ASTM D6730-22

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.
Designation: D6730 − 22
Standard Test Method for
Determination of Individual Components in Spark Ignition
Engine Fuels by 100-Metre Capillary (with Precolumn) High-
Resolution Gas Chromatography
This standard is issued under the fixed designation D6730; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* on the gasoline samples in the interlaboratory cooperative
study, this test method is applicable to samples containing less
1.1 This test method covers the determination of individual
than 25% by mass of olefins. However, some interfering
hydrocarbon components of spark-ignition engine fuels and
co-elution with the olefins above C is possible, particularly if
their mixtures containing oxygenate blends (MTBE, ETBE, 7
blending components or their higher boiling cuts such as those
ethanol, and so forth) with boiling ranges up to 225°C. Other
derived from fluid catalytic cracking (FCC) are analyzed, and
light liquid hydrocarbon mixtures typically encountered in
the total olefin content may not be accurate. AnnexA1 of this
petroleum refining operations, such as blending stocks
(naphthas, reformates, alkylates, and so forth) may also be test method compares results of the test method with other test
analyzed; however, statistical data was obtained only with
methods for selected components, including olefins, and sev-
blended spark-ignition engine fuels.
eral group types for several interlaboratory cooperative study
samples. Although benzene, toulene, and several oxygenates
1.2 Based on the cooperative study results, individual com-
are determined, when doubtful as to the analytical results of
ponent concentrations and precision are determined in the
these components, confirmatory analyses can be obtained by
range from 0.01% to approximately 30% by mass. The test
method may be applicable to higher and lower concentrations using the specific test methods listed in the reference section.
for the individual components; however, the user must verify
1.4.1 Total olefins in the samples may be obtained or
the accuracy if the test method is used for components with
confirmed, or both, if necessary, by Test Method D1319
concentrations outside the specified ranges.
(percentbyvolume)orothertestmethods,suchasthosebased
1.3 This test method also determines methanol, ethanol, on multidimentional PONA-type of instruments.
t-butanol, methyl t-butyl ether (MTBE), ethyl t-butyl ether
1.5 If water is or is suspected of being present, its concen-
(ETBE), and t-amyl methyl ether (TAME) in spark ignition
tration may be determined, if desired, by the use of Test
engine fuels in the concentration range from 1% to 30% by
Method D1744 or equivalent. Other compounds containing
mass. However, the cooperative study data provided insuffi-
oxygen,sulfur,nitrogen,andsoforth,mayalsobepresent,and
cient statistical data for obtaining a precision statement for
may co-elute with the hydrocarbons. If determination of these
these compounds.
specific compounds is required, it is recommended that test
1.4 Although a majority of the individual hydrocarbons
methods for these specific materials be used, such as Test
present are determined, some co-elution of compounds is
Methods D4815 and D5599 for oxygenates, and Test Method
encountered. If this test method is utilized to estimate bulk
D5623 for sulfur compounds, or equivalent.
hydrocarbongroup-typecomposition(PONA),theuserofsuch
data should be cautioned that some error will be encountered
1.6 The values stated in SI units are to be regarded as
duetoco-elutionandalackofidentificationofallcomponents
standard. No other units of measurement are included in this
present. Samples containing significant amounts of naphthenic
standard.
(for example, virgin naphthas) constituents above n-octane
1.7 This standard does not purport to address all of the
may reflect significant errors in PONA-type groupings. Based
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
This test method is under the jurisdiction of ASTM Committee D02 on
mine the applicability of regulatory limitations prior to use.
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.04.0L on Gas Chromatography Methods.
1.8 This international standard was developed in accor-
Current edition approved Nov. 1, 2022. Published November 2022. Originally
dance with internationally recognized principles on standard-
approved in 2001. Last previous edition approved in 2021 as D6730–21. DOI:
10.1520/D6730-22. ization established in the Decision on Principles for the
*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
D6730 − 22
Development of International Standards, Guides and Recom- it is partitioned into individual components which are sensed
mendations issued by the World Trade Organization Technical with a flame ionization detector as they elute from the end of
Barriers to Trade (TBT) Committee. the column. The detector signal is presented on a strip chart
recorder or digitally, or both, by way of an integrator or
2. Referenced Documents
integrating computer. Each eluting component is identified by
comparing its retention time to that established by analyzing
2.1 ASTM Standards:
reference standards or samples under identical conditions. The
D1319TestMethodforHydrocarbonTypesinLiquidPetro-
concentration of each component in percent by mass is
leum Products by Fluorescent Indicator Adsorption
determined by normalization of the peak areas after correction
D1744Test Method for Determination of Water in Liquid
with detector response factors. Unknown components are
Petroleum Products by Karl Fischer Reagent (Withdrawn
reported as a total unknown percent by mass.
2016)
D3700Practice for Obtaining LPG Samples Using a Float-
5. Significance and Use
ing Piston Cylinder
D4057Practice for Manual Sampling of Petroleum and
5.1 Knowledge of the individual component composition
Petroleum Products
(speciation) of gasoline fuels and blending stocks is useful for
D4177Practice for Automatic Sampling of Petroleum and
refinery quality control and product specification. Process
Petroleum Products
control and product specification compliance for many indi-
D4307Practice for Preparation of Liquid Blends for Use as
vidual hydrocarbons can be determined through the use of this
Analytical Standards
test method.
D4626Practice for Calculation of Gas Chromatographic
5.2 This test method is adopted from earlier development
Response Factors
4,5,6,7
and enhancement. The chromatographic operating condi-
D4815Test Method for Determination of MTBE, ETBE,
tions and column tuning process, included in this test method,
TAME, DIPE, tertiary-Amyl Alcohol and C to C Alco-
1 4
were developed to provide and enhance the separation and
hols in Gasoline by Gas Chromatography
subsequent determination of many individual components not
D5580Test Method for Determination of Benzene,Toluene,
obtained with previous single-column analyses. The column
Ethylbenzene, p/m-Xylene, o-Xylene, C and Heavier
temperatureprogramprofileisselectedtoaffordthemaximum
Aromatics, and Total Aromatics in Finished Gasoline by
resolutionofpossibleco-elutingcomponents,especiallywhere
Gas Chromatography
these are of two different compound types (for example, a
D5599Test Method for Determination of Oxygenates in
paraffin and a naphthene).
Gasoline by Gas Chromatography and Oxygen Selective
5.3 Although a majority of the individual hydrocarbons
Flame Ionization Detection
present in petroleum distillates are determined, some co-
D5623Test Method for Sulfur Compounds in Light Petro-
elution of compounds is encountered. If this test method is
leum Liquids by Gas Chromatography and Sulfur Selec-
utilized to determine bulk hydrocarbon group-type composi-
tive Detection
tion (PONA), the user of such data should be cautioned that
E355PracticeforGasChromatographyTermsandRelation-
some error will be encountered due to co-elution and a lack of
ships
identification of all components present. Samples containing
E594Practice for Testing Flame Ionization Detectors Used
significantamountsofolefinicornaphthenic,orboth,constitu-
in Gas or Supercritical Fluid Chromatography
ents above octane may reflect significant errors in PONA-type
E1510Practice for Installing Fused Silica Open Tubular
groupings.
Capillary Columns in Gas Chromatographs
5.4 If water is or is suspected of being present, its concen-
3. Terminology
tration is determined by the use of Test Method D1744. Other
3.1 Definitions—This test method makes reference to many
compounds containing oxygen, sulfur, nitrogen, and so forth
common gas chromatographic procedures, terms, and relation-
may also be present, and may co-elute with the hydrocarbons.
ships. Detailed definitions can be found in Practice E355.
When known co-elution exists, these are noted in the test
method data tables. If determination of these specific com-
4. Summary of Test Method
pounds is required, it is recommended that test methods for
4.1 A representative sample of the petroleum liquid is
introduced into a gas chromatograph equipped with an open
Johansen, N.G., and Ettre, L.S., “Retention Index Values of Hydrocarbons on
tubular (capillary) column coated with a methyl silicone liquid
Open Tubular Columns Coated with Methyl Silicone Liquid Phases,”
phase,modifiedwithacapillaryprecolumn.Heliumcarriergas
Chromatographia, Vol 5, No. 10, October 1982.
transports the vaporized sample through the column, in which 5
Johansen, N.G., Ettre, L.S., and Miller, R.L., “Quantitative Analysis of
Hydrocarbons by Structural Group Type in Gasolines and Distillates. Part 1,”
Journal of Chromatography, Vol 256, 1983, pp. 393–417.
2 6
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Kopp, V.R., Bones, C.J., Doerr, D.G., Ho, S.P., and Schubert, A.J., “Heavy
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Hydrocarbon/Volatility Study: Fuel Blending and Analysis for the Auto/Oil Air
Standards volume information, refer to the standard’s Document Summary page on Quality Improvement Research Program,” SAE Paper No. 930143, March 1993.
the ASTM website. Schubert, A.J. and Johansen, N.J., “Cooperative Study to Evaluate a Standard
The last approved version of this historical standard is referenced on Test Method for the Speciation of Gasolines by Capillary Gas Chromatography,”
www.astm.org. SAE Paper No. 930144, March 1993.
D6730 − 22
these specific materials be used, such as Test Method D4815 11 for a description of the column performance specifications
and D5599 for oxygenates, Test Method D5580 for aromatics, and Annex A1 for a description of the column modification
and Test Method D5623 for sulfur compounds. procedure.
6.4.1 The primary gas chromatographic column used for
this test method will meet the following specifications.
6. Apparatus
Material fused silica
6.1 Gas Chromatograph—Instrumentation capable of col-
Length 100 m
umn oven temperature programming, from subambient (5°C)
Internal diameter 0.25 mm
Liquid phase methyl silicone
to at least 200°C, in 0.1°C⁄min or less rate increments, is
Film thickness 0.50 µm
required. Multi-step column oven temperature programming is
Theoretical plates, n, pentane at 35 °C ; 400 000 to 500 000
required, consisting of an initial hold time, an initial tempera-
Retention factor, k, pentane at 35 °C 0.45 to 0.50
Resolution, R, t-butanol and 2-methylbutene-2 at 3.25 to 5.25
ture program followed by an isothermal temperature hold and
35 °C
another programmed temperature rise.Aheated flash vaporiz-
Peak symmetry, t-butanol at 35 °C > 1.0 to < 5.0
ing injector designed to provide a linear sample split injection
6.4.2 Precolumn—A variable length (1m to 4m) of 5%
(that is, 200:1) is required for proper sample introduction. The
phenyl/95% dimethylpolysiloxane fused silica open tubular
associatedcarriergascontrolsmustbeofsufficientprecisionto
column (0.25mm inside diameter) is added to the front
provide reproducible column flows and split ratios in order to
(injector) end of the 100m column, as described in AnnexA1.
maintain analytical integrity. A hydrogen flame ionization
detector,withassociatedgascontrolsandelectronics,designed
7. Reagents and Materials
for optimum response with open tubular columns, shall con-
7.1 Carrier Gas—Helium, 99.999% pure. (Warning—
formtothespecificationsasdescribedinPracticeE594,aswell
Helium, air, nitrogen, compressed gas under pressure.)
as having an operating temperature range of up to at least
250°C.
7.2 Oxidant—Air, 99.999% pure. (Warning—see 7.1.)
6.2 Sample Introduction—Manual or automatic liquid
7.3 Detector Makeup Gas—Nitrogen, 99.999 % pure.
sample injection to the splitting injector may be employed.
(Warning—see 7.1.)
Automated injections are highly recommended. Micro-
7.4 Fuel Gas—Hydrogen, 99.999% pure. (Warning—
syringes, auto-syringe samplers, or valves capable of 0.1µLto
Hydrogen, flammable gas under high pressure.)
0.5µL. injections are suitable. It should be noted that some
7.5 Reference Standards:
syringes and improper injection techniques as well as inad-
7.5.1 Purity of Reagents—Reagent grade chemicals shall be
equatesplitterdesigncouldresultinsamplefractionation.This
used in all tests. Unless otherwise indicated, it is intended that
must be determined in accordance with Section 10.
all reagents conform to the specifications of the Committee on
6.3 Electronic Integrator—Any electronic integration de- 8
AnalyticalReagentsoftheAmericanChemicalSociety where
vice used for quantitating these analyses shall meet or exceed
such specifications are available. Other grades may be used,
these minimum requirements:
provided it is first ascertained that the reagent is of sufficiently
6.3.1 Capacity to handle 400 or more peaks per analysis.
high purity to permit its use without lessening the accuracy of
6.3.2 Normalized area percent calculation with response
the determination.
factors.
7.5.2 Methanol—(Warning—These materials are flam-
6.3.3 Noise and spike rejection. mable and may be harmful or fatal, if ingested or inhaled.).
7.5.3 Ethanol—Only absolute ethanol of 99.5 minimum
6.3.4 Accurate area determination of fast (1s to 2 s) peaks
percent meets the requirements of this test method.
(10Hz or greater sampling rate).
(Warning—see 7.5.2.)
6.3.5 Maintain peak detection sensitivity for narrow and
7.5.4 Hydrocarbon and Other Component References—
broad peaks.
Individual and mixed component reference materials are com-
6.3.6 Positive and negative sloping baseline correction.
mercially available and may be used to establish qualitative
6.3.7 Perpendicular drop and tangent skimming as needed.
and quantitative calibration. (Warning—see 7.5.2.)
6.3.8 Display of baseline used to ensure correct peak area
7.5.5 System and Column Evaluation Mixture—A quantita-
determination.
tively prepared mixture, complying with Practice D4307,of
6.4 Open Tubular Column—The column used for this test individual hydrocarbons and oxygenates of interest is used for
system and column evaluation (see Table 1). (Warning—see
method consists of a primary (100m) analytical column and a
precolumn. The ability to provide the required component 7.5.2.) Fig. 1 is a chromatogram of the recommended mixture
in Table 1.
separations is dependent on the precise control of the column
selectivity, which is typically slightly more than that exhibited
by current commercially available columns. Some older
columns, and columns that have a sample residue from
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington,
repeated use without conditioning, may exhibit the required
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
polarity. Until adequate columns are commercially available,
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
the currently used methyl silicone columns can be modified or
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
tuned to meet the method column specifications. See Section copeial Convention, Inc. (USPC), Rockville, MD.
D6730 − 22
TABLE 1 System and Column Evaluation Mixture
9.2 Determine the required length of the precolumn in
% accordance with AnnexA1.Adjust the operating conditions of
Ethanol 8.00
the gas chromatograph to those listed in Table 2 or as
n-pentane 2.00
determined by Section 12 and Annex A1.
t-butanol 0.50
2-methylbutene-2 2.50
9.3 During setup and, when not performing analyses, it is
2,3-dimethylbutane 0.50
advisabletoturnoffthecryogenicoperationandsetthecolumn
Methyl-t-butyl ether 10.00
n-hexane 2.00 oven temperature at 35°C. Attach the column outlet to the
1-methylcyclopentene 0.50
flame ionization detector inlet and check for leaks throughout
Benzene 1.00
thesystem.Ifleaksarefound,tightenorreplacefittingsbefore
Cyclohexane 28.90
3-ethylpentane 0.20
proceeding.
1,2t-dimethylcyclopentane 0.50
9.4 Confirm or adjust, or both, the column carrier gas flow
n-heptane 2.00
2,3,3-trimethylpentane 0.50
rate by making injections of methane or natural gas. The
Toluene 7.00
methane retention time shall be 7.00 min 6 0.02 min with the
n-octane 2.00
column oven temperature at 35 °C,whichresultsinanaverage
Ethylbenzene 25.00
p-xylene 1.00
linear velocity of 24cm⁄s, as determined using Eq 1.This will
2,3-dimethylheptane 0.20
result in a methane retention time of 6.53min at 5°C. Raising
n-nonane 2.00
or lowering the carrier gas pressure to the injector makes flow
5-methylnonane 0.20
1-methyl-2-ethylbenzene 0.50
rate adjustment. A starting point of 277kPa (40psig) helium
n-decane 1.00
pressure is recommended, although columns requiring as high
n-undecane 0.50
as 332kPa (48psig) helium have been encountered.
1,2,3,5-tetramethylbenzene 0.25
Naphthalene 0.50
averagelineargasvelocity:u ~cm/s! 5columnlength ~cm!/t
ave M~s!
n-dodecane 0.25
1-methylnaphthalene 0.25
(1)
n-tridecane 0.25
9.5 After final adjustment of the carrier gas flow rate, note
the carrier gas inlet pressure. Measure and, if necessary,
readjust the injector split flow rate to give the specified or
8. Sampling desired split ratio. Calculate the column outlet flow rate using
9.5.1 and the split ratio using 9.5.2.
8.1 Hydrocarbon liquids with Reid vapor pressures of
9.5.1 Column Carrier Gas Flow Rate (at outlet):
110kPa (16psi) or less may be sampled either into a floating
9.5.1.1 P = (head pressure (psig) + ambient pressure)/
piston cylinder or into an open container (PracticesD4057and
ambient pressure.
D4177). If the sample as received does not meet the upper
2 3
9.5.1.2 j = compressibility factor = 3/2((P −1)/(P −1)).
boiling range requirements of 1.1, it may be necessary to
9.5.1.3 u = u /j = column outlet velocity.
o ave
extend the analysis time and raise the upper column tempera-
2 2
9.5.1.4 A = pi(r) = column cross-sectional area (cm ).
c
ture of this test method to ensure complete elution of higher
where r = column internal radius (cm).
boiling range sample material from the column.
9.5.1.5 Flow rate (cm /min) = u × A × 60.
0 c
8.1.1 Piston Cylinder Sampling—Refer to Practice D3700
9.5.2 Injection Split Ratio—(Split flow rate + column flow
for instructions on transferring a representative sample of a
rate)/column flow rate.
hydrocarbonfluidfromasourceintoafloatingpistoncylinder.
9.5.3 Example—Using a 100m × 0.25mm capillary col-
Add inert gas to the ballast side of the floating piston cylinder
umn:
to achieve a pressure of 350kPa (45psi) above the vapor
9.5.3.1 U = 100 × 100/6.98 × 60 = 23.88 cm/s.
ave
pressure of the sample.
9.5.3.2 P = 40 psig + 12.0/12.0 = 4.33.
8.1.2 Open Container Sampling—Refer to Practice D4057
9.5.3.3 j = 3/2((18.778-1)/(81.370-1)) = 0.33
for instructions on manual sampling from bulk storage into
9.5.3.4 u = 23.88/0.33 = 71.96 cm/s.
o
open containers. Stopper the container immediately after tak-
2 −4 2
9.5.3.5 A = pi(0.025/2) =4.9×10 cm .
c
ing a sample.
−4 3
9.5.3.6 Flowrate=71.96×4.9×10 ×60=2.12cm /min.
8.2 Preserve the sample by cooling to approximately 4°C
9.5.3.7 Split Ratio = (192 + 2.12)/2.12 = 91.6:1.
and maintaining that temperature prior to analysis.
9.6 Make a blank analysis (no sample injection) run to
8.3 Transfer an aliquot of the cooled sample to a precooled
ensure proper instrument operation and further condition the
septum vial and seal immediately.
column and instrumentation. If stray peaks or a rising baseline
signal is observed, the column oven shall be kept at the upper
8.4 Obtain the test specimen for analysis directly from the
temperature until the baseline becomes steady and returns to
sealed septum vial, for either manual or automatic injection.
within approximately 5% of the starting temperature detector
9. Preparation of Apparatus
signal.
9.1 Install the 100m column and, if required, a precolumn 9.7 After any extended conditioning period, or if the instru-
according to the manufacturer’s or supplier’s instructions and ment has been shut down, it is advisable to repeat 9.4, 9.5, and
AnnexA1.SeePracticeE1510/8forrecommendedinstallation 9.6 to ensure proper carrier gas flows are being used and the
procedures. column is clean.
D6730 − 22
FIG. 1 DHA Speciation Analysis—System and Column Evaluation Mixture (7.5.5)
D6730 − 22
TABLE 2 GC Operating Conditions
10.4 Report and use only those combinations of conditions
Column Temperature Program from 10.2 that result in 3% or less relative error. This is the
Initial temperature 5 °C
splitter linearity range.
Initial time 10 min.
First program rate 5.0 ° ⁄min
11. Column Evaluation
First hold temperature 50 °C
First hold time to the elution of ethylbenzene (;50 min)
11.1 In order to establish that a column will perform as
Second program rate 1.5 ° ⁄min
required, the following specifications shall be determined for
Final temperature 200 °C
Final hold time 5 min
new column acceptability and are useful for periodic evalua-
Injector
tion of column deterioration. These specification determina-
Temperature 250 °C
tions can be made with or without a precolumn, since the
Split ratio 150:1
Sample size 0.1 µL – 0.2 µL precolumnwillhavelittleeffectontheirvalues.SeeAnnexA1,
Detector
Fig.A1.1,forexamplesofthesedeterminations.Afterperform-
Type flame Ionization
ing the steps in Sections 9 and 10, analyze the column
Temperature 250 °C
Use manufacturers recommended detector gas flows or:
performance mixture (7.5.5) at 35°C isothermal, at least
Fuel gas hydrogen at 30 mL/min
through heptane. The remainder of the analysis may be
Oxidant air at 300 mL/min
ignored,buttheremainingcomponentsmustbeelutedfromthe
Make-up gas, where required nitrogen at 20 mL/min
Carrier Gas
column prior to performing another analysis. Setting the
Type helium
column temperature to 220°C for an additional 20min will be
Pressure ; 277 kPa (40 psig)
sufficient.
Average linear velocity 24 cm/s at 35 °C
11.2 Calculate the retention factor (k) for pentane at 35°C:
k 5 ~t 2 t !/t (3)
R M M
where:
10. Split Injection Linearity
t = gas holdup time (methane), and
M
t = retention time for pentane, min.
R
10.1 Splitting injector linearity must be established to de-
termine proper quantitative parameters and limits. The split
11.2.1 The retention factor must be between 0.45 and 0.50
ratio used is dependent upon the split linearity characteristics for proper application of this test method.
of the particular injector and the sample retention factor of the
11.3 Calculate the column efficiency using the pentane
column. The retention factor of a particular column for a
peak:
sample component is proportional to the amount of liquid
n 55.545 t /w (4)
~ !
R 1/2h
phase (loading or film thickness) and the ratio of the column
temperature to the component boiling point (vapor pressure).
where:
Overloading of the column may cause loss of resolution for
n = column efficiency (theoretical plates),
some components and, since overloaded peaks are skewed,
t = retention time of pentane, and
R
variance in retention times. This can lead to erroneous com-
w = peak width at half height.
1/2h
ponent identification. During column evaluations and split
11.3.1 Thecolumnefficiencymustbeatleast400000plates
linearity studies, be aware of any peaks that may appear front
for proper application of this test method.
skewed, indicating column overload. Note the component size
and avoid conditions leading to this problem during actual 11.4 The selectivity of apparently identical columns toward
hydrocarbons may vary regarding oxygenated compounds;
analyses.
eitherduetoextraneousmaterialsintheliquidphase,ordueto
10.2 Set the injector temperature and split ratio to the
activity of the column wall surface. The addition of a precol-
followingvaluesand,foreachsetofconditionsinjectthelisted
umnhaslittleifanyaffectontheselectivitytowardoxygenates
quantitiesofthesystemandcolumnevaluationmixture(7.5.5),
(see AnnexA1, Fig.A1.4). The relative resolution of oxygen-
using the operating conditions listed in Table 2 or as deter-
atesisinherenttothequalityoftheprimary100mcolumn,and
mined in Section 12.
is specified by the resolution of t-butanol from
split: 100:1
injector temperature: 250 °C< > sample: 0.2 µL, 0.5 µL, 1.0 µL 2-methylbutene-2 at 35°C. Calculate the resolution:
split: 200:1
R 52~t 2 t !/1.699~w 1w !
split: 100:1
R22M2Butene22 RTBA 1/2h22M2Butene22 1/2hTBA
injector temperature: 300 °C< > sample: 0.2 µL, 0.5 µL, 1.0 µL
split: 200:1
(5)
10.3 Compare the calculated concentrations to the known
11.4.1 Theresolutionforthispairat35°Cmustbebetween
standard concentrations after calculating the corrected area
3.25 and 5.25.
normalization using the response factors from 13.2 and Table
11.5 Extraneouscolumneffects,orinstrumentaleffectssuch
A1.1.
asanactiveinjectorliner,maycauseadsorptionofoxygenated
% relativeerror5 (2)
compounds,commonlyseenandreferredtoastailing,andmay
increase their retention. If this effect is caused by instrumental
100 3 concentrationdetermined
~
activity, the problem should be corrected. If the column is
2concentrationknown)/concentrationknown inherentlyactive,anewcolumnshouldbeobtained.Ameasure
D6730 − 22
ofthetailingcanbemadeandspecifiedbyapplyingaskewness
calculation, which determines a ratio of the distances from the
peak apex perpendicular to the front and back of the peak at
5% of the peak height. See Annex A1, Fig. A1.3 for an
example of this calculation.
skewness 5B/A (6)
11.5.1 This test method shall be made using the t-butanol
peak (0.5%) in the analysis of the column performance
mixture (7.5.5) at 35°C isothermal. The skewness ratio must
be greater than 1.0 and not more than 5.0.
12. Optimization of Instrument Operating Conditions FIG. 2 i-butane/methanol and ethanol/3-methyl-butene-1
12.1 The column temperature programming profile is de-
pendent upon the individual column characteristics. Table 2
pentene-1 and 2-methyl-butene-1, t-butanol will appear re-
lists the programming profile determined for a 100m methyl
solved between c-pentene-2 and 2-methylbutene-2.
silicone column with a precolumn as determined in AnnexA1.
12.3.2.1 Higher temperatures will move the alcohols into
The profile is determined by establishing satisfactory separa-
the peaks ahead of them.At 35°C the alcohols will be located
tions for the sets of sample components listed in 12.3.Itisnot ahead of the pentene-1 and c-pentene-2, respectively (Fig. 3).
practical to expect complete separation of all components, so
12.3.3 2,3-dimethylbutane/methyl-t-butylether—This sepa-
theoptimumforeachcolumnmaycontainsomecompromises, ration is critical and the 5°C hold for 10min determines its
also dependent upon any particular other separations deemed
success. The retention indices should be about 569.5, 571.5,
important.
and 574.0 for 2,3-dimethylbutane, MTBE, and
2-methylpentane, respectively. If the MTBE is too close to the
12.2 The use of retention indices to numerically express the
2,3-DMC , use a 9min initial hold. If too close to the 2-MC
relative location of components among themselves and to 4 5
use an 11min hold (Fig. 4).
surrounding normal paraffins is a convenient convention. The
12.3.4 1-methylcyclopentene/benzene—This is a key sepa-
indices are also useful in providing a system of component
ration that is used to specify the column selectivity. Changing
identification with complex analyses such as this. There are
column temperature produces only slight differences in this
several schemes for calculating retention indices, the first of
resolution (Fig. 5).
which is the Kovats method, developed to express the loga-
12.3.4.1 The 50°C column temperature is held isothermal
rithmic relationship of retention times of a homologous series
until the elution of ethylbenzene. This is variable due to slight
ofcompoundswhenchromatographedisothermally.Whilethis
differences in the column retention factor.
test method is not an isothermal column temperature
12.3.5 2,3,3-trimethylpentane/toluene—This is a key sepa-
procedure, it does contain isothermal steps and the longer
ration that is used to specify the column selectivity. Column
temperature program step is a slow rate.The use of the Kovats
temperature has very little effect on this resolution, which is
indices provides a closer relationship to previous work in this
controlled by the column selectivity for aromatics (Fig. 6).
field than using the linear index format.
12.3.6 p-xylene/2,3-dimethylheptane—This is a key separa-
12.2.1 The formula for the calculation of Kovats retention
tion which limits the maximum length of the precolumn. If the
indices is:
column selectivity is too great the aromatics are retained and
RI 5100 3 ~n1~log~t ! 2log~t !!/~log~t ! 2log~t !!! (7)
i i n n11 n
this separation is not achieved. If this resolution is excessive
and the separation in 12.3.5 is insufficient, the precolumn
where:
should be lengthened slightly. Lowering the 50°C hold tem-
RI = retention index,
perature to 48°C will increase this separation (Fig. 7).
n = carbon number of n-paraffin,
t = retention time of component,
i
t = retention time of preceding n-paraffin, and
n
t = retention time of next n-paraffin.
n+1
12.3 The following examples show the key or critical
separations required for this analysis.Typical retention indices
are given, and a description of the effect of instrumental
conditions on the separation is provided.
12.3.1 i-butane/methanol and ethanol/3-methylbutene-1—
The initial starting temperature of 5°C is dictated by these
separations.Alower starting temperature is not necessary and
a higher temperature would effect the next set. The retention
indicesshouldbeabout380formethanoland456.5forethanol
(Fig. 2).
12.3.2 i-propanol/2-methylbutene-1 and t-butanol/2-
FIG. 3 i propanol/2-methyl/butene-1 and t butanol/2-
methylbutene-2—i-propanol will appear resolved between methylbutene-2
D6730 − 22
FIG. 7 p-xylene/2,3-dimethylheptane
theratein0.1°⁄minincrementstoincreasetheresolution.This
rate is also dictated by the separation requirements in 12.3.8.
The proper rate will provide for both separations (Fig. 8).
FIG. 4 2,3-dimethylbutane/methyl-t butylether
12.3.8 1-methylnaphthalene/tridecane—The recommended
final column temperature program rate of 1.5°⁄min. should
also provide this separation. If the 1-MeNaph/n-C resolution
is incomplete this rate may be adjusted to provide sufficient
separation. Lower the rate in 0.1°⁄min. increments to increase
the resolution (Fig. 9).
13. Calibration
13.1 Qualitative—Determine the retention times of compo-
nentsbyanalyzingknownreferencemixturesorsamplesunder
identical conditions. Calculate retention indices from these
data using 12.2. TableA1.1 provides a listing of typical values
for this test method.
13.2 Quantitative, Hydrocarbons—Use theoretical response
factors for correction of the detector response of hydrocarbons
determined by this test method, unless response factors have
been determined experimentally. The response of an FID to
hydrocarbons is determined by the ratio of the molecular
FIG. 5 1-methylcyclopentene/benzene
weight of the carbon in the analyte to the total molecular
weight of the analyte. If experimentally determined response
factors are to be used, they must be determined using known
purity individual standards and calculated using Practice
D4626. The response factors, as listed in Table 3, are relative
to that calculated for heptane. Calculations are based on the
following equation:
F 5 C 3 C 1 H 3H / C 3 0.83905 / C (8)
~~~~~ ! ~ !! ! ! !
i aw n aw n n aw
FIG. 6 2,3,3-trimethylpentane/toluene
12.3.7 l17 (Unknown)/1,2-methylethylbenzene —The un-
known isoparaffin (l17) appears to be a component of alkylate
and must be resolved from the aromatic. If the resolution is
incomplete the final column temperature program rate of
1.5°⁄min. is adjusted to provide sufficient separation. Increase FIG. 8 l17 (unknown)/1,2-methylethylbenzene
D6730 − 22
15.1.1 Proper component identification using retention in-
dicesrequirestheuseof windowssurroundingeachRIvaluein
order to account for the analysis to analysis variations. The
following windows have been found to provide satisfactory
identification for this test method.
Indices Window
100 – 300 ± 15
300 – 400 ± 2.6
400 – 500 ± 1.5
500 – 885 ± 0.6
885 – 900 ± 0.5
> 900 ± 0.6
15.2 Obtaintheareaforeachpeak.Multiplyeachpeakarea
FIG. 9 1-methylnaphthalene/tridecane
by its appropriate response factor, taken from Table 2 or
determined separately with standards, to obtain corrected peak
areas. Use a response factor of 1.000 for unknown peaks.
15.3 Ifrequired,determinetheconcentrationofwaterinthe
where:
sample using Test Method D1744, or an equivalent method.
F = relative response factor for a hydrocarbon type group
i
The total concentration of any other materials not determined
of a particular carbon number.
by this test method should also be obtained.
C = atomic weight of carbon 12.011,
aw
C = number of carbon molecules in the group,
n
15.4 Thecorrectedpeakareasarenormalizedto100%orto
H = atomic weight of hydrogen, 1.008,
aw
100% minus the concentrations determined in 15.3.
H = number of hydrogen molecules in the group,
n
component% m/m 5correctedpeakarea (9)
~ !
0.83905 is the correction factor with heptane as unity
(1.0000), and
3 100 2% undetected /totalcorrectedpeakarea
~ !
0.7487 is used with methane as unity.
16. Report
13.3 Quantitative, Oxygenates—Determineresponsefactors
for methanol, ethanol, and other oxygenated compounds ex-
16.1 Report the concentration of each component as mass
perimentally. The principles in Practice D4626 should be %, % (m/m), to the nearest 0.001% (m/m).
appliedwhendeterminingtheseresponsefactors.Theresponse
16.2 These individual component data may be grouped by
of the flame ionization detector for oxygenated compounds is
summing the concentration of compounds in each particular
not directly (theoretically) related to mass concentration. A
group type such as paraffin, isoparaffin, olefin, aromatic,
study has indicated that the FID response is linear for the
naphthene, oxygenates, and unknowns. Commercially avail-
conditions of this test method (see Figs. 10 and 11). Each
able software may be used to provide this function, as well as
individual apparatus must be calibrated using gravimetrically
calculation of other properties of petroleum liquids. See the
prepared standards, covering the sample concentration ranges
caution in 5.3.
expected and the scope of this test method. Standards used
must comply with the requirements in Section 7. Figs. 10 and
17. Precision and Bias
11 present calibration data for six oxygenates as determined in
17.1 Repeatability—The difference in two test results ob-
a preliminary cooperative study report for calibration of this
tainedbythesameoperatorwiththesameapparatusinagiven
test method. Precision data will be prepared when more data
laboratory under constant operating conditions on test samples
becomes available.
takenfromthesamelaboratorysampleshould,inthelongrun,
in the normal and correct operation of the test method not
14. Sample Analysis Procedure
exceed the values given in Table 4 and Table A1.3 for the
14.1 Adjust the instrument operating variables to the values
gasoline components.
specified in Table 1 or as determined in Section 12.
17.2 Reproducibility—The difference between two single
14.2 Set the recorder or integration device, or both, for
and independent measurements on test samples taken from the
accurate presentation and collection of the data.
same bulk sample should, in the long run, in the normal and
correct operation of the test method, not exceed the values
14.3 Inject an appropriate size sample (as determined in
given in Table 4 and TableA1.3 for the gasoline components.
Section10)intotheinjectionportandstarttheanalysis.Obtain
a chromatogram and a peak integration report.
17.3 Bias—No information can be presented on the bias of
the procedure in this test method for measuring hydrocarbon
15. Calculation
concentrations because no material having an accepted refer-
ence value is available.
15.1 Identify each peak by matching retention indices (or
retention times) with those for known reference standards or
samplecomponents.Ifacomputingintegratorisused,examine
SupportingdataisavailablefromASTMInternationalHeadquartersintheform
thechromatographicdataforproperpeakintegration.Examine
of a research report. Request RR:D02-1518. Contact ASTM Customer Service at
the report to ensure peaks are properly identified. service@astm.org.
D6730 − 22
TABLE 3 Theoretical FID Relative Response Factors
Carbon No. Saturated Paraffins Unsaturated Paraffins Saturated Naphthenes Unsaturated Naphthenes Aromatics
1 1.1207 - - - -
2 1.0503 - - - -
3 1.0268 0.9799 - - -
4 1.0151 0.9799 - - -
5 1.0080 0.9799 0.9799 0.9517 -
6 1.0034 0.9799 0.9799 0.9564 0.9095
7 1.0000 0.9799 0.9799 0.9598 0.9195
8 0.9975 0.9799 0.9799 0.9623 0.9271
9 0.9955 0.9799 0.9799 0.9642 0.9329
10 0.9940 0.9799 0.9799 0.9658 0.9376
11 0.9927 0.9799 0.9799 0.9671 0.9415
12 0.9916 0.9799 0.9799 0.9681 0.9447
13 0.9907 0.9799 0.9799 0.9690 0.9474
14 0.9899 0.9799 0.9799 0.9698 0.9497
15 0.9893 0.9799 0.9799 0.9705 0.9517
18. Keywords PIONA; PONA
18.1 detailed hydrocarbon analysis; DHA; gas chromotog-
raphy; hydrocarbons; open tubular column; oxygenates;
D6730 − 22
FIG. 10 Determination of Oxygenate Response—DHA Speciation Analysis
D6730 − 22
FIG. 11 Graphical Representation Determination of Oxygenate Response—DHA Speciation Analysis
D6730 − 22
TABLE 4 Repeatability and Reproducibility of DHA Determinations
NOTE1—ThefollowingisapartiallistofprecisiondatathathasbeenpreparedbystatisticiansofCS94inaccordancewithRR:D2-1007,andrepresents
their best estimate of the cooperative study data. The complete precision data set appears in Annex A1., Table A1.3.
NOTE 2—For each analyte to qualify for a precision statement, it must be present in at least six samples, and detected by at least six laboratories, at
least once. The (repeatability standard deviation)/mean value for each analyte/sample combination must be less than or equal to 0.1, as per LOQ
requirements which, while not a standard, is what CS94 is recommending.
NOTE 3—
Legend:
r = lower 95% confidence limit of r ,
min est
r = repeatability estimate in percent of concentration,
est
r = upper 95% confidence limit of r ,
max est
R ,R , = for reproducibility,
min est
R
max
C = lower concentration limit that r , R is applicable, and
min est est
C = upper concentration limit that r , R is applicable.
max est est
Component Average RI r r r R R R C C
min est max min est max min max
n-butane 400.00 6.8 9.9 13.9 15.3 32.4 59.1 1.02 3.75
i-pentane 477.45 5.9 7.2 8.7 8.5 14.8 23.8 2.48 13.38
Pentene-1 490.83 5.2 7.5 10.5 9.7 13.8 19 0.06 0.43
n-pentane 500.00 5.2 6.5 8.1 7.1 10.4 14.8 1.06 3.49
Cyclopentane 566.84 3.8 4.9 6.2 7 10.1 14 0.07 0.59
2,3-dimethylbutane 569.24 2.9 3.2 3.5 5.1 8.5 13.1 0.7 1.91
n-hexane 600.00 2 2.4 2.9 3.6 5.1 6.9 0.33 2.52
Methylcyclopentane 625.86 2.2 2.6 3.1 4.5 6.4 8.7 0.37 2.35
1-methylcyclopentene 648.71 1.9 2.7 3.7 7.9 8.7 9.6 0.17 0.82
Benzene 649.92 2.6 3.6 4.8 5.5 9 13.7 0.17 1.58
Cyclohexane 657.81 2.7 3.7 4.9 8.2 14.8 24.3 0.07 0.9
2-methylhexane 667.61 1.6 2.2 2.9 5.1 6.1 7.2 0.39 1.09
2,2,4-trimethylpentane 688.48 2.4 3.2 4.1 7.4 11.4 16.7 0.1 11.26
n-heptane 700.00 2.5 3.4 4.5 7.7 10.8 14.7 0.21 1.06
Methylcyclohexane 717.89 2.8 3.4 4 4.1 5.9 8.2 0.11 1.2
2,3,4-trimethylpentane 746.83 2.3 3.8 6 5.8 7.8 10.3 0.08 4.26
Toluene 751.77 1.9 2.7 3.8 10.8 13.5 16.5 1.99 10.34
2-methylheptane 764.14 3.5 4.9 6.6 4.8 6.1 7.5 0.15 0.63
n-octane 800.00 2.2 3.6 5.5 6.5 15.7 30.9 0.14 0.75
Ethylbenzene 854.65 2.2 3.2 4.4 7.2 10.6 14.9 0.62 2.62
1,3-dimethylbenzene 864.22 2.6 3.3 4.2 9.7 12.5 15.7 1.55 6.66
3-methyloctane 880.24 5.1 8.5 13 8.7 15.5 24.9 0.07 0.29
n-nonane 900.20 3.9 6.4 9.8 8.6 10.3 12.2 0.06 0.34
n-propylbenzene 946.33 2.8 5 8.1 7.6 11.9 17.7 0.21 0.77
1,4-methylethylbenzene 956.22 3.5 5.3 7.7 5.1 7.7 11.1 0.32 1.19
1,3,5-trimethylbenzene 961.92 3.7 5.5 7.7 5.4 8.3 12.1 0.39 1.21
2-methylnonane 971.77 6.5 10.6 16.2 17.5 25.9 36.6 0.03 0.19
1,2,4-trimethylbenzene 983.40 4.2 5.7 7.5 7.8 10.6 13.9 1.19 4.32
n-decane 1000.20 7.5 9.2 11.1 12.1 17.9 25.3 0.03 0.25
1,2,3-trimethylbenzene 1006.88 3.8 5.8 8.5 7.2 8.5 10 0.28 0.96
n-undecane 1100.00 8.6 13.9 21 24.4 40 61.2 0.03 0.18
1,2,3,5-tetramethylbenzene 1108.79 6.4 7.8 9.3 10.2 13.9 18.3 0.21 0.51
Naphthalene 1168.01 6.1 8.5 11.3 12.9 16.9 21.5 0.13 0.4
n-dodecane 1200.00 12.2 16.7 22.1 20.2 32.9 50 0.01 0.11
2-methylnaphthalene 1282.57 7.6 11.1 15.4 17.5 22.3 28 0.05 0.5
D6730 − 22
ANNEX
(Mandatory Information)
A1. PROCEDURE FOR ADJUSTING THE SELECTIVITY OF A DHA METHYL SILICONE OPEN TUBULAR COLUMN
A1.1 Thesuccessfulapplicationofthistestmethodishighly silicone column used. One metre of 1.0µm precolumn is
dependentupontheselectivityofthecolumnused.New100m equivalent to a 100m column with 0.5µm of 0.1% phenyl
× 0.25mm 0.5µm methyl silicone open tubular fused silica methyl silicone liquid phase.
columnswilllikelynothavesufficientselectivityforaromatics
A1.4 Figs. A1.5-A1.8 illustrate the resolution of the
to function properly. Critical to the successful analysis of
methylcyclopentene-1 and benzene pair with a new column
reformulated and oxygenated spark engine motor fuels is
andone,two,andthreemetresofprecolumn.Thekeysegment
column inertness and component selectivity. Inertness of the
of the chromatogram is expanded to better illustrate the
primary 100m column affects the retention and adsorption of
resolution of this component pair.
the oxygenates such as alcohols and ethers, while selectivity
for the aromatic compounds is controlled by the liquid phase.
A1.5 The preliminary evaluation of the 100m column will
Until adequate commercial columns are available, it will be
providetheuserwithinformationregardingtheinitiallengthof
necessary to slightly increase the column selectivity, which is
precolumn with which to start the tuning process. Dependent
accomplished by the addition of a short precolumn containing
upon the methylcyclopentene-1 and benzene resolution, an
a moderately selective liquid phase.
initial precolumn of between 1m and4mis selected; which
ever provides a resolution greater than 1.2.
A1.2 Priortomakinganyprecolumnadditionstothe100m
methyl silicone capillary column, determine that the main
A1.6 The final tuning will consist of reducing the precol-
column meets the column specifications outlined in 6.4.1 and
umn length, probably in increments of 0.25m, until the proper
determined in S
...