ASTM D7171-05(2011)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7171 − 05(Reapproved 2011)
Standard Test Method for
Hydrogen Content of Middle Distillate Petroleum Products
by Low-Resolution Pulsed Nuclear Magnetic Resonance
Spectroscopy
This standard is issued under the fixed designation D7171; 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 Low-Resolution Nuclear Magnetic Resonance Spectros-
copy
1.1 This test method covers the determination of the hydro-
D5291Test Methods for Instrumental Determination of
gen content of middle distillate petroleum products using a
Carbon, Hydrogen, and Nitrogen in Petroleum Products
low-resolution pulsed nuclear magnetic resonance (NMR)
and Lubricants
spectrometer. The boiling range of distillates covered by the
D6299Practice for Applying Statistical Quality Assurance
test method is 150 to 390°C. While this test method may be
and Control Charting Techniques to Evaluate Analytical
applicable to middle distillates outside this boiling range, in
Measurement System Performance
such cases the precision statements may not apply. The test
D6708Practice for StatisticalAssessment and Improvement
methodisgenerallybasedonTestMethodsD3701andD4808,
of Expected Agreement Between Two Test Methods that
with a major difference being the use of a pulsed NMR
Purport to Measure the Same Property of a Material
spectrometerinsteadofacontinuouswaveNMRspectrometer.
2.2 Other Documents:
1.2 The values stated in SI units are to be regarded as
MIL-DTL-5624U Military Detail Specification, Turbine
standard. No other units of measurement are included in this
Fuel, Aviation, Grades JP-4 and JP-5
standard.
MIL-DTL-83133EMilitary Detail Specification, Turbine
1.2.1 The preferred units are mass%.
Fuels, Aviation, Kerosene Types, NATO F-34, (JP-8),
1.3 This standard does not purport to address all of the
NATO F-35, and JP-8+100
safety concerns, if any, associated with its use. It is the
MIL-PRF-16884K Military Performance Specification,
responsibility of the user of this standard to establish appro-
Fuel, Naval Distillate
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
3. Terminology
3.1 Definitions:
2. Referenced Documents
2 3.1.1 calibration, n—the determination of the values of the
2.1 ASTM Standards:
significant parameters by comparison with values indicated by
D3701Test Method for Hydrogen Content of Aviation
a set of calibration standards.
Turbine Fuels by Low Resolution Nuclear Magnetic
Resonance Spectrometry
3.1.2 calibration curve (or calibration line), n—the graphi-
D4057Practice for Manual Sampling of Petroleum and
cal or mathematical representation of a relationship between
Petroleum Products
the assigned (known) values of calibration standards and the
D4808 Test Methods for Hydrogen Content of Light
measured responses from the measurement system.
Distillates, Middle Distillates, Gas Oils, and Residua by
3.1.3 calibration standard, n—a standard having an as-
signed (known) value (reference value) for use in calibrating a
measurementinstrumentorsystem.Thisstandardisnotusedto
This test method is under the jurisdiction of ASTM Committee D02 on
determine the accuracy of the measurement instrument or
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
system (see check standard).
Subcommittee D02.03 on Elemental Analysis.
Current edition approved May 1, 2011. Published August 2011. Originally
approved in 2005. Last previous edition approved in 2005 as D7171–05. DOI:
10.1520/D7171-05R11.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from NavalAir Systems Command,AIR-4.4.5, Patuxent River, MD
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM 20670.
Standards volume information, refer to the standard’s Document Summary page on Available from ASC/ENSI, Wright-Patterson AFB, OH 45433-7107.
the ASTM website. Available from Naval Sea Systems Command, SEA03R42, Washington, DC.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7171 − 05 (2011)
3.1.4 check standard, n—a material having an assigned procurement requirement of the following military fuels: JP-5
(known) value (reference value) used to determine the accu- specified in MIL-DTL-5624U, JP-8 specified in MIL-DTL-
racyofthemeasurementinstrumentorsystem.Thisstandardis 83133E, and Naval Distillate specified in MIL-PRF-16884K.
not used to calibrate the measurement instrument or system
5.2 This test method provides a simple and precise alterna-
(see calibration standard).
tive to existing test methods (D3701, D4808, and D5291) for
3.1.5 low resolution nuclear magnetic resonance (NMR)
determining the hydrogen content of petroleum distillate prod-
spectroscopy, n—a form of NMR spectroscopy using a simple
ucts.
NMR analyzer that employs a low magnetic field and conse-
6. Apparatus
quentially low NMR frequency. An example is proton NMR
below 60 MHz. Resolution is expressed as time at half height
6.1 Nuclear Magnetic Resonance Spectrometer:
of signal and is typically 1 millisecond (ms) or less.
6.1.1 This test method requires a low-resolution pulsed
instrumentcapableofmeasuringanuclearmagneticresonance
3.1.6 nuclear magnetic resonance (NMR) spectroscopy,
signal due to hydrogen atoms in the sample in a linear fashion
n—that form of spectroscopy concerned with radio-frequency-
over the filling volume of interest.The instrument includes the
induced transitions between magnetic energy levels of atomic
following:
nuclei.
6.1.1.1 Permanent magnet to provide the necessary static
3.1.7 radio frequency, n—the range of frequencies of elec-
magnetic field for the NMR test,
tromagnetic radiation between 3 kHz and 300 GHz.
6.1.1.2 Sample compartment containing a radio frequency
3.1.8 recycle delay, n—NMR spectrometer parameter set-
(RF) coil for excitation and detection, and
ting for the time delay that allows magnetization recovery.
6.1.1.3 Electronic unit to control and monitor the resonance
3.1.9 relaxation time constant (T ), n—a numerical value
conditioninvolvingmagnettemperaturecontrolandfieldoffset
which is a measure of magnetization relaxation time following
coils.
an excitation pulse of an NMR spectrometer.
6.1.2 The test method also requires that the instrument have
theabilitytoequilibratesampleswithintheprobeataconstant
4. Summary of Test Method
temperature (that is, 35°C or 40°C).
4.1 AtestspecimenisanalyzedinapulsedNMRspectrom-
6.2 Conditioning Block—Block of aluminum alloy drilled
eter calibrated with reference standard materials. The analyzer
with holes of sufficient size to accommodate the nominal 18
records in a nondestructive fashion the total NMR signal,
mm diameter test cells to a depth of at least 42 mm and with
which arises from the absolute amount of hydrogen atoms in
a centrally positioned well to house a temperature-sensing
thereferencestandardsandtestsample.Theabsolutehydrogen
device, such as a thermometer or thermocouple.
signalintensityreportedbythepulsedNMRinstrumentforthe
6.3 Conditioning Apparatus—Bath or other temperature
standard and test specimens is normalized by the correspond-
control device (into which the conditioning block is inserted)
ing sample mass.The resulting signal-per-gram ratios are used
forcontrollingblocktemperatureto35 60.2°Cor40 60.2°C.
as a means of comparing theoretical hydrogen contents of the
standardswiththatofthesample.Theresultisexpressedasthe
6.4 Test Cell—Glass tube (with a flat or round bottom) with
hydrogen content (on a mass% basis) of the sample.
an outside diameter of 17.6 to 18.1 mm and an inside diameter
of15.2to16.4mm.Anytubelengththatpermitseasyinsertion
4.2 Toensureanaccuratemeasureoftheabsolutehydrogen
intoandremovalfromtheNMRsamplechambermaybeused.
contentofthereferencestandardsandsample,itisnecessaryto
ensure that the measured hydrogen signal intensity is always
6.5 Polytetrafluorethylene (PTFE) Plug—Device made of
directly proportional to the absolute hydrogen content of the
PTFE used to tightly fit and close the test cells.An example of
standards and sample.
one type of PTFE plug design is shown in Fig. 1.
4.3 Undercounting of the reference standard with respect to
6.6 Insertion Rod—Straight, rigid rod with a threaded end
the sample is avoided by a number of strategies, including
(to screw into the PTFE plug) for inserting and removing the
accurate filling into the linear response region of the sample
PTFE plugs from the test cells. Any diameter and length rod
compartment so that the mass recorded for the sample repre-
that facilitates easy plug insertion and removal may be used.
sents the true amount measured by NMR, and use of a recycle
6.7 Analytical Balance—Top loading pan-type balance, ca-
delay considerably greater than the longest relaxation time
pable of weighing the test cells in an upright position to an
constant (T ) for the sample.
accuracy of 0.001 g or better.
5. Significance and Use
6.8 Volume Transferring Device—Capableofaccuratelyand
repeatedly delivering a fixed volume of material within 61%
5.1 Hydrogen content represents a fundamental quality of a
petroleum distillate that has been correlated with many of the or better, for use in preparing test specimens and standards for
analysis. A 10-mL capacity serological pipet with 0.1 mL
performance characteristics of that product. Combustion prop-
erties of gas turbine fuels are related primarily to hydrogen marked subdivisions has been found suitable to use.
content. As hydrogen content of these fuels decreases, soot
7. Reagents and Materials
deposits, exhaust smoke, and thermal radiation increase. Soot
deposits and thermal radiation can increase to the point that 7.1 Purity of Reagents—Reagent grade chemicals shall be
combustor liner burnout will occur. Hydrogen content is a used in all tests. Unless otherwise indicated, it is intended that
D7171 − 05 (2011)
TABLE 1 Hydrogen Content of Reference Standards
Compound Mass % Hydrogen
dodecane 15.386
pentadecane 15.185
2-nonanone 12.756
ethyl caprate 12.077
octyl acetate 11.703
ethyl heptanoate 11.466
3-cyclohexanepropionic acid 10.324
cyclohexyl acetate 9.924
diethyl malonate 7.552
2-phenylethyl acetate 7.367
canbeusedtomonitortheprecisionandstabilityofthetesting
process as described in Section 15.
8. Hazards
8.1 Wear appropriate personal protective equipment when
workingwiththematerialsinSection7.Transferallreagentsin
a fume hood and immediately seal containers tightly. Avoid
prolonged or repeated exposure to materials.
9. Sampling
9.1 Take a homogeneous sample in accordance with Prac-
tice D4057. Mix the sample prior to taking a representative
aliquot as the test specimen.
FIG. 1 Example of a PTFE Plug (not to scale)
10. Preparation of Test Specimens and Standards
10.1 Fig. 1 is an example of a PTFE plug. Dimensions may
all reagents conform to the specifications of the Committee on
be varied to best seal the chosen test cell. Drill and thread the
Analytical Reagents of theAmerican Chemical Society where
plug hole to mate the insertion rod thread. All test cells and
such specifications are available. Other grades may be used,
PTFE plugs used shall be well cleaned and dry. Weigh a clean
provided it is first ascertained that the reagent is of sufficiently
emptytestcellandPTFEplug(W )onananalyticalbalanceto
high purity to permit its use without lessening the accuracy of
the nearest 0.001 g. Use of a jig for supporting the test cell on
the determination.
the balance pan is recommended for flat bottom test cells and
required for round bottom test cells. For round bottom test
7.2 List of Available Calibration, Reference, or Check
cells, a paper clip dispenser (with hole in top) works well for
Standards (see Table 1). (Warning—Irritant. Combustible.
this function. Transfer a fixed volume (in accordance with the
Avoid breathing vapor. Avoid contact with eyes, skin, and
tolerances specified in 6.8) of a reference standard or test
clothing.) applies to all of the following:
specimen into the test cell to a fill height of nominally 32 mm
7.2.1 3-cyclohexanepropionic acid, 99% minimum purity.
(representing a nominal 6 mL volume). The choice of fill
7.2.2 cyclohexyl acetate, 99% minimum purity.
height is not critical, but fill height shall be the same for all
7.2.3 diethyl malonate, 99% minimum purity.
standardsandsamplestoensuregoodresults.Usethesametest
7.2.4 dodecane, 99% minimum purity.
cell source (that is, manufacturer and part number) for all
7.2.5 ethyl caprate, 99% minimum purity.
standards and test specimens. This will ensure uniformity of
7.2.6 ethyl heptanoate, 99% minimum purity.
fluid height in the NMR sample compartment, an important
7.2.7 2-nonanone, 99% minimum purity.
parameter in the test method. Take care to not introduce the
7.2.8 octyl acetate, 99% minimum purity.
fluid down the side of the test cell. Seal the reference standard
7.2.9 pentadecane, 99% minimum purity.
container immediately after the material transfer to minimize
7.2.10 2-phenylethyl acetate, 99% minimum purity.
moisture pickup. Using the insertion rod with a PTFE plug
7.3 Quality Control (QC) Samples, preferably are portions
attached, push the PTFE plug into the test cell until it is just
ofoneormorepetroleumdistillatematerialsthatarestableand
above the liquid surface (that is, nominal 1 cm), keeping the
representative of the samples of interest. These QC samples
tube upright. Gently twisting the plug as it is inserted will aid
theescapeofairfromthetestcellandnormallyensurethatthe
lip of the plug is turned up around the entire circumference.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
Unscrew the insertion rod carefully without disturbing the
listed by the American Chemical Society, see Annual Standards for Laboratory
plug. Weigh the filled, sealed test cell (W ) on the analytical
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
balance to the nearest 0.001 g. Determine the sample mass
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. from the difference (W − W ) of the two weighings.
2 1
D7171 − 05 (2011)
10.2 Repeat 10.1 for all standards and test specimens. instrument. Similarly, run the other calibration standards to
complete the calibration.
11. Preparation of Apparatus
12.4 Insert a con
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