ASTM D7423-23

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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
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Designation: D7423 − 17 D7423 − 23
Standard Test Method for
Determination of Oxygenates in C2, C3, C4, and C5
Hydrocarbon Matrices by Gas Chromatography and Flame
Ionization Detection
This standard is issued under the fixed designation D7423; 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 gas chromatographic procedure for the quantitative determination of organic oxygenates in C2,
C3, C4, and C5 matrices by multidimensional gas chromatography and flame ionization detection. This test method is applicable
when the hydrocarbon matrices have a final boiling point not greater than 200 °C. Oxygenate compounds include, but are not
limited to, those listed in Table 1. The linear working range for oxygenates is 0.50 mg ⁄kg to 100 mg ⁄kg.
1.2 This test method is intended to determine the mass concentration of each oxygenate in the hydrocarbon matrix. Oxygenate
compound identification is determined by reference standards and column elution retention order.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
1.4 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.
1.4.1 The user is advised to obtain LPG safety training for the safe operation of this test method procedure and related activities.
The eLearning training course “Liquefied Petroleum Gases Sampling Safety” is available on the ASTM.org website.
1.5 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:
D1265 Practice for Sampling Liquefied Petroleum (LP) Gases, Manual Method
D1835 Specification for Liquefied Petroleum (LP) Gases
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.D0.04 on C4 and C5 Hydrocarbons.
Current edition approved June 1, 2017March 1, 2023. Published July 2017March 2023. Originally approved in 2009. Last pervious edition approved in 20162017 as
D7423 – 16a.D7423 – 17. DOI: 10.1520/D7423-17.10.1520/D7423-23.
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
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7423 − 23
TABLE 1 Oxygenates and Typical Retention Times
Components Retention Time (min)
Dimethyl ether 6.18
Diethyl ether 8.44
Acetaldehyde 8.89
Ethyl tert-butyl ether 10.66
Methyl tert-butyl ether (MTBE) 10.92
Diisopropyl ether 11.22
Propionaldehyde (Propanal) 12.00
Tertiary amyl methyl ether (TAME) 13.19
Propyl ether 14.00
Isobutylaldehyde 14.10
Butylaldehyde 14.50
Methanol 14.91
Acetone 15.39
Isovaleraldehyde 16.00
Valeraldehyde 16.10
2-Butanone (MEK) 17.14
Ethanol 17.51
N-propyl alcohol and isopropanol 19.20 (co-elution)
Allyl Alcohol 20.00
Isobutanol, Tert-butyl alcohol, Sec-Butanol 20.24 (co-elution)
N-butanol 20.84
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
D6849 Practice for Storage and Use of Liquefied Petroleum Gases (LPG) in Sample Cylinders for LPG Test Methods
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E355 Practice for Gas Chromatography Terms and Relationships
3. Terminology
3.1 Additional terminology related to the practice of gas chromatography can be found in Practice E355.
3.2 Definitions:
3.2.1 liquefied petroleum gas (LPG), n—a mixture of normally gaseous hydrocarbons, predominantly propane or butane, or both,
that has been liquefied by compression or cooling, or both, to facilitate storage, transport, and handling. D4175
3.2.2 oxygenate, n—an oxygen-containing ashless organic compound, such as an alcohol or ether, which may be used as a fuel
or fuel supplement. D4175
3.3 Definitions of Terms Specific to This Standard:
3.3.1 Dean’s switching method—method, n—representative aliquot of sample is injected on-column using a sample valve (or via
a gas chromatograph split inlet). The sample passes onto a nonpolar column, which elutes the lighter hydrocarbons in boiling point
order to the analytical column and backflushes the heavier hydrocarbons to vent. The oxygenate compounds elute from the
analytical column and are detected via a flame ionization detector.
3.3.2 Dean’s switching method direct inject—inject, n—gas chromatographic valve configuration equipped with a valve connected
directly to the precolumn. This technique is commonly used for the determination of oxygenates in ethene and propene
concentrates. This configuration provides the lowest detection limits such as those commonly required for ethene and propene
concentrates.
3.3.3 Dean’s switching method equipped with a split inlet—inlet, n—gas chromatographic valve configuration equipped with a gas
chromatograph split inlet for sample introduction into the precolumn. This configuration is commonly used for the determination
of oxygenates in C5 hydrocarbon mixtures. This technique using this configuration might not provide the detection limits noted
in the scope of this test method. If lower detection limits are required, then the user should consider using the on-column valve
direct injection technique.
D7423 − 23
3.3.4 valve cut method—method, n—commonly used for the determination of oxygenates in C4 hydrocarbon mixtures. This
technique using a split inlet might not provide the detection limits noted in the scope of this test method. If lower detection limits
are required, then the user should consider using the on-column valve direct injection technique.
3.3.5 valve cut method equipped with a split inlet—inlet, n—representative aliquot of sample is injected via a gas chromatograph
split inlet for sample introduction into the precolumn. The sample passes onto a nonpolar column, which elutes the lighter
hydrocarbons in boiling point order to the analytical column and the heavier hydrocarbons to vent. The oxygenate compounds elute
from the analytical column and are detected via a flame ionization detector.
3.4 Acronyms:
3.4.1 DIPE—diisopropylether.
3.4.2 ETBE—ethyl tert-butylether.
3.4.3 MEK—2-butanone.
3.4.4 MTBE—methyl tert-butylether.
3.4.5 TAME—tert-amyl methylether.
3.4.6 PLOT—porous layer open tubular capillary column.
3.4.7 WCOT—wall coated open tubular capillary column.
4. Summary of Test Method
4.1 This test method shall be configured using either the Dean’s switching method or the valve cut method. Each method shall
be configured using an on-column valve direct inject technique or a gas chromatograph split inlet. The on-column valve direct
inject technique is configured by connecting the head of the precolumn directly to the injection valve.
4.2 The detector response and retention times for each oxygenate peak in a calibration standard is measured and used to externally
calibrate the flame ionization detector response. The concentration of each oxygenate is calculated by the external standard
technique. Calibration materials are listed in Table 1.
5. Significance and Use
5.1 The determination of oxygenates is important in the manufacture of ethene, propene, 1-3 butadiene, C4 hydrocarbons, and C5
hydrocarbons. Alcohols, ethers, aldehydes, and ketones are trace impurities in these hydrocarbons. Oxygenates decrease catalyst
activity in downstream polymerization processes.
6. Apparatus
6.1 Gas Chromatograph—Any gas chromatograph equipped with a flame ionization detector (FID) and having sensitivity of
0.01 mg ⁄kg. The gas chromatograph must be capable of linear temperature control from 50 °C to 320 °C for the capillary column
oven. The gas chromatograph must be capable of controlling multiple valve events. Carrier gas flow controllers and or electronic
pressure control modules shall be capable of precise control where the required flow rates are low (see Table 2). Pressure control
devices and gages shall be capable of precise control for the typical pressures required. The temperature program rate must repeat
to within 0.1 °C and provide retention time repeatability of 0.05 min throughout the temperature program.
6.2 Carrier Gas Preparation:
6.2.1 Moisture present in the carrier gas causes chromatographic problems. The oxygenates column has very high retention. Due
to this characteristic, moisture and trace impurities in the carrier gas are trapped at the beginning of this column. Therefore carrier
gas filters or the use of any device which can be used to eliminate trace levels of oxygen and water are strongly recommended.
D7423 − 23
TABLE 2 Chromatographic Operating Conditions
Parameter Dean’s Switch (Fig. 1) Dean’s Switch (Fig. 2) Valve Cut (Fig. 3)
Valve 1°C Ambient Ambient Ambient
Valve 1 °C Ambient Ambient Ambient
Valve 1 Sample Size, μL 2 2 2
Valve 2°C 150 150 150
Valve 2 °C 150 150 150
Valve 2 Sample Size, μL - mL 500 – 2 500 – 2 500 – 2
Injector, °C Not Applicable 250 250
A A
Split Ratio Not Applicable 1:1 - x 1:1 - x
Backflush, min 2.0 – 4.0 2.0 – 4.0 2.0 – 4.0
Column Oven Standby, °C 200 200 200
Initial Column Oven, °C 50 50 50
Initial Hold, min 5 5 5
Rate, °C/min 10 10 10
Final Column Oven, °C 240 240 220
Final Hold, min 5 5 5
Precolumn Flow, mL/min 5 5 5
Analytical Column Flow, mL/min 7 7 7
Needle Valve 1 Flow, mL/min 15 15 Not Applicable
Needle Valve 2 Flow, mL/min 6 6 Not Applicable
Detector, °C 300 300 300
B B B
Detector Range
A
Split ratio shall be experimentally determined using appropriate gravimetric standards to obtain the desired minimum detection requirements.
B
Detector Range—Adjust the detector range to a setting which shall provide sufficient voltage to assure the detection of small concentrations of each oxygenate but as
to avoid detector signal saturation.
Additionally, frequent reconditioning and longer than usual column condition times may be necessary to maintain the performance
of this column for the most accurate results from this test method.
6.2.2 Carrier Gas Filters—Oxygen and molecular sieve type moisture filters.
6.3 Columns:
6.3.1 Nonpolar (Precolumn) Column—This column performs a pre-separation of the light hydrocarbon fraction up to and
including TAME. Any column with equivalent or better chromatographic efficiency and selectivity to that described in 6.3.2 can
be used.
6.3.2 WCOT Methyl Silicone Column, 25 m long by 0.53 mm inside diameter fused silica WCOT column with a 1.0 μm film
thickness of crosslinked methyl siloxane. A column of this description was used in the repeatability study referred to in Section
16.
6.4 Polar (Analytical) Column—This column performs a separation of the oxygenates from volatile hydrocarbons in the same
boiling point range. The oxygenates and remaining hydrocarbons are backflushed to vent through the nonpolar column. Any
column with equivalent or better chromatographic efficiency and selectivity to that described in 6.4.1 can be used.
6.4.1 Oxygenates PLOT column, 10 m long by 0.53 mm inside diameter, with a stationary phase composed of a barium sulfate
adsorbent mixture, coated onto a fused silica column. At a minimum the column should have sufficient retention for methanol that
it elute after n-tridecane (RI > 1300) and must have sufficient efficiency and capacity to resolve the oxygenates listed in Table 1
to provide accurate quantitative results equivalent to those shown in Section 16. A column of this description was used in the
repeatability study referred to in Section 16.
6.5 Sample Introduction:
6.5.1 Switching Valve—A valve with an operating temperature of 225 °C and operating pressure of 27.57 bar, to be located within
a heated enclosure or in the main oven. The valve shall be of low volume design and not contribute significantly to
chromatographic deterioration.
6.5.2 Liquid Sampling Valve—A valve with an operating temperature of 75 °C and operating pressure of 68.94 bar, to be located
outside of the oven and used in sampling propane concentrates, butane samples or other LPG samples. The repeatability of this
test is dependent upon a consistent cylinder pressure. It is strongly suggested that the use of a floating piston cylinder be used and
that the sample be pressurized to 13.78 bar above the vapor pressure of the sample prior to sampling.
D7423 − 23
6.5.3 Low Pressure Liquid Sampling—A valve syringe adapter may be used to sample low vapor pressure liquids such as C5
concentrates.
6.5.4 Low Pressure Gas Sampling Valve—A valve with an operating temperature of 225 °C and operating pressure of 27.57 bar
to be placed in a heated enclosure maintained at approximately 150 °C and used to sample ethene vapor. An external sample loop
is installed on this valve. A 1000 μL sample loop has been used successfully. The sample loop sample size shall be sized
experimentally to provide desired detection limits. This valve must reproduce to within 5 percent 5 % relative standard deviation
on each component.
6.5.5 Heated Valve Enclosure—Any enclosure capable of maintaining the valve and sample loop at 150 °C.
6.5.6 Connecting Tees—Any tees that can provide an inert connection.
6.5.7 Tubing—Any tubing capable of providing an inert connection.
6.5.8 Needle Valve—Micrometering valve capable of low flow control 2 mL ⁄min to 90 mL ⁄min.
6.6 Data Acquisition—Any computerized data acquisition system shall be used for peak area integration and graphic presentation
of the chromatogram. Alternatively any integrator system can also be used for chromatographic peak area integration.
7. Reagents and Materials
7.1 Purity of Reagents—Before preparing the calibration standards, determine the purity of the oxygenate stocks and make
corrections for the impurities found. Whenever possible, use stocks of 98 % purity or better. The calibration materials are listed
in Table 1.
7.2 Calibration Standard Mixture—A standard mixture containing known concentrations of each oxygenate listed in Table 1
should be prepared gravimetrically. This mixture shall be used as an external calibration standard.
7.3 Compressed Hydrogen—Less than 1 mg ⁄kg hydrocarbon impurities for FID fuel gas.
7.4 Compressed Helium—Gas purity 99.999 %. Note that helium supplies often contain low level amounts of water. Water can
dramatically deteriorate the performance of the analytical column (oxygenates column). It is strongly recommended that the use
of a molecular sieve or other suitable water removal system be implemented to eliminate the possibility of contaminating the
analytical column with oxygen or water.
7.5 Compressed Air—Zero grade (gas purity 99.999 %).
7.6 Instrument Air—Compressed air for pneumatic actuation of valves.
8. Sampling
8.1 Every effort should be made to ensure that the sample is representative of the source from which it is taken. Follow the
recommendations of Practice D1265, D1835, D6849 or their equivalent, when obtaining and storing samples from bulk storage
or pipelines.
9. Installation of Carrier Gas Filters
9.1 The carrier gas shall require pretreatment with an oxygen and water removal system.
9.2 On the gas chromatograph carrie
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