ASTM D5769-10(2015)
(Test Method)Standard Test Method for Determination of Benzene, Toluene, and Total Aromatics in Finished Gasolines by Gas Chromatography/Mass Spectrometry
Standard Test Method for Determination of Benzene, Toluene, and Total Aromatics in Finished Gasolines by Gas Chromatography/Mass Spectrometry
SIGNIFICANCE AND USE
5.1 Test methods to determine benzene and the aromatic content of gasoline are necessary to assess product quality and to meet fuel regulations.
5.2 This test method can be used for gasolines that contain oxygenates (alcohols and ethers) as additives. It has been determined that the common oxygenates found in finished gasoline do not interfere with the analysis of benzene and other aromatics by this test method.
SCOPE
1.1 This test method covers the determination of benzene, toluene, other specified individual aromatic compounds, and total aromatics in finished motor gasoline, including gasolines containing oxygenated blending components, by gas chromatography/mass spectrometry (GC/MS).
1.2 This test method has been tested for the following concentration ranges, in liquid volume percent, for the following aromatics: benzene, 0.1 % to 4 %; toluene, 1 % to 13 %; and total (C6 to C12) aromatics, 10 % to 42 %. The round-robin study did not test the method for individual hydrocarbon process streams in a refinery, such as reformates, fluid catalytic cracked naphthas, and so forth, used in the blending of gasolines.
1.3 Results are reported to the nearest 0.01 % for benzene and 0.1 % for the other aromatics by liquid volume.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to its use.
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Designation: D5769 − 10(Reapproved 2015)
Standard Test Method for
Determination of Benzene, Toluene, and Total Aromatics in
Finished Gasolines by Gas Chromatography/Mass
Spectrometry
This standard is issued under the fixed designation D5769; 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 D4052 Test Method for Density, Relative Density, and API
Gravity of Liquids by Digital Density Meter
1.1 This test method covers the determination of benzene,
D4057 Practice for Manual Sampling of Petroleum and
toluene, other specified individual aromatic compounds, and
Petroleum Products
total aromatics in finished motor gasoline, including gasolines
D4307 Practice for Preparation of Liquid Blends for Use as
containing oxygenated blending components, by gas
Analytical Standards
chromatography/mass spectrometry (GC/MS).
1.2 This test method has been tested for the following
3. Terminology
concentration ranges, in liquid volume percent, for the follow-
3.1 Definitions of Terms Specific to This Standard:
ing aromatics: benzene, 0.1 % to 4 %; toluene, 1 % to 13 %;
3.1.1 aromatic—any hydrocarbon compound containing a
and total (C6 to C12) aromatics, 10 % to 42 %. The round-
benzene or naphthalene ring.
robin study did not test the method for individual hydrocarbon
process streams in a refinery, such as reformates, fluid catalytic
3.1.2 calibrated aromatic component—the individual aro-
cracked naphthas, and so forth, used in the blending of
matic components that have a specific calibration.
gasolines.
3.1.3 cool on-column injector—in gas chromatography,a
1.3 Results are reported to the nearest 0.01 % for benzene
direct sample introduction system that is set at a temperature at
and 0.1 % for the other aromatics by liquid volume.
orbelowtheboilingpointofsolutesorsolventoninjectionand
then heated at a rate equal to or greater than the column.
1.4 The values stated in SI units are to be regarded as
Normally used to eliminate boiling point discrimination on
standard. No other units of measurement are included in this
injection or to reduce adsorption on glass liners within
standard.
injectors, or both. The sample is injected directly into the head
1.5 This standard does not purport to address all of the
of the capillary column tubing.
safety concerns, if any, associated with its use. It is the
3.1.4 open split interface—GC/MS interface used to main-
responsibility of the user of this standard to establish appro-
tain atmospheric pressure at capillary column outlet and to
priate safety and health practices and determine the applica-
eliminate mass spectrometer vacuum effects on the capillary
bility of regulatory limitations prior to its use.
column. Can be used to dilute the sample entering the mass
2. Referenced Documents spectrometer to maintain response linearity.
2.1 ASTM Standards:
3.1.5 reconstructed ion chromatogram (RIC)—a limited
D1298 Test Method for Density, Relative Density, or API mass chromatogram representing the intensities of ion mass
Gravity of Crude Petroleum and Liquid Petroleum Prod- spectrometric currents for only those ions having particular
ucts by Hydrometer Method
mass to charge ratios. Used in this test method to selectively
extract or identify aromatic components in the presence of a
complex hydrocarbon matrix, such as gasoline.
This test method is under the jurisdiction of ASTM Committee D02 on
3.1.6 retention gap—in gas chromatography, refers to a
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.04.0M on Mass Spectroscopy.
deactivated precolumn which acts as a zone of low retention
CurrenteditionapprovedJune1,2015.PublishedJuly2015.Originallyapproved
power for reconcentrating bands in space. The polarity of the
in 1995. Last previous edition approved in 2010 as D5769 – 10. DOI: 10.1520/
precolumn must be similar to that of the analytical column.
D5769-10R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.1.7 split ratio—in capillary gas chromatography, the ratio
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
of the total flow of carrier gas to the sample inlet versus the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. flow of the carrier gas to the capillary column, expressed by:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5769 − 10 (2015)
split ratio 5 S1C /C (1) 6.1.1 System equipped with temperature-programmable gas
~ !
chromatographsuitableforsplitinjectionswithWCOTcolumn
where:
or cool-on-column injector that allows the injection of small
S = flow rate at the splitter vent, and
(for example, 0.1 µL) samples at the head of the WCOT
C = flow rate at the column outlet.
columnoraretentiongap.Anautosamplerismandatoryforthe
3.1.8 total ion chromatogram (TIC)—mass spectrometer
on-column injections.
computer output representing either the summed intensities of
6.1.2 WCOT column containing dimethylpolysiloxane
all scanned ion currents or a sample of the current in the ion
bonded stationary phase, meeting the specification in the
beam for each spectrum scan plotted against the corresponding
followingtable.Foron-columninjections,acolumncontaining
spectrum number. Generally, it can be correlated with a flame
a thicker film of stationary phase, such as 4–5 µm, is recom-
ionization detector chromatogram.
mended to prevent column sample overload.
3.1.9 uncalibrated aromatic component—individual aro-
Resolution R between 1,3,5-
2 t12 t2
s d
trimethylbenzene and 1-methyl-2-
matics for which a calibration is not available. These compo-
R5
1.699sy21y1d
ethylbenzene at the 3 mass % level
nents are estimated from the calibration of several calibrated
each must be equal to or greater than
t2 = retention time of 1,3,5-
aromatic components.
2.0
trimethylbenzene
t1 = retention time of
3.1.10 wall coated open tubular (WCOT)—a type of capil-
1-methyl-2-ethylbenzene
lary column prepared by coating or bonding the inside wall of
y2 = peak width at half height
the capillary with a thin film of stationary phase.
of 1,3,5-trimethylbenzene
y1 = peak width at half height
4. Summary of Test Method
1-methyl-2-ethyl benzene
4.1 A gas chromatograph equipped with a dimethylpolysi-
6.2 Mass Spectrometry:
loxane WCOT column is interfaced to a fast scanning mass
6.2.1 Mass spectrometer capable of producing electron
spectrometer that is suitable for capillary column GC/MS
impactspectraat70,orhigher,electronvoltsorequivalent,and
analyses. The sample is injected either through a capillary
capable of scanning the range of the specified quantitation
splitter port or a cool-on-column injector capable of introduc-
masses or m/e. The mass scan range shall cover the masses of
ing a small sample size without overloading the column. The
interest for quantitation and should yield at least 5 scans across
capillarycolumnisinterfaceddirectlytothemassspectrometer
the peak width at half peak width fora1to3 mass percent
orbywayofanopensplitinterfaceorotherappropriatedevice.
toluene and cover the masses of interest for quantitation. A
4.2 Calibrationisperformedonamassbasis,usingmixtures
scan range of 41 to 200 daltons is adequate.
of specified pure aromatic hydrocarbons. Volume percent data
6.2.2 The mass spectrometer must be capable of being
is calculated from the densities of the individual components
interfaced to a gas chromatograph and WCOT columns. The
and the density of the sample.Amultipoint calibration consist-
interface must be at a high enough temperature to prevent
ing of at least five levels and bracketing the expected concen-
condensation of components boiling up to 220 °C, usually
trations of the specified individual aromatics is required.
20 °C above the final column temperature is adequate. Direct
Specified deuterated hydrocarbons are used as the internal
column interface to the mass spectrometer can be used. An
standards, for example, d6-benzene for quantitating benzene.
open split interface with computer controlled programmable
Unidentified aromatic hydrocarbons present that have not been
flow controller(s) can also be used, particularly with cool
specifically calibrated for are quantitated using the calibration
on-column injections, to maintain all aromatic components
ofanadjacentcalibratedcompoundandsummedwiththeother
within the linearity of the mass spectrometer and at the same
aromatic components to obtain a total aromatic concentration
time maintain detectability of lower concentration aromatic
of the sample.
components. For example, a higher open-split-interface
4.3 Specified quality control mixture(s), such as synthetic make-up gas flow can be used for the high concentration
quality control mixtures must be analyzed to monitor the components,suchastolueneandxylenes,andalowermake-up
performance of the calibrated GC/MS system. Analysis of a gas flow rate may be used during the elution of the lower
gasoline as a reference material is strongly recommended. concentration benzene and C9+ components. Other interfaces
maybeusedprovidedthecriteriaspecifiedinSections9and10
5. Significance and Use
are met.
5.1 Test methods to determine benzene and the aromatic
6.2.3 A computer system shall be interfaced to the mass
content of gasoline are necessary to assess product quality and
spectrometer to allow acquisition of continuous mass scans or
to meet fuel regulations.
totalionchromatogram(TIC)forthedurationofthechromato-
graphic program and be able to analyze repeatedly 0.01 mass
5.2 This test method can be used for gasolines that contain
percent 1,4-diethylbenzene with the specified signal/noise ratio
oxygenates (alcohols and ethers) as additives. It has been
of 5. Software must be available to allow searching any
determined that the common oxygenates found in finished
GC/MS run for specific ions or reconstructed ions and plotting
gasolinedonotinterferewiththeanalysisofbenzeneandother
the intensity of the ions with respect to time or scan number.
aromatics by this test method.
The ability to integrate the area under a specific ion plot peak
6. Apparatus
is essential for quantitation. The quantitation software must
6.1 Gas Chromatography: allow linear least squares or quadratic nonlinear regression and
D5769 − 10 (2015)
quantitation with multiple internal standards. It is also recom- 7.4 Standards for Calibration and Identification—Aromatic
mendedthatsoftwarebeavailabletoautomaticallyperformthe hydrocarbons used to prepare standards should be 99 % or
identification of aromatic components as specified in 13.1.1.
greater purity (see Table 1). If reagents of high purity are not
available, an accurate assay of the reagent shall be performed
7. Reagents and Materials
using a properly calibrated GC or other techniques. The
7.1 Carrier Gas—Helium and hydrogen have been used
concentration of the impurities that overlap the other calibra-
successfully. The recommended minimum purity of the carrier
tion components shall be known and used to correct the
gas used is 99.999 mol percent. Additional purification using
concentration of the calibration components. The use of only
commercially available scrubbing reagents may be necessary
high purity reagents is strongly recommended because of the
to remove trace oxygen, which may deteriorate the perfor-
error that may be introduced from impurity corrections. Stan-
mance of the GC WCOT. (Warning—Helium and hydrogen
dards are used for calibration as well as for establishing the
are supplied under high pressure. Hydrogen can be explosive
identification by retention time in conjunction with mass
and requires special handling. Hydrogen monitors that auto-
spectral match (see 13.1.1). Naphthalene is hygroscopic and
matically shut off supply to the GC in case of serious leaks are
should be stored away from high humidity.
available from GC supply manufacturers.)
7.2 Dilution Solvents—Reagent grade 2,2,4-
8. Sampling
trimethylpentane (iso-octane), n-heptane, n-nonane,
8.1 Every effort should be made to ensure that the sample is
cyclohexane, or toluene, or a combination thereof, used as a
representative of the fuel source from which it is taken. Follow
solvent in the preparation of the calibration mixtures.
the recommendations of Practice D4057, or its equivalent,
(Warning—The gasoline samples and solvents used as re-
when obtaining samples from bulk storage or pipelines. Sam-
agents such as iso-octane, cyclohexane, n-heptane, n-octane,
and toluene, are flammable and may be harmful or fatal if pling to meet certain regulatory specifications may require the
ingested or inhaled. Benzene is a known carcinogen. Use with use of specific sampling procedures. Consult appropriate regu-
properventilation.Safetyglassesandglovesarerequiredwhile
lations.
preparing samples and standards. Samples should be kept in
8.2 Appropriate steps should be taken to minimize the loss
well ventilated laboratory areas.)
oflighthydrocarbonsfromthegasolinesamplewhilesampling
NOTE 1—Toluene should be used as a solvent only for the preparation
and during analyses. Upon receipt in the laboratory, chill the
of C9+ components and shall be free from interfering aromatics.
sample in its original container to between 0 to 5°C before and
7.3 Internal Standards—Deuterated analogs of benzene,
after a sample aliquot is removed for analysis.
ethylbenzene, and naphthalene, as specified in Table 1, shall be
8.3 After the sample is prepared for analysis with internal
used as internal standards because of their similar chromato-
standard(s), chill the sample and fill the autosampler vial to
graphic characteristics as the components analyzed. The use of
approximately 90 % of its volume. The remainder of the
a fourth internal standard toluene-d8 is recommended. Deuter-
ated naphthalene is hygroscopic and should be stored away sample should be re-chilled immediately and protected from
from high humidity. evaporation for further analyses, if necessary. To prevent
TABLE 1 Mass Spectrometer Quantitation Ions for Sample Components and Internal Standards
Compound CAS Primary Ion Internal Standard ISTD ION
No. (Dalton) (ISTD) (Dalton)
Benzene 71-43-2 78 Benzene-d6 84 + 83
Toluene 108-88-3 92 Ethylbenzene-d10 or 116 + 115 or 100 + 99
toluene-d8
Ethylbenzene 100-41-4 106 Ethylbenzene-d10 116 + 115
1,3-Dimethylbenzene 108-38-3 106 Ethylbenzene-d10 116 + 115
1,4-Dimethylbenzene 106-42-3 106 Ethylbenzene-d10 116 + 115
1,2-Dimethylbenzene 95-47-6 106 Ethylbenzene-
...
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: D5769 − 10 D5769 − 10 (Reapproved 2015)
Standard Test Method for
Determination of Benzene, Toluene, and Total Aromatics in
Finished Gasolines by Gas Chromatography/Mass
Spectrometry
This standard is issued under the fixed designation D5769; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the determination of benzene, toluene, other specified individual aromatic compounds, and total
aromatics in finished motor gasoline, including gasolines containing oxygenated blending components, by gas chromatography/
mass spectrometry (GC/MS).
1.2 This test method has been tested for the following concentration ranges, in liquid volume percent, for the following
aromatics: benzene, 0.10.1 % to 4 %; toluene, 11 % to 13 %; and total (C6 to C12) aromatics, 1010 % to 42 %. The round-robin
study did not test the method for individual hydrocarbon process streams in a refinery, such as reformates, fluid catalytic cracked
naphthas, and so forth, used in the blending of gasolines.
1.3 Results are reported to the nearest 0.01 % for benzene and 0.1 % for the other aromatics by liquid volume.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to its use.
2. Referenced Documents
2.1 ASTM Standards:
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4307 Practice for Preparation of Liquid Blends for Use as Analytical Standards
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 aromatic—any hydrocarbon compound containing a benzene or naphthalene ring.
3.1.2 calibrated aromatic component—the individual aromatic components that have a specific calibration.
3.1.3 cool on-column injector—in gas chromatography, a direct sample introduction system that is set at a temperature at or
below the boiling point of solutes or solvent on injection and then heated at a rate equal to or greater than the column. Normally
used to eliminate boiling point discrimination on injection or to reduce adsorption on glass liners within injectors, or both. The
sample is injected directly into the head of the capillary column tubing.
3.1.4 open split interface—GC/MS interface used to maintain atmospheric pressure at capillary column outlet and to eliminate
mass spectrometer vacuum effects on the capillary column. Can be used to dilute the sample entering the mass spectrometer to
maintain response linearity.
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
D02.04.0M on Mass Spectroscopy.
Current edition approved May 1, 2010June 1, 2015. Published August 2010July 2015. Originally approved in 1995. Last previous edition approved in 20042010 as
D5769D5769 – 10.–04. DOI: 10.1520/D5769-10.10.1520/D5769-10R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5769 − 10 (2015)
3.1.5 reconstructed ion chromatogram (RIC)—a limited mass chromatogram representing the intensities of ion mass
spectrometric currents for only those ions having particular mass to charge ratios. Used in this test method to selectively extract
or identify aromatic components in the presence of a complex hydrocarbon matrix, such as gasoline.
3.1.6 retention gap—in gas chromatography, refers to a deactivated precolumn which acts as a zone of low retention power for
reconcentrating bands in space. The polarity of the precolumn must be similar to that of the analytical column.
3.1.7 split ratio—in capillary gas chromatography, the ratio of the total flow of carrier gas to the sample inlet versus the flow
of the carrier gas to the capillary column, expressed by:
split ratio 5 ~S1C!/C (1)
where:
S = flow rate at the splitter vent, and
C = flow rate at the column outlet.
3.1.8 total ion chromatogram (TIC)—mass spectrometer computer output representing either the summed intensities of all
scanned ion currents or a sample of the current in the ion beam for each spectrum scan plotted against the corresponding spectrum
number. Generally, it can be correlated with a flame ionization detector chromatogram.
3.1.9 uncalibrated aromatic component—individual aromatics for which a calibration is not available. These components are
estimated from the calibration of several calibrated aromatic components.
3.1.10 wall coated open tubular (WCOT)—a type of capillary column prepared by coating or bonding the inside wall of the
capillary with a thin film of stationary phase.
4. Summary of Test Method
4.1 A gas chromatograph equipped with a dimethylpolysiloxane WCOT column is interfaced to a fast scanning mass
spectrometer that is suitable for capillary column GC/MS analyses. The sample is injected either through a capillary splitter port
or a cool-on-column injector capable of introducing a small sample size without overloading the column. The capillary column
is interfaced directly to the mass spectrometer or by way of an open split interface or other appropriate device.
4.2 Calibration is performed on a mass basis, using mixtures of specified pure aromatic hydrocarbons. Volume percent data is
calculated from the densities of the individual components and the density of the sample. A multipoint calibration consisting of
at least five levels and bracketing the expected concentrations of the specified individual aromatics is required. Specified deuterated
hydrocarbons are used as the internal standards, for example, d6-benzene for quantitating benzene. Unidentified aromatic
hydrocarbons present that have not been specifically calibrated for are quantitated using the calibration of an adjacent calibrated
compound and summed with the other aromatic components to obtain a total aromatic concentration of the sample.
4.3 Specified quality control mixture(s), such as synthetic quality control mixtures must be analyzed to monitor the performance
of the calibrated GC/MS system. Analysis of a gasoline as a reference material is strongly recommended.
5. Significance and Use
5.1 Test methods to determine benzene and the aromatic content of gasoline are necessary to assess product quality and to meet
fuel regulations.
5.2 This test method can be used for gasolines that contain oxygenates (alcohols and ethers) as additives. It has been determined
that the common oxygenates found in finished gasoline do not interfere with the analysis of benzene and other aromatics by this
test method.
6. Apparatus
6.1 Gas Chromatography:
6.1.1 System equipped with temperature-programmable gas chromatograph suitable for split injections with WCOT column or
cool-on-column injector that allows the injection of small (for example, 0.1 μL) 0.1 μL) samples at the head of the WCOT column
or a retention gap. An autosampler is mandatory for the on-column injections.
6.1.2 WCOT column containing dimethylpolysiloxane bonded stationary phase, meeting the specification in the following table.
For on-column injections, a column containing a thicker film of stationary phase, such as 4–5 μm, is recommended to prevent
column sample overload.
D5769 − 10 (2015)
Resolution R between 1,3,5-
2st12t2d
trimethylbenzene and 1-methyl-2-
R 5
ethylbenzene at the 3 mass % level 1.699sy21y1d
each must be equal to or greater than t2 = retention time of 1,3,5-
2.0
trimethylbenzene
t1 = retention time of
1-methyl-2-ethylbenzene
y2 = peak width at half height
of 1,3,5-trimethylbenzene
y1 = peak width at half height
1-methyl-2-ethyl benzene
6.2 Mass Spectrometry:
6.2.1 Mass spectrometer capable of producing electron impact spectra at 70, or higher, electron volts or equivalent, and capable
of scanning the range of the specified quantitation masses or m/e. The mass scan range shall cover the masses of interest for
quantitation and should yield at least 5 scans across the peak width at half peak width for a 1 to 3 mass percent toluene and cover
the masses of interest for quantitation. A scan range of 41 to 200 daltons is adequate.
6.2.2 The mass spectrometer must be capable of being interfaced to a gas chromatograph and WCOT columns. The interface
must be at a high enough temperature to prevent condensation of components boiling up to 220°C,220 °C, usually 20°C20 °C
above the final column temperature is adequate. Direct column interface to the mass spectrometer can be used. An open split
interface with computer controlled programmable flow controller(s) can also be used, particularly with cool on-column injections,
to maintain all aromatic components within the linearity of the mass spectrometer and at the same time maintain detectability of
lower concentration aromatic components. For example, a higher open-split-interface make-up gas flow can be used for the high
concentration components, such as toluene and xylenes, and a lower make-up gas flow rate may be used during the elution of the
lower concentration benzene and C9+ components. Other interfaces may be used provided the criteria specified in Sections 9 and
10 are met.
6.2.3 A computer system shall be interfaced to the mass spectrometer to allow acquisition of continuous mass scans or total ion
chromatogram (TIC) for the duration of the chromatographic program and be able to analyze repeatedly 0.01 mass percent
1,4-diethylbenzene with the specified signal/noise ratio of 5. Software must be available to allow searching any GC/MS run for
specific ions or reconstructed ions and plotting the intensity of the ions with respect to time or scan number. The ability to integrate
the area under a specific ion plot peak is essential for quantitation. The quantitation software must allow linear least squares or
quadratic nonlinear regression and quantitation with multiple internal standards. It is also recommended that software be available
to automatically perform the identification of aromatic components as specified in 13.1.1.
7. Reagents and Materials
7.1 Carrier Gas—Helium and hydrogen have been used successfully. The recommended minimum purity of the carrier gas used
is 99.999 mol percent. Additional purification using commercially available scrubbing reagents may be necessary to remove trace
oxygen, which may deteriorate the performance of the GC WCOT. (Warning—Helium and hydrogen are supplied under high
pressure. Hydrogen can be explosive and requires special handling. Hydrogen monitors that automatically shut off supply to the
GC in case of serious leaks are available from GC supply manufacturers.)
7.2 Dilution Solvents—Reagent grade 2,2,4-trimethylpentane (iso-octane), n-heptane, n-nonane, cyclohexane, or toluene, or a
combination thereof, used as a solvent in the preparation of the calibration mixtures. (Warning—The gasoline samples and
solvents used as reagents such as iso-octane, cyclohexane, n-heptane, n-octane, and toluene, are flammable and may be harmful
or fatal if ingested or inhaled. Benzene is a known carcinogen. Use with proper ventilation. Safety glasses and gloves are required
while preparing samples and standards. Samples should be kept in well ventilated laboratory areas.)
NOTE 1—Toluene should be used as a solvent only for the preparation of C9+ components and shall be free from interfering aromatics.
7.3 Internal Standards—Deuterated analogs of benzene, ethylbenzene, and naphthalene, as specified in Table 1, shall be used
as internal standards because of their similar chromatographic characteristics as the components analyzed. The use of a fourth
internal standard toluene-d8 is recommended. Deuterated naphthalene is hygroscopic and should be stored away from high
humidity.
7.4 Standards for Calibration and Identification—Aromatic hydrocarbons used to prepare standards should be 99 % or greater
purity (see Table 1). If reagents of high purity are not available, an accurate assay of the reagent shall be performed using a properly
calibrated GC or other techniques. The concentration of the impurities that overlap the other calibration components shall be
known and used to correct the concentration of the calibration components. The use of only high purity reagents is strongly
recommended because of the error that may be introduced from impurity corrections. Standards are used for calibration as well
as for establishing the identification by retention time in conjunction with mass spectral match (see 13.1.1). Naphthalene is
hygroscopic and should be stored away from high humidity.
D5769 − 10 (2015)
TABLE 1 Mass Spectrometer Quantitation Ions for Sample Components and Internal Standards
Compound CAS Primary Ion Internal Standard ISTD ION
No. (Dalton) (ISTD) (Dalton)
Benzene 71-43-2 78 Benzene-d6 84 + 83
Toluene 108-88-3 92 Ethylbenzene-d10 or 116 + 115 or 100 + 99
toluene-d8
Ethylbenzene 100-41-4 106 Ethylbenzene-d10 116 + 115
1,3-Dimethylbenzene 108-38-3 106 Ethylbenzene-d10 116 + 115
1,4-Dimethylbenzene 106-42-3 106 Ethylbenzene-d10 116 + 115
1,2-Dimethylbenzene 95-47-6 106 Ethylbenzene-d10 116 + 115
(1-Methylethyl)-benzene 98-82-8 120 Ethylbenzene-d10 116 + 115
Propyl-benzene 103-65-1 120 Ethylbenzene-d10 116 + 115
1-Methyl-3-ethylbenzene 620-14-4 120 Ethylbenzene-d10 116 + 115
1-Methyl-4-ethylbenzene 622-96-8 120 Ethylbenzene-d10 116 + 115
1,3,5-Trimethylbenzene 108-67-8 120 Ethylbenzene-d10 116 + 115
1-Methyl-2-ethylbenzene 611-14-3 120 Ethylbenzene-d10 116 + 115
1,2,4-Trimethylbenzene 95-63-6 120 Ethylbe
...
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