ASTM D6379-11(2019)
(Test Method)Standard Test Method for Determination of Aromatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates—High Performance Liquid Chromatography Method with Refractive Index Detection
Standard Test Method for Determination of Aromatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates—High Performance Liquid Chromatography Method with Refractive Index Detection
SIGNIFICANCE AND USE
5.1 Accurate quantitative information on aromatic hydrocarbon types can be useful in determining the effects of petroleum processes on production of various finished fuels. This information can also be useful for indicating the quality of fuels and for assessing the relative combustion properties of finished fuels.
SCOPE
1.1 This test method covers a high performance liquid chromatographic test method for the determination of mono-aromatic and di-aromatic hydrocarbon contents in aviation kerosenes and petroleum distillates boiling in the range from 50 °C to 300 °C, such as Jet A or Jet A-1 fuels. The total aromatic content is calculated from the sum of the individual aromatic hydrocarbon-types.
Note 1: Samples with a final boiling point greater than 300 °C that contain tri-aromatic and higher polycyclic aromatic compounds are not determined by this test method and should be analyzed by Test Method D6591 or other suitable equivalent test methods.
1.2 This test method is calibrated for distillates containing from 10 %to 25 % m/m mono-aromatic hydrocarbons and from 0 % to 7 % m/m di-aromatic hydrocarbons.
1.3 The precision of this test method has been established for kerosene boiling range distillates containing from 10 % to 25 % m/m mono-aromatic hydrocarbons and from 0 % to 7 % m/m di-aromatic hydrocarbons.
1.4 Compounds containing sulfur, nitrogen, and oxygen are possible interferents. Mono-alkenes do not interfere, but conjugated di- and poly-alkenes, if present, are possible interferents.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: D6379 − 11 (Reapproved 2019)
Designation: 436/01
Standard Test Method for
Determination of Aromatic Hydrocarbon Types in Aviation
Fuels and Petroleum Distillates—High Performance Liquid
Chromatography Method with Refractive Index Detection
This standard is issued under the fixed designation D6379; 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.
INTRODUCTION
This test method is intended to be technically equivalent to IP 436-01 with an identical title. The
ASTM format for test methods has been used, and where possible, equivalent ASTM test methods
have replaced the IP or ISO standards.
The test method is intended to be used as one of several possible alternative instrumental test
methods that are aimed at quantitative determination of hydrocarbon types in fuels. This does not
imply that a correlation necessarily exists between this and any other test method intended to give this
information, and it is the responsibility of the user to determine such correlation if necessary.
1. Scope 1.4 Compounds containing sulfur, nitrogen, and oxygen are
possible interferents. Mono-alkenes do not interfere, but con-
1.1 This test method covers a high performance liquid
jugated di- and poly-alkenes, if present, are possible interfer-
chromatographic test method for the determination of mono-
ents.
aromatic and di-aromatic hydrocarbon contents in aviation
1.5 This standard does not purport to address all of the
kerosenes and petroleum distillates boiling in the range from
safety concerns, if any, associated with its use. It is the
50 °C to 300 °C, such as Jet A or Jet A-1 fuels. The total
responsibility of the user of this standard to establish appro-
aromatic content is calculated from the sum of the individual
priate safety, health, and environmental practices and deter-
aromatic hydrocarbon-types.
mine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accor-
NOTE 1—Samples with a final boiling point greater than 300 °C that
contain tri-aromatic and higher polycyclic aromatic compounds are not
dance with internationally recognized principles on standard-
determined by this test method and should be analyzed by Test Method
ization established in the Decision on Principles for the
D6591 or other suitable equivalent test methods.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.2 This test method is calibrated for distillates containing
Barriers to Trade (TBT) Committee.
from 10 %to 25 % m/m mono-aromatic hydrocarbons and
from 0 % to 7 % m/m di-aromatic hydrocarbons.
2. Referenced Documents
1.3 The precision of this test method has been established
2.1 ASTM Standards:
for kerosene boiling range distillates containing from 10 % to
D4052 Test Method for Density, Relative Density, and API
25 % m/m mono-aromatic hydrocarbons and from 0 % to 7 %
Gravity of Liquids by Digital Density Meter
m/m di-aromatic hydrocarbons.
D4057 Practice for Manual Sampling of Petroleum and
Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.04.0C on Liquid Chromatography.
Current edition approved June 1, 2019. Published August 2019. Originally
approved in 1999. Last previous edition approved in 2011 as D6379 – 11. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D6379-11R19. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
In the IP, this test method is under the jurisdiction of the Standardization Standards volume information, refer to the standard’s Document Summary page on
Committee. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6379 − 11 (2019)
D6591 Test Method for Determination of Aromatic Hydro- petroleum processes on production of various finished fuels.
carbon Types in Middle Distillates—High Performance Thisinformationcanalsobeusefulforindicatingthequalityof
Liquid Chromatography Method with Refractive Index fuels and for assessing the relative combustion properties of
Detection finished fuels.
2.2 Energy Institute Standards:
IP 436 Test method for determination of automatic hydro- 6. Apparatus
carbon types in aviation fuels and petroleum distillates—
6.1 High Performance Liquid Chromatograph (HPLC)—
High performance liquid chromatography method with
Any high performance liquid chromatograph capable of pump-
refractive index
ing the mobile phase at flow rates between 0.5 mL⁄min and
1.5 mL⁄min with a precision better than 0.5 % and a pulsation
3. Terminology
of<1 %fullscaledeflectionunderthetestconditionsdescribed
3.1 Definitions of Terms Specific to This Standard:
in Section 9. See Fig. 1.
3.1.1 di-aromatic hydrocarbons (DAHs), n—compounds
6.2 Sample Injection System—The sample injection system
that have a longer retention time on the specified polar column
shall be capable of injecting 10 µL (nominal) of sample
than the MAHs.
solution with a repeatability better than 2 %.
3.1.2 mono-aromatic hydrocarbons (MAHs),
6.2.1 An equal and constant volume of the calibration and
n—compounds that have a longer retention time on the
sample solutions shall be injected into the chromatograph.
specifiedpolarcolumnthanthenon-aromatichydrocarbonsbut
Both manual and automatic sample injection systems (using
a shorter retention time than the di-aromatic hydrocarbons.
either complete or partial filling of the sample loop) will, when
3.1.3 non-aromatic hydrocarbons, n—compounds that have
used correctly, meet the repeatability requirements laid down
a shorter retention time on the specified polar column than the
in 6.2. When using the partial loop filling mode, it is recom-
mono-aromatic hydrocarbons.
mended that the injection volume should be less than half the
3.1.4 total aromatic hydrocarbons, n—sum of the MAHs
total loop volume. For complete filling of the loop, best results
and DAHs.
are obtained by overfilling the loop at least six times.
6.2.2 Sample injection volumes other than 10 µL (typically
NOTE 2—The elution characteristics of aromatic and non-aromatic
in the range from 3 µL to 20 µL) may be used provided they
compounds on the specified polar column have not been specifically
determined for this test method. Published and unpublished data indicate
meettherequirementslaiddownforinjectionrepeatability(see
the major constituents for each hydrocarbon type as follows: (1) Non-
6.2), refractive index sensitivity and linearity (see 9.4 and
aromatic hydrocarbons: acyclic and cyclic alkanes (paraffins and
10.1), and column resolution (see 9.4)
naphthenes), mono-alkenes (if present). (2) MAHs: benzenes, tetralins,
indanes, thiophenes, conjugated poly-alkenes. (3) DAHs: naphthalenes,
6.3 Sample Filter (Optional)—A microfilter of porosity
biphenyls, indenes, fluorenes, acenaphthenes, benzothiophenes.
0.45 µm or less, which is chemically-inert towards hydrocar-
bon solvents, is recommended for the removal of particulate
4. Summary of Test Method
matter from the sample solutions.
4.1 The test portion is diluted 1:1 with the mobile phase,
6.4 Column System—Any stainless steel HPLC column(s)
such as heptane, and a fixed volume of this solution injected
packed with an approved amino-bonded (or polar amino/
into a high performance liquid chromatograph fitted with a
cyano-bonded) silica stationary phase is suitable, provided it
polar column. This column has little affinity for the non-
meets the resolution requirements laid down in 9.4.3. Column
aromatic hydrocarbons and exhibits a pronounced selectivity
lengths from 150 mm to 300 mm with an internal diameter
for aromatic hydrocarbons. As a result of this selectivity, the
from 4 mm to 5 mm and packed with 3 µm or 5 µm particle
aromatic hydrocarbons are separated from the non-aromatic
size stationary phase have been found to be satisfactory. The
hydrocarbons into distinct bands in accordance with their ring
useofaguardcolumn(forexample,30 mmby4.6 mminternal
structure, that is, MAHs and DAHs.
diameter) packed with silica or amino-bonded silica is recom-
4.2 The column is connected to a refractive index detector
mended but not essential.
that detects the components as they elute from the column.The
6.5 HPLC Column Oven—Any suitable HPLC column oven
electronic signal from the detector is continually monitored by
(block heating or air circulating) capable of maintaining a
a data processor. The amplitudes of the signals (peak areas)
constant temperature (61 °C) within the range from 20 °C to
from the sample aromatics are compared with those obtained
40 °C.
from previously-run calibration standards in order to calculate
the percent m/m MAHs and DAHs in the sample. The sum of
NOTE 3—The refractive index detector is sensitive to both sudden and
the MAHs and DAHs is reported as the total aromatic content
gradual changes in the temperature of the eluent. All necessary precau-
(percent m/m) of the sample. tions should be taken to establish constant temperature conditions
throughout the liquid chromatograph system.
5. Significance and Use
NOTE 4—Alternative forms of temperature control, for example,
temperature-controlled laboratories, are permitted.
5.1 Accurate quantitative information on aromatic hydro-
carbon types can be useful in determining the effects of
3 4
Available from Energy Institute, 61 New Cavendish St., London, W1G 7AR, Stationary phases known to give suitable results include Spherisorb 3NH ,
U.K., http://www.energyinst.org. Spherisorb 5NH , Partisil 5 PAC, and Partisphere 5 PAC.
D6379 − 11 (2019)
FIG. 1 Example Chromatogram of an Aviation Fuel Showing Integration Points and Aromatic Hydrocarbon Type Groups
6.6 Refractive Index Detector—Any refractive index detec- 7.3 1-Methylnaphthalene, ≥98 % pure. (Warning—Gloves
tor may be used provided it is capable of being operated over should be worn when handling aromatic compounds (for
the refractive index range from 1.3 to 1.6, meets the sensitivity example, disposable vinyl gloves).)
requirement specified in 9.4.2, gives a linear response over the
NOTE 7—Purity is determined by gas chromatography with flame
calibration range, and has a suitable output signal for the data
ionization detection. The highest purity standards available should be
system. If the refractive index detector has a facility for
used. Standards of ≥98 % purity are commercially available from all
independent temperature control, it is recommended that this is major suppliers.
set at the same temperature as the column oven.
7.4 o-Xylene (1,2-Dimethylbenzene), ≥98 % pure.
6.7 Computer or Computing Integrator—Any data system
8. Sampling
can be used provided it is compatible with the refractive index
detector, has a minimum sampling rate of 1 Hz, and is capable
8.1 The laboratory fuel sample from which an aliquot is
of peak area and retention time measurement. The data system
being drawn for the purposes of this test method shall be
should also have minimum facilities for post-analysis data
representative of the lot of fuel. The laboratory sample should
processing, such as baseline correction and reintegration. The
be obtained by following Practice D4057 or D4177,ora
ability to perform automatic peak detection and identification
similar standard.
and to calculate sample concentrations from peak area mea-
surements is recommended but not essential.
9. Apparatus Preparation
6.8 Volumetric Flasks, Grade B, or better, of 10 mL and
9.1 Set up the chromatograph, injection system, column and
100 mL capacity.
column oven, refractive index detector, and computing inte-
grator in accordance with the appropriate equipment manuals.
6.9 Analytical Balance, accurate to 60.0001 g.
The HPLC column shall be installed in the column oven.
7. Reagents
NOTE 8—The column oven is optional if alternative arrangements are
made to maintain a constant temperature environment, for example, a
7.1 Cyclohexane, ≥99 % pure.
temperature-controlled laboratory (see 6.5).
NOTE 5—Cyclohexane may contain benzene as an impurity.
9.2 Adjust the flow rate of the mobile phase to a constant
7.2 Heptane, HPLC Grade. For use as HPLC mobile phase.
1.0 mL⁄min 6 0.2 mL⁄min and ensure that the reference cell
(Warning—Hydrocarbon solvents are highly flammable and
oftherefractiveindexdetectorisfullofmobilephase(see6.6).
may cause irritation by inhalation, ingestion, or skin contact.)
Allow the temperature of the column oven (and refractive
index detector if equipped with temperature control) to stabi-
NOTE 6—It is recommended practice to degas the HPLC mobile phase
before use. lize.
D6379 − 11 (2019)
TABLE 1 Concentration Standards
9.2.1 To minimize drift, it is essential to make sure that the
referencecellisfullofsolvent.Thebestwaytoaccomplishthis Calibration Standard
AB C D
iseitherto (1)flushthemobilephasethroughthereferencecell
Cyclohexane g/100 mL 5.0 2.0 0.5 0.1
(then isolate the reference cell to prevent evaporation of the
o-xylene g/100 mL 15.0 5.0 1.0 0.1
solvent) immediately prior to analysis, or (2) continuously 1-Methylnaphthalene g/100 mL 5.0 1.0 0.2 0.05
make up for solvent evaporation by supplying a steady flow
through the reference cell. The makeup flow is optimized so
NOTE 13—If peak area repeatabilities are poor, check to see that the
that reference and analytical cell mismatch due to drying-out,
injection system is working optimally and that the baseline is stable
temperature, or pressure gradients are minimized. Typically
(minimal drift) and noise-free.
this can be accomplished with a makeup flow set at one tenth
of the analytical flow.
10. Procedure
NOTE 9—The flow rate may be adjusted (typically within the range 10.1 Calibration:
from 0.8 mL⁄min to 1.2 mL⁄min) to an optimum value to meet the
10.1.1 Prepare four calibration standards (A, B, C, and D),
resolution requirements specified in 9.4.3.
in accordance with the concentrations given in Table 1,by
9.3 Prepare a system resolution standard (SRS) by weighing
weighing, to the nearest 0.0001 g, the appropriate materials
cyclohexane (1.0 g 6 0.1 g), o-xylene (0.5 g 6 0.05 g), and into 100 mLvolumetric flasks and making up to the mark with
1-methylnaphthalene (0.05 g 6 0.005 g) into a 100 mL volu-
heptane.
metric flask and makin
...
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: D6379 − 11 D6379 − 11 (Reapproved 2019)
Designation: 436/01
Standard Test Method for
Determination of Aromatic Hydrocarbon Types in Aviation
Fuels and Petroleum Distillates—High Performance Liquid
Chromatography Method with Refractive Index Detection
This standard is issued under the fixed designation D6379; 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.
INTRODUCTION
This test method is intended to be technically equivalent to IP 436-01 with an identical title. The
ASTM format for test methods has been used, and where possible, equivalent ASTM test methods
have replaced the IP or ISO standards.
The test method is intended to be used as one of several possible alternative instrumental test
methods that are aimed at quantitative determination of hydrocarbon types in fuels. This does not
imply that a correlation necessarily exists between this and any other test method intended to give this
information, and it is the responsibility of the user to determine such correlation if necessary.
1. Scope*Scope
1.1 This test method covers a high performance liquid chromatographic test method for the determination of mono-aromatic and
di-aromatic hydrocarbon contents in aviation kerosineskerosenes and petroleum distillates boiling in the range from 5050 °C to
300°C,300 °C, such as Jet A or Jet A-1 fuels. The total aromatic content is calculated from the sum of the individual aromatic
hydrocarbon-types.
NOTE 1—Samples with a final boiling point greater than 300°C300 °C that contain tri-aromatic and higher polycyclic aromatic compounds are not
determined by this test method and should be analyzed by Test Method D6591 or other suitable equivalent test methods.
1.2 This test method is calibrated for distillates containing from 10 to %to 25 % m/m mono-aromatic hydrocarbons and from
00 % to 7 % m/m di-aromatic hydrocarbons.
1.3 The precision of this test method has been established for kerosinekerosene boiling range distillates containing from 1010 %
to 25 % m/m mono-aromatic hydrocarbons and from 00 % to 7 % m/m di-aromatic hydrocarbons.
1.4 Compounds containing sulfur, nitrogen, and oxygen are possible interferents. Mono-alkenes do not interfere, but conjugated
di- and poly-alkenes, if present, are possible interferents.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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
D02.04.0C on Liquid Chromatography.
Current edition approved May 1, 2011June 1, 2019. Published June 2011August 2019. Originally approved in 1999. Last previous edition approved in 20042011 as
D6379D6379 – 11.–04. DOI: 10.1520/D6379-11.10.1520/D6379-11R19.
In the IP, this test method is under the jurisdiction of the Standardization Committee.
*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
D6379 − 11 (2019)
2. Referenced Documents
2.1 ASTM Standards:
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
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D6591 Test Method for Determination of Aromatic Hydrocarbon Types in Middle Distillates—High Performance Liquid
Chromatography Method with Refractive Index Detection
2.2 Energy Institute Standards:
IP 436 Test Methodmethod for Determination of Automatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates-
High Performance Liquid Chromatography Method with Refractive Indexdetermination of automatic hydrocarbon types in
aviation fuels and petroleum distillates—High performance liquid chromatography method with refractive index
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 di-aromatic hydrocarbons (DAHs), n—compounds that have a longer retention time on the specified polar column than
the MAHs.
3.1.2 mono-aromatic hydrocarbons (MAHs), n—compounds that have a longer retention time on the specified polar column than
the non-aromatic hydrocarbons but a shorter retention time than the di-aromatic hydrocarbons.
3.1.3 non-aromatic hydrocarbons, n—compounds that have a shorter retention time on the specified polar column than the
mono-aromatic hydrocarbons.
3.1.4 total aromatic hydrocarbons, n—sum of the MAHs and DAHs.
NOTE 2—The elution characteristics of aromatic and non-aromatic compounds on the specified polar column have not been specifically determined for
this test method. Published and unpublished data indicate the major constituents for each hydrocarbon type as follows: (1) Non-aromatic hydrocarbons:
acyclic and cyclic alkanes (paraffins and naphthenes), mono-alkenes (if present). (2) MAHs: benzenes, tetralins, indanes, thiophenes, conjugated
poly-alkenes. (3) DAHs: naphthalenes, biphenyls, indenes, fluorenes, acenaphthenes, benzothiophenes.
4. Summary of Test Method
4.1 The test portion is diluted 1:1 with the mobile phase, such as heptane, and a fixed volume of this solution injected into a
high performance liquid chromatograph fitted with a polar column. This column has little affinity for the non-aromatic
hydrocarbons and exhibits a pronounced selectivity for aromatic hydrocarbons. As a result of this selectivity, the aromatic
hydrocarbons are separated from the non-aromatic hydrocarbons into distinct bands in accordance with their ring structure, that
is, MAHs and DAHs.
4.2 The column is connected to a refractive index detector that detects the components as they elute from the column. The
electronic signal from the detector is continually monitored by a data processor. The amplitudes of the signals (peak areas) from
the sample aromatics are compared with those obtained from previously-run calibration standards in order to calculate the percent
m/m MAHs and DAHs in the sample. The sum of the MAHs and DAHs is reported as the total aromatic content (percent m/m)
of the sample.
5. Significance and Use
5.1 Accurate quantitative information on aromatic hydrocarbon types can be useful in determining the effects of petroleum
processes on production of various finished fuels. This information can also be useful for indicating the quality of fuels and for
assessing the relative combustion properties of finished fuels.
6. Apparatus
6.1 High Performance Liquid Chromatograph (HPLC)—Any high performance liquid chromatograph capable of pumping the
mobile phase at flow rates between 0.50.5 mL ⁄min and 1.51.5 mL mL/min ⁄min with a precision better than 0.5 % and a pulsation
of <1 % full scale deflection under the test conditions described in Section 9. See Fig. 1.
6.2 Sample Injection System—The sample injection system shall be capable of injecting 10 μL 10 μL (nominal) of sample
solution with a repeatability better than 2 %.
6.2.1 An equal and constant volume of the calibration and sample solutions shall be injected into the chromatograph. Both
manual and automatic sample injection systems (using either complete or partial filling of the sample loop) will, when used
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.
Available from Energy Institute, 61 New Cavendish St., London, WIGW1G 7AR, U.K.U.K., http://www.energyinst.org.
D6379 − 11 (2019)
FIG. 1 Example Chromatogram of an Aviation Fuel Showing Integration Points and Aromatic Hydrocarbon Type Groups
correctly, meet the repeatability requirements laid down in 6.2. When using the partial loop filling mode, it is recommended that
the injection volume should be less than half the total loop volume. For complete filling of the loop, best results are obtained by
overfilling the loop at least six times.
6.2.2 Sample injection volumes other than 10 μL 10 μL (typically in the range from 33 μL to 20 μL) 20 μL) may be used
provided they meet the requirements laid down for injection repeatability (see 6.2), refractive index sensitivity and linearity (see
9.4 and 10.1), and column resolution (see 9.4)
6.3 Sample Filter (Optional)—A microfilter of porosity 0.45 μm 0.45 μm or less, which is chemically-inert towards hydrocarbon
solvents, is recommended for the removal of particulate matter from the sample solutions.
6.4 Column System—Any stainless steel HPLC column(s) packed with an approved amino-bonded (or polar amino/cyano-
bonded) silica stationary phase is suitable, provided it meets the resolution requirements laid down in 9.4.3. Column lengths from
150150 mm to 300 mm 300 mm with an internal diameter from 44 mm to 5 mm 5 mm and packed with 33 μm or 5 μm 5 μm
particle size stationary phase have been found to be satisfactory. The use of a guard column (for example, 3030 mm by
4.6-mm4.6 mm internal diameter) packed with silica or amino-bonded silica is recommended but not essential.
6.5 HPLC Column Oven—Any suitable HPLC column oven (block heating or air circulating) capable of maintaining a constant
temperature (61°C)(61 °C) within the range from 2020 °C to 40°C.40 °C.
NOTE 3—The refractive index detector is sensitive to both sudden and gradual changes in the temperature of the eluent. All necessary precautions
should be taken to establish constant temperature conditions throughout the liquid chromatograph system.
NOTE 4—Alternative forms of temperature control, for example, temperature-controlled laboratories, are permitted.
6.6 Refractive Index Detector—Any refractive index detector may be used provided it is capable of being operated over the
refractive index range from 1.3 to 1.6, meets the sensitivity requirement specified in 9.4.2, gives a linear response over the
calibration range, and has a suitable output signal for the data system. If the refractive index detector has a facility for independent
temperature control, it is recommended that this is set at the same temperature as the column oven.
6.7 Computer or Computing Integrator—Any data system can be used provided it is compatible with the refractive index
detector, has a minimum sampling rate of 1 Hz, 1 Hz, and is capable of peak area and retention time measurement. The data system
should also have minimum facilities for post-analysis data processing, such as baseline correction and reintegration. The ability
to perform automatic peak detection and identification and to calculate sample concentrations from peak area measurements is
recommended but not essential.
6.8 Volumetric Flasks, Grade B, or better, of 10 mL and 100 mL 10 mL and 100 mL capacity.
Stationary phases known to give suitable results include Spherisorb 3NH , Spherisorb 5NH , Partisil 5 PAC, and Partisphere 5 PAC.
2 2
D6379 − 11 (2019)
6.9 Analytical Balance, accurate to 60.0001 g.60.0001 g.
7. Reagents
7.1 Cyclohexane, ≥99 % pure.
NOTE 5—Cyclohexane may contain benzene as an impurity.
7.2 Heptane, HPLC Grade. For use as HPLC mobile phase. (Warning—Hydrocarbon solvents are highly flammable and may
cause irritation by inhalation, ingestion, or skin contact.)
NOTE 6—It is recommended practice to degas the HPLC mobile phase before use.
7.3 1-Methylnaphthalene, ≥ 98 % ≥98 % pure. (Warning—Gloves should be worn when handling aromatic compounds (for
example, disposable vinyl gloves).)
NOTE 7—Purity is determined by gas chromatography with flame ionization detection. The highest purity standards available should be used. Standards
of ≥ 98 % ≥98 % purity are commercially available from all major suppliers.
7.4 o-Xylene (1,2-Dimethylbenzene) , (1,2-Dimethylbenzene), ≥ 98 % ≥98 % pure.
8. Sampling
8.1 The laboratory fuel sample from which an aliquot is being drawn for the purposes of this test method shall be representative
of the lot of fuel. The laboratory sample should be obtained by following Practice D4057 or D4177, or a similar standard.
9. Apparatus Preparation
9.1 Set up the chromatograph, injection system, column and column oven, refractive index detector, and computing integrator
in accordance with the appropriate equipment manuals. The HPLC column shall be installed in the column oven.
NOTE 8—The column oven is optional if alternative arrangements are made to maintain a constant temperature environment, for example, a
temperature-controlled laboratory (see 6.5).
9.2 Adjust the flow rate of the mobile phase to a constant 1.01.0 mL ⁄min 6 0.20.2 mL mL/min ⁄min and ensure that the
reference cell of the refractive index detector is full of mobile phase (see 6.66.6.1).). Allow the temperature of the column oven
(and refractive index detector if equipped with temperature control) to stabilize.
9.2.1 To minimize drift, it is essential to make sure that the reference cell is full of solvent. The best way to accomplish this
is either to (1) flush the mobile phase through the reference cell (then isolate the reference cell to prevent evaporation of the
solvent) immediately prior to analysis, or (2) continuously make up for solvent evaporation by supplying a steady flow through
the reference cell. The makeup flow is optimized so that reference and analytical cell mismatch due to drying-out, temperature,
or pressure gradients are minimized. Typically this can be accomplished with a makeup flow set at one tenth of the analytical flow.
NOTE 9—The flow rate may be adjusted (typically within the range from 0.80.8 mL ⁄min to 1.21.2 mL mL/min) ⁄min) to an optimum value to meet
the
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