ASTM D7398-23

Standard Test Method for Boiling Range Distribution of Fatty Acid Methyl Esters (FAME) in the Boiling Range from 100 °C to 615 °C by Gas Chromatography

SIGNIFICANCE AND USE
5.1 The boiling range distribution of FAMES provides an insight into the composition of product related to the transesterification process. This gas chromatographic determination of boiling range can be used to replace conventional distillation methods for product specification testing with the mutual agreement of interested parties.  
5.2 Biodiesel (FAMES) exhibits a boiling point rather than a distillation curve. The fatty acid chains in the raw oils and fats from which biodiesel is produced are mainly comprised of straight chain hydrocarbons with 16 to 18 carbons that have similar boiling temperatures. The atmospheric boiling point of biodiesel generally ranges from 330 °C to 357 °C. The Specification D6751 value of 360 °C max at 90 % off by Test Method D1160 was incorporated as a precaution to ensure the fuel has not been adulterated with high boiling contaminants.
SCOPE
1.1 This test method covers the determination of the boiling range distribution of fatty acid methyl esters (FAME). This test method is applicable to FAMES (biodiesel, B100) having an initial boiling point greater than 100 °C and a final boiling point less than 615 °C at atmospheric pressure as measured by this test method.  
1.2 The test method can also be applicable to blends of diesel and biodiesel (B1 through B100), however precision for these samples types has not been evaluated.  
1.3 The test method is not applicable for analysis of petroleum containing low molecular weight components (for example naphthas, reformates, gasolines, crude oils).  
1.4 Boiling range distributions obtained by this test method are not equivalent to results from low efficiency distillation such as those obtained with Test Method D86 or D1160, especially the initial and final boiling points.  
1.5 This test method uses the principles of simulated distillation methodology. See Test Methods D2887, D6352, and D7213.  
1.6 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.  
1.7 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.  
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2023
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.04.0H - Chromatographic Distribution Methods

Relations

• Replaces: ASTM D7398-21 - Standard Test Method for Boiling Range Distribution of Fatty Acid Methyl Esters (FAME) in the Boiling Range from 100 °C to 615 °C by Gas Chromatography
• Effective Date: 01-Nov-2023
• Refers: ASTM D86-23a - Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
• Effective Date: 01-Dec-2023
• Refers: ASTM D86-23ae1 - Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
• Effective Date: 01-Dec-2023
• Refers: ASTM D7213-23 - Standard Test Method for Boiling Range Distribution of Petroleum Distillates in the Boiling Range from 100 °C to 615 °C by Gas Chromatography
• Effective Date: 01-Nov-2023
• Refers: ASTM D2887-23 - Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
• Effective Date: 01-Jul-2023
• Refers: ASTM D86-23 - Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
• Effective Date: 01-Mar-2023
• Refers: ASTM D2887-22e1 - Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
• Effective Date: 01-Sep-2022
• Refers: ASTM D7213-15(2019) - Standard Test Method for Boiling Range Distribution of Petroleum Distillates in the Boiling Range from 100 °C to 615 °C by Gas Chromatography
• Effective Date: 01-Dec-2019

Overview

ASTM D7398-23 is the internationally recognized standard test method for determining the boiling range distribution of fatty acid methyl esters (FAME), commonly known as biodiesel, using gas chromatography. The procedure covers FAMEs and biodiesel blends (B1 through B100) with boiling points spanning from 100 °C to 615 °C. This method offers a more precise and efficient alternative to traditional low-efficiency distillation techniques, providing key insights into product composition and the effects of the transesterification process utilized in biodiesel production. By delivering accurate boiling point data, ASTM D7398-23 supports biodiesel product specification, quality control, and regulatory compliance.

Key Topics

• Boiling Range Distribution: Measures the percentage of sample vaporized at various boiling points, crucial for FAME quality and process evaluation.
• Gas Chromatography Methodology: Simulates distillation by separating FAME components in a non-polar column, providing reproducible results, especially compared to conventional distillation (such as ASTM D86 or D1160).
• Applicability: Applies to neat biodiesel (B100) and blends (B1 to B100), with the standard’s validated range covering FAMEs that boil above 100 °C and below 615 °C.
• Not for Petroleum Fractions: Excludes petroleum products containing low molecular weight components (naphthas, gasolines, crude oils).
• Precision and Calibration: Employs n-paraffin standards for calibration, ensuring the boiling range is matched to atmospheric equivalent temperatures.
• Safety and Environmental Considerations: Users must ensure proper laboratory safety, health, and environmental practices when applying this method.

Applications

• Biodiesel Product Specification: ASTM D7398-23 is used to verify that FAME-based fuels meet industry standards and regulatory requirements, such as the maximum boiling point limit (360 °C at 90% off) to avoid contamination by high boiling substances.
• Quality Assurance in Production: Determines the effects of the transesterification process by analyzing the boiling point profile, thus ensuring fuel purity and consistency.
• Regulatory Compliance: Supports adherence to legal and market acceptance criteria for biodiesel blends, aligning with ASTM D6751 for biodiesel fuel blendstock.
• Replacement of Conventional Distillation: Enables mutual agreement between parties to utilize gas chromatography for specification testing, providing a faster and often more informative result than traditional distillation.
• Blends Evaluation: Applicable for a wide range of biodiesel/petrodiesel blends (B1-B100), though precision data for blends is noted as not fully established within this method.

Related Standards

• ASTM D6751: Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels
• ASTM D86 & ASTM D1160: Test methods for distillation of petroleum products at atmospheric and reduced pressures
• ASTM D2887, D6352, D7213: Gas chromatographic methods for boiling range distribution of petroleum products
• ASTM D4626: Practice for calculation of gas chromatographic response factors
• ASTM E355, E594, E1510: Gas chromatography practices related to terminology, flame ionization detectors, and column installation

Practical Value

Adopting ASTM D7398-23 allows laboratories, producers, and regulators to achieve reliable, reproducible characterization of the boiling profile in biodiesel products. This enhances quality control across supply chains, ensures compliance with international fuel standards, and supports the sustainability and performance of biodiesel as a renewable energy source. By utilizing state-of-the-art gas chromatography, the method saves time and reduces complexity in the testing process compared to traditional distillation, while providing detailed data on FAME molecular distribution critical to fuel performance and regulatory compliance.

Keywords: ASTM D7398-23, FAME boiling range, biodiesel gas chromatography, boiling range distribution, biodiesel testing, fuel quality control, simulated distillation, biodiesel standards.

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: D7398 − 23
Standard Test Method for
Boiling Range Distribution of Fatty Acid Methyl Esters
(FAME) in the Boiling Range from 100 °C to 615 °C by Gas
Chromatography
This standard is issued under the fixed designation D7398; 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* mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This test method covers the determination of the boiling
range distribution of fatty acid methyl esters (FAME). This test
2. Referenced Documents
method is applicable to FAMES (biodiesel, B100) having an
2.1 ASTM Standards:
initial boiling point greater than 100 °C and a final boiling
D86 Test Method for Distillation of Petroleum Products and
point less than 615 °C at atmospheric pressure as measured by
Liquid Fuels at Atmospheric Pressure
this test method.
D1160 Test Method for Distillation of Petroleum Products at
1.2 The test method can also be applicable to blends of
Reduced Pressure
diesel and biodiesel (B1 through B100), however precision for
D2887 Test Method for Boiling Range Distribution of Pe-
these samples types has not been evaluated.
troleum Fractions by Gas Chromatography
1.3 The test method is not applicable for analysis of
D2892 Test Method for Distillation of Crude Petroleum
petroleum containing low molecular weight components (for
(15-Theoretical Plate Column)
example naphthas, reformates, gasolines, crude oils).
D4626 Practice for Calculation of Gas Chromatographic
Response Factors
1.4 Boiling range distributions obtained by this test method
D6352 Test Method for Boiling Range Distribution of Pe-
are not equivalent to results from low efficiency distillation
troleum Distillates in Boiling Range from 174 °C to
such as those obtained with Test Method D86 or D1160,
700 °C by Gas Chromatography
especially the initial and final boiling points.
D6751 Specification for Biodiesel Fuel Blendstock (B100)
1.5 This test method uses the principles of simulated distil-
for Middle Distillate Fuels
lation methodology. See Test Methods D2887, D6352, and
D7213 Test Method for Boiling Range Distribution of Pe-
D7213.
troleum Distillates in the Boiling Range from 100 °C to
1.6 The values stated in SI units are to be regarded as
615 °C by Gas Chromatography
standard. The values given in parentheses are for information
E355 Practice for Gas Chromatography Terms and Relation-
only.
ships
E594 Practice for Testing Flame Ionization Detectors Used
1.7 This standard does not purport to address all of the
in Gas or Supercritical Fluid Chromatography
safety concerns, if any, associated with its use. It is the
E1510 Practice for Installing Fused Silica Open Tubular
responsibility of the user of this standard to establish appro-
Capillary Columns in Gas Chromatographs
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3. Terminology
1.8 This international standard was developed in accor-
dance with internationally recognized principles on standard- 3.1 Definitions:
ization established in the Decision on Principles for the
3.1.1 This test method makes reference to many common
Development of International Standards, Guides and Recom- gas chromatographic procedures, terms, and relationships.
Detailed definitions of these can be found in Practices E355,
E594, and E1510.
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 D02.04.0H on Chromatographic Distribution Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2023. Published November 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2007. Last previous edition approved in 2021 as D7398 – 21. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7398-23. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7398 − 23
3.1.2 biodiesel, n—fuel composed of mono-alkyl esters of 4. Summary of Test Method
long chain fatty acids derived from vegetable oils or animal
4.1 The boiling range distribution by distillation is simu-
fats, designated B100.
lated by the use of gas chromatography. A non-polar open
3.2 Definitions of Terms Specific to This Standard: tubular (capillary) gas chromatographic column is used to elute
the hydrocarbon and FAME components of the sample in order
3.2.1 area slice, n—area resulting from the integration of the
of increasing boiling point.
chromatographic detector signal within a specified retention
time interval. In area slice mode (6.4.2), peak detection
4.2 A sample aliquot is diluted with a viscosity reducing
parameters are bypassed and the detector signal integral is
solvent and introduced into the chromatographic system. The
recorded as area slices of consecutive, fixed duration time
solvent shall be apolar and not interfere with measurement of
intervals.
the sample in the 100 °C to 615 °C range. Sample vaporization
is provided by separate heating of the point of injection or in
3.2.2 atmospheric equivalent temperature (AET),
conjunction with column oven heating.
n—temperature converted from the measured vapor tempera-
ture obtained at sub-ambient pressure to atmospheric equiva-
4.3 The column oven temperature is raised at a reproducible
lent temperature (AET) corresponding to the equivalent boiling
linear rate to effect separation of the FAME components in
point at atmospheric pressure, 101.3 kPa (760 mm Hg), The
order of increasing boiling point relative to a n-paraffin
AET is the expected distillate temperature if the distillation
calibration mixture. The elution of sample components is
was performed at atmospheric pressure and there was no
quantitatively determined using a flame ionization detector.
thermal decomposition.
The detector signal integral is recorded as area slices for
consecutive retention time intervals during the analysis.
3.2.3 corrected area slice, n—area slice corrected for base-
line offset, by subtraction of the exactly corresponding area
4.4 Retention times of known normal paraffin hydrocarbons,
slice in a previously recorded blank (non-sample) analysis.
spanning the scope of the test method (C – C ), are deter-
5 60
mined and correlated to their boiling point temperatures. The
3.2.4 cumulative corrected area, n—accumulated sum of
normalized cumulative corrected sample areas for each con-
corrected area slices from the beginning of the analysis through
secutive recorded time interval are used to calculate the boiling
a given retention time, ignoring any non-sample area (for
range distribution. The boiling point temperature at each
example, solvent).
reported percent off increment is calculated from the retention
3.2.5 initial boiling point (IBP), n—temperature (corre-
time calibration.
sponding to the retention time) at which a cumulative corrected
4.5 The retention time versus boiling point curve is cali-
area count equal to 0.5 % of the total sample area under the
brated with normal paraffin hydrocarbons since these boiling
chromatogram is obtained.
points are well defined. A mixture of FAMEs is analyzed to
3.2.6 final boiling point (FBP), n—temperature (corre-
check column resolution. A triglyceride is analyzed to verify
sponding to the retention time) at which a cumulative corrected
the system’s ability to detect unreacted oil.
area count equal to 99.5 % of the total sample area under the
chromatogram is obtained.
5. Significance and Use
3.2.7 slice rate, n—frequency of data sampling or the
5.1 The boiling range distribution of FAMES provides an
frequency of data bunching provided that the frequency of data
insight into the composition of product related to the transes-
acquisition is larger than the frequency of bunching. The unit
terification process. This gas chromatographic determination of
of frequency is points/seconds or Hz.
boiling range can be used to replace conventional distillation
3.2.8 slice time, n—cumulative slice rate (analysis time)
methods for product specification testing with the mutual
associated with each area slice throughout the chromatographic
agreement of interested parties.
analysis. The slice time is the time at the end of each
5.2 Biodiesel (FAMES) exhibits a boiling point rather than
contiguous area slice.
a distillation curve. The fatty acid chains in the raw oils and
3.2.9 total sample area, n—cumulative corrected area, from
fats from which biodiesel is produced are mainly comprised of
the initial point to the final area point.
straight chain hydrocarbons with 16 to 18 carbons that have
similar boiling temperatures. The atmospheric boiling point of
3.3 Abbreviations:
biodiesel generally ranges from 330 °C to 357 °C. The Speci-
3.3.1 A common abbreviation of hydrocarbon compounds is
fication D6751 value of 360 °C max at 90 % off by Test
to designate the number of carbon atoms in the compound. A
Method D1160 was incorporated as a precaution to ensure the
prefix is used to indicate the carbon chain form, while a
fuel has not been adulterated with high boiling contaminants.
subscripted suffix denotes the number of carbon atoms (for
example, normal decane n-C ; iso-tetradecane = i-C ).
10 14
6. Apparatus
3.3.2 A common abbreviation for FAME compounds is to
designate the number of carbon atoms and number of double 6.1 Chromatograph—The following gas chromatographic
bonds in the compound. The number of carbon atoms is system performance characteristics are required:
denoted by a number after the “C” and the number following 6.1.1 Column Oven—Capable of sustained and linear pro-
a colon indicates the number of double bonds (for example, grammed temperature operation from near ambient (for ex-
C16:2 ; FAME with 16 carbon atoms and 2 double bonds). ample 35 °C to 50 °C) up to 400 °C.
D7398 − 23
6.1.2 Column Temperature Programmer—The chromato- done by means of an electronic integrator or computer based
graph must be capable of linear programmed temperature chromatography data system. The integrator/computer system
operation up to 400 °C at selectable linear rates up to shall have normal chromatographic software for measuring the
20 °C ⁄min. The programming rate must be sufficiently repro- retention time and areas of eluting peaks (peak detection
ducible to obtain the retention time repeatability of 0.03 min mode). In addition, the system shall be capable of converting
(3 s) for each component in the calibration mixture described the continuously integrated detector signal into area slices of
in 7.3. fixed duration (area slice mode). These contiguous area slices,
6.1.3 Detector—This test method requires a flame ioniza- collected for the entire analysis, are stored for later processing.
The electronic range of the integrator/computer (for example,
tion detector (FID). The detector must meet or exceed the
following specifications as detailed in Practice E594. The 1 V, 10 V) shall be operated within the linear range of the
detector/electrometer system used.
specification of flame jet orifice is approximately 0.45 mm
(0.018 in.).
NOTE 1—Some gas chromatographs have an algorithm built into their
6.1.3.1 Operating Temperature, 400 °C.
operating software that allows a mathematical model of the baseline
6.1.3.2 Sensitivity, >0.005 coulombs/g carbon. profile to be stored in memory. This profile is automatically subtracted
-11
from the detector signal on subsequent sample runs to compensate for the
6.1.3.3 Minimum Detectability, 1 × 10 g carbon / s.
column bleed. Some integration systems also store and automatically
6.1.3.4 Linear Range, >10
subtract a blank analysis from subsequent analytical determinations.
6.1.3.5 Connection of the column to the detector must be
such that no temperature below the column temperature exists. 7. Reagents and Materials
Refer to Practice E1510 for proper installation and condition-
7.1 Gases—The following compressed gases are utilized for
ing of the capillary column.
the operation of the gas chromatograph.
6.1.4 Sample Inlet System—Any sample inlet system ca-
7.1.1 Helium, 99.999 %. (Warning—Compressed gas un-
pable of meeting the performance specification in 6.1.5 and 7.3
der high pressure.) This gas can be used as carrier gas. Ensure
may be used. Programmed temperature vaporization (PTV)
sufficient pressure for a constant carrier gas flow rate. It is not
and programmable cool on-column injection systems have
to contain more than 5 mL ⁄m of oxygen and the total amount
been used successfully.
of impurities are not to exceed 10 mL ⁄m .
6.1.5 Carrier Gas Flow Control—The chromatograph shall
7.1.2 Nitrogen, 99.999 %. (Warning—Compressed gas un-
be equipped with carrier flow control capable of maintaining
der high pressure.) This gas can be used as carrier gas. Ensure
constant carrier gas flow control through the column through-
sufficient pressure for a constant carrier gas flow rate. It is not
out the column temperature program cycle as measured with
to contain more than 5 mL ⁄m of oxygen and the total amount
the use of flow a sensor. Flow rate must be maintained within
of impurities are not to exceed 10 mL ⁄m .
1 % through out the temperature program.
7.1.3 Hydrogen, 99.999 %. (Warning—Extremely flam-
mable gas under high pressure.) The total impurities are not to
6.2 Microsyringe—A microsyringe with a 23 gauge or
exceed 10 mL/m . This gas can be used as carrier gas. Ensure
smaller stainless steel needle is used for on-column sample
sufficient pressure for a constant carrier gas flow rate. It is also
introduction. Syringes of 0.1 μL to 10 μL capacity are avail-
used as fuel for the flame ionization detector (FID).
able.
7.1.4 Air, 99.999 %. (Warning—Compressed gas under
6.2.1 Automatic syringe injection is recommended to
high pressure and supports combustion.) Total impurities are
achieve best precision.
not to exceed 10 mL ⁄m . This gas is used to sustain combus-
6.3 Column—This test method is limited to the use of
tion in the flame ionization detector (FID).
non-polar wall coated open tubular (WCOT) columns of high
7.2 Solvents—Unless otherwise indicated, it is intended that
thermal stability. Glass, fused silica, and stainless steel
all solvents conform to the specifications of the committee on
columns, with a 0.53 mm diameter have been successfully
analytical Reagents of the American Chemical Society where
used. Cross-linked or bonded 100 % dimethyl-polysiloxane
such specifications are available. Other grades may be used
stationary phases with film thickness of 0.5 μm to 1.0 μm have
provided it is first ascertained that the solvent is of sufficiently
been used. The column length and liquid phase film thickness
high purity to permit its use without lessening the accuracy of
shall allow the elution of at least C n-paraffin (BP = 615 °C)
the determination.
and triolein. The column and conditions shall provide separa-
7.2.1 Carbon Disulfide (CS ), 99+ % pure. (Warning—
tion of typical petroleum hydrocarbons and saturated FAMES
Extremely flammable and toxic liquid.) Used as a viscosity
in order of increasing boiling point and meet the column
reducing solvent and as a means of reducing mass of sample
resolution requirements of 8.2.1. The column shall provide a
introduced onto the column to ensure linear detector response
resolution between five (5) and fifteen (15) using the test
and reduced peak skewness. It is miscible with FAMES and
method operating conditions.
6.4 Data Acquisition System:
6.4.1 Recorder—A 0 mV to 1 mV range recording potenti-
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington,
ometer or equivalent, with a full-scale response time of 2 s or
DC. For suggestions on the testing of reagents not listed by the American Chemical
less may be used to provide a graphical display.
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
6.4.2 Integrator—Means shall be provided for determining
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
the accumulated area under the chromatogram. This can be copeial Convention, Inc. (USPC), Rockville, MD.
D7398 − 23
provides a relatively small response with the FID. The quality 7.3.1 Qualitative FAME Mixture—A qualitative mixture of
(hydrocarbon content) is determined by this test method prior FAMES (nominally C8:0 to C24:0) dissolved in a suitable
to use as a sample diluent.
solvent. A final concentration of approximately one part of
7.2.2 Cyclohexane (C H ), (99+ % pure) (Warning— FAME mixture to one hundred parts of solvent is required. The
6 12
Flammable. Health hazard.) Used as a viscosity reducing
qualitative mixture contains at least 9 known FAMES (for
solvent. It is miscible with asphaltic hydrocarbons, however, it example, C8:0, C10:0, C12:0, C14:0, C16:0, C18:0, C20:0,
responds well to the FID. Cyclohexane will interfere with the
C22:0, C24:0). Boiling points of FAMES are listed in Table 2.
elution of lower boiling normal paraffins. The quality (hydro- This FAME qualitative mixture is used to calculate resolution
carbon content) is determined by this test method prior to use
of C16:0 and C18:0 (see 8.2.1). It may also be used to insure
as a sample diluent.
that retention time shifts as column ages does not exceed
60.15 min (to be determined from the experimental BP versus
7.3 Calibration Mixture—A qualitative mixture of
RT curve).
n-paraffins (nominally C to C ) dissolved in a suitable
5 60
7.3.2 Quantitative Triglyceride Mixture—A quantative mix-
solvent. A final concentration of approximately one part of
ture of triglyceride (triolein) dissolved in a suitable solvent. A
n-paraffin mixture to one hundred parts of solvent is required.
final concentration of approximately 10 mass ppm is required.
At least one compound in the mixture must have a boiling point
lower than the initial boiling point of the sample being One qualitative mixture meeting the requirement of 7.3.1 and
analyzed, as defined in the scope of this test method (1.1). The 7.3.2 may be used. This triglyceride reponse mixture is used to
calibration mixture must contain at least 13 known n-paraffins verify response to unreacted oils (see 8.2.2.1).
(for example, C , C , C , C , C , C , C , C , C , C , C ,
6 7 8 9 10 12 16 20 30 40 50
7.4 Response Linearity Mixture—Prepare a quantitatively
C , C ). Boiling points of n-paraffins are listed in Table 1.
52 60
weighed mixture of at least ten individual paraffins (>99 %
NOTE 2—A suitable calibration mixture can be obtained by dissolving
purity), covering the boiling range of the test method. The
a polyolefin wax in a volatile solvent (for example, carbon disulfide or
highest boiling point component shall be at least n-C60. The
cyclohexane). Solutions of one part polyolefin wax to one hundred parts
mixture shall contain n-C40. Use a suitable solvent to provide
solvent can be prepared. Lower boiling point paraffins will have to be
a solution of each component at approximately 0.5 % to 2.0 %
added to ensure conformance with 7.3. Fig. 1 illustrates a typical
calibration mixture chromatogram. by mass.
A,B
TABLE 1 Boiling Points of n-Paraffins
Carbon Number Boiling Point °C Boiling Point °F Carbon Number Boiling Point °C Boiling Point °F
5 36 97 33 474 885
6 69 156 34 481 898
7 98 209 35 489 912
8 126 258 36 496 925
9 151 303 37 503 937
10 174 345 38 509 948
11 196 385 39 516 961
12 216 421 40 522 972
13 235 456 41 528 982
14 254 488 42 534 993
15 271 519 43 540 1004
16 287 548 44 545 1013
17 302 576 45 550 1022
18 316 601 46 556 1033
19 330 626 47 561 1042
20 344 651 48 566 1051
21 356 674 49 570 1058
22 369 695 50 575 1067
23 380 716 51 579 1074
24 391 736 52 584 1083
25 402 755 53 588 1090
26 412 774 54 592 1098
27 422 791 55 596 1105
28 431 808 56 600 1112
29 440 825 57 604 1119
30 449 840 58 608 1126
31 458 856 59 612 1134
32 466 870 60 615 1139
A
API Project 44, 72-10-31, is believed to have provided the original normal paraffin boiling point data that are listed in Table 1. However, over the years some of the data
contained in both API Project 44 (Thermodynamics Research Center Hydrocarbon Project) and Test Method D7398 have changed, and they are no longer equivalent. Table
1 represents the current normal paraffin boiling point values accepted by Subcommittee D02.04 and found in all test methods under the jurisdiction of Section D02.04.0H.
B
Test Method D7398 has traditionally used n-paraffin boiling points rounded to the nearest whole degree for calibration. The boiling points listed in Table 1 are correct to
the nearest whole number in both degrees Celsius and degrees Fahrenheit. However, if a conversion is made from one unit to the other and then rounded to a whole
number, the results will not agree with the table values for a few carbon numbers. For example, the boiling point of n-heptane is 98 425 °C which is correctly rounded to
98 °C in the table. However, converting 98.425 °C gives 209.165 °F, which rounds to 209 °F, while converting 98 °C gives 208.4 °F, which rounds to 208 °F. Carbon
numbers 2, 4, 7, 8, 9, 13, 14, 15, 16, 25, 27, and 32 are affected by rounding.
D7398 − 23
FIG. 1 Typical Calibration Curve with Plot
7.5 Reference Material—A reference sample that has been 8.1.2 When attaching the column to the detector inlet,
analyzed by laboratories participating in the test method ensure that the end of the column terminates as close as
cooperative study. Consensus values for the boiling range possible to the FID jet. Follow the instructions in Practice
distribution of this sample is being determined. E1510.
8.1.3 Periodically inspect the FID and, if necessary, remove
8. Preparation of Apparatus
any foreign deposits formed in the detector from combustion of
8.1 Gas Chromatograph Setup: silicone liquid phase or other materials. Such deposits will
change the response characteristics of the detector.
8.1.1 Place the gas chromatograph and ancillary equipment
into operation in accordance with the manufacturers instruc- 8.1.4 The inlet liner and initial portion of the column must
tions. Recommended operating conditions are shown in Table be periodically inspected and replaced if necessary to remove
3. extraneous deposits or sample residue.
D7398 − 23
TABLE 2 FAME and Triglyceride Boiling Point Table
NOTE 1—Boiling points of FAMEs and triglycerides are normally published in the literature at reduced pressure. This table compares the converted
to AET literature BP values from one source to the BP values as determined by extrapolating the retention time of the FAME from the retention time/BP
of the preceding and the following n-paraffin from a chromatographic run using the conditions of this method.
A B C
FAME Name Alternate Name BP °C AET BP °C Extrapolated BP °C
C8:0 Octanoic Acid, Methyl Ester Methyl caprylate 83 200 197
C10:0 Decanoic Acid, Methyl Ester Methyl caprate 114 237 237
C12:0 Dodecanoic Acid, Methyl Ester Methyl laurate 141 270 272
C14:0 Tetradecanoic Acid, Methyl Ester Methyl Myristate 155-7 308 304
C16:0 Hexadecanoic Acid, Methyl Ester Methyl palmitate 148 330 332
C18:0 Octadecanoic Acid, Methyl Ester Methyl stearate 215 357 358
C20:0 Eicosanoic Acid, Methyl Ester Methyl arachidate 215-16 369 382
C22:0 Docosanoic Acid, Methyl Ester Methyl behenate 224-5 375 404
C24:0 Tetracosanoic Acid, Methyl Ester 413 425
15 18
C18 235-40
Triglyceride Triolein 375
C18 606
Triglyceride Triolein
A
Reduced pressure boiling points in degrees Celsius and mm Hg as published in CRC Handbook of Chemistry & Physics, 61st Edition.
B
Atmospheric equivalent temperature calculated as per Test Method D2892 equations. At present there is insufficient evidence that TBP (Test Method D2892) yields
distillation curves equivalent to those that may be obtained by classical vacuum distillations.
C
Boiling point extropolated from retention time of n-paraffins under the condition of this chromatographic method. The relative good agreement with the boiling point
determined by using n-paraffins to calibrate the retention time indicates the validity of such calibration.
TABLE 3 Recommended Operating Conditions
R 5 2 t 2 t / 1.699 w 1w (1)
~ ! ~ ~ !!
2 1 2 1
Injector cool on-column or PTV
where:
Injection temperature oven-track mode or programmed;
initial temperature 100 °C
R = resolution,
initial hold 0 minutes
t = time for the C16:0 peak maximum,
program rate 10 °C ⁄min
t = time for the C18:0 peak maximum,
final temperature 385 °C
Auto sampler required for best precision w = peak width, at half height, of the C16:0 peak and,
Data collection data is collected as independent area slices
w = peak width, at half height, of the C18:0 peak.
(average data collection rate is 1.0 Hz or one sample/s)
Column capillary, 4 m × 0.53 mm ID
8.2.2 Detector Response Calibration—This test method as-
film thickness; 1.0 microns (polydimethylsiloxane)
sumes that the FID response to petroleum hydrocarbons is
Flow conditions UHP helium at 10 mL/min (constant flow)
proportional to the mass of individual components. This shall
(make-up gas helium)
Detector Flame Ionization;
be verified when the system is put in service, and whenever any
Temperature: 390 °C
changes are made to the system or operational parameters.
Oven program initial oven temperature 35 °C,
Analyze the response linearity mixture (7.4) using the identical
initial hold 0 min.,
program rate 10 °C ⁄min.,
procedure to be used for the analysis of samples (Section 9).
final oven temperature 385 °C,
Calculate the relative response factor for each n-paraffin
Sample size 0.5 microliter
(relative to n-tetracontane) as per Practice D4626 and Eq 2:
Sample dilution 2 % by mass in carbon disulfide
Calibration dilution 1 % by mass in carbon disulfide
F 5 ~M /A !/~M /A ! (2)
n n n 40 40
where:
F = relative response factor,
n
8.1.5 Column Conditioning—A new column will require
M = mass of the n-paraffin in the mixture,
n
conditioning at the upper test method operating temperature to
A = peak area of the n-paraffin in the mixture,
n
reduce or eliminate significant liquid phase bleed, resulting in M = mass of the n-tetracontane in the mixture and,
A = peak area of th
...

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: D7398 − 21 D7398 − 23
Standard Test Method for
Boiling Range Distribution of Fatty Acid Methyl Esters
(FAME) in the Boiling Range from 100 °C to 615 °C by Gas
Chromatography
This standard is issued under the fixed designation D7398; 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 the boiling range distribution of fatty acid methyl esters (FAME). This test
method is applicable to FAMES (biodiesel, B100) having an initial boiling point greater than 100 °C and a final boiling point less
than 615 °C at atmospheric pressure as measured by this test method.
1.2 The test method can also be applicable to blends of diesel and biodiesel (B1 through B100), however precision for these
samples types has not been evaluated.
1.3 The test method is not applicable for analysis of petroleum containing low molecular weight components (for example
naphthas, reformates, gasolines, crude oils).
1.4 Boiling range distributions obtained by this test method are not equivalent to results from low efficiency distillation such as
those obtained with Test Method D86 or D1160, especially the initial and final boiling points.
1.5 This test method uses the principles of simulated distillation methodology. See Test Methods D2887, D6352, and D7213.
1.6 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.7 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.
1.8 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:
D86 Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure
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
D02.04.0H on Chromatographic Distribution Methods.
Current edition approved Nov. 1, 2021Nov. 1, 2023. Published November 2021November 2023. Originally approved in 2007. Last previous edition approved in 2021 as
D7398 – 11 (2021).D7398 – 21. DOI: 10.1520/D7398-21.10.1520/D7398-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7398 − 23
D1160 Test Method for Distillation of Petroleum Products at Reduced Pressure
D2887 Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography
D2892 Test Method for Distillation of Crude Petroleum (15-Theoretical Plate Column)
D4626 Practice for Calculation of Gas Chromatographic Response Factors
D6352 Test Method for Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 °C to 700 °C by Gas
Chromatography
D6751 Specification for Biodiesel Fuel Blendstock (B100) for Middle Distillate Fuels
D7213 Test Method for Boiling Range Distribution of Petroleum Distillates in the Boiling Range from 100 °C to 615 °C by Gas
Chromatography
E355 Practice for Gas Chromatography Terms and Relationships
E594 Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
E1510 Practice for Installing Fused Silica Open Tubular Capillary Columns in Gas Chromatographs
3. Terminology
3.1 Definitions:
3.1.1 This test method makes reference to many common gas chromatographic procedures, terms, and relationships. Detailed
definitions of these can be found in Practices E355, E594, and E1510.
3.1.2 biodiesel, n—fuel composed of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats,
designated B100.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 area slice, n—area resulting from the integration of the chromatographic detector signal within a specified retention time
interval. In area slice mode (6.4.2), peak detection parameters are bypassed and the detector signal integral is recorded as area
slices of consecutive, fixed duration time intervals.
3.2.2 atmospheric equivalent temperature (AET), n—temperature converted from the measured vapor temperature obtained at
sub-ambient pressure to atmospheric equivalent temperature (AET) corresponding to the equivalent boiling point at atmospheric
pressure, 101.3 kPa (760 mm Hg), The AET is the expected distillate temperature if the distillation was performed at atmospheric
pressure and there was no thermal decomposition.
3.2.3 corrected area slice, n—area slice corrected for baseline offset, by subtraction of the exactly corresponding area slice in a
previously recorded blank (non-sample) analysis.
3.2.4 cumulative corrected area, n—accumulated sum of corrected area slices from the beginning of the analysis through a given
retention time, ignoring any non-sample area (for example, solvent).
3.2.5 initial boiling point (IBP), n—temperature (corresponding to the retention time) at which a cumulative corrected area count
equal to 0.5 % of the total sample area under the chromatogram is obtained.
3.2.6 final boiling point (FBP), n—temperature (corresponding to the retention time) at which a cumulative corrected area count
equal to 99.5 % of the total sample area under the chromatogram is obtained.
3.2.7 slice rate, n—frequency of data sampling or the frequency of data bunching provided that the frequency of data acquisition
is larger than the frequency of bunching. The unit of frequency is points/seconds or Hz.
3.2.8 slice time, n—cumulative slice rate (analysis time) associated with each area slice throughout the chromatographic analysis.
The slice time is the time at the end of each contiguous area slice.
3.2.9 total sample area, n—cumulative corrected area, from the initial point to the final area point.
3.3 Abbreviations:
D7398 − 23
3.3.1 A common abbreviation of hydrocarbon compounds is to designate the number of carbon atoms in the compound. A prefix
is used to indicate the carbon chain form, while a subscripted suffix denotes the number of carbon atoms (for example, normal
decane n-C ; iso-tetradecane = i-C ).
10 14
3.3.2 A common abbreviation for FAME compounds is to designate the number of carbon atoms and number of double bonds in
the compound. The number of carbon atoms is denoted by a number after the “C” and the number following a colon indicates the
number of double bonds (for example, C16:2 ; FAME with 16 carbon atoms and 2 double bonds).
4. Summary of Test Method
4.1 The boiling range distribution by distillation is simulated by the use of gas chromatography. A non-polar open tubular
(capillary) gas chromatographic column is used to elute the hydrocarbon and FAME components of the sample in order of
increasing boiling point.
4.2 A sample aliquot is diluted with a viscosity reducing solvent and introduced into the chromatographic system. The solvent
shall be apolar and not interfere with measurement of the sample in the 100 °C to 615 °C range. Sample vaporization is provided
by separate heating of the point of injection or in conjunction with column oven heating.
4.3 The column oven temperature is raised at a reproducible linear rate to effect separation of the FAME components in order of
increasing boiling point relative to a n-paraffin calibration mixture. The elution of sample components is quantitatively determined
using a flame ionization detector. The detector signal integral is recorded as area slices for consecutive retention time intervals
during the analysis.
4.4 Retention times of known normal paraffin hydrocarbons, spanning the scope of the test method (C – C ), are determined and
5 60
correlated to their boiling point temperatures. The normalized cumulative corrected sample areas for each consecutive recorded
time interval are used to calculate the boiling range distribution. The boiling point temperature at each reported percent off
increment is calculated from the retention time calibration.
4.5 The retention time versus boiling point curve is calibrated with normal paraffin hydrocarbons since these boiling points are
well defined. A mixture of FAMEs is analyzed to check column resolution. A triglyceride is analyzed to verify the system’s ability
to detect unreacted oil.
5. Significance and Use
5.1 The boiling range distribution of FAMES provides an insight into the composition of product related to the transesterification
process. This gas chromatographic determination of boiling range can be used to replace conventional distillation methods for
product specification testing with the mutual agreement of interested parties.
5.2 Biodiesel (FAMES) exhibits a boiling point rather than a distillation curve. The fatty acid chains in the raw oils and fats from
which biodiesel is produced are mainly comprised of straight chain hydrocarbons with 16 to 18 carbons that have similar boiling
temperatures. The atmospheric boiling point of biodiesel generally ranges from 330 °C to 357 °C. The Specification D6751 value
of 360 °C max at 90 % off by Test Method D1160 was incorporated as a precaution to ensure the fuel has not been adulterated
with high boiling contaminants.
6. Apparatus
6.1 Chromatograph—The following gas chromatographic system performance characteristics are required:
6.1.1 Column Oven—Capable of sustained and linear programmed temperature operation from near ambient (for example 35 °C
to 50 °C) up to 400 °C.
6.1.2 Column Temperature Programmer—The chromatograph must be capable of linear programmed temperature operation up to
400 °C at selectable linear rates up to 20 °C ⁄min. The programming rate must be sufficiently reproducible to obtain the retention
time repeatability of 0.03 min (3 s) for each component in the calibration mixture described in 7.3.
D7398 − 23
6.1.3 Detector—This test method requires a flame ionization detector (FID). The detector must meet or exceed the following
specifications as detailed in Practice E594. The specification of flame jet orifice is approximately 0.45 mm (0.018 in.).
6.1.3.1 Operating Temperature, 400 °C.
6.1.3.2 Sensitivity, >0.005 coulombs/g carbon.
-11
6.1.3.3 Minimum Detectability, 1 × 10 g carbon / s.
6.1.3.4 Linear Range, >10
6.1.3.5 Connection of the column to the detector must be such that no temperature below the column temperature exists. Refer
to Practice E1510 for proper installation and conditioning of the capillary column.
6.1.4 Sample Inlet System—Any sample inlet system capable of meeting the performance specification in 6.1.5 and 7.3 may be
used. Programmed temperature vaporization (PTV) and programmable cool on-column injection systems have been used
successfully.
6.1.5 Carrier Gas Flow Control—The chromatograph shall be equipped with carrier flow control capable of maintaining constant
carrier gas flow control through the column throughout the column temperature program cycle as measured with the use of flow
a sensor. Flow rate must be maintained within 1 % through out the temperature program.
6.2 Microsyringe—A microsyringe with a 23 gauge or smaller stainless steel needle is used for on-column sample introduction.
Syringes of 0.1 μL to 10 μL capacity are available.
6.2.1 Automatic syringe injection is recommended to achieve best precision.
6.3 Column—This test method is limited to the use of non-polar wall coated open tubular (WCOT) columns of high thermal
stability. Glass, fused silica, and stainless steel columns, with a 0.53 mm diameter have been successfully used. Cross-linked or
bonded 100 % dimethyl-polysiloxane stationary phases with film thickness of 0.5 μm to 1.0 μm have been used. The column length
and liquid phase film thickness shall allow the elution of at least C n-paraffin (BP = 615 °C) and triolein. The column and
conditions shall provide separation of typical petroleum hydrocarbons and saturated FAMES in order of increasing boiling point
and meet the column resolution requirements of 8.2.1. The column shall provide a resolution between five (5) and fifteen (15) using
the test method operating conditions.
6.4 Data Acquisition System:
6.4.1 Recorder—A 0 mV to 1 mV range recording potentiometer or equivalent, with a full-scale response time of 2 s or less may
be used to provide a graphical display.
6.4.2 Integrator—Means shall be provided for determining the accumulated area under the chromatogram. This can be done by
means of an electronic integrator or computer based chromatography data system. The integrator/computer system shall have
normal chromatographic software for measuring the retention time and areas of eluting peaks (peak detection mode). In addition,
the system shall be capable of converting the continuously integrated detector signal into area slices of fixed duration (area slice
mode). These contiguous area slices, collected for the entire analysis, are stored for later processing. The electronic range of the
integrator/computer (for example, 1 V, 10 V) shall be operated within the linear range of the detector/electrometer system used.
NOTE 1—Some gas chromatographs have an algorithm built into their operating software that allows a mathematical model of the baseline profile to be
stored in memory. This profile is automatically subtracted from the detector signal on subsequent sample runs to compensate for the column bleed. Some
integration systems also store and automatically subtract a blank analysis from subsequent analytical determinations.
7. Reagents and Materials
7.1 Gases—The following compressed gases are utilized for the operation of the gas chromatograph.
D7398 − 23
7.1.1 Helium, 99.999 %. (Warning—Compressed gas under high pressure.) This gas can be used as carrier gas. Ensure sufficient
pressure for a constant carrier gas flow rate. It is not to contain more than 5 mL ⁄m of oxygen and the total amount of impurities
are not to exceed 10 mL ⁄m .
7.1.2 Nitrogen, 99.999 %. (Warning—Compressed gas under high pressure.) This gas can be used as carrier gas. Ensure sufficient
pressure for a constant carrier gas flow rate. It is not to contain more than 5 mL ⁄m of oxygen and the total amount of impurities
are not to exceed 10 mL ⁄m .
7.1.3 Hydrogen, 99.999 %. (Warning—Extremely flammable gas under high pressure.) The total impurities are not to exceed 10
mL/m . This gas can be used as carrier gas. Ensure sufficient pressure for a constant carrier gas flow rate. It is also used as fuel
for the flame ionization detector (FID).
7.1.4 Air, 99.999 %. (Warning—Compressed gas under high pressure and supports combustion.) Total impurities are not to
exceed 10 mL ⁄m . This gas is used to sustain combustion in the flame ionization detector (FID).
7.2 Solvents—Unless otherwise indicated, it is intended that all solvents conform to the specifications of the committee on
analytical Reagents of the American Chemical Society where such specifications are available. Other grades may be used provided
it is first ascertained that the solvent is of sufficiently high purity to permit its use without lessening the accuracy of the
determination.
7.2.1 Carbon Disulfide (CS ), 99+ % pure. (Warning—Extremely flammable and toxic liquid.) Used as a viscosity reducing
solvent and as a means of reducing mass of sample introduced onto the column to ensure linear detector response and reduced peak
skewness. It is miscible with FAMES and provides a relatively small response with the FID. The quality (hydrocarbon content)
is determined by this test method prior to use as a sample diluent.
7.2.2 Cyclohexane (C H ), (99+ % pure) (Warning—Flammable. Health hazard.) Used as a viscosity reducing solvent. It is
6 12
miscible with asphaltic hydrocarbons, however, it responds well to the FID. Cyclohexane will interfere with the elution of lower
boiling normal paraffins. The quality (hydrocarbon content) is determined by this test method prior to use as a sample diluent.
7.3 Calibration Mixture—A qualitative mixture of n-paraffins (nominally C to C ) dissolved in a suitable solvent. A final
5 60
concentration of approximately one part of n-paraffin mixture to one hundred parts of solvent is required. At least one compound
in the mixture must have a boiling point lower than the initial boiling point of the sample being analyzed, as defined in the scope
of this test method (1.1). The calibration mixture must contain at least 13 known n-paraffins (for example, C , C , C , C , C , C ,
6 7 8 9 10 12
C , C , C , C , C , C , C ). Boiling points of n-paraffins are listed in Table 1.
16 20 30 40 50 52 60
NOTE 2—A suitable calibration mixture can be obtained by dissolving a polyolefin wax in a volatile solvent (for example, carbon disulfide or cyclohexane).
Solutions of one part polyolefin wax to one hundred parts solvent can be prepared. Lower boiling point paraffins will have to be added to ensure
conformance with 7.3. Fig. 1 illustrates a typical calibration mixture chromatogram.
7.3.1 Qualitative FAME Mixture—A qualitative mixture of FAMES (nominally C8:0 to C24:0) dissolved in a suitable solvent. A
final concentration of approximately one part of FAME mixture to one hundred parts of solvent is required. The qualitative mixture
contains at least 9 known FAMES (for example, C8:0, C10:0, C12:0, C14:0, C16:0, C18:0, C20:0, C22:0, C24:0). Boiling points
of FAMES are listed in Table 2. This FAME qualitative mixture is used to calculate resolution of C16:0 and C18:0 (see 8.2.1). It
may also be used to insure that retention time shifts as column ages does not exceed 60.15 min (to be determined from the
experimental BP versus RT curve).
7.3.2 Quantitative Triglyceride Mixture—A quantative mixture of triglyceride (triolein) dissolved in a suitable solvent. A final
concentration of approximately 10 mass ppm is required. One qualitative mixture meeting the requirement of 7.3.1 and 7.3.2 may
be used. This triglyceride reponse mixture is used to verify response to unreacted oils (see 8.2.2.1).
7.4 Response Linearity Mixture—Prepare a quantitatively weighed mixture of at least ten individual paraffins (>99 % purity),
covering the boiling range of the test method. The highest boiling point component shall be at least n-C60. The mixture shall
contain n-C40. Use a suitable solvent to provide a solution of each component at approximately 0.5 % to 2.0 % by mass.
ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference Materials, American Chemical Society, Washington, DC. For
suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and
the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D7398 − 23
A,B
TABLE 1 Boiling Points of n-Paraffins
Carbon Number Boiling Point °C Boiling Point °F Carbon Number Boiling Point °C Boiling Point °F
5 36 97 33 474 885
6 69 156 34 481 898
7 98 209 35 489 912
8 126 258 36 496 925
9 151 303 37 503 937
10 174 345 38 509 948
11 196 385 39 516 961
12 216 421 40 522 972
13 235 456 41 528 982
14 254 488 42 534 993
15 271 519 43 540 1004
16 287 548 44 545 1013
17 302 576 45 550 1022
18 316 601 46 556 1033
19 330 626 47 561 1042
20 344 651 48 566 1051
21 356 674 49 570 1058
22 369 695 50 575 1067
23 380 716 51 579 1074
24 391 736 52 584 1083
25 402 755 53 588 1090
26 412 774 54 592 1098
27 422 791 55 596 1105
28 431 808 56 600 1112
29 440 825 57 604 1119
30 449 840 58 608 1126
31 458 856 59 612 1134
32 466 870 60 615 1139
A
API Project 44, 72-10-31, is believed to have provided the original normal paraffin boiling point data that are listed in Table 1. However, over the years some of the data
contained in both API Project 44 (Thermodynamics Research Center Hydrocarbon Project) and Test Method D7398 have changed, and they are no longer equivalent. Table
1 represents the current normal paraffin boiling point values accepted by Subcommittee D02.04 and found in all test methods under the jurisdiction of Section D02.04.0H.
B
Test Method D7398 has traditionally used n-paraffin boiling points rounded to the nearest whole degree for calibration. The boiling points listed in Table 1 are correct to
the nearest whole number in both degrees Celsius and degrees Fahrenheit. However, if a conversion is made from one unit to the other and then rounded to a whole
number, the results will not agree with the table values for a few carbon numbers. For example, the boiling point of n-heptane is 98 425 °C which is correctly rounded to
98 °C in the table. However, converting 98.425 °C gives 209.165 °F, which rounds to 208 °F,209 °F, while converting 98 °C gives 208.4 °F, which rounds to 208 °F. Carbon
numbers 2, 4, 7, 8, 9, 13, 14, 15, 16, 25, 27, and 32 are affected by rounding.
7.5 Reference Material—A reference sample that has been analyzed by laboratories participating in the test method cooperative
study. Consensus values for the boiling range distribution of this sample is being determined.
8. Preparation of Apparatus
8.1 Gas Chromatograph Setup:
8.1.1 Place the gas chromatograph and ancillary equipment into operation in accordance with the manufacturers instructions.
Recommended operating conditions are shown in Table 3.
8.1.2 When attaching the column to the detector inlet, ensure that the end of the column terminates as close as possible to the FID
jet. Follow the instructions in Practice E1510.
8.1.3 Periodically inspect the FID and, if necessary, remove any foreign deposits formed in the detector from combustion of
silicone liquid phase or other materials. Such deposits will change the response characteristics of the detector.
8.1.4 The inlet liner and initial portion of the column must be periodically inspected and replaced if necessary to remove
extraneous deposits or sample residue.
8.1.5 Column Conditioning—A new column will require conditioning at the upper test method operating temperature to reduce
or eliminate significant liquid phase bleed, resulting in a stable chromatographic baseline. Follow the guidelines outlined in
Practice E1510.
8.2 System Performance Specification:
D7398 − 23
FIG. 1 Typical Calibration Curve with Plot
8.2.1 Column Resolution—The column resolution, influenced by both the column physical parameters and operating conditions,
affects the overall determination of boiling range distribution. Resolution is therefore specified to maintain equivalence between
different systems (laboratories) employing this test method. Resolution is determined using Eq 1 and the C16:0 and C18:0 FAMES
from a calibration mixture analysis (or a retention time boiling point mixture) (see 7.3.1). Resolution (R) shall be at least five (5)
and not more than fifteen (15), using the identical conditions employed for sample analyses.
R 5 2 t 2 t / 1.699 w 1w (1)
~ ! ~ ~ !!
2 1 2 1
where:
R = resolution,
D7398 − 23
TABLE 2 FAME and Triglyceride Boiling Point Table
NOTE 1—Boiling points of FAMEs and triglycerides are normally published in the literature at reduced pressure. This table compares the converted
to AET literature BP values from one source to the BP values as determined by extrapolating the retention time of the FAME from the retention time/BP
of the preceding and the following n-paraffin from a chromatographic run using the conditions of this method.
A B C
FAME Name Alternate Name BP °C AET BP °C Extrapolated BP °C
C8:0 Octanoic Acid, Methyl Ester Methyl caprylate 83 200 197
C10:0 Decanoic Acid, Methyl Ester Methyl caprate 114 237 237
C12:0 Dodecanoic Acid, Methyl Ester Methyl laurate 141 270 272
C14:0 Tetradecanoic Acid, Methyl Ester Methyl Myristate 155-7 308 304
C16:0 Hexadecanoic Acid, Methyl Ester Methyl palmitate 148 330 332
C18:0 Octadecanoic Acid, Methyl Ester Methyl stearate 215 357 358
C20:0 Eicosanoic Acid, Methyl Ester Methyl arachidate 215-16 369 382
C22:0 Docosanoic Acid, Methyl Ester Methyl behenate 224-5 375 404
C24:0 Tetracosanoic Acid, Methyl Ester 413 425
15 18
C18 235-40
Triglyceride Triolein 375
C18 606
Triglyceride Triolein
A
Reduced pressure boiling points in degrees Celsius and mm Hg as published in CRC Handbook of Chemistry & Physics, 61st Edition.
B
Atmospheric equivalent temperature calculated as per Test Method D2892 equations. At present there is insufficient evidence that TBP (Test Method D2892) yields
distillation curves equivalent to those that may be obtained by classical vacuum distillations.
C
Boiling point extropolated from retention time of n-paraffins under the condition of this chromatographic method. The relative good agreement with the boiling point
determined by using n-paraffins to calibrate the retention time indicates the validity of such calibration.
TABLE 3 Recommended Operating Conditions
Injector cool on-column or PTV
Injection temperature oven-track mode or programmed;
initial temperature 100 °C
initial hold 0 minutes
program rate 10 °C ⁄min
final temperature 385 °C
Auto sampler required for best precision
Data collection data is collected as independent area slices
(average data collection rate is 1.0 Hz or one sample/s)
Column capillary, 4 m × 0.53 mm ID
film thickness; 1.0 microns (polydimethylsiloxane)
Flow conditions UHP helium at 10 mL/min (constant flow)
(make-up gas helium)
Detector Flame Ionization;
Temperature: 390 °C
Oven program initial oven temperature 35 °C,
initial hold 0 min.,
program rate 10 °C ⁄min.,
final oven temperature 385 °C,
Sample size 0.5 microliter
Sample dilution 2 % by mass in carbon disulfide
Calibration dilution 1 % by mass in carbon disulfide
t = time for the C16:0 peak maximum,
t = time for the C18:0 peak maximum,
w = peak width, at half height, of the C16:0 peak and,
w = peak width, at half height, of the C18:0 peak.
8.2.2 Detector Response Calibration—This t
...