ASTM D4735-19

Standard Test Method for Determination of Trace Thiophene in Refined Benzene by Gas Chromatography

SIGNIFICANCE AND USE
4.1 This test method is suitable for setting specifications on benzene and for use as an internal quality control tool where benzene is either produced or used in a manufacturing process.  
4.2 This test method was found applicable for determining thiophene in refined benzene conforming to the specifications described in Specification D2359 and may be applicable toward other grades of benzene if the user has taken the necessary precautions as described in the text.
SCOPE
1.1 This test method covers the determination of thiophene in refined benzene in the range from 0.80 to 1.80 mg/kg for the Flame Photometric Detector (FPD), and from 0.14 to 2.61 mg/kg for the Pulsed Flame Photometric Detector (PFPD). For the PFPD, the minimum level of quantitation (LOQ) is 0.14 mg/kg and the minimum level of detection (LOD) is 0.04 mg/kg, as described in ASTM Research Report RR:D16-1038.2 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 This test method has been found applicable to benzene characteristic of the type described in Specifications D2359 and D4734 and may be applicable to other types or grades of benzene only after the user has demonstrated that the procedure can completely resolve thiophene from the other organic contaminants contained in the sample.  
1.3 The following applies to all specified limits in this test method: for purposes of determining conformance to applicable specification using this test method, an observed value or a calculated value shall be rounded off “to the nearest unit” in the last right-hand digit used in expressing the specification limit in accordance with the rounding-off method of Practice E29.  
1.4 The values stated in SI units are to be regarded as 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 7.  
1.6 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

• Status: Published
• Publication Date: 31-May-2019
• ICS: 71.080.15 - Aromatic hydrocarbons
• Technical Committee: D16 - Aromatic, Industrial, Specialty and Related Chemicals
• Drafting Committee: D16.04 - Instrumental Analysis

Relations

• Refers: ASTM D4734-20 - Standard Specification for Refined Benzene-545
• Effective Date: 01-Apr-2020
• Refers: ASTM D2359-19 - Standard Specification for Refined Benzene-535
• Effective Date: 01-Nov-2019
• Refers: ASTM D4734-19 - Standard Specification for Refined Benzene-545
• Effective Date: 01-Nov-2019
• Refers: ASTM E260-96(2019) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Sep-2019
• Refers: ASTM D2359-18a - Standard Specification for Refined Benzene-535
• Effective Date: 01-Nov-2018
• Refers: ASTM D4734-18a - Standard Specification for Refined Benzene-545
• Effective Date: 01-Nov-2018
• Refers: ASTM D4734-18 - Standard Specification for Refined Benzene-545
• Effective Date: 01-Mar-2018
• Refers: ASTM D2359-18 - Standard Specification for Refined Benzene-535
• Effective Date: 01-Mar-2018
• Refers: ASTM D2359-17 - Standard Specification for Refined Benzene-535
• Effective Date: 01-Jun-2017
• Refers: ASTM D4734-17 - Standard Specification for Refined Benzene-545
• Effective Date: 01-Jun-2017
• Refers: ASTM D6809-02(2016) - Standard Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
• Effective Date: 01-Nov-2016
• Refers: ASTM D4734-16 - Standard Specification for Refined Benzene-545
• Effective Date: 01-Jun-2016
• Refers: ASTM D2359-16 - Standard Specification for Refined Benzene-535
• Effective Date: 01-Jun-2016
• Refers: ASTM D4307-99(2015) - Standard Practice for Preparation of Liquid Blends for Use as Analytical Standards
• Effective Date: 01-Oct-2015
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014

Overview

ASTM D4735-19 is the Standard Test Method for the Determination of Trace Thiophene in Refined Benzene by Gas Chromatography, developed by ASTM International. This test method addresses the need for precise quantitative determination of trace levels of thiophene, a sulfur-containing compound, in refined benzene. Accurate detection of thiophene is critical for maintaining benzene quality standards, meeting regulatory requirements, and ensuring the reliability of downstream manufacturing processes.

The method utilizes gas chromatography (GC), specifically employing flame photometric detectors (FPD) or pulsed flame photometric detectors (PFPD), to measure thiophene concentrations with high sensitivity and reproducibility. The typical detection range for FPD is 0.80 to 1.80 mg/kg, and for PFPD, it extends from 0.14 to 2.61 mg/kg. This procedure is suitable for benzene that meets the specifications of ASTM D2359 and D4734, and may be applicable to other grades where complete separation of thiophene from other organics can be demonstrated.

Key Topics

• Trace Analysis of Thiophene: Quantitative determination of low-level thiophene impurities in benzene.
• Gas Chromatography (GC): Utilization of GC with FPD or PFPD for sensitive and selective sulfur detection.
• Quality Assurance: Suitable for both specification setting and internal quality control during benzene production or utilization.
• Applicable Concentration Ranges:
  • FPD: 0.80 to 1.80 mg/kg
  • PFPD: 0.14 to 2.61 mg/kg
  • Detection and quantitation limits may be adjusted with modifications to the analytical parameters.
• Applicability: Designed for refined benzene per ASTM D2359 and ASTM D4734; potential for adaptation to other benzene grades with caution.
• Reporting and Rounding: Data is rounded per ASTM E29 for specification conformance.

Applications

ASTM D4735-19 finds practical application in various industrial and laboratory settings where the purity of benzene is essential:

• Benzene Production Facilities: Used as a quality control tool to ensure refined benzene meets established specifications for thiophene content.
• Petrochemical and Chemical Manufacturing: Ensures that benzene feedstocks used in synthesis processes are free from excessive sulfur contamination, which could affect product quality and catalyst performance.
• Regulatory Compliance: Assists companies in meeting environmental and product quality regulations regarding sulfur content in aromatic compounds.
• Research and Development: Provides a standard approach for analytical laboratories developing new methods or validating existing procedures for trace sulfur analysis.
• Process Optimization: Enables monitoring and control of refining and distillation operations to minimize thiophene levels and avoid process disruptions.

Related Standards

Several other ASTM standards and technical practices are referenced or relevant to the implementation of ASTM D4735-19:

• ASTM D2359 - Specification for Refined Benzene-535
• ASTM D4734 - Specification for Refined Benzene-545
• ASTM D1193 - Specification for Reagent Water
• ASTM D3437, D4057, D4177 - Practices for Sampling and Handling Liquid Cyclic Products and Petroleum Products
• ASTM D4307 - Practice for Preparation of Liquid Blends for Analytical Standards
• ASTM E29 - Practice for Using Significant Digits in Test Data
• ASTM E260, E355 - Practices for Gas Chromatography Techniques
• ASTM E840 - Practice for Using Flame Photometric Detectors in Gas Chromatography
• ASTM D6809 - Guide for Quality Control and Quality Assurance for Aromatic Hydrocarbons
• OSHA Regulations – Addressing chemical safety and exposure (particularly for benzene)

Practical Value

Implementing ASTM D4735-19 enables consistent monitoring and certification of benzene quality regarding thiophene impurities. The standard supports operational excellence, compliance, and risk mitigation in the handling and processing of benzene by providing clear and validated analytical methodology. By adhering to this standard, stakeholders can ensure the reliability and safety of benzene supply chains, as well as compliance with industry best practices and regulatory frameworks.

Keywords: ASTM D4735-19, thiophene determination, benzene quality, gas chromatography, flame photometric detector, pulsed flame photometric detector, sulfur impurities, petrochemical analysis, quality control, aromatic hydrocarbons

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:D4735 −19
Standard Test Method for
Determination of Trace Thiophene in Refined Benzene by
Gas Chromatography
This standard is issued under the fixed designation D4735; 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* 1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This test method covers the determination of thiophene
ization established in the Decision on Principles for the
in refined benzene in the range from 0.80 to 1.80 mg/kg for the
Development of International Standards, Guides and Recom-
Flame Photometric Detector (FPD), and from 0.14 to 2.61
mendations issued by the World Trade Organization Technical
mg/kg for the Pulsed Flame Photometric Detector (PFPD). For
Barriers to Trade (TBT) Committee.
the PFPD, the minimum level of quantitation (LOQ) is 0.14
mg/kg and the minimum level of detection (LOD) is 0.04
2. Referenced Documents
mg/kg,asdescribedinASTMResearchReportRR:D16-1038.
The range of the test method may be extended by modifying 3
2.1 ASTM Standards:
the sample injection volume, split ratios, calibration range, or
D1193 Specification for Reagent Water
sample dilution with thiophene-free solvent.
D2359 Specification for Refined Benzene-535
1.2 This test method has been found applicable to benzene
D3437 Practice for Sampling and Handling Liquid Cyclic
characteristic of the type described in Specifications D2359
Products
and D4734 and may be applicable to other types or grades of
D4057 Practice for Manual Sampling of Petroleum and
benzeneonlyaftertheuserhasdemonstratedthattheprocedure
Petroleum Products
can completely resolve thiophene from the other organic
D4177 Practice for Automatic Sampling of Petroleum and
contaminants contained in the sample.
Petroleum Products
D4307 Practice for Preparation of Liquid Blends for Use as
1.3 The following applies to all specified limits in this test
Analytical Standards
method: for purposes of determining conformance to appli-
D4734 Specification for Refined Benzene-545
cable specification using this test method, an observed value or
D6809 Guide for Quality Control and Quality Assurance
a calculated value shall be rounded off “to the nearest unit” in
Procedures for Aromatic Hydrocarbons and Related Ma-
the last right-hand digit used in expressing the specification
limit in accordance with the rounding-off method of Practice terials
E29 Practice for Using Significant Digits in Test Data to
E29.
Determine Conformance with Specifications
1.4 The values stated in SI units are to be regarded as
E177 Practice for Use of the Terms Precision and Bias in
standard.
ASTM Test Methods
1.5 This standard does not purport to address all of the
E260 Practice for Packed Column Gas Chromatography
safety concerns, if any, associated with its use. It is the
E355 Practice for Gas ChromatographyTerms and Relation-
responsibility of the user of this standard to establish appro-
ships
priate safety, health, and environmental practices and deter-
E691 Practice for Conducting an Interlaboratory Study to
mine the applicability of regulatory limitations prior to use.
Determine the Precision of a Test Method
For specific hazard statements, see Section 7.
E840 PracticeforUsingFlamePhotometricDetectorsinGas
Chromatography
E1510 Practice for Installing Fused Silica Open Tubular
This test method is under the jurisdiction of ASTM Committee D16 on
Capillary Columns in Gas Chromatographs
Aromatic, Industrial, Specialty and Related Chemicals and is the direct responsi-
bility of Subcommittee D16.04 on Instrumental Analysis.
CurrenteditionapprovedJune1,2019.PublishedJuly2019.Originallyapproved
in 1987. Last previous edition approved in 2015 as D4735 – 15. DOI: 10.1520/
D4735-19. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Supporting data have been filed at ASTM International Headquarters and may contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
beobtainedbyrequestingResearchReportRR:D16-1038.ContactASTMCustomer Standards volume information, refer to the standard’s Document Summary page on
Service at [e-mail]. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4735−19
TABLE 1 Thiophene in Benzene Instrumental Conditions
Column A B C D
1 1 1
Tubing 6 ft 3 ⁄8in.Ni 15ftby ⁄8 in. stainless steel 10 ft by ⁄8 in. stainless steel 30 meter, Fused Silica,
0.25 (or 0.32) mm ID
A
Phase TCEEP SP-1000 OV-351 Bonded Polyethylene Glycol
(PEG/CW)
Concentration, weight % 7 10 10 0.5 (or 1.0) micron film thickness
B
Support Chromosorb P-AW Supelcoport Chromosorb P-AW N/A
Mesh 100/120 60/80 80/100 N/A
Gas chromatographic conditions
Inlet 150 170 180 200
Carrier Gas helium helium helium helium
Carrier Flow, mL/min 30 30 30 1.0–1.5
Split Ratio N/A N/A N/A 50:1
Column Temperature, °C 70 90 70 50°C for 1 mi., 10°C/min to
200°C, hold for 1 min
Detector FPD FPD FPD PFPD
(optimize flows per (tuned for Sulfur)
manufacturer’s instructions) BG-12 Filter
2 mm combustor
H , mL/min 140 140 140 11.5
flow optimized for S mode
Air I, mL/min 80 80 80 12.0
flow optimized for S mode
Air 2, mL/min 70 70 70 10.0
flow optimized for S mode
Temperature (°C) 220 220 250 250
A
Tetracyanoethylated pentaerythritol or pentrile.
B
Chromosorb P is a registered trademark of the Manville Corp.
2.2 Other Document: dures.An automatic sampler is recommended. The GC should
OSHA Regulations, 29 CFR paragraphs 1910.1000 and
have the following performance characteristics:
1910.1200
5.1.1 Column Temperature Programmer—The chromato-
graph shall be capable of linear programmed temperature
3. Summary of Test Method
operation over a range sufficient for the separation of the
3.1 The thiophene concentration in refined benzene is de-
compounds of interest. The programming shall be sufficiently
termined at the milligram thiophene per kilogram sample level
reproducible to obtain retention time repeatability throughout
using conventional gas-liquid chromatography with a flame
the scope of the analysis.
photometric detector (FPD) or pulsed flame photometric de-
5.1.2 Sample Inlet System—The sample inlet system shall
tector (PFPD). A reproducible volume of sample is injected.
have variable temperature control capable of operating con-
Quantitative results are obtained by the external standard
tinuously at a temperature up to the maximum column tem-
technique using the measured peak area of thiophene.
perature employed. The sample inlet system shall allow a
4. Significance and Use constant volume of sample to be injected by means of a
syringe. For the PFPD a heated flash vaporizing injector
4.1 This test method is suitable for setting specifications on
designed to provide a linear sample split injection (that is,
benzene and for use as an internal quality control tool where
50:1) is required for proper sample introduction. The associ-
benzene is either produced or used in a manufacturing process.
ated carrier gas flow controls shall be of sufficient precision to
4.2 This test method was found applicable for determining
provide reproducible column flows and split ratios in order to
thiophene in refined benzene conforming to the specifications
maintain analytical integrity.
described in Specification D2359 and may be applicable
toward other grades of benzene if the user has taken the
5.2 Column—The column shall provide complete resolution
necessary precautions as described in the text.
of thiophene from benzene and any other hydrocarbon impu-
rities because of potential quenching effects by hydrocarbons
5. Apparatus
on the light emissions from the thiophene. The columns
5.1 Gas Chromatograph—Any chromatograph having a
described in Table 1 have been judged satisfactory. The user is
flame photometric detector (FPD or PFPD) may be used which
referred to Practice E1510 for assistance on installing fused
can operate at the typical conditions described in Table 1. The
silica capillary columns into the gas chromatograph.
user is referred to Practices E260 and E355 for additional
5.3 Detector—Any flame photometric detector (FPD or
information about gas chromatography principles and proce-
PFPD) can be used, provided it has sufficient sensitivity to
produceaminimumpeakheighttwicethatofthebasenoisefor
AvailablefromU.S.GovernmentPrintingOfficeSuperintendentofDocuments,
a4-µLinjectionontheFPD,ora1.0-µLinjectionforthePFPD
732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
www.access.gpo.gov. of 0.5 mg/kg thiophene in benzene. The user is referred to
D4735−19
Practice E840 for assistance in optimizing the operation and isatin solution, with successive 100-mL portions of concen-
performance of the FPD. trated sulfuric acid until the H SO layer is light yellow or
2 4
colorless. Wash the benzene with 100 mL of water, then twice
5.4 Data Acquisition System—The use of an electronic
with 100 mL of cadmium chloride solution (CdCl ). Finally,
integrating device or computer data system is recommended
wash with another 100-mL portion of water and filter the
for determining the detector response.The device and software
benzene through medium filter paper into a storage bottle,
shall have the following capabilities: a) graphic presentation of
stopper the bottle tightly and save for future use. Commercial
the chromatogram, b) digital display of chromatographic peak
sources of thiophene-free benzene are available and can be
areas, c) identification of peaks by retention time or relative
used as an alternative to this cleanup procedure.
retention time, or both, d) calculation and use of response
factors, and e) internal standardization, external 6.9 Sulfuric Acid—Concentrated H SO .
2 4
standardization, and data presentation.
6.10 Thiophene.
5.5 Microsyringe, 5 or 10-µL capacity. 6.10.1 Stock solutions of thiophene in benzene are commer-
cially available and can be used for preparation of calibration
5.6 Volumetric Flasks, 50, 100 and 500-mL capacity.
standards.
5.7 Separatory Funnel, 1-L capacity.
7. Hazards
6. Reagents and Materials
7.1 Benzene is considered a hazardous material. Consult
6.1 Purity of Reagents—Reagent grade chemicals shall be
current OSHA regulations and supplier’s Safety Data Sheets,
used in all tests. Unless otherwise indicated, it is intended that
and l
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4735 − 15 D4735 − 19
Standard Test Method for
Determination of Trace Thiophene in Refined Benzene by
Gas Chromatography
This standard is issued under the fixed designation D4735; 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*
1.1 This test method covers the determination of thiophene in refined benzene in the range from 0.80 to 1.80 mg/kg for the
Flame Photometric Detector (FPD), and from 0.14 to 2.61 mg/kg for the Pulsed Flame Photometric Detector (PFPD). For the
PFPD, the minimum level of quantitation (LOQ) is 0.14 mg/kg and the minimum level of detection (LOD) is 0.04 mg/kg, as
described in ASTM Research Report RR:D16-1038. 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 This test method has been found applicable to benzene characteristic of the type described in Specifications D2359 and
D4734 and may be applicable to other types or grades of benzene only after the user has demonstrated that the procedure can
completely resolve thiophene from the other organic contaminants contained in the sample.
1.3 The following applies to all specified limits in this test method: for purposes of determining conformance to applicable
specification using this test method, an observed value or a calculated value shall be rounded off “to the nearest unit” in the last
right-hand digit used in expressing the specification limit in accordance with the rounding-off method of Practice E29.
1.4 The values stated in SI units are to be regarded as 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For specific hazard statements, see Section 7.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
D2359 Specification for Refined Benzene-535
D3437 Practice for Sampling and Handling Liquid Cyclic Products
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D4307 Practice for Preparation of Liquid Blends for Use as Analytical Standards
D4734 Specification for Refined Benzene-545
D6809 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E260 Practice for Packed Column Gas Chromatography
E355 Practice for Gas Chromatography Terms and Relationships
This test method is under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons Aromatic, Industrial, Specialty and Related Chemicals and is the direct
responsibility of Subcommittee D16.04 on Instrumental Analysis.
Current edition approved June 1, 2015June 1, 2019. Published July 2015July 2019. Originally approved in 1987. Last previous edition approved in 20142015 as
D4735 – 09 (2014).D4735 – 15. DOI: 10.1520/D4735-15.10.1520/D4735-19.
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D16-1038. Contact ASTM Customer
Service at [e-mail].
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4735 − 19
TABLE 1 Thiophene in Benzene Instrumental Conditions
Column A B C D
1 1 1
Tubing 6 ft 3 ⁄8 in. Ni 15 ft by ⁄8 in. stainless steel 10 ft by ⁄8 in. stainless steel 30 meter, Fused Silica,
0.25 (or 0.32) mm ID
A
Phase TCEEP SP-1000 OV-351 Bonded Polyethylene Glycol
(PEG/CW)
Concentration, weight % 7 10 10 0.5 (or 1.0) micron film thickness
B
Support Chromosorb P-AW Supelcoport Chromosorb P-AW N/A
Mesh 100/120 60/80 80/100 N/A
Gas chromatographic conditions
Inlet 150 170 180 200
Carrier Gas helium helium helium helium
Carrier Flow, mL/min 30 30 30 1.0–1.5
Split Ratio N/A N/A N/A 50:1
Column Temperature, °C 70 90 70 50°C for 1 mi., 10°C/min to
200°C, hold for 1 min
Detector FPD FPD FPD PFPD
(optimize flows per (tuned for Sulfur)
manufacturer’s instructions) BG-12 Filter
2 mm combustor
H , mL/min 140 140 140 11.5
flow optimized for S mode
Air I, mL/min 80 80 80 12.0
flow optimized for S mode
Air 2, mL/min 70 70 70 10.0
flow optimized for S mode
Temperature (°C) 220 220 250 250
A
Tetracyanoethylated pentaerythritol or pentrile.
B
Chromosorb P is a registered trademark of the Manville Corp.
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E840 Practice for Using Flame Photometric Detectors in Gas Chromatography
E1510 Practice for Installing Fused Silica Open Tubular Capillary Columns in Gas Chromatographs
2.2 Other Document:
OSHA Regulations, 29 CFR paragraphs 1910.1000 and 1910.1200
3. Summary of Test Method
3.1 The thiophene concentration in refined benzene is determined at the milligram thiophene per kilogram sample level using
conventional gas-liquid chromatography with a flame photometric detector (FPD) or pulsed flame photometric detector (PFPD).
A reproducible volume of sample is injected. Quantitative results are obtained by the external standard technique using the
measured peak area of thiophene.
4. Significance and Use
4.1 This test method is suitable for setting specifications on benzene and for use as an internal quality control tool where
benzene is either produced or used in a manufacturing process.
4.2 This test method was found applicable for determining thiophene in refined benzene conforming to the specifications
described in Specification D2359 and may be applicable toward other grades of benzene if the user has taken the necessary
precautions as described in the text.
5. Apparatus
5.1 Gas Chromatograph—Any chromatograph having a flame photometric detector (FPD or PFPD) may be used which can
operate at the typical conditions described in Table 1. The user is referred to Practices E260 and E355 for additional information
about gas chromatography principles and procedures. An automatic sampler is recommended. The GC should have the following
performance characteristics:
5.1.1 Column Temperature Programmer—The chromatograph shall be capable of linear programmed temperature operation
over a range sufficient for the separation of the compounds of interest. The programming shall be sufficiently reproducible to obtain
retention time repeatability throughout the scope of the analysis.
Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
www.access.gpo.gov.
D4735 − 19
5.1.2 Sample Inlet System—The sample inlet system shall have variable temperature control capable of operating continuously
at a temperature up to the maximum column temperature employed. The sample inlet system shall allow a constant volume of
sample to be injected by means of a syringe. For the PFPD a heated flash vaporizing injector designed to provide a linear sample
split injection (that is, 50:1) is required for proper sample introduction. The associated carrier gas flow controls shall be of sufficient
precision to provide reproducible column flows and split ratios in order to maintain analytical integrity.
5.2 Column—The column shall provide complete resolution of thiophene from benzene and any other hydrocarbon impurities
because of potential quenching effects by hydrocarbons on the light emissions from the thiophene. The columns described in Table
1 have been judged satisfactory. The user is referred to Practice E1510 for assistance on installing fused silica capillary columns
into the gas chromatograph.
5.3 Detector—Any flame photometric detector (FPD or PFPD) can be used, provided it has sufficient sensitivity to produce a
minimum peak height twice that of the base noise for a 4-μL injection on the FPD, or a 1.0-μL injection for the PFPD of 0.5 mg/kg
thiophene in benzene. The user is referred to Practice E840 for assistance in optimizing the operation and performance of the FPD.
5.4 Data Acquisition System—The use of an electronic integrating device or computer data system is recommended for
determining the detector response. The device and software shall have the following capabilities: a) graphic presentation of the
chromatogram, b) digital display of chromatographic peak areas, c) identification of peaks by retention time or relative retention
time, or both, d) calculation and use of response factors, and e) internal standardization, external standardization, and data
presentation.
5.5 Microsyringe, 5 or 10-μL capacity.
5.6 Volumetric Flasks, 50, 100 and 500-mL capacity.
5.7 Separatory Funnel, 1-L capacity.
6. Reagents and Materials
6.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
6.2 Purity of Water—Unless otherwise indicated, reference to water shall be understood to mean reagent water conforming to
Type IV of Specification D1193.
6.3 Carrier Gas, nitrogen, helium, or hydrogen, chromatographic grade, or shall have a purity of 99.999 % (V/V) or better.
6.4 Hydrogen, zero grade, or shall have a purity of 99.999 % (V/V) or better. (Warning—Hydrogen is an extremely flammable
gas under high pressure.)
6.5 Compressed Air, hydrocarbon-free, or shall have a purity of 99.999 % (V/V) or better. (Warning—Compressed air and
oxygen are gases under high pressure and they support combustion.)
6.6 Cadm
...