ASTM D8071-21

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: D8071 − 21
Standard Test Method for
Determination of Hydrocarbon Group Types and Select
Hydrocarbon and Oxygenate Compounds in Automotive
Spark-Ignition Engine Fuel Using Gas Chromatography with
Vacuum Ultraviolet Absorption Spectroscopy Detection (GC-
VUV)
This standard is issued under the fixed designation D8071; 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* automotive spark-ignition engine fuel, it does not attempt to
speciate all possible components that may occur in automotive
1.1 This test method is a standard procedure for the deter-
spark-ignition engine fuel. In particular, this test method is not
mination in percent mass or percent volume of hydrocarbon
intended as a type of detailed hydrocarbon analysis (DHA).
group types (paraffins, isoparaffins, olefins, naphthenes,
aromatics), methanol, ethanol, benzene, toluene, ethylbenzene, 1.4 The values stated in SI units are to be regarded as
xylenes, naphthalene, and methylnaphthalenes in automotive standard. No other units of measurement are included in this
spark-ignition engine fuels using gas chromatography and standard.
vacuum ultraviolet detection (GC-VUV).
1.5 This standard does not purport to address all of the
1.1.1 Theconcentrationrangesforwhichprecisionhasbeen
safety concerns, if any, associated with its use. It is the
determined are as follows:
responsibility of the user of this standard to establish appro-
Property Units Applicable Range
priate safety, health, and environmental practices and deter-
Paraffins % Volume 3.572 to 23.105
mine the applicability of regulatory limitations prior to use.
Isoparaffins % Volume 22.697 to 71.993
See specific hazard statements in subsection 8.4 and Section 9.
Olefins % Volume 0.011 to 44.002
Olefins % Mass 0.027 to 41.954
1.6 This international standard was developed in accor-
Naphthenes % Volume 0.606 to 18.416
dance with internationally recognized principles on standard-
Aromatics % Volume 14.743 to 58.124
ization established in the Decision on Principles for the
Methanol % Volume 0.063 to 3.426
Ethanol % Mass 0.042 to 15.991
Development of International Standards, Guides and Recom-
Benzene % Volume 0.09 to 1.091
mendations issued by the World Trade Organization Technical
Toluene % Volume 0.698 to 31.377
Barriers to Trade (TBT) Committee.
Ethylbenzene % Volume 0.5 to 3.175
Xylenes % Volume 3.037 to 18.955
Naphthalene % Volume 0.019 to 0.779
2. Referenced Documents
Methylnaphthalenes % Volume 0.21 to 1.484
2.1 ASTM Standards:
1.1.2 This test method may be applicable to other concen-
D1319 Test Method for Hydrocarbon Types in Liquid Petro-
tration ranges, to other properties, or to other hydrocarbon
leum Products by Fluorescent Indicator Adsorption
streams, however precision has not been determined.
D3606 Test Method for Determination of Benzene and
1.2 Individual hydrocarbon components are typically not
Toluene in Spark Ignition Fuels by Gas Chromatography
baseline-separated by the procedure described in this test
D4057 Practice for Manual Sampling of Petroleum and
method, that is, some components will coelute. The coelutions
Petroleum Products
are resolved at the detector using VUV absorbance spectra and
D4307 Practice for Preparation of Liquid Blends for Use as
deconvolution algorithms.
Analytical Standards
D5599 Test Method for Determination of Oxygenates in
1.3 While this test method reports percent mass and percent
Gasoline by Gas Chromatography and Oxygen Selective
volume for several specific components that may be present in
Flame Ionization Detection
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.04.0L on Gas Chromatography Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2021. Published August 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2017. Last previous edition approved in 2020 as D8071 – 20. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D8071-21. the ASTM website.
*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
D8071 − 21
D5769 Test Method for Determination of Benzene, Toluene, giveninTable1).Coelutionsareresolvedbythedetectorusing
and Total Aromatics in Finished Gasolines by Gas vacuum ultraviolet absorbance spectra and deconvolution.
Chromatography/Mass Spectrometry
4.2 The result of the measurement is the determination of
D5842 Practice for Sampling and Handling of Fuels for
the total response areas of the five hydrocarbon classes of
Volatility Measurement
paraffins, isoparaffins, olefins, naphthenes, and aromatics, in
D6300 Practice for Determination of Precision and Bias
addition to several individual species components. The percent
Data for Use in Test Methods for Petroleum Products,
mass concentrations are calculated from the response areas
Liquid Fuels, and Lubricants
using class-based or compound-specific relative response
D6550 Test Method for Determination of Olefin Content of
factors, as appropriate. The percent volume concentrations are
Gasolines by Supercritical-Fluid Chromatography
calculated from the mass concentrations.
D6708 Practice for StatisticalAssessment and Improvement
of Expected Agreement Between Two Test Methods that
5. Significance and Use
Purport to Measure the Same Property of a Material
5.1 The determination of class group composition of auto-
D6730 Test Method for Determination of Individual Com-
motive spark-ignition fuels as well as quantification of various
ponents in Spark Ignition Engine Fuels by 100-Metre
individual species such as oxygenates and aromatics in auto-
Capillary (with Precolumn) High-Resolution Gas Chro-
motive fuels is useful for evaluating quality and expected
matography
performance,aswellascompliancewithvariousgovernmental
regulations.
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
6. Interferences
3.1.1 integration filter, n—a mathematical operation per-
6.1 Interferenceswiththistestmethod,ifany,havenotbeen
formed on an absorbance spectrum for the purpose of convert-
determined.
ing the spectrum to a single-valued response suitable for
representation in a two-dimensional chromatogram plot.
7. Apparatus
3.1.2 library reference spectrum, n—an absorbance spec-
7.1 Gas chromatograph, equipped with automated oven
trum representation of a molecular species stored in a library
temperature control and split/splitless inlet.
database and used for identification of a compound/compound
7.1.1 Flow Controllers—The gas chromatograph must be
class or deconvolution of multiple coeluting compounds.
equipped with mass flow controllers capable of maintaining
3.1.3 response area, n—generally refers to a response
carrier gas flow constant to 61 % over the full operating
summed over a given time interval and has units of absorbance
temperature range of the column. The inlet pressure of the
units (AU).
carrier gas supplied to the gas chromatograph must be at least
485 kPa.This will ensure that the minimum pressure needed to
3.1.3.1 Discussion—A time factor necessary to convert a
compensate for the increase in column back-pressure as the
response area to a true mathematical area cancels out of all
column temperature is maintained.
critical calculations and is omitted.
3.2 Abbreviations:
3.2.1 AU—absorbance units
3.2.2 DHA—detailed hydrocarbon analysis
TABLE 1 Typical Instrument Settings for GC-VUV Automotive
Spark-Ignition Fuel Measurement
3.2.3 GC-VUV—gas chromatography with vacuum ultra-
Column dimensions Capillary, 30m×0.25mmID×
violet spectroscopy detection
0.25 µm film thickness
A
3.2.4 RI—retention index Column phase Nonpolar (for example, 100 %
dimethyl polysiloxane)
3.2.5 RRF—relative response factor
Inlet temperature 250 °C
B
Injection volume 1.0 µL
B
Split ratio 300:1
4. Summary of Test Method
C
Column flow 1.0 mL/min
4.1 An automotive spark-ignition fuel sample is introduced Oven initial temperature 35 °C
Initial hold time 10 min
to a gas chromatographic (GC) system.After volatilization, the
Oven ramp 7 °C/min
effluent is introduced onto a GC column for separation, and
Final oven temperature 200 °C
then detected by a vacuum ultraviolet absorption spectroscopy Final hold time 0 min
3 Detector makeup gas pressure (gauge) 2.1 kPa
detector. The separation is accomplished using a 30 m, non-
Detector scan rate 4.5 Hz
polarphasecapillarycolumnandamoderatelyfasttemperature
Detector flow cell temperature 275 °C
Transfer tube temperature 275 °C
ramp (typical operating parameters of this test method are
A
ColumnswithlowbleedphasessuchasMSgradehavebeensuccessfullyused
for this application (see 11.6)
B
Other injection volumes (see 7.1.2) and split ratios may be used to achieve the
The sole source of supply of the apparatus known to the committee at this time
required benzene response (see 13.2)
C
is VUV-Analytics, Cedar Park, Texas. If you are aware of alternative suppliers,
Gas chromatograph manufacturer’s column flow systems must be set to
please provide this information to ASTM International Headquarters. Your com-
maintain constant flow or gas velocity throughout the temperature ramp. Do not
ments will receive careful consideration at a meeting of the responsible technical
use constant pressure.
committee, which you may attend.
D8071 − 21
7.1.2 Autosampler—It is highly recommended that the gas such specifications are available. Other grades may be used,
chromatograph is equipped with an autosampler. All precision provided it is first ascertained that the reagent is of sufficiently
data were obtained using a GC equipped with an autosampler. high purity to permit its use without lessening the accuracy of
the determination.
7.2 Purge/Makeup Gas, for detector: nitrogen or argon (see
8.2 Helium carrier gas for gas chromatograph, 99.999 %
8.3).
pure.
7.3 Oxygen, Water, Hydrocarbon Filters, to further purify
NOTE 1—Test method performance has not been studied for other
GC carrier gas and detector purge/makeup gas.
carrier gases such as hydrogen or nitrogen.
8.3 Nitrogen, helium, or argon purge/makeup gas for
7.4 Capillary Analytical Column, nonpolar (for example,
dimethyl polysiloxane) phase, dimensions 30 m length, vacuum ultraviolet detector, 99.999 % pure.
0.25 mm internal diameter, 0.25 µm film thickness.
8.4 Methylenechloride,reagentgrade,usedasasolventtest
sample and GC rinse solvent. (Warning—Toxic material. May
7.5 Vacuum Ultraviolet Absorption Spectroscopy Detector,
be combustible at high temperatures.)
capable of measuring 125 nm to 240 nm absorbance spectra
with a wavelength resolution of 1 nm or better.
8.5 Retention time standard consisting of isobutane (iC4),
7.5.1 The detector shall be able to interface with a gas
butane (C4), isopentane (iC5), and pentane through pentade-
chromatographic system and measure an eluent with a scan cane linear alkanes, approximately 1 % by mass each, in
frequency of at least 4.5 Hz with a baseline peak-to-peak noise
suitable solvent such as methylene chloride, used as retention
width over a 10 s interval no greater than 0.002 AU when time markers.
averaged over the following wavelength regions: 125 nm to
8.6 A system validation mixture prepared in compliance
240 nm, 170 nm to 200 nm, 125 nm to 160 nm, and 0.001 AU
with Practice D4307, having the components and approximate
when averaged over the 140 nm to 160 nm wavelength region.
concentrations given in Table 2. The concentrations of the
7.5.2 The detector shall be equipped with a shutter or
equivalent mechanism that allows the detector array to be
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
blocked from the light source in order to perform a “dark”
Standard-Grade Reference Materials, American Chemical Society, Washington,
measurement of electronic noise level.
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
7.5.3 Thedetectorshallbeequippedwithaflowcellcapable
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
of being heated to at least 275 °C.
copeial Convention, Inc. (USPC), Rockville, MD.
7.5.4 The detector shall have an independently controlled
makeup gas capability, capable of providing up to 5 mL⁄min
TABLE 2 System Validation Mixture
additional flow of nitrogen, helium, or argon to the flow cell.
Component Concentration (percent mass)
Cyclopentane 1.1
7.6 Data Processing System,capableofstoringandprocess-
n-Pentane 1.1
ing absorbance scan data and corresponding time.
Cyclohexane 2.1
7.6.1 Data processing system shall include a database li- 2,3-Dimethylbutane 2.1
n-Hexane 2.1
brary of vacuum ultraviolet reference spectra, compound class
1-Hexene 1.5
information, carbon number, density, and approximate reten-
Methylcyclohexane 4
tion index values. Data processing system shall also store 4-Methyl-1-hexene 1.6
n-Heptane 3.5
relative response factors for each hydrocarbon class in addition
1,2-Dimethylcyclohexane 5
to relative response factors for individually reported com-
Isooctane 5
pounds. n-Octane 5
1,2,4-Trimethylcyclohexane 4
7.6.2 Data processing system shall be capable of imple-
n-Nonane 4.5
menting equations and fit procedures that result in deconvolu-
n-Decane 4.5
n-Undecane 3.5
tion of absorbance spectra that contain contributions from
n-Dodecane 3.5
multiple species.
Benzene 2.2
Toluene 2.2
7.6.3 Data processing system shall be capable of binning
trans-Decahydronaphthalene 4
and storing response contributions from each deconvolution
n-Tetradecane 4.5
analysis and reporting a combined total response at the end of
Ethylbenzene 4.5
the analysis. o-Xylene 4
n-Propylbenzene 5
7.6.4 Data processing system shall be capable of imple-
1,2,4-Trimethylbenzene 4.5
menting equations to convert response areas to percent mass 1,2,3-Trimethylbenzene 5
1,2,4,5-Tetramethylbenzene 5
and further convert percent mass to percent volume.
Pentamethylbenzene 5
8. Reagents and Materials Total Paraffins 32.2
Total Isoparaffins 7.1
8.1 Purity of Reagents—Reagent grade chemicals shall be Total Olefins 3.1
Total Naphthenes 20.2
used in all tests. Unless otherwise indicated, it is intended that
Total Aromatics 37.4
all reagents conform to the specifications of the Committee on
Total Xylenes 4.0
Analytical Reagents of the American Chemical Society where
D8071 − 21
prepared system validation mixture should be close to those in 11.6.1 Assess the baseline on either a solvent test sample or
Table 2. a system validation mixture (see 8.6) run. The average absor-
5 bance value (125 nm to 240 nm) of the last 1.0 min section of
8.7 Check standard VUVCS S24, with accepted reference
the baseline at the end of the oven ramp shall be no more than
values (ARV) and tolerance limits as listed in Table 3.
60.0035 AU of the average value (125 nm to 240 nm) of the
NOTE 2—VUVCS S24 is one of the samples included in the ILS for the
initial 1.0 min to 2.0 min range.
determination of method precision as described in Research Report
RR:D02-1909.
12. Calibration and Standardization
9. Hazards
12.1 On installation of GC-VUV apparatus, after significant
9.1 Many of the compounds in automotive spark-ignition maintenance of GC-VUV apparatus, or after a significant
engine fuel or other test samples used in this test method are
method change, establish a retention index file. Run the
toxic, flammable, or both. Safety and sample-handling proce- retentionindexsample(see8.5)usingthesameflowconditions
dures appropriate for working with such materials shall be in and oven ramp profile as measured samples (see Table 1 for
place before attempting to use this test method.
recommended run conditions). Record the retention times of
iC4, C4, iC5, and C5 through C15 linear alkanes. These will
9.2 Hydrogen is flammable and potentially explosive if not
serve as retention time markers.
properly used. Use of hydrogen as a GC carrier gas shall only
12.1.1 Significant method changes include changing the
be done at laboratories experienced with its use, with proper
GC, column type, carrier gas type, or oven ramp profile.
safety procedures in place.
Significant maintenance of the GC-VUV apparatus includes
10. Sampling
changing or trimming the analytical column.
10.1 Refer to Practices D4057 and D5842 for guidelines on
12.2 A list of retention times and retention indices for the
obtaining automotive spark-ignition engine fuel samples for
linear alkanes is used to estimate rough elution times of other
analysis. Samples should be kept refrigerated at approximately
compounds in the VUV library according to an interpolation
4 °C until ready to be analyzed.
scheme. The most convenient retention index scheme sets the
linear alkane retention indices to multiples of 100 according to
11. Preparation of Apparatus
carbon number: butane RI = 400, pentane RI = 500, etc. Each
11.1 Ensure that all gas connections are properly made, compound entry in the VUV library shall have an associated
without leaks.
retention index generated using the same RI scheme.
Otherwise, the associated retention indices do not need to be
11.2 Install oxygen, moisture, and hydrocarbon filters in gas
particularly accurate. The RI values for nonpolar capillary
lines upstream of GC and detector. Maintain gas filters as
chromatography found in the literature or other ASTM test
instructed by manufacturer.
methods, such as Test Method D6730, may be used.
11.3 Install the 30 m column in the GC inlet. Condition the
12.2.1 Once updated, the same retention time marker list is
column according to the column manufacturer’s recommenda-
used for all subsequent automotive spark-ignition fuel mea-
tions prior to installation in the detector.
surements until the next modification or maintenance of the
11.4 Perform maintenance on the GC as suggested by
GC-VUV instrumentation.
manufacturer, such as replacing septum and liner.
12.3 The conversion from response areas to percent mass
11.5 Configure the injector, carrier gas, and other GC
uses class-based or compound-specific relative response fac-
parameters according to Table 1.
tors. The relative response factors account for the differing
areal response per unit mass for the various hydrocarbon
11.6 Inject the solvent test sample defined in 8.4 and run the
classes.
GC-VUV apparatus through a full oven ramp and cool-down
cycle. Repeat.
12.4 For the purpose of this calculation, the response at a
given elution time refers to the absorbance averaged over the
125 nm to 240 nm wavelength region.The response area refers
Available from Spectrum Quality Standards, 17360 Groeschke Rd., Houston,
to the sum of the response over all detector scans within a
TX 77084, https://spectrumstandards.com.
given time region.Atrue area can be generated by multiplying
A this quantity by the time interval between scans. However, this
TABLE 3 Check Sample VUVCS S24 Tolerances
step is unnecessary when the scan rate is kept constant
Property Sample 95 % conf. ⁄99 % coverage
throughout a given measurement. For the purposes of this test
tolerance interval
Aromatics, vol% VUVCS-S24 15.346 to 18.078
method, the response area is taken to be a sum having units of
Benzene, vol% VUVCS-S24 0.616 to 0.712
absorbance units.
Olefins, vol% VUVCS-S24 9.15 to 10.925
Ethanol, mass% VUVCS-S24 10.203 to 11.678
12.5 The response factors are relative to the response of
Paraffins, vol% VUVCS-S24 9.486 to 11.003
methane, which is taken to have a relative response factor of 1.
A
ConsensusresultsforCheckSampleVUVCSS24obtainedfrom21laboratories
in2019.SupportingdatahavebeenfiledatASTMInternationalHeadquartersand
12.6 Relative response factors used to obtain the precision
may be obtained by requesting Research Report RR:D02-1909. Contact ASTM
data in this test method are given in Table 4 and Table 5, and
Customer Service at service@astm.org.
are suitable for use with this test method.
D8071 − 21
TABLE 4 Relative Response Factors for Bulk Hydrocarbon
in Sections 11, 12, and 13 as necessary to ensure tolerances in
Classes
13.3 or 13.4 are met before proceeding.
Hydrocarbon Class Relative Response Factor
Paraffin 0.769
14. Procedure
Isoparaffin 0.781
Olefin 0.465
14.1 Inject the sample into the GC inlet port. Typical GC
Naphthene 0.786
method and detector conditions are given in Table 1.
C + Aromatics 0.296
14.2 The system shall record a dark scan immediately after
start.
TABLE 5 Relative Response Factors for Specific Individual
14.3 The system shall record a reference scan immediately
Compounds and Compound Groups
after the dark scan.
Compound Relative Response Factor
Ethanol 1.029 14.3.1 The reference scan refers to an initial detector scan
Methanol 1.211
used as a reference to convert subsequent detector scans to
Isooctane 0.674
absorbancescans,andisdefinedinAnnexA1.Itisnotalibrary
Benzene 0.258
Toluene 0.267
reference spectrum.
Ethylbenzene 0.284
14.4 The system shall record 125 nm to 240 nm absorbance
Xylenes 0.284
Naphthalene 0.207
spectra and time of scan for each detector scan. Conversion of
1-Methylnaphthalene, 2-Methylnaphthalene 0.250
recorded intensity data to absorbance is given in Annex A1.
14.5 At the end of the GC run, the data collection shall
automatically stop, and the recorded absorbance spectra pro-
13. Pre-Measurement Validation
cessed in order to obtain response areas for each of the
13.1 Before proceeding with measurements after a signifi-
hydrocarbon classes and individual compounds being moni-
cant change or maintenance of the GC-VUV system, the
tored.
procedures in Section 11 shall have been completed, and a
14.5.1 Calculate percent mass for each hydrocarbon group
retention index file generated or verified following the proce-
and each of the individual compounds/compound groups
dure in 12.1 and 12.2.
ethanol, methanol, isooctane, benzene, toluene, ethylbenzene,
and total xylenes.
13.2 Analyzethesystemvalidationmixture(8.6)andverify
that the total response for benzene is 3.5 6 0.25. 14.5.2 Calculate percent volume results from the percent
mass results and class/compound densities.
13.2.1 If the total response is outside the required range,
adjust the detector make-up gas pressure and reanalyze the
14.6 Generateareportdisplayingtheinformationcalculated
systemvalidationmixture,checkingthebenzeneresponseuntil
in 14.5.
itiswithinthespecifiedrange.Increasingthedetectormake-up
gas pressure will decrease the benzene response. Do not adjust
15. Calculation
the make up gas pressure to less than 1.0 kPa or to more than
NOTE 3—See pertinent information on modeling absorbance data in
4.1 kPa.
Annex A2.
13.2.2 If the detector make-up gas pressure has been
15.1 Divide the measured chromatogram into time slices of
changed, reanalyze the retention index sample (12.1 and 12.2)
a given width, ∆t. Define the following parameters:
and establish a new retention index file.Adjusting the detector
15.1.1 A retention index (RI) window,
make-up gas pressure will change retention times. Reanalyze
15.1.2 A chi-squared iteration threshold, expressed as a
the system validation mixture (8.6) and verify the total re-
percentage,
sponse for benzene (13.2).
15.1.3 An R threshold,
13.3 Verify that the system validation mixture results are 15.1.4 A saturation threshold, and
within tolerance limits. 15.1.5 An initial background time region (optional).
13.3.1 The group totals for paraffins, isoparaffins, olefins,
15.2 If an initial background time region is defined, calcu-
naphthenes, and aromatics shall be within 61.0 % by mass of
lateabackgroundspectrumfromtheaverageoftheabsorbance
the known totals.
scans over the background time region.
13.3.2 The benzene, toluene, ethylbenzene, total xylenes,
15.3 Analyze each time slice using the following algorithm:
and isooctane shall be within 60.5 % by mass of their known
15.3.1 Calculate the total absorbance from the sum of the
values.
absorbance scans within the time slice.
13.3.3 The ratio of tetradecane to pentane shall be between
15.3.1.1 If a background spectrum is defined, subtract the
3.8 and 4.5.
background spectrum from each of the individual absorbance
13.4 Analyze the check sample VUVCS S24 as defined in
spectra within the time slice. Sum the resulting background-
8.7. Results shall be within the tolerances stated in Table 3.
subtracted spectra to obtain the total absorbance spectrum for
13.5 If the tolerances in 13.3 or 13.4 are not met, verify the time slice.
functionality of all GC-VUV components, validity of retention 15.3.1.2 If the absorbance value at a given wavelength
time marker list, and validity/quality of the check sample or exceeds the saturation threshold for any of the absorbance
system validation mixture, or both. Repeat setup methodology scans within the time slice, remove the data at that wavelength
D8071 − 21
value from the total absorbance and library reference spectra reject the three-component result and retain the best two-
used in subsequent fits for that time slice. component result, unless the best two-component result was
also rejected, in which case retain the best one-component
15.3.2 Calculate the average retention index of the time
result.
sliceusingtheaverageelutiontimeofthetimesliceandthelist
of retention time markers. A linear interpolation scheme is
15.3.5 The result of the tiered search procedure is a predic-
sufficient.
tion of the number of compounds that contribute to the total
15.3.3 Construct a list consisting of all compounds in the absorbance spectrum, their likely identities, as well as the
VUV reference library within 6RI window of the average best-fit values. “Integrate” the library reference spectra of the
retention index of the time slice. best-fit compounds by averaging them over the 125 nm to
240 nm region, generating an integration factor for each
15.3.4 Perform a tiered search on the total absorbance
compound. Multiply the best-fit values, f, by the correspond-
spectrum, drawing from the constructed list of compounds:
i
ingintegrationfactors.Thesearethecompounds’contributions
15.3.4.1 Construct Eq A2.1 (see Annex A2) assuming a
to the response area of the time slice.
single component contributes to the total absorbance. Select a
compound from the list and assign its library reference 15.3.6 If the R value, determined from
spectrum to A in Eq A2.1. Fit the total absorbance to Eq N
1,ref
A2.1 using general linear least squares. Calculate a metric, ~A 2 A !
( i,meas i,calc
i51
such as the chi-squared statistic: R 5 1 2 (2)
N
¯
N ~A 2 A!
( i,meas
1 1
i51
2 2
x 5 A 2 A (1)
~ !
( i,meas i,calc
N σ
i51 i
is less than the R threshold value, reject the analysis results
where:
for the time slice (optional). Otherwise, add the compound
N = the number of data points in an absorbance spec-
contributionstothetotalclassresponseareasaccordingtotheir
trum fit, class, or to an individual compound’s response area if a
A = the measured total absorbance at data point i,
i,meas compound is one of the speciated compounds given in Table 5.
A = the calculated total absorbance at data point i, and
i,calc If an individual compound in Table 5 also belongs to a
σ = the uncertainty of measured data point i, expressed
i
compound class in Table 4 (for example, isooctane), add its
as a standard deviation
response to the individual compound response area and not to
¯
theclassresponsearea.InEq2, Aisthewavelengthaverageof
If the uncertainty in the measured data have not been
the measured total absorbance spectrum.
estimated, theσ may be set to 1. Normalization by the number
i
of data points, N, is also optional.
15.3.7 Iterate the algorithm until all of the time slices have
15.3.4.2 Repeat the fit for each compound in the list and been analyzed.
retain the fit yielding the best chi-square value, along with the
15.4 Implementation of an analysis criterion for determin-
best-fit compound’s fit value f .
ing whether to analyze a time slice and a background subtrac-
15.3.4.3 Construct Eq A2.1 assuming two compounds con-
tion is permissible. If a background subtraction is used, a
tribute to the total absorbance spectrum. Populate A and
1,ref
criterion for automatically determining that a time region
A in Eq A2.1 with library reference spectra for each
2,ref
should be used as a background spectrum may be defined.
possible pair of compounds from the compound list. Fit the
15.4.1 Absorbance Check 1—Compare the change of a
total absorbance to Eq A2.1 for each pair. Retain the pair
response filter over a time slice. If the response filter changes
resulting in the best chi-squared value along with their fit
by more than the absorbance threshold, then analyze the time
values, f and f . Compare the chi-squared value from the best
1 2
slice. Otherwise, skip the time slice.
two-component fit to the chi-squared value from the best
15.4.1.1 If a time slice is skipped, the background threshold
one-component fit. If the percent improvement of the chi-
may be checked and if the response change over the time slice
squared value for the best two-component fit over the best
is less than the background threshold, update the background
one-component fit is greater than the chi-squared iteration
spectrum using the average absorbance spectrum over the time
threshold, retain the two-component result. Otherwise, reject
slice.
the two-component result and retain the one-component result.
15.4.2 Absorbance Check 2—If the maximum response of
15.3.4.4 Construct Eq A2.1 assuming three compounds
the four filters consisting of average 125 nm to 240 nm
contribute to the total absorbance spectrum. Populate A ,
1,ref
absorbance, average 170 nm to 200 nm absorbance, average
A , and A with library reference spectra for each possible
2,ref 3,ref
125 nm to 160 nm absorbance, and average 140 nm to 160 nm
triplet of compounds from the compound list. Fit the total
absorbance exceeds the maximum response of the same four
absorbance to Eq A2.1 for each triplet. Retain the triplet
filtersappliedtothecurrentbackgroundspectrumbymorethan
resulting in the best chi-squaredvaluealongwiththefitvalues,
three times the absorbance threshold, then analyze the time
f , f , and f . Compare the chi-squared value from the best
1 2 3
slice (and do not update the background spectrum) regardless
three-component fit to the chi-squared value from the best
of the outcome of Absorbance Check 1.
two-component fit. If the percentage improvement of the
chi-squaredvalueforthebestthree-componentfitoverthebest 15.4.3 Other threshold criteria may be used, provided it is
two-component fit is greater than the chi-squared iteration first determined that use of alternative threshold criteria does
threshold, retain the best three-component result. Otherwise, not lessen the accuracy or precision of the test method.
D8071 − 21
15.5 Due to the similarities of absorbance spectra of com- 15.8.1 Calculate the total aromatics percent mass by adding
pounds belonging to the same class, as well as the similarities the percent mass for the individual mono-aromatics in Table 5
ofrelativeresponsefactorsamongcompoundsbelongingtothe to the C + aromatics class percent mass.
sameclass,itisnotnecessarytohaveanexplicitrepresentation
15.8.2 Calculate total isoparaffins percent mass by adding
of all compounds in the VUV reference library. The following
the percent mass for isooctane to the percent mass for the
substitutions for an uncharacterized compound are permissible
isoparaffins class.
and will generally automatically be made by the algorithm:
15.9 Calculate total saturate content by summing the per-
15.5.1 Library reference spectra of similar compound class
cent mass values of the hydrocarbon classes of paraffins,
and similar carbon number.
isoparaffins, and naphthenes.
15.5.2 Linear combinations of spectra of similar compound
class and similar carbon number. 15.10 Convert the percent mass result for analyte or analyte
class, a, to percent volume using:
15.6 If an R threshold is applied, record the amount of
response area rejected by implementation of the R threshold. M
a
ρ
Compare the rejected amount to the total response area at the
a
V 5 100 3 (4)
a N
end of the analysis. If more than 3 % of the response area was
M
i
S D
(
rejected, the analysis should be flagged, and the measurement ρ
i51
i
data and GC-VUV instrumentation should be inspected.
where:
15.7 Table 6 lists values for analysis parameters used in the
M = percent mass for analyte or analyte class a,
a
statistical study given in Section 17, and are suitable for use
M = percent mass for analyte or analyte class i,
i
with this test method.
V = percent volume for analyte or analyte class a,
a
ρ = liquid density for analyte or average relative density
i
15.8 The result of the measurement and analysis procedure
for analyte class i, and
aretotalresponseareasforeachofthehydrocarbonclassesand
ρ = liquid density for analyte or average relative density
a
each individually speciated compound. For a given class or
for analyte class a.
specific compound, a, calculate the percent mass from
The liquid density values may be obtained from various
A 3RRF
a a
M 5 100 3 (3)
a n
literature or ASTM publications. For example, densities for
A 3RRF
i i manyrelevantcompoundsaregiveninTestMethodD6730and
(
i51
in ASTM publication DS4A, Physical Constants of Hydrocar-
1 10
where:
bons C to C . Average density values may be used for
M = percent mass for analyte or analyte class a, densities of bulk PIONA classes or for PIONA classes at
a
A = totalresponseareaforanalyteoranalyteclass a,and
various carbon numbers. Recommended densities for use with
a
RRF = relative response factor for analyte or analyte
this test method are given in Table 7.
a
class a.
15.10.1 Eq 4 shall be applied to percent mass values before
The sum runs over all hydrocarbon classes and speciated the individually speciated aromatics percent mass values are
compounds. added to the C + aromatics percent mass, and before the
TABLE 6 Parameters Used in Analysis of GC-VUV Scan Data
Parameter Value
Time slice width 0.02 min
RI window ±25
Initial background region 1.6 min to 1.8 min
Saturation threshold 0.8 AU
R Threshold 0.4
Background scalar 1.5
Absorbance threshold 0.0005 AU
Background threshold 0.00025 AU
Response filter to apply Average 140 nm to 160 nm absorbance
Absorbance Check 1
Response filter to apply Average 140 nm to 160 nm absorbance
background check
Response filter(s) to apply Average 125 nm to 240 nm absorbance
Absorbance Check 2 Average 170 nm to 200 nm absorbance
Average 125 nm to 160 nm absorbance
Average 140 nm to 160 nm absorbance
Chi-square iteration threshold 60 %
Area reject (15.6) Max3%
D8071 − 21
TABLE 7 Densities for Various Hydrocarbon Classes and
17. Precision and Bias
Individual Compounds
17.1 Precision—The precision of this test method, which
Hydrocarbon Class/Compound Density
was determined by statistical examination of interlaboratory
Paraffin 0.660
Isoparaffin 0.660 results using Practice D6300, is as follows.
Olefin 0.657
17.1.1 Repeatability—The difference between two indepen-
Naphthene 0.774
dentresultsobtainedbythesameoperatorinagivenlaboratory
C + Aromatics 0.872
Ethanol 0.789 applying the same test method with the same apparatus under
Methanol 0.792
constant operating conditions on identical test material within
Isooctane 0.660
short intervals of time would exceed the values computed from
Benzene 0.879
Toluene 0.867 Table 8, where X is the average of the two results, with an
Ethylbenzene 0.867
approximate probability of 5 % (one case in 20 in the long run)
Xylenes 0.870
in the normal and correct operation of the test method.
Naphthalene 1.025
Methylnaphthalenes 1.020 17.1.2 Test Method D8071 reproducibility and repeatability
at selected levels:
Total Aromatics, vol%
Level Rr
isooctane percent mass value is added to the isoparaffins
20 1.415 0.488
percent mass. After the percent volume values are calculated,
28 1.746 0.602
the percent volume values of the mono-aromatics from Table 5 36 2.044 0.705
44 2.318 0.799
shall be added to the percent volume result for the C +
51 2.574 0.887
aromatics class in order to report total aromatics content.
Benzene, vol%
Similarly for isooctane and the isoparaffins class.
Level Rr
0.2 0.012 0.005
15.11 Calculate total saturate percent volume by summing
0.4 0.024 0.008
the percent volume values of the hydrocarbon classes of
0.6 0.037 0.011
0.7 0.050 0.014
paraffins, isoparaffins, and naphthenes.
0.9 0.063 0.017
Olefin, vol%
16. Report
Level Rr
16.1 Report percent mass and percent volume for each of 4 0.629 0.340
13 1.056 0.570
the compound classes (paraffins, isoparaffins, olefins,
21 1.347 0.727
naphthenes, and aromatics), methanol, ethanol, benzene,
30 1.582 0.854
toluene, ethylbenzene, xylenes, naphthalene, and methylnaph- 38 1.784 0.963
thalenes to the nearest 0.01 %. Olefin, mass%
Level Rr
16.1.1 (Optional): Calculate and report oxygen content to
1.0 0.264 0.128
the nearest 0.01 % by mass using Eq 5.
4.1 0.566 0.273
12.1 1.016 0.490
x ·16.0·A
i i
20.1 1.336 0.644
X 5Σ (5)
total
MW
28.0 1.600 0.772
i
36.0 1.832 0.884
where:
X = total % by mass oxygen in the fuel,
total
Supporting data have been filed at ASTM International Headquarters and may
x = % by mass of each oxygenate,
i
beobtainedbyrequestingResearchReportRR:D02-1909.ContactASTMCustomer
16.0 = atomic mass of oxygen,
Service at service@astm.org.
A = numberofoxygenatomsinoxygenatemolecule,and Supporting data for precision of the olefin % by mass data and D6708
i
correlation to ASTM D6550 have been filed at ASTM International Headquarters
and may be obtained by requesting Research Report RR:D02-2009. ContactASTM
MW = molecular mass of the oxygenate.
i
Customer Service at service@astm.org.
TABLE 8 Practice D6300 Precision Analysis (Reproducibility and Repeatability) Outcome
Property Reproducibility Repeatability Applicable Test Result Range
0.63 0.63
Aromatics, vol% 0.2149(X) 0.0741(X) 14.743 to 58.124
1.05 0.75
Benzene, vol% 0.0676(X) 0.0176(X) 0.09 to 1.091
0.48 0.48
Olefins, vol% 0.3115(X) 0.1681(X) 0.011 to 44.002
0.54 0.54
Olefins, mass% 0.2645(X) 0.1276(X) 0.027 to 41.954
0.67 0.67
Ethanol, mass% 0.1424(X+0.002) 0.0497(X+0.002) 0.042 to 15.991
1.06 1.06
Ethylbenzene, vol% 0.0735(X) 0.0237(X) 0.5 to 3.175
Isoparaffins, vol% 1.2933 0.7644 22.697 to 71.993
0.5 0.5
Methanol, vol% 0.2111(X) 0.0348(X) 0.063 to 3.426
0.8 0.8
Methylnaphthalenes, vol% 0.0884(X) 0.0395(X) 0.021 to 1.484
0.88 0.7
Naphthalene, vol% 0.0775(X) 0.0202(X) 0.019 to 0.779
0.38 0.38
Naphthene, vol% 0.4994(X) 0.3301(X) 0.606 to 18.416
0.77 0.77
Paraffins, vol% 0.1257(X) 0.0538(X) 3.572 to 23.105
0.75 0.75
Toluene, vol% 0.0878(X) 0.026(X) 0.698 to 31.377
0.91 0.91
Xylenes, vol% 0.079(X) 0.029(X) 3.037 to 18.955
D8071 − 21
results, with an approximate probability of 5 % (one case in 20
Ethanol, mass%
Level Rr
in the long run) in the normal and correct operation of the test
2 0.193 0.067
method.
5 0.395 0.138
17.1.4 Bias—Since there is no accepted reference material
8 0.554 0.193
11 0.693 0.242
suitable for determining bias for the procedure in this test
14 0.819 0.286
method, no statement of bias is being made.
Ethyl Benzene, vol%
Level Rr 17.2 Relative Bias—A relative bias assessment of Test
0.8 0.056 0.018
Method D8071 versus Test Method D1319 for the determina-
1.3 0.094 0.030
tion of total aromatics in spark ignition fuel was conducted in
1.7 0.132 0.043
2.2 0.171 0.055
accordance with the requirements of Practice D6708 with a
2.7 0.211 0.068
successful outcome. It was based on measurements of total
Isoparaffins, vol%
aromaticsinsparkignitionfuelsbyparticipatinglaboratoriesin
Level Rr
an interlaboratory study and is documented in Research Report
29 1.293 0.764
38 1.293 0.764
RR:D02-1909.
47 1.293 0.764
17.2.1 The degree of agreement between results from Test
57 1.293 0.764
Method D8071 and Test Method D1319 can be further im-
66 1.293 0.764
proved by applying a correlation equation (Eq 6) (Research
Methanol, vol%
Level Rr Report RR:D02-1909). Sample-specific bias, as defined in
0.4 0.139 0.023
Practice D6708, was observed for some samples after applying
1.0 0.213 0.035
the bias-correction for the material types and property range
1.6 0.267 0.044
2.2 0.312 0.051
listed below.
2.8 0.351 0.058
17.2.2 Correlation Equation:
Methyl Naphthalenes, vol%
Predicted Test Method D13195 (6)
Level Rr
0.2 0.020 0.009
0.4 0.045 0.020
Bias-corrected Test Method D8071=
0.7 0.066 0.030
1.0 0.086 0.038
C 2 0.8313
D8071
1.2 0.105 0.047
Naphthalene, vol% where:
Level Rr
C = unrounded volume percent
D8071
0.1 0.009 0.004
0.2 0.021 0.007 total aromatics as reported
0.4 0.032 0.010
by Test Method D8071,
0.5 0.043 0.013
and
0.7 0.053 0.015
Predicted Test Method D1319 = the outcome from Eq 6
Naphthenes, vol%
rounded to the reported
Level Rr
3 0.729 0.482
resolution of Test Method
6 0.979 0.647
D1319.
9 1.153 0.762
12 1.292 0.854
17.2.2.1 Use of this correlation equation to predict Test
15 1.411 0.932
Method D1319 result is only applicable for fuels in the
Paraffins, vol%
concentration range from 14.743 % to 58.124 % by volume as
Level Rr
6 0.481 0.206 reported by Test Method D8071.
9 0.699 0.299
13 0.898 0.384 NOTE 4—The Test Method D1319 concentration range used to develop
16 1.084 0.464 thePracticeD6708assessmentmaynotcovertheentirescopeindicatedin
20 1.261 0.540
the scope of Test Method D1319 for total aromatics.
NOTE 5—The correlation equation was developed from a variety of fuel
Toluene, vol%
Level Rr samples from interlaboratory proficiency test programs; however, it is
4 0.235 0.071
recommended that the correlation equation be verified for samples of
10 0.480 0.145
interest to ensure applicability.
16 0.686 0.207
17.2.2.2 Between-Method Reproducibility (R )—
21 0.874 0.264
xy
27 1.049 0.316
Differences between bias-corrected results from Test Method
D8071 and Test Method D1319, for the sample types and
17.1.3 Reproducibility—The difference between two single
property ranges studied, are expected to exceed the following
and independent results obtained by different operators apply-
between-methods reproducibility (R ), as defined in Practice
xy
ing the same test method in different laboratories using
D6708, about 5 % of the time.
different apparatus on identical test material would exceed the
2 2 0.5
following values in Table 8, where X is the average of the two
R 5 @0.72 ~R ! 1 0.72~R ! # (7)
xy x y
D8071 − 21
recommended that the correlation equation be verified for samples of
where:
interest to ensure applicability.
R = reproducibility of Test Method D8071,
x
17.3.2.2 Between-Method Reproducibility (R )—
R = reproducibility of Test Method D1319 for total
xy
y
Differences between bias-corrected results from Test Method
aromatics, and
D8071 and Test Method D1319, for the sample types and
R = between-method reproducibility as defined in Practice
xy
D6708. property ranges studied, are expected to exceed the following
between-methods reproducibility (R ), as defined in Practice
xy
R comparison at selected X levels (with ethanol):
D6708, about 5 % of the time.
XR R R
x y xy
2 2 0.5
15.0 1.18 3.70 3.30
R 5 @0.41 R 1 0.6 R # (9)
~ ! ~ !
xy x y
25.0 1.63 3.70 3.43
35.0 2.02 3.70 3.58
where:
50.0 2.53 3.70 3.80
R = reproducibility of Test Method D8071,
x
17.3 Relative Bias—A relative bias assessment of Test
R = reproducibility of Test Method D1319 for olefins, and
y
Method D8071 versus Test Method D1319 for the determina-
tion of total olefins in spark ignition fuel was conducted in
R = between-method reproducibility as defined in Practice
xy
accordance with the requirements of Practice D6708 with a
D6708.
successful outcome. It was based on measurements of total
R comparison at selected X levels (with ethanol):
olefinsinsparkignitionfuelsbyparticipatinglaboratoriesinan
XR R R
x y xy
interlaboratory study and is documented in
...