ASTM D3606-24

Standard Test Method for Determination of Benzene and Toluene in Spark Ignition Fuels by Gas Chromatography

SIGNIFICANCE AND USE
5.1 Knowledge of the concentration of benzene may be required for regulatory use, control of gasoline blending, and/or process optimizations.
SCOPE
1.1 This test method covers the quantitation in liquid volume percent of benzene and toluene in finished motor and aviation spark ignition fuels by gas chromatography. This test method has two procedures: Procedure A uses capillary column gas chromatography and Procedure B uses packed column gas chromatography. Procedures A and B have separate precisions.  
1.2 The method has been evaluated for benzene using a D6300-compliant Interlaboratory Study (ILS), with the lowest and highest ILS sample concentration means as follows: (1) Procedure A between 0.12 % and 5.2 % by volume and (2) Procedure B between 0.10 % and 5.0 % by volume.  
1.3 The method has been evaluated for toluene using a D6300-compliant Interlaboratory Study (ILS), with the lowest and highest ILS sample concentration means as follows: (1) Procedure A between 0.4 % and 19.7 % by volume, and (2) Procedure B between 2.0 % and 20.0 % by volume.  
1.4 For reporting, the lowest and highest concentration ranges for benzene and toluene for Procedure A of this test method per Practice D6300 see 13.2.  
1.5 For reporting, the lowest and highest concentration ranges for benzene and toluene for Procedure B of this test method per Practice D6300 see 25.2.  
1.6 For benzene by Procedure A, the following oxygenated fuels are included in the working range: (1) ethanol up to 20 % by volume (E20); (2) methanol up to 10 % by volume (M10). Fuels M85 and E85 were excluded.  
1.7 For benzene by Procedure B the following oxygenated fuels are included in the working range: (1) ethanol up to 20 % by volume (E20); (2) methanol up to 10 % by volume (M10). Fuels M85 and E85 were excluded.  
1.8 For toluene by Procedure A the following oxygenated fuels were included in the working range: (1) ethanol up to 20 % by volume (E20); (2) M85 and E85.  
1.9 For toluene by Procedure B the following oxygenated fuels are included in the working range: (1) ethanol up to 20 % by volume (E20); (2) M85 and E85.  
1.10 Procedure A uses MIBK as the internal standard. Procedure B uses sec-butanol as the internal standard. The use of Procedure B for fuels containing blended butanols requires that sec-butanol be below the detection limit in the fuels as sec-butanol is an internal standard. For Procedure B, an alternative separation column set described in the annex (A2.3, Annex Approach B) uses MEK as the internal standard when butanols may be blended into gasolines.  
1.11 This test method includes a between method bias section for benzene based on Practice D6708 bias assessment between Test Method D3606 Procedure B and Test Method D5769. It is intended to allow Test Method D3606 Procedure B to be used as a possible alternative to Test Method D5769. The Practice D6708 derived benzene correlation equation is applicable for benzene measurements in the reportable range from 0.06 % to 2.76 % by volume as reported by Test Method D3606 Procedure B (see 27.2.1). The correlation complies with EPA’s Performance Based Measurement System (PBMS).  
1.12 Correlation equations are included in the between test methods bias section 14.2.1 of Procedure A to convert Procedure A to the Procedure B volume percent values for benzene and toluene. The correlations are applicable in the concentration ranges of 0.07 % to 5.96 % by volume for benzene and 0.36 % to 20.64 % by volume for toluene as reported by Procedure A.  
1.13 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.  
1.14 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...

General Information

• Status: Published
• Publication Date: 29-Feb-2024
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.04.0L - Gas Chromatography Methods

Relations

• Replaces: ASTM D3606-22 - Standard Test Method for Determination of Benzene and Toluene in Spark Ignition Fuels by Gas Chromatography
• Effective Date: 01-Mar-2024
• Refers: ASTM D6300-24 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Mar-2024
• Refers: ASTM D6708-24 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Mar-2024
• Refers: ASTM D6300-23a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Dec-2023
• Refers: ASTM D6708-21 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-May-2021
• Referred By: ASTM D4815-22 - Standard Test Method for Determination of MTBE, ETBE, TAME, DIPE, tertiary-Amyl Alcohol and C<inf>1</inf> to C<inf>4</inf> Alcohols in Gasoline by Gas Chromatography
• Effective Date: 01-Mar-2024
• Referred By: ASTM D5580-21 - Standard Test Method for Determination of Benzene, Toluene, Ethylbenzene, <emph type="ital"> p/m</emph>-Xylene, <emph type="ital">o</emph>-Xylene, C<inf>9</inf> and Heavier Aromatics, and Total Aromatics in Finished Gasoline by Gas Chromatography
• Effective Date: 01-Mar-2024
• Referred By: ASTM D5769-22 - Standard Test Method for Determination of Benzene, Toluene, and Total Aromatics in Finished Gasolines by Gas Chromatography/Mass Spectrometry
• Effective Date: 01-Mar-2024
• Referred By: ASTM D7719-21a - Standard Specification for High Aromatic Content Unleaded Hydrocarbon Aviation Gasoline Test Fuel
• Effective Date: 01-Mar-2024
• Referred By: ASTM D8071-21 - Standard Test Method for Determination of Hydrocarbon Group Types and Select Hydrocarbon and Oxygenate Compounds in Automotive Spark-Ignition Engine Fuel Using Gas Chromatography with Vacuum Ultraviolet Absorption Spectroscopy Detection (GC-VUV)
• Effective Date: 01-Mar-2024
• Referred By: ASTM D6839-21a - Standard Test Method for Hydrocarbon Types, Oxygenated Compounds, Benzene, and Toluene in Spark Ignition Engine Fuels by Multidimensional Gas Chromatography
• Effective Date: 01-Mar-2024
• Referred By: ASTM D8275-22 - Standard Specification for Gasoline-like Test Fuel for Compression-Ignition Engines
• Effective Date: 01-Mar-2024
• Referred By: ASTM D3764-23 - Standard Practice for Validation of the Performance of Process Stream Analyzer Systems
• Effective Date: 01-Mar-2024
• Referred By: ASTM D6733-01(2020) - Standard Test Method for Determination of Individual Components in Spark Ignition Engine Fuels by 50-Metre Capillary High Resolution Gas Chromatography
• Effective Date: 01-Mar-2024
• Referred By: ASTM D7235-21a - Standard Guide for Establishing a Linear Correlation Relationship Between Analyzer and Primary Test Method Results Using Relevant ASTM Standard Practices
• Effective Date: 01-Mar-2024

Overview

ASTM D3606-24: Standard Test Method for Determination of Benzene and Toluene in Spark Ignition Fuels by Gas Chromatography is a widely recognized analytical method established by ASTM International. This standard provides detailed procedures for quantifying the content of benzene and toluene in liquid volume percent in finished motor gasoline and aviation spark ignition fuels. It utilizes gas chromatography (GC) and outlines two main procedures: Procedure A with capillary columns and Procedure B with packed columns, each with its own performance characteristics.

Knowing the concentration of benzene and toluene in fuels is important for regulatory compliance, process optimization, and effective control of gasoline blending. This method supports accurate and precise hydrocarbon analysis, aiding both fuel producers and regulatory bodies in assessing the quality and safety of spark ignition fuels.

Key Topics

• Gas Chromatography Methods: The standard details two approaches for analysis:
  • Procedure A uses WCOT capillary column GC with flame ionization detection and methyl isobutyl ketone (MIBK) as the internal standard.
  • Procedure B uses packed column GC with thermal conductivity detection and sec-butanol as the internal standard (alternative MEK also referenced for butanol-blended fuels).
• Precision Evaluation: Both procedures have been evaluated through interlaboratory studies, ensuring reliable detection of benzene from 0.10% up to 5.2% and toluene from 0.4% up to 20% by volume (ranges vary by procedure).
• Applicability to Oxygenated Fuels: The method's applicability extends to fuels containing up to 20% ethanol (E20) and up to 10% methanol (M10) for benzene analysis. For toluene, the working range includes higher ethanol and methanol blends such as E85 and M85.
• Regulatory and Quality Assurance: The test supports compliance with environmental and safety regulations (such as U.S. EPA requirements). Correlation and bias assessments facilitate comparison with other ASTM methods (e.g., D5769).
• Reporting: Results are reported in liquid volume percent, with clear reporting ranges established for both benzene and toluene.

Applications

• Regulatory Compliance: The determination of benzene levels is directly linked to meeting statutory limits placed by governmental and environmental agencies due to benzene's classification as a hazardous air pollutant.
• Gasoline Blending Control: Fuel producers leverage this standard to monitor and control aromatic content during gasoline formulation, optimizing engine performance while minimizing environmental impact.
• Quality Control in Fuel Production: Routine application of ASTM D3606 ensures product consistency, reliability, and supports statistical quality control processes.
• Process Optimization: By monitoring benzene and toluene concentrations, refiners can adjust processes to improve yield, meet blending specifications, and reduce undesirable emissions.
• Evaluation of Reformulated and Oxygenated Fuels: The method's suitability for a range of fuel types, including those blended with ethanol and methanol, makes it essential for modern fuel industries adapting to evolving fuel formulations.

Related Standards

• ASTM D5769: Test method for benzene, toluene, and aromatic content via gas chromatography/mass spectrometry (GC/MS), often used in parallel or for cross-validation.
• ASTM D6300: Describes interlaboratory studies for determining precision and bias in test methods.
• ASTM D4057: Provides standardized procedures for manual sampling of petroleum products, ensuring sample integrity before chromatographic analysis.
• ASTM D6708: Outlines the statistical assessment and improvement of agreement between two test methods, used for bias and correlation in D3606.
• ASTM D6299: Focuses on the implementation of statistical quality assurance in analytical measurement systems.
• ASTM E355 and D4175: Supply definitions and terminology relating to gas chromatography and petroleum products.

By following ASTM D3606-24, laboratories ensure reliable, accurate measurement of benzene and toluene content, supporting fuel quality, safety regulations, and environmental compliance. This standard is essential for professionals involved in gasoline analysis, compliance testing, and quality assurance in the petroleum and fuels sector.

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: D3606 − 24
Standard Test Method for
Determination of Benzene and Toluene in Spark Ignition
Fuels by Gas Chromatography
This standard is issued under the fixed designation D3606; 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* 1.9 For toluene by Procedure B the following oxygenated
fuels are included in the working range: (1) ethanol up to 20 %
1.1 This test method covers the quantitation in liquid
by volume (E20); (2) M85 and E85.
volume percent of benzene and toluene in finished motor and
aviation spark ignition fuels by gas chromatography. This test
1.10 Procedure A uses MIBK as the internal standard.
method has two procedures: Procedure A uses capillary column
Procedure B uses sec-butanol as the internal standard. The use
gas chromatography and Procedure B uses packed column gas
of Procedure B for fuels containing blended butanols requires
chromatography. Procedures A and B have separate precisions.
that sec-butanol be below the detection limit in the fuels as
1.2 The method has been evaluated for benzene using a
sec-butanol is an internal standard. For Procedure B, an
D6300-compliant Interlaboratory Study (ILS), with the lowest
alternative separation column set described in the annex (A2.3,
and highest ILS sample concentration means as follows: (1)
Annex Approach B) uses MEK as the internal standard when
Procedure A between 0.12 % and 5.2 % by volume and (2)
butanols may be blended into gasolines.
Procedure B between 0.10 % and 5.0 % by volume.
1.11 This test method includes a between method bias
1.3 The method has been evaluated for toluene using a
section for benzene based on Practice D6708 bias assessment
D6300-compliant Interlaboratory Study (ILS), with the lowest
between Test Method D3606 Procedure B and Test Method
and highest ILS sample concentration means as follows: (1)
D5769. It is intended to allow Test Method D3606 Procedure
Procedure A between 0.4 % and 19.7 % by volume, and (2)
B to be used as a possible alternative to Test Method D5769.
Procedure B between 2.0 % and 20.0 % by volume.
The Practice D6708 derived benzene correlation equation is
1.4 For reporting, the lowest and highest concentration
applicable for benzene measurements in the reportable range
ranges for benzene and toluene for Procedure A of this test
from 0.06 % to 2.76 % by volume as reported by Test Method
method per Practice D6300 see 13.2.
D3606 Procedure B (see 27.2.1). The correlation complies with
1.5 For reporting, the lowest and highest concentration EPA’s Performance Based Measurement System (PBMS).
ranges for benzene and toluene for Procedure B of this test
1.12 Correlation equations are included in the between test
method per Practice D6300 see 25.2.
methods bias section 14.2.1 of Procedure A to convert Proce-
1.6 For benzene by Procedure A, the following oxygenated
dure A to the Procedure B volume percent values for benzene
fuels are included in the working range: (1) ethanol up to 20 %
and toluene. The correlations are applicable in the concentra-
by volume (E20); (2) methanol up to 10 % by volume (M10).
tion ranges of 0.07 % to 5.96 % by volume for benzene and
Fuels M85 and E85 were excluded.
0.36 % to 20.64 % by volume for toluene as reported by
1.7 For benzene by Procedure B the following oxygenated Procedure A.
fuels are included in the working range: (1) ethanol up to 20 %
1.13 The values stated in SI units are to be regarded as
by volume (E20); (2) methanol up to 10 % by volume (M10).
standard. The values given in parentheses are for information
Fuels M85 and E85 were excluded.
only.
1.8 For toluene by Procedure A the following oxygenated
1.14 This standard does not purport to address all of the
fuels were included in the working range: (1) ethanol up to
safety concerns, if any, associated with its use. It is the
20 % by volume (E20); (2) M85 and E85.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
This test method is under the jurisdiction of ASTM Committee D02 on
mine the applicability of regulatory limitations prior to use.
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.04.0L on Gas Chromatography Methods.
1.15 This international standard was developed in accor-
Current edition approved March 1, 2024. Published March 2024. Originally
dance with internationally recognized principles on standard-
approved in 1977. Last previous edition approved in 2022 as D3606 – 22. DOI:
10.1520/D3606-24. ization established in the Decision on Principles for the
*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
D3606 − 24
Development of International Standards, Guides and Recom- the concentration of each component is calculated with refer-
mendations issued by the World Trade Organization Technical ence to the internal standard.
Barriers to Trade (TBT) Committee.
5. Significance and Use
2. Referenced Documents
5.1 Knowledge of the concentration of benzene may be
2.1 ASTM Standards:
required for regulatory use, control of gasoline blending,
D4057 Practice for Manual Sampling of Petroleum and
and/or process optimizations.
Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid
6. Apparatus and Chemicals
Fuels, and Lubricants
6.1 Chromatograph—Any gas chromatograph that has the
D5769 Test Method for Determination of Benzene, Toluene,
capability of performing multidimensional chromatography
and Total Aromatics in Finished Gasolines by Gas
that can be operated at approximately the conditions described
Chromatography/Mass Spectrometry
in this method, and meets all the required chromatographic
D6299 Practice for Applying Statistical Quality Assurance
specifications and method criteria specified in 8.5 and 12.
and Control Charting Techniques to Evaluate Analytical
Measurement System Performance 6.1.1 Sample Introduction System—Automated sample in-
D6300 Practice for Determination of Precision and Bias jection system such as a liquid autosampler.
Data for Use in Test Methods for Petroleum Products,
6.1.2 Injector—Capillary split/splitless injector.
Liquid Fuels, and Lubricants
6.1.3 Detector—At least one flame ionization detector (FID)
D6708 Practice for Statistical Assessment and Improvement
is required. In a two FID configuration, the optional second
of Expected Agreement Between Two Test Methods that
detector is used to monitor the effluent from the pre-column
Purport to Measure the Same Property of a Material
(refer to configuration A in 8.1.1).
E288 Specification for Laboratory Glass Volumetric Flasks
6.2 Columns:
E355 Practice for Gas Chromatography Terms and Relation-
6.2.1 Pre-column—Non-polar, boiling point column, which
ships
performs the first separation of the hydrocarbons. A dimethyl
E694 Specification for Laboratory Glass Volumetric Appa-
polysiloxane phase column with dimensions of 30 m by
ratus
0.25 mm by 0.50 μm has been used successfully. Any column
E969 Specification for Glass Volumetric (Transfer) Pipets
with equivalent or better chromatographic efficiency and se-
E1044 Specification for Glass Serological Pipets (General
lectivity may be used.
Purpose and Kahn)
6.2.2 Analytical Column—This column separates aromatic
E1293 Specification for Glass Measuring Pipets
and non-aromatic compounds. A polyethylene glycol (polar
3. Terminology
‘wax’) column with the dimensions 60 m by 0.32 mm by
1.0 μm has been used successfully. Any column capable of
3.1 This test method makes references to terms whose
meeting the resolution requirement in 8.5 may be employed.
definitions may be found in Practice E355 and Terminology
6.2.3 Restrictor—Uncoated deactivated fused silica. A
D4175.
100 μm by 42.5 cm restrictor was successfully used when
developing this method.
PROCEDURE A—CAPILLARY WCOT GAS
6.3 Chromatography Data System (CDS)—An electronic
CHROMATOGRAPHIC SYSTEMS
device capable of graphical presentation and integration of the
4. Summary of Test Method chromatogram peaks.
4.1 An internal standard, methyl isobutyl ketone (MIBK) is
6.4 Microsyringe—Capable of making injections from
added to the sample which is then introduced into a heated
0.5 μL to 1.0 μL.
capillary or programmed temperature vaporization (PTV) in-
6.5 Volumetric Pipets, Class A—0.5 mL, 1 mL, 5 mL,
jector on a gas chromatograph (GC). The GC is equipped with
10 mL, 15 mL, and 20 mL capacities (see Specifications E694
two columns connected in series. The sample passes first
and E969).
through a column with a nonpolar phase. After toluene has
eluted, the flow through the nonpolar column is reversed,
6.6 Measuring Pipets—1 mL and 2 mL capacities calibrated
flushing out the components heavier than toluene. The toluene in 0.01 mL; 5 mL calibrated in 0.1 mL, for use in dispensing
and lighter components enter a second column which separates
volumes of benzene and toluene not covered by the volumetric
the aromatic and nonaromatic compounds. The eluted compo- pipets (see Specifications E1044 and E1293) during prepara-
nents are detected by a flame ionization detector (FID). The
tion of standard samples (see 9.1).
detector response is recorded, the peak areas are measured, and
NOTE 1—Other manual or automated volume dispensing equipment
capable of delivering the specified volumes within the stated tolerance
limits may be used as an alternative to the requirements stated in 6.5 and
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 6.6.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
6.7 Flasks—Volumetric, 25 mL and 100 mL capacity (see
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Specification E288).
D3606 − 24
6.8 GC Carrier Gas—Helium or hydrogen 99.999 % pure. 8.1.1 Configuration A—Has the capability of monitoring the
(Warning—Compressed gas under high pressure; hydrogen effluent from the pre-column via a restrictor. This is a dual
flammable.) A hydrogen generator may be used. detector system. One FID is used to monitor the analytical
NOTE 2—When using hydrogen carrier gas, use precautions such as
column’s effluent, and the other to monitor the effluent from the
installation of hydrogen sensors in the gas chromatograph oven. It is
pre-column. The second FID provides a quicker approach in
recommended that the hydrogen excess flow, such as from the splitter
determining backflush time. Figs. A1.1 and A1.2 represent
inlet, should be vented to a safe area such as a ventilated hood or
examples of this configuration.
appropriate exhaust approved for such use. Use caution when performing
maintenance by isolating the hydrogen source. 8.1.2 Configuration B—Has the capability of monitoring the
effluent from the pre-column via a restrictor; however, only one
6.9 FID Gas—Air chromatographic grade, dry (Warning—
FID is installed. Figs. A1.3 and A1.4 represent examples of this
Compressed gas under high pressure.) An air generator may be
configuration.
used with purifier.
8.1.3 Configuration C—Does not have the capability to
6.10 FID Gas—Hydrogen, 99.999 % pure (Warning—
monitor the effluent from the pre-column. Figs. A1.5 and A1.6
Compressed gas under high pressure; hydrogen flammable.) A
represent an example of this configuration.
hydrogen generator may be used.
8.2 Conditioning Column—Install the pre-column, analyti-
6.11 FID Make-up Gas, if Required (Refer to Manufactur-
cal column, and the restrictor, if the restrictor is being used as
er’s Requirements)—Nitrogen, 99.999 % pure. (Warning—
in configurations A and B. Condition the columns per manu-
Compressed gas under high pressure.)
facturer’s instructions.
NOTE 3—Reference the instrument manual for specifics on how to
establish required flow rates for a particular vendor’s instrument. 8.3 Determine Time to Backflush (BF)—Or backflush time,
must be empirically determined for each system and column
6.12 Chemicals—(Warning—These chemicals are
set used by the laboratory. Optimization of backflush time is
dangerous, harmful, or fatal if swallowed or inhaled. They are
dependent upon the configuration used.
flammable to extremely flammable. Vapors can cause flash
8.3.1 Configuration A, Dual Detector Configuration—
fires.)
Follow the instrument setup as shown in Figs. A1.1 and A1.2.
6.12.1 Internal Standard—Methyl Isobutyl Ketone (MIBK)
8.3.1.1 Establish analytical parameters set forth in Table
99.5 % pure.
A1.1 or parameters that have met method separation criteria as
6.13 Calibration Standards:
outlined in 8.5. Ensure both detector channels are being
6.13.1 Benzene—99.5 % minimum purity. (Warning—
collected by the CDS.
Carcinogen.)
8.3.1.2 Inject 0.1 μL to 0.5 μL of standard #1 (9.2) or the
6.13.2 Toluene—99.5 % minimum purity.
butanol composite mix (9.5.2) depending on ethanol or butanol
6.13.3 Isooctane (2,2,4–trimethyl pentane)—99.5 % mini-
blended gasoline, respectively. If the gasoline being tested is
mum purity. This is the solvent used for dilution.
blended with ethanol and not butanol, the composite mix
6.14 Method Chemicals for Resolution Validation: described in 9.5.2 for butanol blend does not need to be
6.14.1 Sec-butanol—99.5 % minimum purity.
prepared. However, if the laboratory wants to prepare this
6.14.2 Iso-butanol—99.5 % minimum purity.
composite mix, the composite mix described in 9.5.2 may be
6.14.3 n-butanol—99.5 % minimum purity.
used for establishing backflush time for both blended fuels.
6.14.4 n-propanol—99.5 % minimum purity.
8.3.1.3 Record the time when toluene returns to baseline
6.14.5 Ethanol—99.5 % minimum purity (200 proof).
from the pre-column via the restrictor. A chromatogram from
the pre-column through the restrictor demonstrating this is
7. Sampling
shown in Fig. A1.8 for standard #1, and in Fig. A1.9 for the
7.1 Gasoline—(Warning—Extremely flammable. Vapors composite mix in 9.5.2.
harmful if inhaled.) Samples to be analyzed by this test method 8.3.1.4 Next monitor the effluent from the analytical column
shall be obtained using the procedures outlined in Practice using the backflush time established in 8.3.1.3. Inject standard
D4057. #1 (9.2) or composite mix for butanol blend (9.5.2). Record the
area for toluene.
8. Apparatus, Configurations, and Method Setup
8.3.1.5 Reduce the backflush time by 0.02 min. Inject
standard #1 or composite mix. Record the area for toluene.
8.1 Configuration—Illustrated and discussed in this test
method are three configurations used by the laboratories that Repeat this step until the response for toluene begins to
decrease.
have participated in the interlaboratory study (ILS). Figs. A1.5
and A1.6 contain graphical representations of these configura- 8.3.1.6 The backflush time for the method will be the time
tions and Table A1.1 provides the method parameters. Valve- recorded before the time when toluene decreased. An example
based systems for backflushing may be used and such a chromatogram from the analytical column of standard #1 is in
Fig. A1.10 and an example chromatogram of composite mix
configuration is displayed in Fig. A1.7 and was also used in the
ILS. Other configurations may be used provided all of the described in 9.5.2 is located in Fig. A1.11.
requirements and criteria in this test method are met, such as 8.3.2 Configuration B, Single Detector Configuration—To
signal to noise (S/N), resolution, calibration, quality control monitor the flow from the pre-column to establish the
requirements, and so forth, which are discussed in 8.5 and backflush time, the analytical column is removed from the FID
Section 12. and left in the GC oven as displayed in Fig. A1.3. (Warning—
D3606 − 24
Use caution if using hydrogen as carrier gas; if possible, vent and/or temperature needs to be long enough and temperature
externally of the gas chromatograph’s oven.) The restrictor is high enough to ensure n-butanol elutes from the analytical
installed into the FID. column. Use the composite mix in 9.5.2 for this determination.
8.3.2.1 Follow procedures from 8.3.1.1 through 8.3.1.3. Refer to the chromatogram found in Figs. A1.10 and A1.11.
8.3.2.2 Remove restrictor from the detector and install the 8.5.5 Attaining Detection Limit for Benzene—Using stan-
analytical column in the detector for analysis as shown in Fig. dard mix #7 (9.1), ensure that at least a signal to noise of 50 to
A1.4. 1 is attained for benzene. If this is not achieved, reduce the
8.3.2.3 Follow procedures from 8.3.1.4 to 8.3.1.6. instrument’s split flow or increase the injection volume, not to
8.3.3 Configuration C, No Pre-column Configuration—This exceed 0.5 μL until this criteria is attained.
configuration is not capable of monitoring the chromatography 8.5.6 Calibration Requirements—A linear regression, or
from the pre-column. An example of this configuration is weighted curve, shall meet a criterion correlation coefficient
shown in Figs. A1.5 and A1.6 configuration C. equal to or greater than 0.999.
8.3.3.1 Inject 0.1 μL to 0.5 μL of standard #1 (9.2) or the
9. Calibration and Standardization
composite mix (9.5) depending on ethanol or butanol blended
gasoline using a backflush time equal to the run-time.
9.1 Standards—Prepare seven standards (Table 1) covering
8.3.3.2 Decrease the backflush time by 1 min intervals until
the range 0.06 % to 5 % by volume benzene and 0.5 % to 20 %
toluene is no longer present in the chromatogram.
by volume toluene. For each standard, measure the volume of
8.3.3.3 Increase the backflush time by 0.02 min until tolu-
benzene and of toluene listed below into a 100 mL volumetric
ene provides a stable area count. The shortest time when the
flask. Dilute to volume with isooctane (2,2,4-
toluene has a stable response is the backflush time.
trimethylpentane), with all components and glassware at am-
bient temperature.
8.4 Re-establishing Backflush Time—As the column ages
with use, retention times will become shorter. If the quality
9.2 Final Standard Preparation—Accurately measure
control samples fail, backflush time may need to be re-
1.0 mL of MIBK into a 25 mL-volumetric flask, and fill to the
established on the same column, set especially if a retention
mark using the first standard (9.1). Continue doing this until all
time shift is when a new pre-column, analytical column, and/or
seven (7) blends (concentrations) have been prepared.
restrictor are employed, the backflush time will need to be NOTE 4—Commercially prepared calibration standards may be used,
including those that are pre-mixed with the MIBK internal standard. The
re-established.
purity of target compounds is given in 6.12.
8.5 Method Criteria:
9.3 Chromatographic Analysis—Chromatograph each of the
8.5.1 Verify Resolution for Gasoline Blended With
calibration blends using the conditions established in Section 8
Ethanol—Using the injection volume and other parameters that
using the automated sampling system of the gas chromato-
will be used for sample analysis, inject either composite mix
graph.
described in 9.5.1 or 9.5.2. Benzene shall be sufficiently
9.4 Calibration—Using a computer data system (CDS),
resolved from ethanol and having a resolution (R) value >2.
measure the area of the benzene and toluene aromatic peaks
The internal standard (MIBK) shall have an R value >1.5.
and of the internal standard peak. Calculate the area ratio of the
Refer to Fig. A1.10 for standard #1 or Fig. A1.11 for an
benzene peak area to the MIBK peak area. Plot the concentra-
example chromatogram displaying resolution for composite
tion of benzene versus the area ratio. Make the same calcula-
mix from 9.5.2.
tion and plot similarly for toluene. Refer to Fig. A1.12 for an
8.5.2 Verify Resolution for Gasoline Blended With
example calibration curve. The calibration shall be linear with
Butanol—Using the injection volume and parameters estab-
a correlation coefficient greater than or equal to 0.999. Weigh-
lished above and that will be used for sample analysis, inject
ing the calibration curve 1/y is allowed and will provide
composite mix described in 9.5.2. The resolution requirements
enhanced accuracy for lower concentration target samples.
are as follows: benzene R > 2; MIBK R > 1.5; toluene R > 0.6.
NOTE 5—Some CDS systems plot the area ratio versus the concentra-
Refer to an example chromatogram found in Fig. A1.11.
tion ratio of the benzene and toluene to that of the internal standard.
8.5.3 Resolution calculation may be performed by the CDS
Consult the system guidelines.
or manually. If using a CDS, ensure the CDS is using the
9.5 Composite Mix for Ethanol and Butanol Blends—The
proper resolution calculation, as follows:
composite mix will ensure a necessary separation of ethanol
1.18 T 2 T
~ !
p2 p1
R 5 (1)
p2
W 1W
h1⁄2 h2⁄2
TABLE 1 Seven Standards
where:
Benzene Toluene
R = the resolution of peak 2, Std #
Volume Volume
p2
mL mL
percent percent
T = the retention time of peak 1,
p1
T = the retention time of peak 2, 1 5 5 20 20
p2
2 2.5 2.5 15 15
W = the width of peak 1 at half height, and
h1/2
3 1.25 1.25 10 10
W = the width of peak 2 at half height.
h2/2
4 0.67 0.67 5 5
5 0.33 0.33 2.5 2.5
8.5.4 Determining Method Run Time or Completion of
6 0.12 0.12 1 1
Chromatography for Butanol Blended Gasoline—Because
7 0.06 0.06 0.5 0.5
n-butanol may be an isomer in the butanol blend, the runtime
D3606 − 24
from benzene (R > 2), and that possible contaminants in the example), make six injections of standard #4 (9.2). Calculate
butanol blend will not co-elute with benzene (R > 2), toluene the standard deviation from the six results from the six
(R > 0.6) and MIBK (R > 1.5). injections. Calculate 2.77 × the standard deviation obtained.
9.5.1 Composite Mix for Ethanol Blend—Prepare a solution This quantity shall meet repeatability as published 14.1.1.
by volume that is 20 % ethanol, 1 % benzene, 4 % MIBK and Thereafter establish statistical quality control charting (SQC)
20 % toluene in iso-octane. This solution may also be used to for each batch of analysis analyzed using a production a sample
determine the backflush time. similar in composition to samples to be analyzed.
9.5.2 Composite Mix for Ethanol and Butanol Blends—
12.2 Reference Material—Analyze one or more reference
Prepare a solution by volume that is 20 % ethanol, 1 %
material of known accepted reference value (ARV), such as
benzene, 4 % sec-butanol, 0.1 % n-propanol, 4 % MIBK, 20 %
from NIST and/or an independent certified control standard, or
toluene, 20 % iso-butanol, 5 % n-butanol in iso-octane. This
meeting the check standard requirement as specified in Practice
solution may also be used to determine the backflush time.
D6299 upon setting up the test method, post maintenance
(calibration, column replacement, cut time adjustments, and so
10. Procedure
forth) and at least quarterly to confirm proper set-up and
10.1 Preparation of Sample—Accurately measure 1.0 mL of
calibration of the gas chromatograph. Test results shall agree
MIBK into a 25 mL volumetric flask. Fill to the mark with the with within the 95 % confidence level or reproducibility of the
sample to be analyzed and mix well.
benzene or toluene components divided by the square root of 2.
In addition follow any other specification requirements per
10.2 Chromatographic Analysis—Chromatograph the
regulatory or commercial application(s). Monitor the perfor-
sample, using the conditions established in Section 8 and as
mance of the reference material(s) using SQC charting in
used for the calibration. The GC column flow must be turned
accordance with Practice D6299.
to backflush mode at the time determined in 8.3 so that
undesirable components do not enter the analytical column.
13. Report
Fig. A1.13 is an example of a Test Method D3606 proficiency
13.1 Report the benzene and toluene contents in liquid
sample analyzed using configuration A.
volume percent to the nearest 0.01 %, and indicate that the
10.3 Interpretation of Chromatogram—Identify the
results are from “D3606 Procedure A.”
benzene, toluene, and the internal standard MIBK peaks from
13.2 In accordance with Practice D6300, to accommodate
the retention times of the standards.
normal random testing variation, the lowest reportable test X
NOTE 6—The order of elution will be nonaromatic hydrocarbons,
benzene, MIBK and toluene using the dimethyl poly siloxane and polar
result in volume percent is computed as follows:
column combination used in the ILS.
X 5 lowest reportable test result of this test method
10.4 Measurement of Area—Measure the areas under the
5 @lowest retained ILS sample mean
benzene, toluene aromatic peaks and under the MIBK peak.
2 R ~evaluated at the lowest retained ILS sample mean!# (4)
11. Calculation
13.2.1 For benzene: X = 0.07
lowest reportable
13.2.2 For toluene: X = 0.36
11.1 Calculate the ratios of the peak areas of benzene and lowest reportable
toluene to the peak area of MIBK. Determine from the
13.3 In accordance with Practice D6300, to accommodate
calibration curve the liquid volume percent of benzene and
normal random testing variation, the highest reportable test X
toluene corresponding to the calculated peak ratios. A CDS that
result in volume percent is computed as follows:
has the capability of processing this calibration and quantitat-
X 5 highest reportable test result of this test method
ing results may be used.
5 @highest retained ILS sample mean
11.2 If the results are desired on a mass basis, convert to
1 R evaluated at the highest retained ILS sample mean (5)
~ !#
mass percent as follows:
13.3.1 For benzene: X = 5.96
Benzene, mass percent 5 V ⁄ D × 0.8844 (2) highest reportable
~ !
B
13.3.2 For toluene: X = 19.7
highest reportable
where:
14. Precision and Bias
V = volume percent benzene, and
B
D = relative density of sample at 15.6/15.6 °C (60/60 °F).
14.1 The following criteria should be used for judging the
acceptability of results (95 % confidence). The user should
Toluene, mass percent 5 ~V ⁄ D! × 0.8719 (3)
T
choose the precision statement that reflects the concentration
where:
range of each component under study.
V = volume percent toluene, and
T 14.1.1 Repeatability—The difference between two indepen-
D = relative density of sample at 15.6/15.6 °C (60/60 °F).
dent results obtained by the same operator in a given laboratory
applying the same test method with the same apparatus under
12. Quality Control
12.1 Test for System Stability and Repeatability—On setting
Supporting data have been filed at ASTM International Headquarters and may
up the method for the first time and thereafter when major
be obtained by requesting Research Report RR:D02-2004. Contact ASTM Customer
maintenance is performed (change in columns and flows, for Service at [e-mail].
D3606 − 24
TABLE 3 Reproducibility–Procedure A (WCOT Column)
constant operating conditions on identical test material within
short intervals of time would exceed the values in Table 2 with
NOTE 1—X = the average of two results in volume percent of the
an approximate probability of 5 % (one case in 20 in the long
component; each result is to be within the ranges given below.
run) in the normal and correct operation of the test method.
Component Volume percent Reproducibility
14.1.2 Reproducibility—The difference between two single
Benzene 0.12 to 5.2 0.1462 (X + 0.2)
Toluene 0.4 to 19.7 0.04659 (X + 0.5)
and independent results obtained by different operators apply-
ing the same test method in different laboratories using
different apparatus on identical test material would exceed the
TABLE 4 Repeatability/Reproducibility Example
values in Table 3 with an approximate probability of 5 % (one
(Benzene)–Procedure A (WCOT Column)
case in 20 in the long run) in the normal and correct operation
Benzene
of the test method. Repeatability Reproducibility
Volume percent
NOTE 7—The sample compositions and results of the cooperative study
0.10 0.010 0.044
are filed at ASTM International.
0.20 0.013 0.058
0.30 0.016 0.073
14.2 Bias—Since there is no accepted reference method
0.40 0.019 0.088
suitable for measuring bias for this method, no statement of
0.50 0.022 0.102
bias can be made.
0.60 0.026 0.117
0.70 0.029 0.132
14.2.1 Between Method Bias between Procedure A and
0.80 0.032 0.146
Procedure B for Benzene:
0.90 0.035 0.161
14.2.1.1 A between method bias assessment of Test Method
1.00 0.038 0.175
2.00 0.070 0.322
D3606 Procedure A versus Procedure B for the determination
3.00 0.102 0.468
of benzene in spark-ignition fuel (gasolines) was conducted
4.00 0.134 0.614
using data from the ILS of Procedure A which also included a
5.00 0.167 0.760
parallel ILS using Procedure B using identical samples. The
assessment was performed in accordance with the requirements
TABLE 5 Repeatability/Reproducibility Example
of Practice D6708 with a successful outcome and is docu-
(Toluene)–Procedure A (WCOT Column)
mented in Research Report RR:D02-2004.
Toluene
Repeatability Reproducibility
NOTE 8—Procedure B is based on the original version of D3606 which
Volume percent
uses packed columns and which has been used by regulatory agencies for
0.4 0.016 0.042
benzene. Users of this D3606 test method should consult proper regula-
1.0 0.027 0.070
tions on its use as regulations may change.
2.0 0.044 0.116
3.0 0.062 0.163
14.2.1.2 The degree of agreement between results from Test
4.0 0.080 0.210
Method D3606 Procedure A versus Procedure B can be further
5.0 0.097 0.256
6.0 0.115 0.303
improved by applying a correlation equation (Eq 6) (Research
3 7.0 0.133 0.349
Report RR:D02-2004 ). There were no discernable sample-
8.0 0.150 0.396
specific biases as determined by D6708.
9.0 0.168 0.443
10.0 0.186 0.489
14.2.1.3 Correlation Equation:
11.0 0.203 0.536
14.2.1.4
12.0 0.221 0.582
13.0 0.239 0.629
Predicted D3606 Procedure B benzene
14.0 0.256 0.676
5 bias corrected Procedure A benzene 5 C 10.017 (6)
15.0 0.274 0.722
procedure A
16.0 0.292 0.769
where:
17.0 0.309 0.815
18.0 0.327 0.862
C = volume percent benzene as reported by Test
procedure A
19.0 0.345 0.909
Method D3606 Procedure A.
20.0 0.362 0.955
(1) The correlation equation is applicable to test results in
the range of 0.07 % to 5.96 % by volume as determined and
reported by Test Method D3606 Procedure A.
of toluene was conducted using data from the ILS of Procedure
14.2.2 Between Method Bias between Procedures A and B
A which also included a parallel ILS using Procedure B using
Toluene:
identical samples. The assessment was performed in accor-
14.2.2.1 A between method bias assessment of Test Method
dance with the requirements of Practice D6708 with a success-
D3606 Procedure A versus Procedure B for the determination
ful outcome and is documented in Research Report RR:D02-
2004.
14.2.2.2 The degree of agreement between results from Test
TABLE 2 Repeatability–Procedure A (WCOT Column)
Method D3606 Procedure A toluene versus Procedure B
NOTE 1—X = the average of two results in volume percent of the
toluene can be further improved by applying a correlation
component; each result is to be within the ranges below.
equation (Eq 7) (Research Report RR:D02-2004 ). There were
Component Volume percent Repeatability
no discernable sample-specific biases as defined in Practice
Benzene 0.12 to 5.2 0.03202 (X + 0.2)
D6708.
Toluene 0.4 to 19.7 0.01767 (X + 0.5)
14.2.2.3 Correlation Equation:
D3606 − 24
TABLE 6 Comparison of Precision between Procedure A and
18. Apparatus
Procedure B in the Range of 0.10 % to 1.50 % Volume for
18.1 Chromatograph—Any multidimensional packed col-
Benzene
umn gas chromatographic instrument configuration that has a
Procedure A Procedure B
Benzene backflush system and thermal conductivity detector, and that
percent Repeatability Reproducibility Repeatability Reproducibility
can meet the specification of this test method, such as column
volume
resolution, can be used.
0.10 0.010 0.044 0.013 0.063
0.30 0.016 0.073 0.019 0.089 18.1.1 Two backflush systems are shown. Fig. A2.1 is a
0.50 0.022 0.102 0.025 0.115
switching valve system and Fig. A2.2 is a pressure system.
0.70 0.029 0.132 0.031 0.141
Either one can be used.
0.90 0.035 0.161 0.037 0.167
1.10 0.042 0.190 0.043 0.193
18.2 Columns:
1.30 0.048 0.219 0.049 0.219
18.2.1 Columns A (Precolumn) and B (Analytical
1.50 0.054 0.249 0.055 0.245
Column)—Annex A2.2 gives an example of a commercial
column set that has been used successfully for samples
containing ethanol. In addition, Annex A2.4 gives an additional
column set originally proposed by the U.S. Environmental
14.2.2.4
Protection Agency (EPA) that may be adequate for this
Predicted D3606 Procedure B toluene
analyses. Other packed column sets that give a resolution from
5 bias corrected Procedure A toluene 5 1.01*C 2 0.025 ethanol as specified in 21.3 may be used.
Procedure A
(7)
18.3 Chromatography Data System (CDS)—An electronic
device capable of graphical presentation and integration of the
where:
chromatogram peaks.
C = volume percent toluene as reported by Test
Procedure A
18.4 Microsyringe—5 μL capacity.
Method D3606 Procedure A.
(1) The correlation equation is applicable to test results as
18.5 Volumetric Pipets, Class A—0.5 mL, 1 mL, 5 mL,
determined and reported by Test Method D3606 Procedure A in
10 mL, 15 mL, and 20 mL capacities (see Specifications E694
the range of 0.36 % to 20.64 % by volume toluene.
and E969).
18.6 Measuring Pipets—1 mL and 2 mL capacities cali-
15. Keywords
brated in 0.01 mL; 5 mL calibrated in 0.1 mL, for use in
15.1 aviation gasoline; benzene; gas chromatography; gaso-
dispensing volumes of benzene and toluene not covered by the
line; multidimensional gas chromatography; spark ignition
volumetric pipets (see Specifications E1044 and E1293) during
fuels; toluene
preparation of standard samples.
NOTE 9—Other volume dispensing equipment capable of delivering the
specified volumes within the stated tolerance limits may be used as an
PROCEDURE B—PACKED GAS
alternative to the requirements stated in 18.5 and 18.6.
CHROMATOGRAPHIC COLUMNS
18.7 Flasks—Class A volumetric (see Specification E288),
25 mL and 100 mL capacity.
16. Summary of Test Method
19. Materials
16.1 An internal standard, sec-butanol, is added to the
sample. The sample is then introduced into a gas chromato-
19.1 Carrier Gas—Helium, 99.99 % mol pure or better.
graph (GC) equipped with two packed GC columns connected
(Warning—Compressed gas under high pressure.)
in series. The sample passes first through a pre-column packed
19.2 Solvents:
with a nonpolar or equivalent phase, which separates the
19.2.1 Methanol—Reagent grade. (Warning—Flammable.
lighter components according to boiling point. After toluene
Vapor harmful. Can be fatal or cause blindness if swallowed or
has eluted, the flow through the nonpolar column is reversed,
inhaled.)
flushing out the components heavier than toluene. The lighter
19.3 Internal Standard:
components then pass through an analytical column packed
19.3.1 sec-butanol—99.5 % mol minimum purity. Free of
with a stationary phase capable of separating benzene and
benzene and toluene. (Warning—Flammable. Vapor can be
toluene from ethanol and other hydrocarbons and oxygenates
harmful.)
such as methanol, MTBE, TAME, ETBE, and butanols. The
eluted components are detected by a thermal conductivity
19.4 Calibration Standards:
+
detector (TCD). The detector response is recorded, the peak
19.4.1 Benzene—99 % mol. (Warning—Poison. Carcino-
areas are measured and the concentration of each component is
gen. Harmful or fatal if swallowed. Extremely flammable.
calculated with reference to the internal standard.
Vapors can cause flash fires.)
+
19.4.2 Isooctane (2,2,4–trimethyl pentane)—99 % mol.
17. Significance and Use
(Warning—Extremely flammable. Harmful if inhaled.)
17.1 Knowledge of the concentration of benzene may be 19.4.3 Toluene—(Warning—Flammable. Vapor harmful.)
+
required for regulatory use, control of gasoline blending, 19.4.4 n-nonane—99 % mol. (Warning—Flammable. Va-
and/or process optimizations. por harmful.)
D3606 − 24
TABLE 7 Seven Standard Samples
20. Sampling
Benzene Toluene
20.1 Spark Ignition Fuel (for example, “Gasoline”)—
Std #
Volume % mL Volume % mL
(Warning—Extremely flammable. Vapors harmful if inhaled.)
1 5 5 20 20
Samples to be analyzed by this test method shall be obtained
2 2.5 2.5 15 15
using the procedures outlined in Practice D4057.
3 1.25 1.25 10 10
4 0.67 0.67 5 5
21. Configuration of Apparatus and Establishment of
5 0.33 0.33 2.5 2.5
6 0.12 0.12 1 1
Conditions
7 0.06 0.06 0.5 0.5
21.1 Following manufacturer’s guidelines and/or suggested
details in A2.2, A2.3, and A2.4 optimize the chromatographic
system.
1.18~T 2 T !
p2 p1
21.1.1 Column System Setup for Valve Backflushing—The R 5 (8)
p2
W 1W
h1⁄2 h2⁄2
following procedure provides a general guideline for optimiz-
where:
ing a system using valve switching as shown in Fig. A2.1.
Several operational conditions are given in Table A2.1.
R = the resolution of peak 2,
p2
21.1.1.1 Set the valve in the forward flow mode with T = the retention time of peak 1,
p1
T = the retention time of peak 2,
columns A and B in series (Fig. A2.2), and adjust the primary
p2
W = the width of peak 1 at half height, and
flow control to give the desired flow. Measure the flow rate at h1/2
W = the width of peak 2 at half height.
the detector vent, sample side. h2/2
21.1.1.2 Set the valve in the backflush position, measure the
21.4 To ensure proper resolution at low concentration
flow rate at the detector vent, sample side. If the flow has
ranges, the ethanol needs to have minimal peak tailing. A2.2
changed, adjust the secondary or auxiliary flow control to
and A2.4 describe the recommended peak symmetry for
obtain the correct flow. Flows should match to within 61 cm /
ethanol and the ethanol/benzene resolution required. It is
min.
recommended that final system optimization be verified against
21.1.1.3 Change the valve from forward flow to the
certified reference materials containing benzene at several
backflush position several times and observe the baseline.
concentration levels of interest and ethanol present at a level in
There should be no baseline shift or drift after the initial valve
the expected samples to confirm the accuracy of the analyses.
kick that results from the pressure surge. If there is a baseline
22. Calibration and Standardization
shift, increase or decrease the secondary flow control slightly
to balance the baseline. A persistent drift could indicate leaks
22.1 Standard Samples—Prepare seven standard samples
somewhere in the system.
(Table 7) covering the range 0.06 % to 5 % by volume benzene
and 0.5 % to 20 % by volume toluene as follows: For each
21.2 Determine Time to Backflush—The time to backflush
standard, measure the volume of benzene and of toluene listed
will vary for each column system and must be determined
below into a 100 mL volumetric flask. Dilute to volume with
experimentally as follows. Table A2.1 gives examples of
backflush times. Prepare a mixture of 5 % by volume isooctane isooctane (2,2,4–trimethyl pentane), with all components and
glassware at ambient temperature.
in n-nonane. With the valve configuration in the forward flow
mode, inject 1 μL of the isooctane-n-nonane mixture. Allow the
22.2 Calibration Blends—Accurately measure 1.0 mL of
chromatogram to run until the n-nonane has eluted and the
sec-butanol into a 25 mL volumetric flask, and fill to the mark
detector signal has returned to baseline. Measure the time in
with the first standard sample (22.1). Continue doing this until
seconds, from the injection until the detector signal returns to
all blends have been prepared.
baseline between the isooctane and n-nonane peaks. At this
NOTE 10—Commercially prepared calibration standards may be used,
point all of the isooctane, but essentially none of the n-nonane, including those that are pre-mixed with the sec-butanol internal standard.
should have eluted. Repeat the run, including the injection, but
22.3 Chromatographic Analysis—Chromatograph each of
switching the system to the backflush mode at the predeter-
the calibration blends using the conditions established in 21.4
mined “time to backflush.” This should result in a chromato-
using the following injection technique:
gram of isooctane with little or no n-nonane visible. If
22.4 Injection of Sample:
necessary, make additional runs, adjusting the “time to
22.4.1 Use an automatic liquid sample injection system. If
backflush” until this condition of all the isooctane and little or
manual injections are to be made, the injection technique in
no n-nonane is attained. The “time to backflush” so established,
22.4.2 is necessary so that sharp symmetrical peaks will be
including the actual valve operations, must be used in all
obtained.
subsequent calibrations and analyses. It is also valid to set
backflush time after toluene elutes. NOTE 11—ILS precision was based using automated injection systems.
21.3 Resolution of Ethanol/Benzene and Sec-butanol Ben- 22.4.2 Flush the 5 μL microsyringe at least three times with
zene Pairs—Resolution calculation may be performed by the the sample mixture and then fill with about 3 μL of the sample.
CDS or manually. The resolution shall be greater than 1.5 using (Avoid including any air bubbles in the syringe). Slowly eject
calibration standard 4 (Table 7) for benzene. If using a CDS, the sample until 2.0 μL remains in the syringe; wipe the needle
ensure the CDS is using the proper resolution calculation, as with tissue and draw back the plunger to admit 1 μL to 2 μL of
follows: air into the syringe. Insert the needle of the syringe through the
D3606 − 24
septum cap of the chromatograph and push until the barrel of 25. Report
the syringe is resting against the septum cap; then push the
25.1 Report the benzene and toluene contents in liquid
plunger to the hilt and remove the syringe immediately from
volume percent to the nearest 0.01 %. Indicate that result is
the chromatograph.
from “D3606 Procedure B.”
22.5 Calibration—Measure the area of both aromatic peaks
25.2 In accordance with Practice D6300, to accommodate
and of the internal standard peak. Calculate the ratio of the
normal random testing variation, the lowest reportable test X
benzene peak area to the sec-butanol and the ratio of concen-
result in volume percent is computed as follows:
trations of benzene to that of the sec-butanol. Plot the area
X 5 lowest reportable test result of this test method
ratios versus and concentration ratios. Make the same calcula-
5 lowest retained ILS sample mean
@
tion and plot for toluene. The calibrations shall be linear (Fig.
A2.6).
2 R ~evaluated at the lowest retained ILS sample mean!# (11)
NOTE 12—Some CDS systems plot the area ratio versus the concentra-
25.2.1 For benzene: X = 0.04
tion ratio of the benzene and toluene to that of the internal standard. lowest reportable
25.2.2 For toluene: X = 1.7
Consult the system guidelines.
lowest reportable
25.3 In accordance with Practice D6300, to accommodate
23. Procedure
normal random testing variation, the highest reportable test X
23.1 Preparation of Sample—Accurately measure 1.0 mL of
result in volume percent is computed as follows:
sec-butanol into a 25 mL volumetric flask. Fill to the mark with
X 5 highest reportable test result of this test method
the sample to be tested and mix well.
5 @highest retained ILS sample mean
23.2 Chromatographic Analysis—Chromatograph the
1 R evaluated at the highest retained ILS sample mean (12)
~ !#
sample, using the conditions established in Section 21 “time to
backflush” and the injection technique described in 22.4. The 25.3.1 For benzene: X = 5.25
highest reportable
valves must be turned to backflush mode at the time deter- 25.3.2 For toluene: X = 21.2
highest reportable
mined in 21.2 so that undesirable components do not enter
26. Quality Control
Column B.
26.1 Test for System Stability and Repeatability—On setting
23.3 Interpretation of Chromatogram—Identify on the chro-
up the method for the first time and thereafter when major
matogram the benzene, toluene, and the internal standard
main
...

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: D3606 − 22 D3606 − 24
Standard Test Method for
Determination of Benzene and Toluene in Spark Ignition
Fuels by Gas Chromatography
This standard is issued under the fixed designation D3606; 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 quantitation in liquid volume percent of benzene and toluene in finished motor and aviation spark
ignition fuels by gas chromatography. This test method has two procedures: Procedure A uses capillary column gas
chromatography and Procedure B uses packed column gas chromatography. Procedures A and B have separate precisions.
1.2 The method has been evaluated for benzene using a D6300-compliant Interlaboratory Study (ILS), with the lowest and highest
ILS sample concentration means as follows: (1) Procedure A between 0.12 % and 5.2 % by volume and (2) Procedure B between
0.10 % and 5.0 % by volume.
1.3 The method has been evaluated for toluene using a D6300-compliant Interlaboratory Study (ILS), with the lowest and highest
ILS sample concentration means as follows: (1) Procedure A between 0.4 % and 19.7 % by volume, and (2) Procedure B between
2.0 % and 20.0 % by volume.
1.4 For reporting, the lowest and highest concentration ranges for benzene and toluene for Procedure A of this test method per
Practice D6300 see 13.2.
1.5 For reporting, the lowest and highest concentration ranges for benzene and toluene for Procedure B of this test method per
Practice D6300 see 25.2.
1.6 For benzene by Procedure A, the following oxygenated fuels are included in the working range: (1) ethanol up to 20 % by
volume (E20); (2) methanol up to 10 % by volume (M10). Fuels M85 and E85 were excluded.
1.7 For benzene by Procedure B the following oxygenated fuels are included in the working range: (1) ethanol up to 20 % by
volume (E20); (2) methanol up to 10 % by volume (M10). Fuels M85 and E85 were excluded.
1.8 For toluene by Procedure A the following oxygenated fuels were included in the working range: (1) ethanol up to 20 % by
volume (E20); (2) M85 and E85.
1.9 For toluene by Procedure B the following oxygenated fuels are included in the working range: (1) ethanol up to 20 % by
volume (E20); (2) M85 and E85.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.04.0L on Gas Chromatography Methods.
Current edition approved Sept. 1, 2022March 1, 2024. Published October 2022March 2024. Originally approved in 1977. Last previous edition approved in 20212022 as
D3606 – 21.D3606 – 22. DOI: 10.1520/D3606-22.10.1520/D3606-24.
*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
D3606 − 24
1.10 Procedure A uses MIBK as the internal standard. Procedure B uses sec-butanol as the internal standard. The use of Procedure
B for fuels containing blended butanols requires that sec-butanol be below the detection limit in the fuels as sec-butanol is an
internal standard. For Procedure B, an alternative separation column set described in the annex (A2.3, Annex Approach B) uses
MEK as the internal standard when butanols may be blended into gasolines.
1.11 This test method includes a between method bias section for benzene based on Practice D6708 bias assessment between Test
Method D3606 Procedure B and Test Method D5769. It is intended to allow Test Method D3606 Procedure B to be used as a
possible alternative to Test Method D5769. The Practice D6708 derived benzene correlation equation is applicable for benzene
measurements in the reportable range from 0.06 % to 2.88 %2.76 % by volume as reported by Test Method D3606 Procedure B
(see 27.2.1). The correlation complies with EPA’s Performance Based Measurement System (PBMS).
1.12 Correlation equations are included in the between test methods bias section 14.2.1 of Procedure A to convert Procedure A
to the Procedure B volume percent values for benzene and toluene. The correlations are applicable in the concentration ranges of
0.07 % to 5.96 % by volume for benzene and 0.36 % to 20.64 % by volume for toluene as reported by Procedure A.
1.13 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.14 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.
1.15 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:
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D5769 Test Method for Determination of Benzene, Toluene, and Total Aromatics in Finished Gasolines by Gas
Chromatography/Mass Spectrometry
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
D6708 Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport
to Measure the Same Property of a Material
E288 Specification for Laboratory Glass Volumetric Flasks
E355 Practice for Gas Chromatography Terms and Relationships
E694 Specification for Laboratory Glass Volumetric Apparatus
E969 Specification for Glass Volumetric (Transfer) Pipets
E1044 Specification for Glass Serological Pipets (General Purpose and Kahn)
E1293 Specification for Glass Measuring Pipets
3. Terminology
3.1 This test method makes references to terms whose definitions may be found in Practice E355 and Terminology D4175.
PROCEDURE A—CAPILLARY WCOT GAS CHROMATOGRAPHIC SYSTEMS
4. Summary of Test Method
4.1 An internal standard, methyl isobutyl ketone (MIBK) is added to the sample which is then introduced into a heated capillary
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.
D3606 − 24
or programmed temperature vaporization (PTV) injector on a gas chromatograph (GC). The GC is equipped with two columns
connected in series. The sample passes first through a column with a nonpolar phase. After toluene has eluted, the flow through
the nonpolar column is reversed, flushing out the components heavier than toluene. The toluene and lighter components enter a
second column which separates the aromatic and nonaromatic compounds. The eluted components are detected by a flame
ionization detector (FID). The detector response is recorded, the peak areas are measured, and the concentration of each component
is calculated with reference to the internal standard.
5. Significance and Use
5.1 Knowledge of the concentration of benzene may be required for regulatory use, control of gasoline blending, and/or process
optimizations.
6. Apparatus and Chemicals
6.1 Chromatograph—Any gas chromatograph that has the capability of performing multidimensional chromatography that can be
operated at approximately the conditions described in this method, and meets all the required chromatographic specifications and
method criteria specified in 8.5 and 12.
6.1.1 Sample Introduction System—Automated sample injection system such as a liquid autosampler.
6.1.2 Injector—Capillary split/splitless injector.
6.1.3 Detector—At least one flame ionization detector (FID) is required. In a two FID configuration, the optional second detector
is used to monitor the effluent from the pre-column (refer to configuration A in 8.1.1).
6.2 Columns:
6.2.1 Pre-column—Non-polar, boiling point column, which performs the first separation of the hydrocarbons. A dimethyl
polysiloxane phase column with dimensions of 30 m by 0.25 mm by 0.50 μm has been used successfully. Any column with
equivalent or better chromatographic efficiency and selectivity may be used.
6.2.2 Analytical Column—This column separates aromatic and non-aromatic compounds. A polyethylene glycol (polar ‘wax’)
column with the dimensions 60 m by 0.32 mm by 1.0 μm has been used successfully. Any column capable of meeting the
resolution requirement in 8.5 may be employed.
6.2.3 Restrictor—Uncoated deactivated fused silica. A 100 μm by 42.5 cm restrictor was successfully used when developing this
method.
6.3 Chromatography Data System (CDS)—An electronic device capable of graphical presentation and integration of the
chromatogram peaks.
6.4 Microsyringe—Capable of making injections from 0.5 μL to 1.0 μL.
6.5 Volumetric Pipets, Class A—0.5 mL, 1 mL, 5 mL, 10 mL, 15 mL, and 20 mL capacities (see Specifications E694 and E969).
6.6 Measuring Pipets—1 mL and 2 mL capacities calibrated in 0.01 mL; 5 mL calibrated in 0.1 mL, for use in dispensing volumes
of benzene and toluene not covered by the volumetric pipets (see Specifications E1044 and E1293) during preparation of standard
samples (see 9.1).
NOTE 1—Other manual or automated volume dispensing equipment capable of delivering the specified volumes within the stated tolerance limits may
be used as an alternative to the requirements stated in 6.5 and 6.6.
6.7 Flasks—Volumetric, 25 mL and 100 mL capacity (see Specification E288).
6.8 GC Carrier Gas—Helium or hydrogen 99.999 % pure. (Warning—Compressed gas under high pressure; hydrogen
flammable.) A hydrogen generator may be used.
D3606 − 24
NOTE 2—When using hydrogen carrier gas, use precautions such as installation of hydrogen sensors in the gas chromatograph oven. It is recommended
that the hydrogen excess flow, such as from the splitter inlet, should be vented to a safe area such as a ventilated hood or appropriate exhaust approved
for such use. Use caution when performing maintenance by isolating the hydrogen source.
6.9 FID Gas—Air chromatographic grade, dry (Warning—Compressed gas under high pressure.) An air generator may be used
with purifier.
6.10 FID Gas—Hydrogen, 99.999 % pure (Warning—Compressed gas under high pressure; hydrogen flammable.) A hydrogen
generator may be used.
6.11 FID Make-up Gas, if Required (Refer to Manufacturer’s Requirements)—Nitrogen, 99.999 % pure. (Warning—Compressed
gas under high pressure.)
NOTE 3—Reference the instrument manual for specifics on how to establish required flow rates for a particular vendor’s instrument.
6.12 Chemicals—(Warning—These chemicals are dangerous, harmful, or fatal if swallowed or inhaled. They are flammable to
extremely flammable. Vapors can cause flash fires.)
6.12.1 Internal Standard—Methyl Isobutyl Ketone (MIBK) 99.5 % pure.
6.13 Calibration Standards:
6.13.1 Benzene—99.5 % minimum purity. (Warning—Carcinogen.)
6.13.2 Toluene—99.5 % minimum purity.
6.13.3 Isooctane (2,2,4–trimethyl pentane)—99.5 % minimum purity. This is the solvent used for dilution.
6.14 Method Chemicals for Resolution Validation:
6.14.1 Sec-butanol—99.5 % minimum purity.
6.14.2 Iso-butanol—99.5 % minimum purity.
6.14.3 n-butanol—99.5 % minimum purity.
6.14.4 n-propanol—99.5 % minimum purity.
6.14.5 Ethanol—99.5 % minimum purity (200 proof).
7. Sampling
7.1 Gasoline—(Warning—Extremely flammable. Vapors harmful if inhaled.) Samples to be analyzed by this test method shall be
obtained using the procedures outlined in Practice D4057.
8. Apparatus, Configurations, and Method Setup
8.1 Configuration—Illustrated and discussed in this test method are three configurations used by the laboratories that have
participated in the interlaboratory study (ILS). Figs. A1.5 and A1.6 contain graphical representations of these configurations and
Table A1.1 provides the method parameters. Valve-based systems for backflushing may be used and such a configuration is
displayed in Fig. A1.7 and was also used in the ILS. Other configurations may be used provided all of the requirements and criteria
in this test method are met, such as signal to noise (S/N), resolution, calibration, quality control requirements, and so forth, which
are discussed in 8.5 and Section 12.
8.1.1 Configuration A—Has the capability of monitoring the effluent from the pre-column via a restrictor. This is a dual detector
D3606 − 24
system. One FID is used to monitor the analytical column’s effluent, and the other to monitor the effluent from the pre-column.
The second FID provides a quicker approach in determining backflush time. Figs. A1.1 and A1.2 represent examples of this
configuration.
8.1.2 Configuration B—Has the capability of monitoring the effluent from the pre-column via a restrictor; however, only one FID
is installed. Figs. A1.3 and A1.4 represent examples of this configuration.
8.1.3 Configuration C—Does not have the capability to monitor the effluent from the pre-column. Figs. A1.5 and A1.6 represent
an example of this configuration.
8.2 Conditioning Column—Install the pre-column, analytical column, and the restrictor, if the restrictor is being used as in
configurations A and B. Condition the columns per manufacturer’s instructions.
8.3 Determine Time to Backflush (BF)—Or backflush time, must be empirically determined for each system and column set used
by the laboratory. Optimization of backflush time is dependent upon the configuration used.
8.3.1 Configuration A, Dual Detector Configuration—Follow the instrument setup as shown in Figs. A1.1 and A1.2.
8.3.1.1 Establish analytical parameters set forth in Table A1.1 or parameters that have met method separation criteria as outlined
in 8.5. Ensure both detector channels are being collected by the CDS.
8.3.1.2 Inject 0.1 μL to 0.5 μL of standard #1 (9.2) or the butanol composite mix (9.5.2) depending on ethanol or butanol blended
gasoline, respectively. If the gasoline being tested is blended with ethanol and not butanol, the composite mix described in 9.5.2
for butanol blend does not need to be prepared. However, if the laboratory wants to prepare this composite mix, the composite mix
described in 9.5.2 may be used for establishing backflush time for both blended fuels.
8.3.1.3 Record the time when toluene returns to baseline from the pre-column via the restrictor. A chromatogram from the
pre-column through the restrictor demonstrating this is shown in Fig. A1.8 for standard #1, and in Fig. A1.9 for the composite mix
in 9.5.2.
8.3.1.4 Next monitor the effluent from the analytical column using the backflush time established in 8.3.1.3. Inject standard #1
(9.2) or composite mix for butanol blend (9.5.2). Record the area for toluene.
8.3.1.5 Reduce the backflush time by 0.02 min. Inject standard #1 or composite mix. Record the area for toluene. Repeat this step
until the response for toluene begins to decrease.
8.3.1.6 The backflush time for the method will be the time recorded before the time when toluene decreased. An example
chromatogram from the analytical column of standard #1 is in Fig. A1.10 and an example chromatogram of composite mix
described in 9.5.2 is located in Fig. A1.11.
8.3.2 Configuration B, Single Detector Configuration—To monitor the flow from the pre-column to establish the backflush time,
the analytical column is removed from the FID and left in the GC oven as displayed in Fig. A1.3. (Warning—Use caution if using
hydrogen as carrier gas; if possible, vent externally of the gas chromatograph’s oven.) The restrictor is installed into the FID.
8.3.2.1 Follow procedures from 8.3.1.1 through 8.3.1.3.
8.3.2.2 Remove restrictor from the detector and install the analytical column in the detector for analysis as shown in Fig. A1.4.
8.3.2.3 Follow procedures from 8.3.1.4 to 8.3.1.6.
8.3.3 Configuration C, No Pre-column Configuration—This configuration is not capable of monitoring the chromatography from
the pre-column. An example of this configuration is shown in Figs. A1.5 and A1.6 configuration C.
8.3.3.1 Inject 0.1 μL to 0.5 μL of standard #1 (9.2) or the composite mix (9.5) depending on ethanol or butanol blended gasoline
using a backflush time equal to the run-time.
8.3.3.2 Decrease the backflush time by 1 min intervals until toluene is no longer present in the chromatogram.
D3606 − 24
8.3.3.3 Increase the backflush time by 0.02 min until toluene provides a stable area count. The shortest time when the toluene has
a stable response is the backflush time.
8.4 Re-establishing Backflush Time—As the column ages with use, retention times will become shorter. If the quality control
samples fail, backflush time may need to be re-established on the same column, set especially if a retention time shift is when a
new pre-column, analytical column, and/or restrictor are employed, the backflush time will need to be re-established.
8.5 Method Criteria:
8.5.1 Verify Resolution for Gasoline Blended With Ethanol—Using the injection volume and other parameters that will be used
for sample analysis, inject either composite mix described in 9.5.1 or 9.5.2. Benzene shall be sufficiently resolved from ethanol
and having a resolution (R) value >2. The internal standard (MIBK) shall have an R value >1.5. Refer to Fig. A1.10 for standard
#1 or Fig. A1.11 for an example chromatogram displaying resolution for composite mix from 9.5.2.
8.5.2 Verify Resolution for Gasoline Blended With Butanol—Using the injection volume and parameters established above and that
will be used for sample analysis, inject composite mix described in 9.5.2. The resolution requirements are as follows: benzene R
> 2; MIBK R > 1.5; toluene R > 0.6. Refer to an example chromatogram found in Fig. A1.11.
8.5.3 Resolution calculation may be performed by the CDS or manually. If using a CDS, ensure the CDS is using the proper
resolution calculation, as follows:
1.18 T 2 T
~ !
p2 p1
R 5 (1)
p2
W 1W
h1⁄2 h2⁄2
where:
R = the resolution of peak 2,
p2
T = the retention time of peak 1,
p1
T = the retention time of peak 2,
p2
W = the width of peak 1 at half height, and
h1/2
W = the width of peak 2 at half height.
h2/2
8.5.4 Determining Method Run Time or Completion of Chromatography for Butanol Blended Gasoline—Because n-butanol may
be an isomer in the butanol blend, the runtime and/or temperature needs to be long enough and temperature high enough to ensure
n-butanol elutes from the analytical column. Use the composite mix in 9.5.2 for this determination. Refer to the chromatogram
found in Figs. A1.10 and A1.11.
8.5.5 Attaining Detection Limit for Benzene—Using standard mix #7 (9.1), ensure that at least a signal to noise of 50 to 1 is
attained for benzene. If this is not achieved, reduce the instrument’s split flow or increase the injection volume, not to exceed 0.5
μL until this criteria is attained.
8.5.6 Calibration Requirements—A linear regression, or weighted curve, shall meet a criterion correlation coefficient equal to or
greater than 0.999.
9. Calibration and Standardization
9.1 Standards—Prepare seven standards (Table 1) covering the range 0.06 % to 5 % by volume benzene and 0.5 % to 20 % by
volume toluene. For each standard, measure the volume of benzene and of toluene listed below into a 100 mL volumetric flask.
Dilute to volume with isooctane (2,2,4-trimethylpentane), with all components and glassware at ambient temperature.
9.2 Final Standard Preparation—Accurately measure 1.0 mL of MIBK into a 25 mL-volumetric flask, and fill to the mark using
the first standard (9.1). Continue doing this until all seven (7) blends (concentrations) have been prepared.
NOTE 4—Commercially prepared calibration standards may be used, including those that are pre-mixed with the MIBK internal standard. The purity of
target compounds is given in 6.12.
D3606 − 24
TABLE 1 Seven Standards
Benzene Toluene
Std #
Volume Volume
mL mL
percent percent
1 5 5 20 20
2 2.5 2.5 15 15
3 1.25 1.25 10 10
4 0.67 0.67 5 5
5 0.33 0.33 2.5 2.5
6 0.12 0.12 1 1
7 0.06 0.06 0.5 0.5
9.3 Chromatographic Analysis—Chromatograph each of the calibration blends using the conditions established in Section 8 using
the automated sampling system of the gas chromatograph.
9.4 Calibration—Using a computer data system (CDS), measure the area of the benzene and toluene aromatic peaks and of the
internal standard peak. Calculate the area ratio of the benzene peak area to the MIBK peak area. Plot the concentration of benzene
versus the area ratio. Make the same calculation and plot similarly for toluene. Refer to Fig. A1.12 for an example calibration
curve. The calibration shall be linear with a correlation coefficient greater than or equal to 0.999. Weighing the calibration curve
1/y is allowed and will provide enhanced accuracy for lower concentration target samples.
NOTE 5—Some CDS systems plot the area ratio versus the concentration ratio of the benzene and toluene to that of the internal standard. Consult the
system guidelines.
9.5 Composite Mix for Ethanol and Butanol Blends—The composite mix will ensure a necessary separation of ethanol from
benzene (R > 2), and that possible contaminants in the butanol blend will not co-elute with benzene (R > 2), toluene (R > 0.6) and
MIBK (R > 1.5).
9.5.1 Composite Mix for Ethanol Blend—Prepare a solution by volume that is 20 % ethanol, 1 % benzene, 4 % MIBK and 20 %
toluene in iso-octane. This solution may also be used to determine the backflush time.
9.5.2 Composite Mix for Ethanol and Butanol Blends—Prepare a solution by volume that is 20 % ethanol, 1 % benzene, 4 %
sec-butanol, 0.1 % n-propanol, 4 % MIBK, 20 % toluene, 20 % iso-butanol, 5 % n-butanol in iso-octane. This solution may also
be used to determine the backflush time.
10. Procedure
10.1 Preparation of Sample—Accurately measure 1.0 mL of MIBK into a 25 mL volumetric flask. Fill to the mark with the sample
to be analyzed and mix well.
10.2 Chromatographic Analysis—Chromatograph the sample, using the conditions established in Section 8 and as used for the
calibration. The GC column flow must be turned to backflush mode at the time determined in 8.3 so that undesirable components
do not enter the analytical column. Fig. A1.13 is an example of a Test Method D3606 proficiency sample analyzed using
configuration A.
10.3 Interpretation of Chromatogram—Identify the benzene, toluene, and the internal standard MIBK peaks from the retention
times of the standards.
NOTE 6—The order of elution will be nonaromatic hydrocarbons, benzene, MIBK and toluene using the dimethyl poly siloxane and polar column
combination used in the ILS.
10.4 Measurement of Area—Measure the areas under the benzene, toluene aromatic peaks and under the MIBK peak.
11. Calculation
11.1 Calculate the ratios of the peak areas of benzene and toluene to the peak area of MIBK. Determine from the calibration curve
D3606 − 24
the liquid volume percent of benzene and toluene corresponding to the calculated peak ratios. A CDS that has the capability of
processing this calibration and quantitating results may be used.
11.2 If the results are desired on a mass basis, convert to mass percent as follows:
Benzene, mass percent 5 V ⁄ D ×0.8844 (2)
~ !
B
where:
V = volume percent benzene, and
B
D = relative density of sample at 15.6/15.6 °C (60/60 °F).
Toluene, mass percent 5 ~V ⁄ D! ×0.8719 (3)
T
where:
V = volume percent toluene, and
T
D = relative density of sample at 15.6/15.6 °C (60/60 °F).
12. Quality Control
12.1 Test for System Stability and Repeatability—On setting up the method for the first time and thereafter when major
maintenance is performed (change in columns and flows, for example), make six injections of standard #4 (9.2). Calculate the
standard deviation from the six results from the six injections. Calculate 2.77 × the standard deviation obtained. This quantity shall
meet repeatability as published 14.1.1. Thereafter establish statistical quality control charting (SQC) for each batch of analysis
analyzed using a production a sample similar in composition to samples to be analyzed.
12.2 Reference Material—Analyze one or more reference material of known accepted reference value (ARV), such as from NIST
and/or an independent certified control standard, or meeting the check standard requirement as specified in Practice D6299 upon
setting up the test method, post maintenance (calibration, column replacement, cut time adjustments, and so forth) and at least
quarterly to confirm proper set-up and calibration of the gas chromatograph. Test results shall agree with within the 95 %
confidence level or reproducibility of the benzene or toluene components divided by the square root of 2. In addition follow any
other specification requirements per regulatory or commercial application(s). Monitor the performance of the reference material(s)
using SQC charting in accordance with Practice D6299.
13. Report
13.1 Report the benzene and toluene contents in liquid volume percent to the nearest 0.01 %, and indicate that the results are from
“D3606 Procedure A.”
13.2 In accordance with Practice D6300, to accommodate normal random testing variation, the lowest reportable test X result in
volume percent is computed as follows:
X 5 lowest reportable test result of this test method 5 @lowest retained ILS sample mean 2 R ~evaluated at the lowest retained ILS sample mean!# (4)
13.2.1 For benzene: X = 0.07
lowest reportable
13.2.2 For toluene: X = 0.36
lowest reportable
13.3 In accordance with Practice D6300, to accommodate normal random testing variation, the highest reportable test X result in
volume percent is computed as follows:
X 5 highest reportable test result of this test method 5 @highest retained ILS sample mean 1 R ~evaluated at the highest retained ILS sample mean!#(5)
13.3.1 For benzene: X = 5.96
highest reportable
13.3.2 For toluene: X = 19.7
highest reportable
D3606 − 24
14. Precision and Bias
14.1 The following criteria should be used for judging the acceptability of results (95 % confidence). The user should choose the
precision statement that reflects the concentration range of each component under study.
14.1.1 Repeatability—The difference between two independent results obtained by the same operator in a given laboratory
applying the same test method with the same apparatus under constant operating conditions on identical test material within short
intervals of time would exceed the values in Table 2 with an approximate probability of 5 % (one case in 20 in the long run) in
the normal and correct operation of the test method.
14.1.2 Reproducibility—The difference between two single and independent results obtained by different operators applying the
same test method in different laboratories using different apparatus on identical test material would exceed the values in Table 3
with an approximate probability of 5 % (one case in 20 in the long run) in the normal and correct operation of the test method.
NOTE 7—The sample compositions and results of the cooperative study are filed at ASTM International.
14.2 Bias—Since there is no accepted reference method suitable for measuring bias for this method, no statement of bias can be
made.
14.2.1 Between Method Bias between Procedure A and Procedure B for Benzene:
14.2.1.1 A between method bias assessment of Test Method D3606 Procedure A versus Procedure B for the determination of
benzene in spark-ignition fuel (gasolines) was conducted using data from the ILS of Procedure A which also included a parallel
ILS using Procedure B using identical samples. The assessment was performed in accordance with the requirements of Practice
D6708 with a successful outcome and is documented in Research Report RR:D02-2004.
NOTE 8—Procedure B is based on the original version of D3606 which uses packed columns and which has been used by regulatory agencies for benzene.
Users of this D3606 test method should consult proper regulations on its use as regulations may change.
14.2.1.2 The degree of agreement between results from Test Method D3606 Procedure A versus Procedure B can be further
improved by applying a correlation equation (Eq 6) (Research Report RR:D02-2004 ). There were no discernable sample-specific
biases as determined by D6708.
14.2.1.3 Correlation Equation:
14.2.1.4
Predicted D3606 Procedure B benzene 5 bias corrected Procedure A benzene 5 C 10.017 (6)
procedureA
where:
C = volume percent benzene as reported by Test Method D3606 Procedure A.
procedure A
(1) The correlation equation is applicable to test results in the range of 0.07 % to 5.96 % by volume as determined and reported
by Test Method D3606 Procedure A.
14.2.2 Between Method Bias between Procedures A and B Toluene:
TABLE 2 Repeatability–Procedure A (WCOT Column)
NOTE 1—X = the average of two results in volume percent of the
component; each result is to be within the ranges below.
Component Volume percent Repeatability
Benzene 0.12 to 5.2 0.03202 (X + 0.2)
Toluene 0.4 to 19.7 0.01767 (X + 0.5)
Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D02-2004. Contact ASTM Customer
Service at [e-mail].
D3606 − 24
TABLE 3 Reproducibility–Procedure A (WCOT Column)
NOTE 1—X = the average of two results in volume percent of the
component; each result is to be within the ranges given below.
Component Volume percent Reproducibility
Benzene 0.12 to 5.2 0.1462 (X + 0.2)
Toluene 0.4 to 19.7 0.04659 (X + 0.5)
TABLE 4 Repeatability/Reproducibility Example
(Benzene)–Procedure A (WCOT Column)
Benzene
Repeatability Reproducibility
Volume percent
0.10 0.010 0.044
0.20 0.013 0.058
0.30 0.016 0.073
0.40 0.019 0.088
0.50 0.022 0.102
0.60 0.026 0.117
0.70 0.029 0.132
0.80 0.032 0.146
0.90 0.035 0.161
1.00 0.038 0.175
2.00 0.070 0.322
3.00 0.102 0.468
4.00 0.134 0.614
5.00 0.167 0.760
TABLE 5 Repeatability/Reproducibility Example
(Toluene)–Procedure A (WCOT Column)
Toluene
Repeatability Reproducibility
Volume percent
0.4 0.016 0.042
1.0 0.027 0.070
2.0 0.044 0.116
3.0 0.062 0.163
4.0 0.080 0.210
5.0 0.097 0.256
6.0 0.115 0.303
7.0 0.133 0.349
8.0 0.150 0.396
9.0 0.168 0.443
10.0 0.186 0.489
11.0 0.203 0.536
12.0 0.221 0.582
13.0 0.239 0.629
14.0 0.256 0.676
15.0 0.274 0.722
16.0 0.292 0.769
17.0 0.309 0.815
18.0 0.327 0.862
19.0 0.345 0.909
20.0 0.362 0.955
14.2.2.1 A between method bias assessment of Test Method D3606 Procedure A versus Procedure B for the determination of
toluene was conducted using data from the ILS of Procedure A which also included a parallel ILS using Procedure B using identical
samples. The assessment was performed in accordance with the requirements of Practice D6708 with a successful outcome and
is documented in Research Report RR:D02-2004.
14.2.2.2 The degree of agreement between results from Test Method D3606 Procedure A toluene versus Procedure B toluene can
be further improved by applying a correlation equation (Eq 7) (Research Report RR:D02-2004 ). There were no discernable
sample-specific biases as defined in Practice D6708.
14.2.2.3 Correlation Equation:
14.2.2.4
D3606 − 24
TABLE 6 Comparison of Precision between Procedure A and
Procedure B in the Range of 0.10 % to 1.50 % Volume for
Benzene
Procedure A Procedure B
Benzene
percent Repeatability Reproducibility Repeatability Reproducibility
volume
0.10 0.010 0.044 0.013 0.063
0.30 0.016 0.073 0.019 0.089
0.50 0.022 0.102 0.025 0.115
0.70 0.029 0.132 0.031 0.141
0.90 0.035 0.161 0.037 0.167
1.10 0.042 0.190 0.043 0.193
1.30 0.048 0.219 0.049 0.219
1.50 0.054 0.249 0.055 0.245
Predicted D3606 Procedure B toluene 5 bias corrected Procedure A toluene 5 1.01*C 2 0.025 (7)
ProcedureA
where:
C = volume percent toluene as reported by Test Method D3606 Procedure A.
Procedure A
(1) The correlation equation is applicable to test results as determined and reported by Test Method D3606 Procedure A in the
range of 0.36 % to 20.64 % by volume toluene.
15. Keywords
15.1 aviation gasoline; benzene; gas chromatography; gasoline; multidimensional gas chromatography; spark ignition fuels;
toluene
PROCEDURE B—PACKED GAS CHROMATOGRAPHIC COLUMNS
16. Summary of Test Method
16.1 An internal standard, sec-butanol, is added to the sample. The sample is then introduced into a gas chromatograph (GC)
equipped with two packed GC columns connected in series. The sample passes first through a pre-column packed with a nonpolar
or equivalent phase, which separates the lighter components according to boiling point. After toluene has eluted, the flow through
the nonpolar column is reversed, flushing out the components heavier than toluene. The lighter components then pass through an
analytical column packed with a stationary phase capable of separating benzene and toluene from ethanol and other hydrocarbons
and oxygenates such as methanol, MTBE, TAME, ETBE, and butanols. The eluted components are detected by a thermal
conductivity detector (TCD). The detector response is recorded, the peak areas are measured and the concentration of each
component is calculated with reference to the internal standard.
17. Significance and Use
17.1 Knowledge of the concentration of benzene may be required for regulatory use, control of gasoline blending, and/or process
optimizations.
18. Apparatus
18.1 Chromatograph—Any multidimensional packed column gas chromatographic instrument configuration that has a backflush
system and thermal conductivity detector, and that can meet the specification of this test method, such as column resolution, can
be used.
18.1.1 Two backflush systems are shown. Fig. A2.1 is a switching valve system and Fig. A2.2 is a pressure system. Either one
can be used.
18.2 Columns:
D3606 − 24
18.2.1 Columns A (Precolumn) and B (Analytical Column)—Annex A2.2 gives an example of a commercial column set that has
been used successfully for samples containing ethanol. In addition, Annex A2.4 gives an additional column set originally proposed
by the U.S. Environmental Protection Agency (EPA) that may be adequate for this analyses. Other packed column sets that give
a resolution from ethanol as specified in 21.3 may be used.
18.3 Chromatography Data System (CDS)—An electronic device capable of graphical presentation and integration of the
chromatogram peaks.
18.4 Microsyringe—5 μL capacity.
18.5 Volumetric Pipets, Class A—0.5 mL, 1 mL, 5 mL, 10 mL, 15 mL, and 20 mL capacities (see Specifications E694 and E969).
18.6 Measuring Pipets—1 mL and 2 mL capacities calibrated in 0.01 mL; 5 mL calibrated in 0.1 mL, for use in dispensing
volumes of benzene and toluene not covered by the volumetric pipets (see Specifications E1044 and E1293) during preparation
of standard samples.
NOTE 9—Other volume dispensing equipment capable of delivering the specified volumes within the stated tolerance limits may be used as an alternative
to the requirements stated in 18.5 and 18.6.
18.7 Flasks—Class A volumetric (see Specification E288), 25 mL and 100 mL capacity.
19. Materials
19.1 Carrier Gas—Helium, 99.99 % mol pure or better. (Warning—Compressed gas under high pressure.)
19.2 Solvents:
19.2.1 Methanol—Reagent grade. (Warning—Flammable. Vapor harmful. Can be fatal or cause blindness if swallowed or
inhaled.)
19.3 Internal Standard:
19.3.1 sec-butanol—99.5 % mol minimum purity. Free of benzene and toluene. (Warning—Flammable. Vapor can be harmful.)
19.4 Calibration Standards:
+
19.4.1 Benzene—99 % mol. (Warning—Poison. Carcinogen. Harmful or fatal if swallowed. Extremely flammable. Vapors can
cause flash fires.)
+
19.4.2 Isooctane (2,2,4–trimethyl pentane)—99 % mol. (Warning—Extremely flammable. Harmful if inhaled.)
19.4.3 Toluene—(Warning—Flammable. Vapor harmful.)
+
19.4.4 n-nonane—99 % mol. (Warning—Flammable. Vapor harmful.)
20. Sampling
20.1 Spark Ignition Fuel (for example, “Gasoline”)—(Warning—Extremely flammable. Vapors harmful if inhaled.) Samples to
be analyzed by this test method shall be obtained using the procedures outlined in Practice D4057.
21. Configuration of Apparatus and Establishment of Conditions
21.1 Following manufacturer’s guidelines and/or suggested details in A2.2, A2.3, and A2.4 optimize the chromatographic system.
D3606 − 24
21.1.1 Column System Setup for Valve Backflushing—The following procedure provides a general guideline for optimizing a
system using valve switching as shown in Fig. A2.1. Several operational conditions are given in Table A2.1.
21.1.1.1 Set the valve in the forward flow mode with columns A and B in series (Fig. A2.2), and adjust the primary flow control
to give the desired flow. Measure the flow rate at the detector vent, sample side.
21.1.1.2 Set the valve in the backflush position, measure the flow rate at the detector vent, sample side. If the flow has changed,
adjust the secondary or auxiliary flow control to obtain the correct flow. Flows should match to within 61 cm /min.
21.1.1.3 Change the valve from forward flow to the backflush position several times and observe the baseline. There should be
no baseline shift or drift after the initial valve kick that results from the pressure surge. If there is a baseline shift, increase or
decrease the secondary flow control slightly to balance the baseline. A persistent drift could indicate leaks somewhere in the
system.
21.2 Determine Time to Backflush—The time to backflush will vary for each column system and must be determined
experimentally as follows. Table A2.1 gives examples of backflush times. Prepare a mixture of 5 % by volume isooctane in
n-nonane. With the valve configuration in the forward flow mode, inject 1 μL of the isooctane-n-nonane mixture. Allow the
chromatogram to run until the n-nonane has eluted and the detector signal has returned to baseline. Measure the time in seconds,
from the injection until the detector signal returns to baseline between the isooctane and n-nonane peaks. At this point all of the
isooctane, but essentially none of the n-nonane, should have eluted. Repeat the run, including the injection, but switching the
system to the backflush mode at the predetermined “time to backflush.” This should result in a chromatogram of isooctane with
little or no n-nonane visible. If necessary, make additional runs, adjusting the “time to backflush” until this condition of all the
isooctane and little or no n-nonane is attained. The “time to backflush” so established, including the actual valve operations, must
be used in all subsequent calibrations and analyses. It is also valid to set backflush time after toluene elutes.
21.3 Resolution of Ethanol/Benzene and Sec-butanol Benzene Pairs—Resolution calculation may be performed by the CDS or
manually. The resolution shall be greater than 1.5 using calibration standard 4 (Table 7) for benzene. If using a CDS, ensure the
CDS is using the proper resolution calculation, as follows:
1.18~T 2 T !
p2 p1
R 5 (8)
p2
W 1W
h1⁄2 h2⁄2
where:
R = the resolution of peak 2,
p2
T = the retention time of peak 1,
p1
T = the retention time of peak 2,
p2
W = the width of peak 1 at half height, and
h1/2
W = the width of peak 2 at half height.
h2/2
21.4 To ensure proper resolution at low concentration ranges, the ethanol needs to have minimal peak tailing. A2.2 and A2.4
describe the recommended peak symmetry for ethanol and the ethanol/benzene resolution required. It is recommended that final
system optimization be verified against certified reference materials containing benzene at several concentration levels of interest
and ethanol present at a level in the expected samples to confirm the accuracy of the analyses.
22. Calibration and Standardization
22.1 Standard Samples—Prepare seven standard samples (Table 7) covering the range 0.06 % to 5 % by volume benzene and 0.5
TABLE 7 Seven Standard Samples
Benzene Toluene
Std #
Volume % mL Volume % mL
1 5 5 20 20
2 2.5 2.5 15 15
3 1.25 1.25 10 10
4 0.67 0.67 5 5
5 0.33 0.33 2.5 2.5
6 0.12 0.12 1 1
7 0.06 0.06 0.5 0.5
D3606 − 24
% to 20 % by volume toluene as follows: For each standard, measure the volume of benzene and of toluene listed below into a
100 mL volumetric flask. Dilute to volume with isooctane (2,2,4–trimethyl pentane), with all components and glassware at ambient
temperature.
22.2 Calibration Blends—Accurately measure 1.0 mL of sec-butanol into a 25 mL volumetric flask, and fill to the mark with the
first standard sample (22.1). Continue doing this until all blends have been prepared.
NOTE 10—Commercially prepared calibration standards may be used, including those that are pre-mixed with the sec-butanol internal standard.
22.3 Chromatographic Analysis—Chromatograph each of the calibration blends using the conditions established in 21.4 using the
following injection technique:
22.4 Injection of Sample:
22.4.1 Use an automatic liquid sample injection system. If manual injections are to be made, the injection technique in 22.4.2 is
necessary so that sharp symmetrical peaks will be obtained.
NOTE 11—ILS precision was based using automated injection systems.
22.4.2 Flush the 5 μL microsyringe at least three times with the sample mixture and then fill with about 3 μL of the sample. (Avoid
including any air bubbles in the syringe). Slowly eject the sample until 2.0 μL remains in the syringe; wipe the needle with tissue
and draw back the plunger to admit 1 μL to 2 μL of air into the syringe. Insert the needle of the syringe through the septum cap
of the chromatograph and push until the barrel of the syringe is resting against the septum cap; then push the plunger to the hilt
and remove the syringe immediately from the chromatograph.
22.5 Calibration—Measure the area of both aromatic peaks and of the internal standard peak. Calculate the ratio of the benzene
peak area to the sec-butanol and the ratio of concentrations of benzene to that of the sec-butanol. Plot the area ratios versus and
concentration ratios. Make the same calculation and plot for toluene. The calibrations shall be linear (Fig. A2.6).
NOTE 12—Some CDS systems plot the area ratio versus the concentration ratio of the benzene and toluene to that of the internal standard. Consult the
system guidelines.
23. Procedure
23.1 Preparation of Sample—Accurately measure 1.0 mL of sec-butanol into a 25 mL volumetric flask. Fill to the mark with the
sample to be tested and mix well.
23.2 Chromatographic Analysis—Chromatograph the sample, using the conditions established in Section 21 “time to backflush”
and the injection technique described in 22.4. The valves must be turned to backflush mode at the time determined in 21.2 so that
undesirable components do not enter Column B.
23.3 Interpretation of Chromatogram—Identify on the chromatogram the benzene, toluene, and the internal standard sec-butanol
peaks from the retention times of the standards.
NOTE 13—The order of elution will be nonaromatic hydrocarbons, ethanol, benzene, sec-butanol, and toluene using the prescribed column system in A2.2.
Figs. A2.5 and A2.6 are examples of typical chromatograms.
23.4 Measurement of Area—Measure the areas under the aromatic peaks and under the internal standard peak by CDS.
NOTE 14—The precision statement in Section 26 was developed from data obtained using electronic integrators or on-line computers. The precision
statement may not apply if other methods of integration or peak area measurement are used.
24. Calculation
24.1 Calculate the ratios of the peak areas of benzene
...