ASTM D5599-00
(Test Method)Standard Test Method for Determination of Oxygenates in Gasoline by Gas Chromatography and Oxygen Selective Flame Ionization Detection
Standard Test Method for Determination of Oxygenates in Gasoline by Gas Chromatography and Oxygen Selective Flame Ionization Detection
SCOPE
1.1 This test method covers a gas chromatographic procedure for the quantitative determination of organic oxygenated compounds in gasoline having a final boiling point not greater than 220oC and oxygenates having a boiling point limit of 130oC. It is applicable when oxygenates are present in the 0.1 to 20 % by mass range.
1.2 This test method is intended to determine the mass concentration of each oxygenate compound present in a gasoline. This requires knowledge of the identity of each oxygenate being determined (for calibration purposes). However, the oxygen-selective detector used in this test method exhibits a response that is proportional to the mass of oxygen. It is, therefore, possible to determine the mass concentration of oxygen contributed by any oxygenate compound in the sample, whether or not it is identified. Total oxygen content in a gasoline may be determined from the summation of the accurately determined individual oxygenated compounds. The summed area of other, uncalibrated or unknown oxygenated compounds present, may be converted to a mass concentration of oxygen and summed with the oxygen concentration of the known oxygenated compounds.
1.3 The values stated in SI units are to be regarded as the 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.
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An American National Standard
Designation:D5599–00
Standard Test Method for
Determination of Oxygenates in Gasoline by Gas
Chromatography and Oxygen Selective Flame Ionization
Detection
This standard is issued under the fixed designation D 5599; 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 Products, and Lubricants
D 4307 PracticeforPreparationofLiquidBlendsforUseas
1.1 This test method covers a gas chromatographic proce-
Analytical Standards
dure for the quantitative determination of organic oxygenated
E 594 Practice for Testing Flame Ionization Detectors Used
compounds in gasoline having a final boiling point not greater
in Gas or Supercritical Fluid Chromatography
than 220°C and oxygenates having a boiling point limit of
E 1064 Test Method for Water in Organic Liquids by
130°C. It is applicable when oxygenates are present in the 0.1
Coulometric Karl Fischer Titration
to 20 % by mass range.
E 1510 Practice for Installing Fused Silica Open Tubular
1.2 This test method is intended to determine the mass
Capillary Columns in Gas Chromatographs
concentration of each oxygenate compound present in a gaso-
line.This requires knowledge of the identity of each oxygenate
3. Terminology
being determined (for calibration purposes). However, the
3.1 Definitions:
oxygen-selective detector used in this test method exhibits a
3.1.1 independent reference standards—calibration samples
response that is proportional to the mass of oxygen.Itis,
of the oxygenates which are purchased or prepared from
therefore, possible to determine the mass concentration of
materials independent of the quality control check standards
oxygen contributed by any oxygenate compound in the sample,
and used for intralaboratory accuracy.
whether or not it is identified. Total oxygen content in a
3.1.2 oxygenate, n—an oxygen-containing compound, such
gasoline may be determined from the summation of the
as an alcohol or ether, which may be used as a fuel or fuel
accurately determined individual oxygenated compounds. The
supplement. D 4175
summed area of other, uncalibrated or unknown oxygenated
3.1.3 quality control check standards—calibration samples
compounds present, may be converted to a mass concentration
of the oxygenates for intralaboratory repeatability.
of oxygen and summed with the oxygen concentration of the
known oxygenated compounds.
4. Summary of Test Method
1.3 The values stated in SI units are to be regarded as the
4.1 An internal standard of a noninterfering oxygenate, for
standard.
example, 1,2-dimethoxyethane (ethylene glycol dimethyl
1.4 This standard does not purport to address all of the
ether) is added in quantitative proportion to the gasoline
safety concerns, if any, associated with its use. It is the
sample. A representative aliquot of the sample and internal
responsibility of the user of this standard to establish appro-
standard is injected into a gas chromatograph equipped with a
priate safety and health practices and determine the applica-
capillary column operated to ensure separation of the oxygen-
bility of regulatory limitations prior to use.
ates. Hydrocarbons and oxygenates are eluted from the col-
umn, but only oxygenates are detected with the oxygen-
2. Referenced Documents
selective flame ionization detector (OFID).Adiscussion of this
2.1 ASTM Standards:
detector is presented in Section 6.
D 1744 Test Method for Water in Liquid Petroleum Prod-
4.2 Calibration mixtures are used for determining the reten-
ucts by Karl Fischer Reagent
tion times and relative mass response factors of the oxygenates
D 4175 Terminology Relating to Petroleum, Petroleum
of interest. Suggested calibrant materials are listed in 8.2.
4.3 The peak area of each oxygenate in the gasoline is
measured relative to the peak area of the internal standard. A
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.04.0L on Gas Chromatography.
Current edition approved Nov. 10, 2000. Published November 2000. Originally Annual Book of ASTM Standards, Vol 05.02.
published as D 5599 – 94. Last previous edition D 5599 – 95. Annual Book of ASTM Standards, Vol 14.02.
2 5
Annual Book of ASTM Standards, Vol 05.01. Annual Book of ASTM Standards, Vol 15.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D5599–00
quadratic least-squares fit of the calibrated data of each The CH is subsequently detected with an FID.
oxygenate is applied and the concentration of each oxygenate
6.4 The methanizer consists either of a short porous layer
calculated.
opentubular(PLOT)glasscapillarytubeinternallycoatedwith
aluminum oxide with adsorbed nickel catalyst or stainless steel
NOTE 1—While 1,2-dimethoxyethane has been found to be an appro-
tubing containing a nickel-based catalyst. It is installed within
priate internal standard, other oxygenates may be used provided they are
or before the FID and is operated in the range from 350 to
not present in the sample and do not interfere with any compound of
interest. 450°C, depending on the instrument’s manufacturer.
NOTE 2—Gasolines with high sulfur content may cause a loss in
5. Significance and Use
detector sensitivity thereby limiting the number of samples that can be
5.1 In gasoline blending, the determination of organic
analyzed before the catalyst needs replacement.
oxygenated compounds is important. Alcohols, ethers, and
other oxygenates are added to gasoline to increase the octane
7. Apparatus
number and to reduce tailpipe emissions of carbon monoxide.
7.1 Gas Chromatograph—Any gas chromatograph can be
They must be added in the proper concentration and ratios to
used having the following performance characteristics:
meet regulatory limitations and to avoid phase separation and
7.1.1 Column Temperature Programmer— The chromato-
problems with engine performance or efficiency.
graph must be capable of reproducible linear temperature
5.2 This test method provides sufficient oxygen-to-hydro-
programming over a range sufficient for separation of the
carbon selectivity and sensitivity to allow determination of
components of interest.
oxygenates in gasoline samples without interference from the
7.1.2 Sample Introduction System—Any system capable of
bulk hydrocarbon matrix.
introducing a representative 0.1 to 1.0-µL liquid sample into
the split inlet device of the gas chromatograph. Microlitre
6. Theory of OFID Operation
syringes, autosamplers, and liquid sampling valves have been
6.1 The detection system selective for organic oxygen
used successfully. The split injector should be capable of
consists of a cracking reactor, hydrogenating reactor (metha-
accurate split control in the range from 10:1 to 500:1.
nizer), and a flame ionization detector (FID). The cracking
7.1.3 Carrier and Detector Gas Control— Constant flow
reactor, connected immediately after the gas chromatographic
control of carrier and detector gases is critical to optimum and
capillary column, consists of a Pt/Rh capillary tube. Carbon
consistent analytical performance. Control is best provided by
monoxide (CO) is formed from compounds containing oxygen
the use of pressure regulators and fixed flow restrictors. The
according to the following reaction:
gas flow rates are measured by any appropriate means. The
C H O → zCO1~y/2!H 1~x 2 z!C (1)
x y z 2
supply pressure of the gas delivered to the gas chromatograph
6.2 An excess layer of carbon is created in the Pt/Rh tube of
must be at least 70 kPa (10 psig) greater than the regulated gas
the cracking reactor from the introduction of hydrocarbons at the instrument to compensate for the system back pressure.
from the sample or, if so designed, from a hydrocarbon (for
In general, a supply pressure of 550 kPa (80 psig) will be
example,pentaneorhexane)dopingsystem,orboth.Thislayer
satisfactory.
of carbon facilitates the cracking reaction and suppresses
7.2 OFID Detector System, consisting of a cracking reactor,
hydrocarbon response.
methanizer, and FID.Aschematic of a typical OFID system is
6.3 The carbon monoxide formed in the cracking reactor is
shown in Fig. 1.
convertedtomethaneinthehydrogenatingreactoraccordingto
7.2.1 The detector must meet or exceed the typical specifi-
the following reaction:
cations given in Table 1 of Practice E 594 while operating in
CO 1 3H → CH 1 H O (2) the normal FID mode as specified by the manufacturer.
2 4 2
FIG. 1 Schematic of an OFID
D5599–00
7.2.2 In the OFID mode, the detector shall meet or exceed 8.5.2 Hydrogen, pure grade, 99.9 mol %. ( Warning—
the following specifications: (a) equal to or greater than 10 Hydrogen is an extremely flammable gas under high pressure.)
linearity, (b) less than 100-ppm mass oxygen (1-ng O/s) 8.5.3 Helium or nitrogen as column carrier gas, 99.995 mol
sensitivity, (c) greater than 10 selectivity for oxygen com- % minimum purity, or a blend of 95 % helium/5 % hydrogen,
pounds over hydrocarbons, (d) no interference from coeluting depending on the instrument’s manufacturer. (Warning—
compounds when 0.1 to 1.0-µLsample is injected, (e) equimo- Helium and nitrogen are compressed gases under high pres-
lar response for oxygen. sure.)
7.3 Column—A 60-m by 0.25-mm inside diameter fused 8.5.4 Additional purification of the carrier, air, and hydro-
silica open tubular column containing a 1.0-µm film thickness gen is recommended. Use molecular sieves, Drierite, charcoal,
of bonded methyl silicone liquid phase is used. Equivalent or other suitable agents to remove water, oxygen, and hydro-
columns which provide separation of all oxygenates of interest carbons from the gases.
may be used. 8.6 Sample Container—Glass vials with crimp on or screw-
7.4 Integrator—Use of an electronic integrating device or down sealing caps with self-sealing polytetrafluoroethylene
computer is required. The device and software should have the (PTFE)–faced rubber membranes are used to prepare calibra-
following capabilities: tion standards and samples for analyses.
7.4.1 Graphic presentation of the chromatogram,
9. Preparation of Apparatus
7.4.2 Digital display of chromatographic peak areas,
7.4.3 Identification of peaks by retention time,
9.1 Chromatograph and OFID—Place instrument and de-
7.4.4 Calculation and use of response factors, and
tector into operation in accordance with the manufacturer’s
7.4.5 Internal standard calculation and data presentation.
instructions. Install the capillary column according to Practice
E 1510. Adjust the operating conditions to provide for separa-
8. Reagents and Materials
tion of all oxygenates of interest. Typical conditions used with
the column specified in 7.3 are listed in Table 1.
8.1 Purity of Reagents—Reagents grade chemicals shall be
9.2 System Performance—At the beginning of each day of
used in all tests. Unless otherwise indicated, it is intended that
operation, inject an oxygenate-free gasoline sample into the
all reagents shall conform to the specifications of the Commit-
chromatograph to ensure minimum hydrocarbon response. If
tee onAnalytical Reagents of theAmerican Chemical Society,
hydrocarbon response is detected, the OFID is not operating
where such specifications are available. Other grades may be
effectively and must be optimized according to the manufac-
used, provided it is first ascertained that the reagent is of
turer’s instructions before the sample can be analyzed.
sufficiently high purity to permit its use without lessening the
accuracy of the determination.
10. Calibration and Standardization
8.2 Calibrant Materials—The following compounds may
be used for calibrating the detector: methanol, ethanol,
10.1 Retention Time Identification— Determine the reten-
n-propanol, iso-propanol, n-butanol, tert-butanol, sec-butanol, tion time of each oxygenate component by injecting small
iso-butanol, tert-pentanol, methyl tert-butylether (MTBE), amounts either separately or in known mixtures. Table 2 gives
tert-amylmethylether (TAME), ethyl tert-butylether (ETBE), typical retention times for the oxygenates eluting from a 60-m
di-iso-propylether (DIPE). (Warning—These materials are methyl silicone column temperature programmed according to
very flammable and may be harmful or fatal when ingested, conditions given in Table 1. A chromatogram of a blend of
inhaled, or allowed to be absorbed through the skin.) oxygenates is given in Fig. 2.
8.3 Internal Standard—Use one of the compounds listed in
8.2thatisnotpresentinthesample.Ifallofthematerialsin8.2
TABLE 1 Typical Operating Conditions
are likely to be present in the test sample, use another organic
Temperatures, °C
oxygenate of high-grade purity that is separated from all other
Injector 250
oxygenates present (for example, 1,2-dimethoxyethane).
Column 50°C (hold 10 min), ramp 8°/min to 250°C
8.4 Dopant—If the OFID is so designed, reagent-grade
Detector Methanizer 350–450
pentane is used as a hydrocarbon dopant for the cracking
Reactor 850–1300
reactor. (Warning—Pentane is extremely flammable and
Flows, mL/min
harmful when inhaled.)
Column carrier gas 1
8.5 Instrument Gases—The gases supplied to the gas chro-
Detector gases Air: 300
H :30
matograph and detector are:
Auxiliary (for dopant, if available) H:0.6
8.5.1 Air, zero grade. (Warning—Compressed air is a gas
A
Sample Size 0.1–1.0 µL
under high pressure and supports combustion.)
Split Ratio 100–1
A
Sample size and split ratio must be adjusted so that the oxygenates in the
range from 0.1 to 20.0 mass % are eluted from the column and measured linearly
atthedetector.Eachlaboratorymustestablishandmonitortheconditionsthatare
Reagent Chemicals, American Chemical Society Specifications, American
needed to maintain linearity with their individual instruments. Nonlinearity is most
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
commonly observed when using an OFID with samples containing high levels of
listed by the American Chemical Society, see Analar Standards for Laboratory
individual oxygenates and can be compensated for by either decreasing the
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
sample size, increasing the split ratio, or diluting the sample with an oxygenate-
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
free gasoline. A sample size of 0.5 µL and a split ratio of 100:1 has been used
MD. successfully in most cases.
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