ASTM D7011-15(2019)
(Test Method)Standard Test Method for Determination of Trace Thiophene in Refined Benzene by Gas Chromatography and Sulfur Selective Detection
Standard Test Method for Determination of Trace Thiophene in Refined Benzene by Gas Chromatography and Sulfur Selective Detection
SIGNIFICANCE AND USE
4.1 Accurate gas chromatographic determination of trace levels of thiophene in benzene involves special analytical problems because of the difficulties of trace level analysis. These problems arise from the low concentration levels that need to be measured, the type of column and detector needed for analysis, and the potential interference from the benzene matrix.
4.2 This test method was found applicable for determining thiophene in refined benzene conforming to the specifications described in Specifications D2359, D4734, and D5871 and may be applicable toward other grades of benzene if the user has taken the necessary precautions as described in the text.
4.3 This test method was developed as an alternative technique to Test Method D4735.
SCOPE
1.1 This test method covers the determination of thiophene in refined benzene using gas chromatography and sulfur selective detection. The test method is applicable to the determination of thiophene at levels of 0.02 to 2.18 mg thiophene per kg in benzene (mg/kg) on the AED, 0.03 to 1.87 mg/kg on the PFPD, and 0.03 to 2.11 mg/kg on the SCD. The range of the test method may be extended by modifying the sample injection volume, split ratios, calibration range, or sample dilution with thiophene-free solvent.
1.2 In determining the conformance of the test results using this method to applicable specifications, results shall be rounded off in accordance with the rounding-off method of Practice E29.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 7.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7011 −15 (Reapproved 2019)
Standard Test Method for
Determination of Trace Thiophene in Refined Benzene by
Gas Chromatography and Sulfur Selective Detection
This standard is issued under the fixed designation D7011; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope D2359 Specification for Refined Benzene-535
D3437 Practice for Sampling and Handling Liquid Cyclic
1.1 This test method covers the determination of thiophene
Products
in refined benzene using gas chromatography and sulfur
D4734 Specification for Refined Benzene-545
selective detection. The test method is applicable to the
D4735 Test Method for Determination of Trace Thiophene
determination of thiophene at levels of 0.02 to 2.18 mg
in Refined Benzene by Gas Chromatography
thiophene per kg in benzene (mg/kg) on theAED, 0.03 to 1.87
D5871 Specification for Benzene for Cyclohexane Feed-
mg/kg on the PFPD, and 0.03 to 2.11 mg/kg on the SCD. The
stock
range of the test method may be extended by modifying the
D6809 Guide for Quality Control and Quality Assurance
sample injection volume, split ratios, calibration range, or
Procedures for Aromatic Hydrocarbons and Related Ma-
sample dilution with thiophene-free solvent.
terials
1.2 In determining the conformance of the test results using
E29 Practice for Using Significant Digits in Test Data to
this method to applicable specifications, results shall be
Determine Conformance with Specifications
rounded off in accordance with the rounding-off method of
E177 Practice for Use of the Terms Precision and Bias in
Practice E29.
ASTM Test Methods
1.3 The values stated in SI units are to be regarded as
E691 Practice for Conducting an Interlaboratory Study to
standard. No other units of measurement are included in this
Determine the Precision of a Test Method
standard.
E1510 Practice for Installing Fused Silica Open Tubular
Capillary Columns in Gas Chromatographs
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
2.2 Other Document:
responsibility of the user of this standard to establish appro-
OSHA Regulations, 29 CFR paragraphs 1910.1000 and
priate safety, health, and environmental practices and deter-
1910.1200
mine the applicability of regulatory limitations prior to use.
For specific hazard statements, see Section 7.
3. Summary of Test Method
1.5 This international standard was developed in accor-
3.1 The thiophene concentration in refined benzene is de-
dance with internationally recognized principles on standard-
termined at the sub-mg/kg to low mg/kg level using conven-
ization established in the Decision on Principles for the
tional gas chromatography with a sulfur selective detector. A
Development of International Standards, Guides and Recom-
reproducible volume of sample is injected. Quantitative results
mendations issued by the World Trade Organization Technical
are obtained by the use of the external standard calibration
Barriers to Trade (TBT) Committee.
technique.
2. Referenced Documents
3.2 The method allows the use of a sulfur chemilumines-
2.1 ASTM Standards:
cence detector, atomic emission detector, pulsed flame photo-
D1193 Specification for Reagent Water
metric detector, or any other sulfur selective detector provided
that its performance meets requirements as set forth in 5.4.As
This test method is under the jurisdiction of ASTM Committee D16 on
sulfur compounds elute from the gas chromatographic column,
Aromatic, Industrial, Specialty and Related Chemicals and is the direct responsi-
they are detected and quantified. While the benzene molecule
bility of Subcommittee D16.04 on Instrumental Analysis.
does not contain any sulfur atoms, the possibility of matrix
Current edition approved June 1, 2019. Published June 2019. Originally
approved in 2004. Last previous edition approved in 2015 as D7011 – 15. DOI:
10.1520/D7011-15R19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM AvailablefromU.S.GovernmentPrintingOfficeSuperintendentofDocuments,
Standards volume information, refer to the standard’s Document Summary page on 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
the ASTM website. www.access.gpo.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7011 − 15 (2019)
quenching and interference is a concern, especially for thio- a liquid autosampler or liquid sampling valve is permitted for
phene determination at levels less than about 0.5 mg/kg. The the analysis of thiophene in benzene.
column and conditions specified in Table 1 yield acceptable
5.4 Detector—A sulfur selective detector is used and shall
results with minimal matrix quenching and interference. Em-
meet or exceed the following specifications: (1) linearity or
ploying the column and conditions listed in Table 1 is not a 2
compensated linearity of at least 10 , (2) minimum detectable
requirement to meet the needs of all users. For example, there
level of less than 0.02 mg/kg thiophene in benzene, (3)
is less concern of quenching and interference encountered with 5
selectivity of sulfur to carbon greater than 10 , and (4) absence
thiopheneconcentrationlevelsgreaterthan0.5mg/kg.Usersof
of quenching that affect results under the conditions used for
flame photometric detectors should refer to Test Method
the analysis.
D4735.
5.5 Data Handling System—Use of an electronic integrating
4. Significance and Use device or computer is necessary. The device shall have the
following capabilities: (1) graphic presentation of the
4.1 Accurate gas chromatographic determination of trace
chromatogram, (2) digital display of chromatographic peak
levels of thiophene in benzene involves special analytical
areas, (3) identification of peaks by retention time, and (4)
problems because of the difficulties of trace level analysis.
calculation and use of response factors.
These problems arise from the low concentration levels that
need to be measured, the type of column and detector needed 5.6 Gases:
for analysis, and the potential interference from the benzene 5.6.1 Carrier Gases—Helium or nitrogen of high purity
matrix. (99.995+ %). Additional purification is recommended by the
use of molecular sieves or other suitable agents to remove
4.2 This test method was found applicable for determining
water, oxygen, hydrocarbons, and sulfur contaminants. Gases
thiophene in refined benzene conforming to the specifications
shall be regulated to ensure a constant carrier gas flow rate.
described in Specifications D2359, D4734, and D5871 and
5.6.2 Detector Gases—Hydrogen and air are required as
may be applicable toward other grades of benzene if the user
detector gases (99.995+ % purity). Additionally, oxygen
has taken the necessary precautions as described in the text.
(99.8+ %) may be substituted for air. These gases shall be free
4.3 This test method was developed as an alternative tech-
of interfering contaminants, especially sulfur compounds.
nique to Test Method D4735.
5.6.3 Carrier and Detector Gas Control—Constant flow
control of carrier and detector gases is critical to optimum and
5. Apparatus
consistent analytical performance. Control is best provided by
5.1 Gas Chromatograph—The gas chromatograph shall be
the use of pressure regulators and fixed flow restrictions or
capable of producing retention times for thiophene repeatable
mass flow controllers capable of maintaining gas flow constant
to within 0.05 min. The gas chromatograph shall be equipped
to 61 % at the required flow rates. The gas flow rate is
with an appropriate sulfur selective detector, column for
measuredbyanyappropriatemeans.Thesupplypressureofthe
separation, and sample inlet system for repeatable injection of
gas delivered to the gas chromatograph shall be at least 70 kPa
sample volume.
(10 psig) greater than the regulated gas at the instrument to
compensate for the system back pressure of the flow control-
5.2 Column—Specifications and conditions described in
lers. In general, a supply pressure of 550 kPa (80 psig) is
Table 1 have been judged satisfactory for this analysis.The use
satisfactory.
of any column that permits separation and determination of
thiophene in benzene at levels consistent with the scope of this
5.7 Microsyringes—10, 50, 100, and 250 µL capacity
method is allowed. Specific chromatographic results and con-
(61 % accuracy).
ditions are illustrated in Fig. 1. The user is referred to Practice
5.8 Volumetric Pipettes—0.5, 1.0, and 2.0 mL capacity
E1510 for information on installation of fused silica capillary
(Class A).
columns.
5.9 Volumetric Flasks—10, 50, 100, and 500 mL capacity
5.3 Sample Inlet System—The sample inlet system shall be
(class A).
able to quantitatively transfer the sample to the analytical
column. It shall be capable of introducing constant and 5.10 Separatory Funnel—1 L capacity.
repeatablevolumesofsampleandcalibrationstandards.Useof
6. Reagents and Materials
TABLE 1 Typical Chromatographic Conditions 6.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
Column 30 m length, 0.32 mm internal
diameter, 1 µm thick film,
all reagents shall conform to the specifications of the Commit-
cross-linked polyethylene 4
teeonAnalyticalReagentsoftheAmericanChemicalSociety,
glycol (wax-type)
Oven Temperature 40°C for 2 min; ramp to 100°C
at 10°C/min, hold at
Reagent Chemicals, American Chemical Society Specifications, American
100°C for 1 min
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
Flow Rate 2 mL/min
listed by the American Chemical Society, see Analar Standards for Laboratory
Split Ratio 1:4 to 1:10
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Injection Temperature 125°C
Injection Volume 1-2 µL and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD.
D7011 − 15 (2019)
NOTE 1—The shorter retention time obtained with the SCD is primarily due to the column outlet being at sub-ambient pressure.
FIG. 1 Chromatograms Illustrating the Analysis of a Sample Containing 0.2 mg/kg Thiophene in Benzene Using AED, PFPD and SCD
(Upper, Middle, and Lower Chromatograms, Respectively)
D7011 − 15 (2019)
where such specifications are available. Other grades may be 7.8 Cadmium chloride is a highly toxic cancer causing
used, provided it is first ascertained that the reagent is of agent.
sufficiently high purity to permit its use without lessening the
8. Sample Handling
accuracy of the determination.
8.1 Collect the samples in accordance with Practice D3437.
6.2 Purity of Water—Unless otherwise indicated, reference
towatershallbeunderstoodtomeanreagentwaterconforming
8.2 To preserve sample integrity and prevent the loss of
to Type IV of Specification D1193.
volatile compounds that may be in some samples, collect
samples with a minimal head space and do not uncover
6.3 Benzene, Thiophene-free:
samples any longer than necessary. Some headspace is neces-
6.3.1 In a fume hood, wash 700 mL of benzene in a 1000
sary to prevent containers from rupturing if the possibility for
mL separatory funnel to which has been added 5 mL of isatin
thermal expansion exists. Sample containers shall be free of
solution, with successive 100 mL portions of concentrated
contaminantsthatcouldinterferewiththeanalysis.Analyzethe
sulfuric acid until the acid layer is light yellow to colorless.
specimen as soon as possible after transferring it from the
Wash the benzene with 100 mL of water, then twice with 100
sample container to prevent loss of components or contamina-
mL of cadmium chloride solution (CdCl ). Finally wash with
tion.
another 100 mLportion of water and filter the benzene through
medium filter paper into a storage bottle, stopper the bottle 8.3 Since this procedure is intended for trace level
tightly and save for future use. contamination,careshallbetakentoensurecontainersusedfor
6.3.2 Alternatively, thiophene-free benzene can be pur- thesample,thespecimen,andtheworkingstandarddonotalter
chased commercially and used within this method, if its the sample results.
thiophene level meets the criteria within 10.4.
9. Preparation of Apparatus
6.4 Cadmium Chloride Solution (20 g/L)—Dissolve 20 g of
9.1 The chromatographic separation of trace level sulfur
anhydrouscadmiumchloride(CdCl )into200mLofwaterand
compounds can be complicated by absorption onto active sites
dilute to 1 L.
throughout the chromatographic system. This is less of a
6.5 Chloroform—Reagent grade or better.
problem with thiophene, which is very stable relative to most
6.6 Isatin Solution—Add 0.5 g of isatin to 200 mL of sulfur compounds. The most likely cause of error in this
chloroform. Heat under a fume hood to a temperature just method is presence of thiophene in matrix blanks (see 10.4).
below the boiling point of chloroform (61°C) and maintain for
9.2 Follow the manufacturer’s instructions for mounting the
5 min with stirring. Filter the hot solution through hardened
column into the gas chromatograph and adjusting the instru-
rapid-filter paper into a 250 mL volumetric flask and dilute to
ment to typical conditions as described in Table 1. General
volume with chloroform.
guidelines for the installation of capillary columns can be
found in Practice E1510.
6.7 Stock Solutions—Commercially prepared stock solution
of thiophene in benzene are available for use as calibration
9.3 The gas chromatograph and detector should be placed
standards or for preparation of calibration standards.
intoserviceinaccordancewiththemanufacturer’sinstructions.
6.8 Sulfuric Acid—Concentrated H SO .
2 4
10. Calibration
6.9 Thiophene—Available from commercial sources for
10.1 A manual or electronic calibration curve shall be
preparation of calibration standards, minimum 99 % purity.
prepared for the method of analysis. In some instances, for
example when compliance with a certain specification is
7. Hazards
determined, it is sufficient to use a single point calibration
7.1 Benzene is listed as a known carcinogen and is consid-
according to user needs.
ered a hazardous material. Consult current OSHA regulations
10.2 Prepare a sto
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.