ASTM D7423-09

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7423 − 09
StandardTest 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 and Control Charting Techniques to Evaluate Analytical
Measurement System Performance
1.1 This test method covers the gas chromatographic pro-
D6849 Practice for Storage and Use of Liquefied Petroleum
cedureforthequantitativedeterminationoforganicoxygenates
Gases (LPG) in Sample Cylinders for LPG Test Methods
in C2, C3, C4, and C5 matrices by multidimensional gas
E355 Practice for Gas Chromatography Terms and Relation-
chromatography and flame ionization detection. This test
ships
method is applicable when the hydrocarbon matrices have a
final boiling point not greater than 200°C. Oxygenate com-
3. Terminology
pounds include, but are not limited to, those listed in Table 1.
3.1 Additional terminology related to the practice of gas
The linear working range for oxygenates is 0.50 mg/kg to 100
chromatography can be found in Practice E355.
mg/kg.
3.2 Definitions:
1.2 This test method is intended to determine the mass
3.2.1 liquefied petroleum gas (LPG), n—a mixture of nor-
concentration of each oxygenate in the hydrocarbon matrix.
mally gaseous hydrocarbons, predominantly propane or
Oxygenate compound identification is determined by reference
butane, or both, that has been liquefied by compression or
standards and column elution retention order.
cooling, or both, to facilitate storage, transport, and handling.
1.3 The values stated in SI units are to be regarded as
D4175
standard. No other units of measurement are included in this
3.2.2 oxygenate, n—an oxygen-containing ashless organic
standard.
compound, such as an alcohol or ether, which may be used as
1.4 This standard does not purport to address all of the
a fuel or fuel supplement. D4175
safety concerns, if any, associated with its use. It is the
3.3 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.3.1 Dean’s switching method—representative aliquot of
priate safety and health practices and determine the applica-
sampleisinjectedon-columnusingasamplevalve(orviaagas
bility of regulatory limitations prior to use.
chromatograph split inlet). The sample passes onto a nonpolar
column, which elutes the lighter hydrocarbons in boiling point
2. Referenced Documents
order to the analytical column and backflushes the heavier
2.1 ASTM Standards:
hydrocarbons to vent. The oxygenate compounds elute from
D1265 Practice for Sampling Liquefied Petroleum (LP)
the analytical column and are detected via a flame ionization
Gases, Manual Method
detector.
D1835 Specification for Liquefied Petroleum (LP) Gases
3.3.2 Dean’s switching method direct inject—gas chromato-
D4175 Terminology Relating to Petroleum, Petroleum
graphic valve configuration equipped with a valve connected
Products, and Lubricants
directlytotheprecolumn.Thistechniqueiscommonlyusedfor
D6299 Practice for Applying Statistical Quality Assurance
the determination of oxygenates in ethene and propene con-
centrates. This configuration provides the lowest detection
This test method is under the jurisdiction of ASTM Committee D02 on limitssuchasthosecommonlyrequiredforetheneandpropene
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
concentrates.
D02.D0.04 on C4 Hydrocarbons.
3.3.3 Dean’s switching method equipped with a split inlet—
Current edition approved July 1, 2009. Published September 2009. DOI:
10.1520/D7423-09.
gas chromatographic valve configuration equipped with a gas
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
chromatograph split inlet for sample introduction into the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
precolumn. This configuration is commonly used for the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. determination of oxygenates in C5 hydrocarbon mixtures. This
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7423 − 09
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
technique using this configuration might not provide the 4.2 The detector response and retention times for each
detection limits noted in the scope of this test method. If lower oxygenate peak in a calibration standard is measured and used
detection limits are required, then the user should consider to externally calibrate the flame ionization detector response.
using the on-column valve direct injection technique. The concentration of each oxygenate is calculated by the
external standard technique. Calibration materials are listed in
3.3.4 valve cut method—commonly used for the determina-
Table 1.
tion of oxygenates in C4 hydrocarbon mixtures.This technique
using a split inlet might not provide the detection limits noted
5. Significance and Use
in the scope of this test method. If lower detection limits are
required, then the user should consider using the on-column
5.1 The determination of oxygenates is important in the
valve direct injection technique.
manufacture of ethene, propene, 1-3 butadiene, C4
3.3.5 valve cut method equipped with a split inlet— hydrocarbons, and C5 hydrocarbons. Alcohols, ethers,
representative aliquot of sample is injected via a gas chromato- aldehydes, and ketones are trace impurities in these hydrocar-
graph split inlet for sample introduction into the precolumn. bons. Oxygenates decrease catalyst activity in downstream
The sample passes onto a nonpolar column, which elutes the polymerization processes.
lighter hydrocarbons in boiling point order to the analytical
column and the heavier hydrocarbons to vent. The oxygenate
6. Apparatus
compounds elute from the analytical column and are detected
6.1 Gas Chromatograph—Any gas chromatograph
via a flame ionization detector.
equipped with a flame ionization detector (FID) and having
3.4 Acronyms:
sensitivity of 0.01 mg/kg. The gas chromatograph must be
3.4.1 DIPE—diisopropylether.
capable of linear temperature control from 50 to 320°C for the
3.4.2 ETBE—ethyl tert-butylether. capillary column oven. The gas chromatograph must be ca-
pable of controlling multiple valve events. Carrier gas flow
3.4.3 MEK—2-butanone.
controllers and or electronic pressure control modules shall be
3.4.4 MTBE—methyl tert-butylether.
capableofprecisecontrolwheretherequiredflowratesarelow
3.4.5 TAME—tert-amyl methylether.
(see Table 2). Pressure control devices and gages shall be
capable of precise control for the typical pressures required.
3.4.6 PLOT—porous layer open tubular capillary column.
The temperature program rate must repeat to within 0.1°C and
3.4.7 WCOT—wall coated open tubular capillary column.
provide retention time repeatability of 0.05 min throughout the
temperature program.
4. Summary of Test Method
6.2 Carrier Gas Preparation:
4.1 This test method shall be configured using either the
Dean’s switching method or the valve cut method. Each 6.2.1 Moisture present in the carrier gas causes chromato-
method shall be configured using an on-column valve direct graphic problems. The oxygenates column has very high
inject technique or a gas chromatograph split inlet. The retention. Due to this characteristic, moisture and trace impu-
on-column valve direct inject technique is configured by rities in the carrier gas are trapped at the beginning of this
connecting the head of the precolumn directly to the injection column. Therefore carrier gas filters or the use of any device
valve. which can be used to eliminate trace levels of oxygen and
D7423 − 09
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.
water are strongly recommended.Additionally, frequent recon- within a heated enclosure or in the main oven. The valve shall
ditioning and longer than usual column condition times may be be of low volume design and not contribute significantly to
necessary to maintain the performance of this column for the chromatographic deterioration.
most accurate results from this test method.
6.5.2 Liquid Sampling Valve—A valve with an operating
6.2.2 Carrier Gas Filters—Oxygen and molecular sieve
temperature of 75°C and operating pressure of 68.94 bar, to be
type moisture filters.
located outside of the oven and used in sampling propane
concentrates, butane samples or other LPG samples. The
6.3 Columns:
repeatabilityofthistestisdependentuponaconsistentcylinder
6.3.1 Nonpolar (Precolumn) Column—This column per-
pressure. It is strongly suggested that the use of a floating
forms a pre-separation of the light hydrocarbon fraction up to
piston cylinder be used and that the sample be pressurized to
and including TAME. Any column with equivalent or better
13.78 bar above the vapor pressure of the sample prior to
chromatographic efficiency and selectivity to that described in
sampling.
6.3.2 can be used.
6.5.3 Low Pressure Liquid Sampling—A valve syringe
6.3.2 WCOT Methyl Silicone Column, 25 m long by 0.53
adapter may be used to sample low vapor pressure liquids such
mm inside diameter fused silica WCOT column with a 1.0 µm
as C5 concentrates.
film thickness of crosslinked methyl siloxane.Acolumn of this
6.5.4 Low Pressure Gas Sampling Valve—A valve with an
description was used in the repeatability study referred to in
operating temperature of 225°C and operating pressure of
Section 16.
27.57 bar to be placed in a heated enclosure maintained at
6.4 Polar (Analytical) Column—This column performs a
approximately 150°C and used to sample ethene vapor. An
separation of the oxygenates from volatile hydrocarbons in the
external sample loop is installed on this valve. A1000 µL
same boiling point range. The oxygenates and remaining
sample loop has been used successfully. The sample loop
hydrocarbons are backflushed to vent through the nonpolar
sample size shall be sized experimentally to provide desired
column. Any column with equivalent or better chromato-
detection limits. This valve must reproduce to within 5 percent
graphic efficiency and selectivity to that described in 6.4.1 can
relative standard deviation on each component.
be used.
6.5.5 Heated Valve Enclosure—Any enclosure capable of
6.4.1 Oxygenates PLOT column, 10 m long by 0.53 mm
maintaining the valve and sample loop at 150°C.
inside diameter, with a stationary phase composed of a barium
6.5.6 Connecting Tees—Any tees that can provide an inert
sulfateadsorbentmixture,coatedontoafusedsilicacolumn.At
connection.
a minimum the column should have sufficient retention for
6.5.7 Tubing—Any tubing capable of providing an inert
methanol that it elute after n-tridecane (RI > 1300) and must
connection.
have sufficient efficiency and capacity to resolve the oxygen-
6.5.8 Needle Valve—Micrometering valve capable of low
ates listed in Table 1 to provide accurate quantitative results
flow control 2 to 90 mL/min.
equivalent to those shown in Section 16. A column of this
description was used in the repeatability study referred to in
6.6 Data Acquisition—Any computerized data acquisition
Section 16.
system shall be used for peak area integration and graphic
6.5 Sample Introduction: presentation of the chromatogram.Alternatively any integrator
6.5.1 Switching Valve—A valve with an operating tempera- system can also be used for chromatographic peak area
tureof225°Candoperatingpressureof27.57bar,tobelocated integration.
D7423 − 09
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
usestocksof98%purityorbetter.Thecalibrationmaterialsare
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 and Establishment of
7.4 Compressed Helium—Gas purity 99.999 %. Note that
Conditions
helium supplies often contain low level amounts of water.
...