ASTM D7796-21

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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: D7796 − 17 D7796 − 21
Standard Test Method for
Analysis of Ethyl tert-Butyl Ether (ETBE) by Gas
Chromatography
This standard is issued under the fixed designation D7796; 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 purity of ethyl tert-butyl ether (ETBE) by gas chromatography. It also
provides a procedure to measure impurities in ETBE such as C to C olefins, methyl, isopropyl and tert-butyl alcohols, methyl
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sec-butyl and methyl tert-amyl ethers, acetone, and methyl ethyl ketone.
1.2 This test method is not applicable to the determination of ETBE in gasoline.
1.3 Water cannot be determined by this test method and shall be measured by a procedure such as Test Method D6304 and the
result used to normalize the chromatographic values.
1.4 Most of the impurities in ETBE are resolved by the test method, however, some co-elution is encountered.
1.5 This test method is inappropriate for impurities that boil at temperatures higher than 180 °C or for impurities that cause poor
or no response in a flame ionization detector, such as water.
1.6 The values stated in SI units of measurement are preferred and used throughout the standard. Alternate units, in common
usage, are also provided to improve clarity and aid the user of this test method.
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:
D3700 Practice for Obtaining LPG Samples Using a Floating Piston Cylinder
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
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 Oct. 1, 2017Dec. 1, 2021. Published November 2017December 2021. Originally approved in 2012. Last previous edition approved in 20122017
as D7796 – 12.D7796 – 17. DOI: 10.1520/D7796-17.10.1520/D7796-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org.
*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
D7796 − 21
D4307 Practice for Preparation of Liquid Blends for Use as Analytical Standards
D4626 Practice for Calculation of Gas Chromatographic Response Factors
D6304 Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl
Fischer Titration
D7618 Specification for Ethyl Tertiary-Butyl Ether (ETBE) for Blending with Aviation Spark-Ignition Engine Fuel
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—This test method makes reference to many common and gas chromatographic procedures, terms, and
relationships. Detailed definitions of these can be found in Practices E355 and E594, and Terminology D4175.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 C to C olefins, n—common olefin impurities in ETBE including unreacted feedstock and dimers or trimers of feed such
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as trimethylpentene or pentamethylheptene.
4. Summary of Test Method
4.1 A representative aliquot of the ETBE product sample is introduced into a gas chromatograph equipped with a methyl silicon
bonded phase fused silica open tubular column. Helium 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.
4.2 The detector signal is processed by an electronic data acquisition system or integrating computer. Each eluting component is
identified by comparing its retention time to those established by analyzing standards under identical conditions.
4.3 The concentration of each component in mass percent is determined by normalization of the peak areas after each peak area
has been corrected by a detector response multiplication factor and the water content of the sample. The detector response factors
are determined by analyzing prepared standards with the concentrations similar to those encountered in the sample.
5. Significance and Use
5.1 The presence of impurities in ETBE product can have a deleterious effect upon the value of ETBE as a fuel additive.
Oxygenate and olefin contents are of primary concern. This test method provides a knowledge of the composition of ETBE
product. This is useful in the evaluation of process operations control, in the valuation of the product, and for regulatory purposes.
6. Interferences
6.1 Cyclopentane and 2,3-dimethylbutane have been observed to co-elute with MTBE. However, these are not commonly found
impurities in MTBE, and MTBE is typically present at very low concentrations in ETBE.
7. Apparatus
7.1 Gas Chromatograph—Instrumentation capable of operating at the conditions listed in Table 1. A heated flash vaporizing
injector designed to provide a linear sample split injection (that is, 200:1) 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. Pressure control devices and gages shall be designed to attain the linear velocity required in the column used (for
example, if a 150 m column is used, a pressure of approximately 550 kPa (80 psig) is required). A hydrogen flame ionization
detector with associated gas controls and electronics, designed for optimum response with open tubular columns, is required.
7.2 Sample Introduction—Manual or automatic liquid syringe sample injection to the splitting injector is employed. Devices
capable of 0.1 μL to 0.5 μL injections are suitable. It should be noted that inadequate splitter design, or poor injection technique,
or both, can result in poor resolution. Overloading of the column can also cause loss of resolution for some components and, since
overloaded peaks are skewed, variation in retention times. Watch for any skewed peaks that indicate overloading during column
evaluation. Observe the component size and where possible, avoid conditions leading to this problem during the analyses.
D7796 − 21
TABLE 1 Typical Operating Conditions
Column Temperature Program
Column length 50 m 100 m 150 m
Initial temperature 40 °C 50 °C 60 °C
Initial hold time 13 min 13 min 13 min
Program rate 10 °C ⁄min 10 °C ⁄min 10 °C ⁄min
Final temperature 180 °C 180 °C 180 °C
Final hold time 3 min 7 min 20 min
Injector
Temperature 200 °C
Split ratio 200:1
Sample size 0.1 μL to 0.5 μL
Detector
Type flame ionization
Temperature 250 °C
Fuel gas hydrogen ('30 mL ⁄min)
Oxidizing gas air ('300 mL ⁄min)
Make-up gas nitrogen ('30 mL/min)
Carrier Gas
Type helium
Average linear velocity 20 cm ⁄s – 24 cm/s
7.3 Open Tubular Column —This test method utilizes a fused silica open tubular column with non-polar methyl silicone bonded
(cross-linked) phase internal coating such as one of the following:
Column length 50 m 100 m 150 m
Film thickness 0.5 μm 0.5 μm 1.0 μm
Internal diameter 0.20 mm 0.25 mm 0.25 mm
Other columns with equal or greater resolving power may be used. A minimum resolution between trans-2-pentene and
tert-butanol, and between cis-2-pentene and tert-butanol of 1.3 is required. The 150 m column is expected to decrease the
likelihood of co-elution of impurities.
7.4 Electronic Data Acquisition System—Any data acquisition and integration device used for quantification of these analyses shall
meet or exceed these minimum requirements:
7.4.1 Capacity for at least 50 peaks per analysis,
7.4.2 Normalized area percent calculations with response factors,
7.4.3 Identification of individual components based on retention time,
7.4.4 Noise and spike rejection capability,
7.4.5 Sampling rate for fast (<1 s) peaks,
7.4.6 Positive and negative sloping baseline correction,
7.4.7 Peak detection sensitivity compensation for narrow and broad peaks, and
7.4.8 Non-resolved peaks separated by perpendicular drop or tangential skimming as needed.
8. Reagents and Materials
8.1 Carrier Gas, helium, 99.99 % pure. (Warning—Compressed gas under high pressure.)
8.2 Fuel Gas, hydrogen, 99.99 % pure. (Warning—Extremely flammable gas under pressure.)
Petrocol DH series columns from Supelco, Inc., Bellefonte, PA were used to obtain the retention data and example chromatogram shown in this standard. Other suitable
columns are available commercially.
D7796 − 21
8.3 Ethyl tert-Butyl Ether, 99.99 % pure. (Warning—Flammable liquid. Harmful if inhaled.)
8.4 Oxidant, air, oil free. (Warning—Compressed gas under high pressure.)
8.5 Make-Up Gas, nitrogen, 99.99 % pure. (Warning—Compressed gas under high pressure.)
8.6 Reference Standards:
8.6.1 tert-Amyl methyl ether. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.2 Butane. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.3 tert-Butanol. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.4 sec-Butyl methyl ether. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.5 4,4-Dimethyl-2-neopentyl-1-pentene. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.6 Isobutylene. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.7 Methanol. (Warning—Toxic flammable liquid. Harmful if inhaled or ingested.)
8.6.8 2-Methyl-2-butene. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.9 Methyl tert-butyl ether, 99+ % pure. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.10 2,2,4,6,6-Pentamethyl-3-heptene. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.11 n-Pentane. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.12 cis-2-Pentene. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.13 trans-2-Pentene. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.14 2,4,4-Trimethyl-1-pentene. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.15 2,4,4-Trimethyl-2-pentene. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.16 Dimethyl ether. (Warning—Extremely flammable gas. Harmful if inhaled.)
8.6.17 Diethyl ether. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.18 2,2,4-Trimethylpentane. (Warning—Flammable liquid. Harmful if inhaled.)
8.6.19 Ethanol. (Warning—Flammable liquid.)
9. Sampling
9.1 ETBE may be sampled either in a floating piston cylinder or into an open container since vapor pressures less than 70 kPa
(10 psi) are expected.
9.1.1 Cylinder Sampling—Refer to Practice D3700 for instructions on transferring a representative sample from a source into a
floating piston cylinder. Add inert gas to the ballast side of the piston to achieve a pressure of 310 kPa (45 psi) above the vapor
pressure of the sample.
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