ASTM D5986-96

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An American National Standard
Designation: D 5986 – 96
Standard Test Method for
Determination of Oxygenates, Benzene, Toluene, C –C
8 12
Aromatics and Total Aromatics in Finished Gasoline by Gas
Chromatography/Fourier Transform Infrared Spectroscopy
This standard is issued under the fixed designation D 5986; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 4307 Practice for Preparation of Liquid Blends for Use as
Analytical Standards
1.1 This test method covers the quantitative determination
of oxygenates: methyl-t-butylether (MTBE), di-isopropyl ether
3. Terminology
(DIPE), ethyl-t-butylether (ETBE), t-amylmethyl ether
3.1 Definitions of Terms Specific to This Standard:
(TAME), methanol (MeOH), ethanol (EtOH), 2-propanol (2-
3.1.1 aromatics—refers to any organic compound contain-
PrOH), t-butanol (t-BuOH), 1-propanol (1-PrOH), 2-butanol
ing a benzene or naphthalene ring.
(2-BuOH), i-butanol (i-BuOH), 1-butanol (1-BuOH); benzene,
3.1.2 calibrated aromatic component—in this test method,
toluene and C –C aromatics, and total aromatics in finished
8 12
refers to the individual aromatic components which have a
motor gasoline by gas chromatography/Fourier Transform
specific calibration.
infrared spectroscopy (GC/FTIR).
3.1.3 cool on-column injector—in gas chromatography,a
1.2 This test method covers the following concentration
direct sample introduction system which is set at a temperature
ranges: 0.1–20 volume % per component for ethers and
at or below the boiling point of solutes or solvent on injection
alcohols; 0.1–2 volume% benzene; 1–15 volume % for toluene,
and then heated at a rate equal to or greater than the column.
10–40 volume % total (C –C ) aromatics.
6 12
Normally used to eliminate boiling point discrimination on
1.3 The method has not been tested by ASTM for refinery
injection or to reduce adsorption, or both, on glass liners within
individual hydrocarbon process streams, such as reformates,
injectors. The sample is injected directly into the head of the
fluid catalytic cracking naphthas, etc., used in blending of
capillary column tubing or retention gap.
gasolines.
3.1.4 Gram-Schmidt chromatogram—a nonselective sum-
1.4 SI units of measurement are preferred and used through-
mation of total intensity from a spectral scan per unit time
out this test method.
which resembles in profile a flame ionization detector chro-
1.5 This standard does not purport to address all of the
matogram.
safety concerns, if any, associated with its use. It is the
3.1.5 retention gap—in gas chromatography, refers to a
responsibility of the user of this standard to establish appro-
deactivated precolumn which acts as a zone of low retention
priate safety and health practices and determine the applica-
power for reconcentrating bands in space. The polarity of the
bility of regulatory limitations prior to use.
precolumn must be similar to that of the analytical column.
2. Referenced Documents 3.1.6 selective wavelength chromatogram (SWC)—in this
test method, refers to a selective chromatogram obtained by
2.1 ASTM Standards:
summing the spectral intensity in a narrow spectral wavelength
D 1298 Practice for Density, Relative Density (Specific
or frequency range as a function of elution time which is
Gravity), or API Gravity of Crude Petroleum and Liquid
2 unique to the compound being quantitated.
Petroleum Products by Hydrometer Method
3.1.7 uncalibrated aromatic component—in this test
D 4052 Test Method for Density and Relative Density of
3 method, refers to individual aromatics for which a calibration is
Liquids by Digital Density Meter
not available and whose concentrations are estimated from the
D 4057 Practice for Manual Sampling of Petroleum and
response factor of a calibrated aromatic component.
Petroleum Product
3.1.8 wall coated open tubular (WCOT)—a type of capil-
lary column prepared by coating or bonding the inside wall of
This test method is under the jurisdiction of ASTM Committee D-2 on
the capillary with a thin film of stationary phase.
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.04 on Hydrocarbon Analysis.
4. Summary of Test Method
Current edition approved July 10, 1996. Published September 1996.
Annual Book of ASTM Standards, Vol 05.01.
4.1 A gas chromatograph equipped with a methylsilicone
Annual Book of ASTM Standards, Vol 05.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5986
WCOT column is interfaced to a Fourier transform infrared
spectrometer. The sample is injected through a cool on-column
injector capable of injecting a small sample size without
overloading the column.
4.2 Calibration is performed using mixtures of specified
pure oxygenates and aromatic hydrocarbons on a mass basis.
Volume % data is calculated from the densities of the indi-
vidual components and the density of the sample. Multipoint
calibrations consisting of at least five levels and bracketing the
concentration of the specified individual aromatics is required.
Unidentified aromatic hydrocarbons present which have not
been specifically calibrated for are quantitated using the
response factor of 1,2,3,5-tetramethylbenzene and summed
with the other calibrated aromatic components to obtain a total
aromatic concentration of the sample.
FIG. 1 Light-Pipe GC/FTIR System
4.3 Specified quality control mixture(s) are analyzed to
monitor the performance of the calibrated GC/FTIR system.
5. Significance and Use
5.1 Test methods to determine oxygenates, benzene, and the
aromatic content of gasoline are necessary to assess product
quality and to meet new fuel regulations.
5.2 This test method can be used for gasolines that contain
oxygenates (alcohols and ethers) as additives. It has been
determined that the common oxygenates found in finished
gasoline do not interfere with the analysis of benzene and other
aromatics by this test method.
6. Apparatus
6.1 Gas Chromatograph:
6.1.1 System equipped with temperature programmable gas
chromatograph suitable for cool-on-column injections. The
injector must allow the introduction of small (for example, 0.1
μL) sample sizes at the head of the WCOT column or a
retention gap. An autosampler is mandatory.
6.1.2 WCOT column containing a methylsilicone stationary
FIG. 2 Vapor Phase Spectrum of Benzene
phase which elutes the aromatic hydrocarbons according to
their boiling points. A column containing a relatively thick film
ene) used as a solvent in the preparation of the calibration
of stationary phase, such as 4 to 5 μm, is recommended to
mixture. Reagent grade. All at 99 % or greater purity. Free
prevent column sample overload.
from detectable oxygenates and aromatics which may interfere
6.2 FTIR Spectrometer:
with the analysis.
6.2.1 This test method requires a light-pipe GC/FTIR sys-
7.2.1 Toluene should be used as a solvent only for the
tem (Fig. 1). No data have been acquired with matrix-isolation
preparation of C + components and must be free from inter-
or other deposition type systems.
fering aromatics.
6.2.2 The spectrometer must be equipped with a mercury-
cadmium-telluride (MCT) detector capable of detecting from at
NOTE 1—Warning: The gasoline samples and solvents used as re-
least 4000 cm-1 to 550 cm-1. agents such as heptane and toluene are flammable and may be harmful or
fatal if ingested or inhaled. Benzene is a known carcinogen. Use with
6.2.3 The lower limit of 550 cm-1 is necessary for the
proper ventilation. Safety glasses and gloves are required while preparing
accurate determination of benzene. Fig. 2 gives an acceptable
samples and standards.
infrared spectra of benzene.
7.3 Internal Standard—1,2-dimethoxyethane (DME) or
7. Reagents and Materials
deuterated compounds, or both, have been used successfully. A
7.1 Carrier Gas—Helium and hydrogen have been used single internal standard such as DME may be used. If other
successfully. The minimum purity of the carrier gas used must internal standards are used, a narrow selective wavelength
be 99.85 mole %. Additional purification using commercially range must be determined to generate a SWC which yields no
available scrubbing reagents is recommended to remove trace interference from other components in the sample.
oxygen which may deteriorate the performance of the GC 7.4 Liquid Nitrogen, supplied from low pressure dewar.
WCOT column. Required for cooling of the MCT detector. Dewar may be
7.2 Dilution Solvents—n-heptane and methylbenzene (tolu- connected through an electronic solenoid to the MCT cooling
D 5986
TABLE 2 GC/FTIR Aromatic Hydrocarbons Calibration
reservoir for unattended operation.
Components (Calibrated Aromatic Components)
NOTE 2—Warning: Helium and hydrogen are supplied under high
Compound CAS No.
pressure. Hydrogen can be explosive and requires special handling.
Benzene 71-43-2
Hydrogen monitors that automatically shut off supply to the GC in case of
Methylbenzene 108-88-3
serious leaks are available from GC supply manufacturers.
Ethylbenzene 100-41-4
1,3-Dimethylbenzene 108-38-3
7.5 Spectrometer Purge Gas,N dry air has not been tested,
1,4-Dimethylbenzene 106-42-3
but should be adequate.
1,2-Dimethylbenzene 95-47-6
(1-Methylethyl)-benzene 98-82-8
NOTE 3—The FTIR spectrometer can be protected by installing appro-
Propyl-benzene 103-65-1
priate filters to remove volatile oils or contaminants that may be present
1-methyl-3-ethylbenzene 620-14-4
in commercial low quality nitrogen supplies. A liquid nitrogen dewar may
1-methyl-4-ethylbenzene 622-96-8
be used as a source for the nitrogen purge.
1,3,5-trimethylbenzene 108-67-8
1-methyl-2-ethylbenzene 611-14-3
7.6 Standards for Calibration and Identification, all at 99 %
1,2,4-trimethylbenzene 95-63-6
1,2,3-trimethylbenzene 526-73-8
or greater purity (Table 1 and Table 2). If reagents of high
Indan 496-11-7
purity are not available, an accurate assay of the reagent must
1,4-diethylbenzene 105-05-5
be performed using a properly calibrated GC or other tech-
Butylbenzene 104-51-8
niques. The concentration of the impurities which overlap the 1,2-Diethylbenzene 135-01-3
1,2,4,5-Tetramethylbenzene 95-93-2
other calibration components must be known and used to
1,2,3,5-Tetramethylbenzene 527-53-7
correct the concentration of the calibration components. Be-
Naphthalene 91-20-3
cause of the error that may be introduced from impurity 2-methyl-naphthalene 91-57-6
1-methyl-naphthalene 90-12-0
corrections, the use of only high purity reagents is strongly
recommended. Standards are used for calibration as well for
Table 1 and Table 2 by mass according to Practice D 4307.
establishing the identification by retention time in conjunction
with spectral match. Prepare calibration solutions as described in 9.1-9.1.4 for each
set. Adjust these concentrations, as necessary, to ensure that the
8. Sampling
concentrations of the components in the actual samples are
8.1 Make every effort to ensure that the sample is represen-
bracketed by the calibration concentrations. Solid components
tative of the fuel source from which it is taken. Follow the
are weighed directly into the flask or vial. The specified
recommendations of Practice D 4057 or its equivalent when
volumes of each calibration component are weighed into 100
obtaining samples from bulk storage or pipelines. Sampling to
mL volumetric flasks or 100 mL septum capped vials. Prepare
meet certain regulatory specifications may require the use of
a calibration standard as follows. Cap and record the tare
specific sampling procedures. Consult appropriate regulations.
weight of the 100 mL volumetric flask or vial to 0.1 mg.
8.2 Take appropriate steps to minimize the loss of light
Remove the cap and carefully add components to the flask or
hydrocarbons from the gasoline sample while sampling and
vial starting with the least volatile component. Cap the flask
during analyses. Upon receipt in the laboratory chill the sample
and record the net mass (Wi) of the aromatic component added
in its original container to 0 to 5°C (32 to 40°F) before and
to 0.1 mg. Repeat the addition and weighing procedure for each
after a sample is obtained for analysis.
component. Similarly add the internal standard and record its
8.3 After the sample is prepared for analysis with internal
net mass (Ws) to 0.1 mg. Store the capped calibration standards
standard(s), chill the sample and transfer to an appropriate
in a refrigerator at 0 to 5°C (32 to 40°F) when not in use.
autosampler vial with minimal headspace. Re-chill the remain-
NOTE 4—Mix all calibration solutions for at least 30 s on a Vortex
der of the sample immediately and protect from evaporation for
mixer after preparation or equivalent. Highly precise sample robotic
further analyses, if necessary.
sample preparation systems are available commercially. These systems
may be used provided that the results for the quality control reference
9. Calibration Procedure
material (Section 11) are met when prepared in this manner.
9.1 Preparation of Calibration Standards—Prepare multi-
9.1.1 Ethers and Alcohols:
component calibration standards using the compounds listed in
9.1.1.1 Three sets of at least six calibration levels each
TABLE 1 GC/FTIR Oxygenates Calibration Components (eighteen total solutions) are prepared bracketing the 0 to 20
volume % range. Set 1: for MTBE, DIPE, ETBE, TAME; Set
Compound CAS
2: MeOH, EtOH, 2-PrOH, t-BuOH; and Set 3: 1-PrOH,
Methyl-t-butyl ether (MTBE) 1634-04-4
Ethyl-t-butyl ether (ETBE) 637-92-3 2-BuOH, i-BuOH, 1-BuOH.
Methyl-t-amyl ether (TAME) 994-05-8
9.1.1.2 For each above Set: 1, 3, 5, 10, 15, and 20 mL
Di-isopropyl ether (DIPE) 108-20-3
aliquots of each component are pipetted into respective 100 mL
Methanol 67-56-1
Ethanol 64-17-5 volumetric flasks or vials while accurately recording the
2-Propanol 67-63-0
masses. For example, for Set 1, into flask one add 1.0 mL
t-Butanol 75-65-0
MTBE, 1.0 mL DIPE, 1.0 mL ETBE, 1.0 mL TAME; into flask
1-Propanol 71-23-6
2-Butanol 15892-23-6 two add 3.0 mL MTBE, 3.0 mL DIPE, 3.0 mL ETBE, 3.0 mL
Isobutanol 78-83-1
TAME; and so forth. Add the oxygenate in reverse order of
1-Butanol 71-36-3
their boiling points. The above procedure produces six calibra-
1,2-dimethoxyethane (DME) (Internal Standard) 110-71-4
tion solutions for each set with the concentrations of each
D 5986
analyte at 1, 3, 5, 10, 15, and 20 volume %. 10.0 mL of DME and o-xylenes each from 1 to 10 volume
...