ASTM D7974-21

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Designation: D7974 − 15 D7974 − 21
Standard Test Method for
Determination of Farnesane, Saturated Hydrocarbons, and
Hexahydrofarnesol Content of Synthesized Iso-Paraffins
(SIP) Fuel for Blending with Jet Fuel by Gas
Chromatography
This standard is issued under the fixed designation D7974; 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 Scope*
1.1 This test method covers the determination of farnesane (2,6,10-trimethyldodecane), saturated hydrocarbons, and hexahydro-
farnesol content in synthesized iso-paraffins (SIP) fuel for blending with jet fuel by gas chromatography.
1.2 Farnesane is determined from 96 % to 99.9 % by mass. Sum of saturated hydrocarbons including farnesane is determined from
97 % to 99.9 % by mass, and hexahydrofarnesol is determined from 0.02 % to 2.0 % by mass.
1.3 This test method does identify and quantify main impurities or group type of impurities but does not purport to identify all
individual components that can be present in synthesized iso-paraffins (SIP) fuel for jet fuel blending.
1.4 This test method is inappropriate for impurities that boil at temperatures higher than 460 °C or for impurities that cause poor
or no response in a flame ionization detector.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4307 Practice for Preparation of Liquid Blends for Use as Analytical Standards
D7566 Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.04.0L on Gas Chromatography Methods.
Current edition approved March 15, 2015Jan. 1, 2021. Published June 2015January 2021. Originally approved in 2015. Last previous edition approved in 2015 as
D7974 – 15. DOI: 10.1520/D7974-15.10.1520/D7974-21.
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.
*A Summary of Changes section appears at the end of this standard
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D7974 − 21
E355 Practice for Gas Chromatography Terms and Relationships
E594 Practice for Testing Flame Ionization Detectors Used in Gas or Supercritical Fluid Chromatography
3. Terminology
3.1 Definitions:
3.1.1 This test method makes reference to many common gas chromatographic procedures, terms, and relationships. Detailed
definitions can be found in Practices E355 and E594.
3.1.2 saturated hydrocarbons, n—paraffinic and naphthenic compounds.
4. Summary of Test Method
4.1 A representative aliquot of the synthesized iso-paraffins (SIP) fuel sample is introduced into a gas chromatograph equipped
with a 5 % phenyl-methylpolysiloxane bonded phase capillary column. Helium or hydrogen carrier gas transports the vaporized
aliquot through the column where the components are separated by the chromatographic process. Components are sensed by a
flame ionization detector as they elute from the column. The detector signal is processed by an electronic data acquisition system.
The farnesane and its impurities are identified by comparing their relative retention times to the ones reported in the method.
Identification has been previously performed analyzing reference samples by mass spectrometry under identical conditions. The
concentrations of all components are determined in mass percent area by normalization of the peak areas.
5. Significance and Use
5.1 Synthesized iso-paraffins (SIP) fuel are being approved for blending with jet fuel provided that they meet a purity specification
of more than 97 % farnesane, more than 98 % saturated hydrocarbons, and less than 1.5 % hexahydrofarnesol in accordance with
Specification D7566. This test method provides a method of determining the percentage of farnesane (purity) in the synthesized
iso-paraffins (SIP) fuel for blending with jet fuel.
6. Apparatus
6.1 Gas Chromatograph, capable of operating at the conditions listed in Table 1. A heated flash vaporizing injector designed to
provide a linear sample split injection (for example, 100:1) is required for proper sample introduction. Carrier gas controls shall
be of adequate precision to provide reproducible column flows and split ratios in order to maintain analytical integrity. A hydrogen
flame ionization detector with associated gas controls and electronics, designed for optimum response with open tubular columns,
is required.
6.2 Sample Introduction—Manual or automatic liquid syringe sample injection to the splitting injector is employed. Devices
capable of 1.0 μL injections are suitable.
TABLE 1 Typical Operating Conditions
Column Temperature Program
Column length 30 m
Column inner diameter 0.25 mm
Film thickness 0.25 μm
Initial temperature 50 °C
Initial hold time 0 min
Program rate 3 °C ⁄min
Final temperature 270 °C
Final hold time 20 min
Injector
Temperature 300 °C
Split ratio 100:1
Sample size 1.0 μL
Detector
Type Flame ionization
Temperature 300 °C
Fuel gas Hydrogen ('40 mL/min)
Oxidizing gas Air ('400 mL/min)
Make-up gases Helium ('45 mL/min) or
Nitrogen ('45 mL/min)
Carrier Gas
Type Helium or Hydrogen
Flow rate 1 mL/min (Constant)
D7974 − 21
6.3 Column—This test method utilizes a fused silica open tubular column with non-polar 5 % phenyl-methylpolysiloxane bonded
(cross-linked) phase internal coating.
6.3.1 Open tubular column with a non-polar 5 % phenyl-methylpolysiloxane bonded (cross-linked) phase internal coating; a 30 m
long by 0.25 mm internal diameter column with a 0.25 μm film thickness has been found to be suitable.
6.4 Electronic Data Acquisition System—Any data acquisition and integration device used for quantification of these analyses shall
meet or exceed these minimum requirements:
6.4.1 Normalized percent calculation based on peak area,
6.4.2 Identification of individual components based on retention time,
6.4.3 Noise and spike rejection capability,
6.4.4 Sampling rate of 5 Hz.
7. Reagents and Materials
7.1 Carrier Gas, Helium or hydrogen, with a minimum purity of 99.9 % mol. Oxygen removal systems and gas purifiers should
be used. (Warning—Helium, compressed gas under high pressure.) (Warning—Hydrogen, extremely flammable gas under high
pressure.) The use of hydrogen sensors in the oven is strongly recommended that can shutoff the hydrogen source in case the
hydrogen leaks.
7.2 Detector Gases, Hydrogen, air, nitrogen, and helium. The minimum purity of the gases used should be 99.9 % mol for the
hydrogen, nitrogen, and helium. The air should be hydrocarbon-free grade with a minimum purity of 99.0 % mol. Gas purifiers
are recommended for the detector gases. (Warning—Hydrogen, extremely flammable gas under high pressure.) (Warning—Air
and helium, compressed gases under high pressure.)
7.3 Blank of Solvent, n-Hexane with a minimum purity of 99.0 %.
7.4 Validation Mixture for Apparatus Performance Checks:
7.4.1 Solvent, n-Octane with a minimum purity of 99.0 %.
7.4.2 Standards, n-decane, n-dodecane, n-tetradecane, n-hexadecane with a minimum purity of 99.0 %.
8. Sampling
8.1 See Practice D4057 for general sampling. Transfer an aliquot of synthesized iso-paraffins (SIP) fuel sample into a septum vial
and seal. Obtain the test sample for analysis directly from the sealed septum vial, for either manual or automatic syringe injection.
9. Preparation of Apparatus
9.1 Install and condition column in accordance with manufacturer’s or supplier’s instructions. After conditioning, attach column
outlet to flame ionization detector inlet and check for leaks throughout the system. When leaks are found, tighten or replace fittings
before proceeding.
9.1.1 When using hydrogen as carrier gas, column conditioning shall be performed after connecting the column to the detector.
9.2 Adjust the operating conditions of the gas chromatograph (Table 1) and allow the system to equilibrate.
9.3 Performance Checks—The apparatus shall be checked in regular intervals to make sure that it is in perfect working condition.
Performance checks are realized by analyzing a calibration mixture in the analytical conditions defined in Table 1.
D7974 − 21
9.3.1 Linearity Verification—Verify linearity by analyzing a series of diluted standards or equivalent spread across the farnesane
content range of the method in order to have at the minimums 15 degrees of freedom. Standard deviation of the residuals shall
be less than 0.5 % which corresponds to a 95 % confidence interval of 1 %. Annex A1 gives an example of how linearity may be
confirmed.
9.3.2 Calibration Mixture Preparation—Weigh the same amount of n-decane, n-dodecane, n-tetradecane, and n-hexadecane.
Dilute the mixture in n-octane in order to obtain a concentration of 2 % mass of each component. See Practice D4307.
9.3.3 Column Effıciency—Calculate the number of theoretical plates on n-tetradecane peak using Eq 1:
n 5 5.545~R t
...