
who manufacture carbon dioxide specifically for SFE or SFC ganic Compound Vapors (Activated Charcoal Tube Ad-
applications.SFEorSFCCO productsofferedwithaclaimof sorption Method)
adherence to this guide will meet certain absolute purity and D3687 Practice forAnalysis of Organic CompoundVapors
contaminantdetectabilityrequirementsmatchedtotheneedsof Collected by the Activated Charcoal Tube Adsorption
current SFE or SFC techniques. The use of this guide allows Methods
differentSFEorSFCCO productofferingstobecomparedon D4178 Practice for Calibrating Moisture Analyzers
an equal purity basis. D4532 Test Method for Respirable Dust in Workplace
1.3 This guide considers contaminants to be those compo- Atmosphere
nentsthateithercausedetectorsignalsthatinterferewiththose E260 Practice for Packed Column Gas Chromatography
of the target analytes or physically impede the SFE or SFC E355 Practice for Gas Chromatography Terms and Rela-
experiment. tionships
1.4 The values stated in SI units are to be regarded as the E594 Practice forTesting Flame Ionization Detectors Used
standard. in Gas Chromatography
1.5 This standard does not purport to address all of the E697 Practice for Use of Electron-Capture Detectors in
safety concerns, if any, associated with its use. It is the Gas Chromatography
responsibility of the user of this standard to establish appro- E 1449 Guide for Supercritical Fluid Chromatography
priate safety and health practices and determine the applica- Terms and Relationships
bility of regulatory limitations prior to use.
Annual Book of ASTM Standards, Vol 05.01.
1 3
This guide is under the jurisdiction of ASTM Committee E13 on Molecular Discontinued—See 1992 Annual Book of ASTM Standards, Vol 05.01.
Spectroscopy and is the direct responsibility of Subcommittee E13.19 on Chroma- Annual Book of ASTM Standards, Vol 11.03.
tography. Annual Book of ASTM Standards, Vol 05.02.
Current edition approved Sept. 10, 1995. Published December, 1995. Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1747
E1510 Practice for Installing Fused Silica Open Tubular detrimental to both SFE and SFC applications. Species repre-
Capillary Columns in Gas Chromatographs sentative of this class include nonchromatographicable hydro-
2.2 CGA Publications: carbonsorhalocarbonoils,greases,andinorganicparticles(for
CGA P-1 Safe Handling of Compressed Gases in Contain- example, silica). A maximum concentration of 1 ppm will be
ers considered acceptable.
CGA V-7 Standard for Hydrogen Piping Systems at Con-
4. Purity Specifications for SFE or SFC Grade CO
sumer Locations
4.1 This guide proposes the following minimum purity
CGA P-9 The Inert Gases: Argon, Nitrogen and Helium
specifications for CO for each of the classes of contaminants,
CGAV-7 Standard Method of Determining Cylinder Valve
based on the demands of currently practiced SFE or SFC
Outlets Connections for Industrial Gas Mixtures
techniques.
CGA P12 Safe Handling of Cryogenic Liquids
4.1.1 Liquid-Phase Contaminants Specification:
G6 Carbon Dioxide
4.1.1.1 SFE grade carbon dioxide is intended to be used as
HB-3 Handbook of Compressed Gases
an extraction solvent from which a significant concentration of
3. Classification self-containedcontaminatesispossiblebecauserelativelylarge
(>50 g) amounts of carbon dioxide may be used. Because each
3.1 This guide covers the following four different classes of
impurity cannot be identified, a known amount of internal
compounds:
referencecompounds(forexample,HDandHCB)willbeused
3.1.1 Liquid-Phase Contaminants—Thesearematerialsdis-
during the analysis to quantify contaminants on a relative
solved in the CO liquid phase that can be volatilized below
weight basis. Total contaminant levels will be expressed in ng
300°C and resolved chromatographically using a gas chroma-
of contaminant per g of CO and defined as that amount of
tography (CG) column; and detected by either a flame ioniza-
impurity that will produce a detector signal at the “typical”
tion (FI) or electron capture (EC) detector (D). Species
detection limits for an FID or ECD found in 1.0 g of CO .The
representative of this class include moderate (100 to 600)
1-g amount of carbon dioxide was selected as a convenient
molecular weight hydrocarbons and halocarbons (oils and
mass from which the chemist could relate carbon dioxide
lubricants).
contamination levels with the amount of carbon dioxide
NOTE 1—Liquid-phase contaminant levels are defined in terms of the
required for his/her analysis by a simple ratio.
lowestlimitofdetectorresponse(LLDR) forFIDsorECDsonly,because
4.1.1.2 SFC grade carbon dioxide is intended to be used as
they are the primary detectors used with SFE or SFC techniques.
a mobile phase material transferred directly from a chromato-
However, the purification procedures used by the gas supplier to remove
graphic column to a detector (FID or ECD) without pre-
FID- and ECD-responsive contaminants are assumed to be effective for
contaminants responsive to other (for example, NPD, MS, IR, UV, etc.) concentration(seePracticeE355).Acceptedinternalreference
detectors.
compounds (for example, HD and HCB) will be used as
Because a wide variety of contaminants are found in liquid-phase CO
surrogate contaminants. Contaminant levels will be expressed
as a consequence of its source, full speculation of every impurity by the
in ng of contaminant per g of CO and will be defined as that
gas supplier is impractical. All liquid-phase contaminants are therefore
amount which will produce a detector signal 20 times greater
quantified relative to two representative internal primary reference stan-
than the “typical” detection limit for FID and 25 times greater
dards: hexadecane (HD or C H ) for the FID and hexachlorobenzene
16 34
than an ECD at the lowest detectable limit for a single peak.A
(HCB or C Cl ) for the ECD. Contaminant limits are defined on a mass
6 6
basis for single peaks and for the sum of all detector responses. total of 200 times the lowest detectable limit will be set for all
contaminants for a specific detector.
3.1.2 Moisture—Although water is sparingly (<0.1 %
4.1.1.3 When specifying a FID response for SFE, the
weight) soluble in liquid-phase CO , more than 10 ppm of
maximum amount of any one contaminant (that is, one peak in
moisture may result in physical interference resulting from ice
the chromatogram) will be 1 ng/g of liquid-phase CO . This is
formation during SFC or SFE applications. A maximum limit
equivalent to 1 ppb on a mass basis, or 1 ppb w/w. The
of 1 ppm of water in the carbon dioxide will be considered
maximum amount of all FID-responsive contaminants (that is,
acceptable.
the sum of all peaks in the chromatogram) will be 10 ng/g of
3.1.3 Gas-Phase Contaminants—Gaseous, noncondensible
liquid-phase CO or 10 ppb w/w. Contaminant concentrations
moleculesreleaseduponvaporizationofliquidCO mayactas
are expressed in terms of the equivalent response for hexade-
interferencesduringSFCapplications;thisislessofaproblem
cane, the internal standard, regardless of the actual identity of
inSFEapplications.Speciesrepresentativeofthisclassinclude
the contaminant.
oxygen and light hydrocarbons, such as methane, ethane, and
4.1.1.4 When specifying an FID response for SFC, the
propane.Acombinedmaximumconcentrationinthegasphase
generally accepted LLDR for a FID is 0.25 6 0.1 ng for a
of 10 ppm will be considered acceptable.
singlecomponentwithasignal-to-noiseratioof3:1.Therefore,
3.1.4 Nonvolatile—Materials that leave a nonvolatile (boil-
“20” 3 0.25 ng = 5 ng to the detector (one peak), and
ing point >250°C) residue following the vaporization of liquid
“200” 30.25 ng=50 ng total detector response. If all 5 ng of
CO , such as small particles and high-boiling solutes, are
the contaminant comes from1gof liquid-phase carbon
dioxide,thesinglecomponentimpuritylevelwouldbe50ppb.
This assumes that1gof carbon dioxide arrives at the detector
Available from Compressed Gas Association, Inc., 1725 Jefferson Davis
at one time, and the density of the CO is 1 g/mL. Under
Highway, Arlington, VA 22202-4100. 2
Poole, C. F., and Poole, S. K., Chromatography Today, Elsevier, 1991, p. 86. typical SFC conditions of ;400 atm and 75°C, less than 0.1 g
E 1747
of CO actually reaches the FID when using a 0.25 mm inside 4.1.5 Nonvolatile Contaminants Specification—The maxi-
diameter column with a 15-s wide peak. Therefore, the mum amount of nonvolatile residue acceptable is 1 mg/g of
contamination level acceptable for SFC applications would be CO or 1 ppm (w/w).
less than 16 ppb on an absolute basis for a single peak (see 4.1.6 Specification Summary—Proposed minimum specifi-
cations for SFE and SFC CO are summarized in Table 1.
Practice E594).
4.1.1.5 ECD Detector—For SFE, the maximum amount of
5. Gas Handling and Safety
any one contaminant (that is, one peak in the chromatogram)
5.1 The safe handling of compressed gases and cryogenic
will be 0.2 ng/g of liquid-phase CO . This is equivalent to 0.2
liquidsforuseinchromatographyistheresponsibilityofevery
ppb w/w, or 200 ppt w/w, on a mass basis. The maximum
laboratory. The Compressed Gas Association, Inc. (CGA), a
amount of all ECD-responsive contaminants (that is, the sum
member group of specialty and bulk gas suppliers, publishes
of all peaks in the chromatogram) will be 2 ng/g of liquid-
the following guidelines to assist the laboratory chemist in
phase CO or 2 ppb w/w. Contaminant concentrations are
establishing a safe work environment: CGA P-1, CGA V-7,
expressed in terms of the equivalent response for hexachlo-
CGA P-9, CGAV-7, CGA P12, G6, and HB-3.
robenzene, the internal standard, regardless of the actual
identity of the contaminant (see Practice E697).
6. Representative Analysis Method for Liquid-Phase
4.1.1.6 For SFC applications, the ECD is >5 times more
Contaminants
sensitive than the FID, assuming two halogen atoms per
6.1 Contaminants dissolved in the liquid phase of CO are
molecule. Therefore, the total concentration of a single ECD 2
the most critical to the success of an SFE or SFC experiment.
impurity is proposed to be 1 ng/g of CO or 1 ppb. The total
Theliteratureprovidesawidevarietyofanalyticalmethodsfor
amount of ECD impurities considered acceptable is 10 ng/g of
detectingliquid-phasetracecontaminants,anyofwhichcanbe
CO or 10 ppb.
used by gas suppliers as long as the method can achieve the
4.1.2 Higher-Purity Materials—The specifications and
detectability and statistical requirements recommended in this
methodologyproposedinthisguidecanbeusedtocertifyCO
guide.
materials with higher-purity specifications. To certify such
6.2 Adsorbent Concentration Method—Outlined below is a
materials, gas suppliers must vary (increase) the quantity of
representative method for liquid-phase contaminants, referred
CO collected and adjust the quantity of internal standard used
to as the adsorbent concentration method.
for calibration. Contaminant concentrations are expressed in
6.2.1 The method is included to develop the quantitation
terms of the equivalent responses for the internal standards
and statistical calculations discussed in Section 8; however,
recommended above and reported on a mass basis relative to
this guide does not mandate its use.
the mass of CO collected. The applicable detector must be
6.2.2 Apparatus:
specified.
6.2.2.1 Gas Chromatograph—The procedure requires a gas
4.1.2.1 Minimum-purity CO contains a total of 10 ng of
chromatograph equipped with both an FID and an ECD. The
FID-responsive contaminants per g of CO (10 ppb w/w), with
LLDR for the FID must be 0.25 ng 6 0.1 ng of HD at a
no single FID-responsive contaminant greater than 1 ng/g (1
signal-to-noise ratio of 3:1. The LLDR for the ECD must be
ppbw/w).Higher-specificationCO ,forexample,maycontain
0.05ng 60.02ngHCB.Thedetectorsarejoinedtothecolumn
a total of 1 ppb w/w of FID-responsive contaminants, with no
using a “Y” separator and are back-pressure split at a 10:1
single contaminant greater than 0.1 ppb w/w.
FID-ECD ratio (see Practices E260 and E1510).
4.1.2.2 Gas suppliers are free to manufacture materials with
(1) Also, the gas chromatograph must be equipped to
purity specifications as stringent as they choose. SFC and SFE
accommodateanexternalthermaldesorptionandcryofocusing
practitioners may use the purity reporting standards defined
unit, and it must be configured for wide-bore, open-tubular
here as a basis for needs assessment and product comparison.
columns and temperature programming up to 270°C.
No “grading” nomenclature is recommended in this guide.
(2) Any common detector recording device may be use
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.