ASTM D7423-09(2014)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7423 − 09(Reapproved 2014)
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 D6299 Practice for Applying Statistical Quality Assurance
and Control Charting Techniques to Evaluate Analytical
1.1 This test method covers the gas chromatographic pro-
Measurement System Performance
cedureforthequantitativedeterminationoforganicoxygenates
D6849 Practice for Storage and Use of Liquefied Petroleum
in C2, C3, C4, and C5 matrices by multidimensional gas
Gases (LPG) in Sample Cylinders for LPG Test Methods
chromatography and flame ionization detection. This test
E355 Practice for Gas Chromatography Terms and Relation-
method is applicable when the hydrocarbon matrices have a
ships
final boiling point not greater than 200°C. Oxygenate com-
pounds include, but are not limited to, those listed in Table 1.
3. Terminology
The linear working range for oxygenates is 0.50 mg/kg to 100
3.1 Additional terminology related to the practice of gas
mg/kg.
chromatography can be found in Practice E355.
1.2 This test method is intended to determine the mass
3.2 Definitions:
concentration of each oxygenate in the hydrocarbon matrix.
3.2.1 liquefied petroleum gas (LPG), n—a mixture of nor-
Oxygenate compound identification is determined by reference
mally gaseous hydrocarbons, predominantly propane or
standards and column elution retention order.
butane, or both, that has been liquefied by compression or
1.3 The values stated in SI units are to be regarded as
cooling, or both, to facilitate storage, transport, and handling.
standard. No other units of measurement are included in this
D4175
standard.
3.2.2 oxygenate, n—an oxygen-containing ashless organic
1.4 This standard does not purport to address all of the
compound, such as an alcohol or ether, which may be used as
safety concerns, if any, associated with its use. It is the
a fuel or fuel supplement. D4175
responsibility of the user of this standard to establish appro-
3.3 Definitions of Terms Specific to This Standard:
priate safety and health practices and determine the applica-
3.3.1 Dean’s switching method—representative aliquot of
bility of regulatory limitations prior to use.
sampleisinjectedon-columnusingasamplevalve(orviaagas
chromatograph split inlet). The sample passes onto a nonpolar
2. Referenced Documents
column, which elutes the lighter hydrocarbons in boiling point
2.1 ASTM Standards:
order to the analytical column and backflushes the heavier
D1265 Practice for Sampling Liquefied Petroleum (LP)
hydrocarbons to vent. The oxygenate compounds elute from
Gases, Manual Method
the analytical column and are detected via a flame ionization
D1835 Specification for Liquefied Petroleum (LP) Gases
detector.
D4175 Terminology Relating to Petroleum, Petroleum
3.3.2 Dean’s switching method direct inject—gas chromato-
Products, and Lubricants
graphic valve configuration equipped with a valve connected
directlytotheprecolumn.Thistechniqueiscommonlyusedfor
1 the determination of oxygenates in ethene and propene con-
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of centrates. This configuration provides the lowest detection
Subcommittee D02.D0.04 on C4 Hydrocarbons.
limitssuchasthosecommonlyrequiredforetheneandpropene
CurrenteditionapprovedMay1,2014.PublishedJuly2014.Originallyapproved
concentrates.
in 2009. Last pervious edition approved in 2009 as D7423 – 09. DOI: 10.1520/
D7423-09R14.
3.3.3 Dean’s switching method equipped with a split inlet—
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
gas chromatographic valve configuration equipped with a gas
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
chromatograph split inlet for sample introduction into the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. precolumn. This configuration is commonly used for the
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D7423 − 09 (2014)
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
determination of oxygenates in C5 hydrocarbon mixtures. This 4.2 The detector response and retention times for each
technique using this configuration might not provide the oxygenate peak in a calibration standard is measured and used
detection limits noted in the scope of this test method. If lower to externally calibrate the flame ionization detector response.
detection limits are required, then the user should consider The concentration of each oxygenate is calculated by the
using the on-column valve direct injection technique. external standard technique. Calibration materials are listed in
Table 1.
3.3.4 valve cut method—commonly used for the determina-
tion of oxygenates in C4 hydrocarbon mixtures.This technique
5. Significance and Use
using a split inlet might not provide the detection limits noted
5.1 The determination of oxygenates is important in the
in the scope of this test method. If lower detection limits are
manufacture of ethene, propene, 1-3 butadiene, C4
required, then the user should consider using the on-column
hydrocarbons, and C5 hydrocarbons. Alcohols, ethers,
valve direct injection technique.
aldehydes, and ketones are trace impurities in these hydrocar-
3.3.5 valve cut method equipped with a split inlet—
bons. Oxygenates decrease catalyst activity in downstream
representative aliquot of sample is injected via a gas chromato-
polymerization processes.
graph split inlet for sample introduction into the precolumn.
The sample passes onto a nonpolar column, which elutes the
6. Apparatus
lighter hydrocarbons in boiling point order to the analytical
6.1 Gas Chromatograph—Any gas chromatograph
column and the heavier hydrocarbons to vent. The oxygenate
equipped with a flame ionization detector (FID) and having
compounds elute from the analytical column and are detected
sensitivity of 0.01 mg/kg. The gas chromatograph must be
via a flame ionization detector.
capable of linear temperature control from 50 to 320°C for the
3.4 Acronyms:
capillary column oven. The gas chromatograph must be ca-
3.4.1 DIPE—diisopropylether.
pable of controlling multiple valve events. Carrier gas flow
3.4.2 ETBE—ethyl tert-butylether.
controllers and or electronic pressure control modules shall be
capableofprecisecontrolwheretherequiredflowratesarelow
3.4.3 MEK—2-butanone.
(see Table 2). Pressure control devices and gages shall be
3.4.4 MTBE—methyl tert-butylether.
capable of precise control for the typical pressures required.
3.4.5 TAME—tert-amyl methylether.
The temperature program rate must repeat to within 0.1°C and
3.4.6 PLOT—porous layer open tubular capillary column. provide retention time repeatability of 0.05 min throughout the
temperature program.
3.4.7 WCOT—wall coated open tubular capillary column.
6.2 Carrier Gas Preparation:
4. Summary of Test Method
6.2.1 Moisture present in the carrier gas causes chromato-
4.1 This test method shall be configured using either the graphic problems. The oxygenates column has very high
Dean’s switching method or the valve cut method. Each retention. Due to this characteristic, moisture and trace impu-
method shall be configured using an on-column valve direct rities in the carrier gas are trapped at the beginning of this
inject technique or a gas chromatograph split inlet. The column. Therefore carrier gas filters or the use of any device
on-column valve direct inject technique is configured by which can be used to eliminate trace levels of oxygen and
connecting the head of the precolumn directly to the injection water are strongly recommended.Additionally, frequent recon-
valve. ditioning and longer than usual column condition times may be
D7423 − 09 (2014)
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 Sample Size, µL 2 2 2
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
BBB
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.
necessary to maintain the performance of this column for the be of low volume design and not contribute significantly to
most accurate results from this test method. chromatographic deterioration.
6.2.2 Carrier Gas Filters—Oxygen and molecular sieve
6.5.2 Liquid Sampling Valve—A valve with an operating
type moisture filters.
temperature of 75°C and operating pressure of 68.94 bar, to be
located outside of the oven and used in sampling propane
6.3 Columns:
concentrates, butane samples or other LPG samples. The
6.3.1 Nonpolar (Precolumn) Column—This column per-
repeatabilityofthistestisdependentuponaconsistentcylinder
forms a pre-separation of the light hydrocarbon fraction up to
pressure. It is strongly suggested that the use of a floating
and including TAME. Any column with equivalent or better
piston cylinder be used and that the sample be pressurized to
chromatographic efficiency and selectivity to that described in
13.78 bar above the vapor pressure of the sample prior to
6.3.2 can be used.
sampling.
6.3.2 WCOT Methyl Silicone Column, 25 m long by
6.5.3 Low Pressure Liquid Sampling—A valve syringe
0.53 mm inside diameter fused silica WCOT column with a
adapter may be used to sample low vapor pressure liquids such
1.0 µm film thickness of crosslinked methyl siloxane. A col-
as C5 concentrates.
umn of this description was used in the repeatability study
6.5.4 Low Pressure Gas Sampling Valve—A valve with an
referred to in Section 16.
operating temperature of 225°C and operating pressure of
6.4 Polar (Analytical) Column—This column performs a
27.57 bar to be placed in a heated enclosure maintained at
separation of the oxygenates from volatile hydrocarbons in the
approximately 150°C and used to sample ethene vapor. An
same boiling point range. The oxygenates and remaining
external sample loop is installed on this valve. A 1000 µL
hydrocarbons are backflushed to vent through the nonpolar
sample loop has been used successfully. The sample loop
column. Any column with equivalent or better chromato-
sample size shall be sized experimentally to provide desired
graphic efficiency and selectivity to that described in 6.4.1 can
detection limits. This valve must reproduce to within 5 percent
be used.
relative standard deviation on each component.
6.4.1 Oxygenates PLOT column, 10 m long by 0.53 mm
6.5.5 Heated Valve Enclosure—Any enclosure capable of
inside diameter, with a stationary phase composed of a barium
maintaining the valve and sample loop at 150°C.
sulfateadsorbentmixture,coatedontoafusedsilicacolumn.At
6.5.6 Connecting Tees—Any tees that can provide an inert
a minimum the column should have sufficient retention for
connection.
methanol that it elute after n-tridecane (RI > 1300) and must
6.5.7 Tubing—Any tubing capable of providing an inert
have sufficient efficiency and capacity to resolve the oxygen-
connection.
ates listed in Table 1 to provide accurate quantitative results
6.5.8 Needle Valve—Micrometering valve capable of low
equivalent to those shown in Section 16. A column of this
flow control 2 to 90 mL/min.
description was used in the repeatability study referred to in
Section 16.
6.6 Data Acquisition—Any computerized data acquisition
6.5 Sample Introduction: system shall be used for peak area integration and graphic
6.5.1 Switching Valve—A valve with an operating tempera- presentation of the chromatogram.Alternatively any integrator
tureof225°Candoperatingpressureof27.57bar,tobelocated system can also be used for chromatographic peak area
within a heated enclosure or in the main oven. The valve shall integration.
D7423 − 09 (2014)
7. Reagents and Materials recommendations of Practice D1265, D1835, D6849 or their
equivalent, when obtaining and storing samples from bulk
7.1 Purity of Reagents—Before preparing the calibration
storage or pipelines.
standards, determine the purity of the oxygenate stocks and
make corrections for the impurities found. Whenever possible,
9. Installation of Carrier Gas Filters
use stocks of 98 % purity or better. The calibration materials
are listed in Table 1.
9.1 The carrier gas shall require pretreatment with an
oxygen and water removal system.
7.2 Calibration Standard Mixture—Astandard mixture con-
taining known concentrations of each oxygenate listed in Table
9.2 Onthegaschromatographcarriergassupplyline,install
1 should be prepared gravimetrically. This mixture shall be
theoxygenandwaterremovalfilters.Anyfilters,trapsorgetter
used as an external calibration standard.
type device can be used to assure removal of both oxygen and
7.3 Compressed Hydrogen—Less than 1 mg/kg hydrocar- water from the carrier gas used for this gas chromatograph.
bon impurities for FID fuel gas.
10. Preparation of Apparatus a
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