ASTM D7111-16(2021)

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: D7111 − 16 (Reapproved 2021)
Standard Test Method for
Determination of Trace Elements in Middle Distillate Fuels
by Inductively Coupled Plasma Atomic Emission
Spectrometry (ICP-AES)
This standard is issued under the fixed designation D7111; 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 2. Referenced Documents
1.1 This test method covers the determination of selected 2.1 ASTM Standards:
elements in middle distillate fuels by inductively coupled D2880 Specification for Gas Turbine Fuel Oils
plasma atomic emission spectrometry (ICP-AES). The specific D3605 Test Method for Trace Metals in Gas Turbine Fuels
elements are listed in Table 1. The concentration range of this by Atomic Absorption and Flame Emission Spectroscopy
test method is approximately 0.1 mg⁄kg to 2.0 mg/kg. The test D4057 Practice for Manual Sampling of Petroleum and
method may be used for concentrations outside of this range; Petroleum Products
however, the precision statements may not be applicable. D4306 Practice for Aviation Fuel Sample Containers for
Middle distillate fuels covered in this test method have all Tests Affected by Trace Contamination
distillation fractions contained within the boiling range of D5185 Test Method for Multielement Determination of
150 °C to 390 °C. This includes, but is not limited to, diesel Used and Unused Lubricating Oils and Base Oils by
fuels and aviation turbine fuels. Inductively Coupled Plasma Atomic Emission Spectrom-
etry (ICP-AES)
1.2 This test method is not intended to analyze insoluble
D6299 Practice for Applying Statistical Quality Assurance
particulates. However, very small particulate matter (smaller
and Control Charting Techniques to Evaluate Analytical
than a micrometre) will be carried into the plasma and be
Measurement System Performance
included in the quantitative analysis.
D6792 Practice for Quality Management Systems in Petro-
1.3 Thistestmethodmaygivearesultthatishigherthanthe
leum Products, Liquid Fuels, and Lubricants Testing
truevalueifananalyteispresentinthesampleinaformwhich
Laboratories
is sufficiently volatile. For example, hexamethyldisiloxane will
D7260 Practice for Optimization, Calibration, and Valida-
generate a biased high result for silicon.
tion of Inductively Coupled Plasma-Atomic Emission
1.4 The values stated in SI units are to be regarded as Spectrometry (ICP-AES) for ElementalAnalysis of Petro-
leum Products and Lubricants
standard.
2.2 Military Standard:
1.5 This standard does not purport to address all of the
MIL-DTL-16884 Fuel, Naval Distillate
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3. Terminology
priate safety, health, and environmental practices and deter-
3.1 Definitions:
mine the applicability of regulatory limitations prior to use.
3.1.1 calibration, n—the determination of the values of the
1.6 This international standard was developed in accor-
significant parameters by comparison with values indicated by
dance with internationally recognized principles on standard-
a set of reference standards.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
3.1.2 calibration curve, n—the graphical or mathematical
mendations issued by the World Trade Organization Technical
representation of a relationship between the assigned (known)
Barriers to Trade (TBT) Committee.
values of standards and the measured responses from the
measurement system.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Subcommittee D02.03 on Elemental Analysis. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved July 1, 2021. Published August 2021. Originally Standards volume information, refer to the standard’s Document Summary page on
approved in 2005. Last previous edition approved in 2016 as D7111 – 16. DOI: the ASTM website.
10.1520/D7111-16R21. Available online at http://quicksearch.dla.mil or http://assistdocs.com
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7111 − 16 (2021)
TABLE 1 Elements and Recommended Wavelengths TABLE 2 Internal Standards, Recommended Wavelengths, and
Approximate Use Concentrations
Element Wavelengths, nm
Internal Wavelength, Concentration,
Aluminum 308.215, 396.153
Standard nm mg/kg
Barium 455.403, 493.408
Calcium 393.366
Scandium 361.383 1-2
Chromium 267.716, 283.563
Yttrium 371.029 1-5
Cobalt 228.615, 236.375, 238.892
Copper 324.752
Iron 259.939
Lithium 670.784
Lead 220.353, 224.688, 283.306
ments in the fuel are calculated by comparing emission
Magnesium 279.553
intensity ratios of the fuel and calibration standards to the
Manganese 257.610
Molybdenum 202.030, 204.597, 281.616
internal standard.
Nickel 221.648, 341.476
4.2 Consult Practice D7260 regrading the optimum opera-
Phosphorus 177.495, 178.287,
185.944, 214.914, 213.618
tion of any ICP-AES system.
Palladium 340.458, 342.124
Platinum 214.423
5. Significance and Use
Potassium 766.490
Sodium 588.995
5.1 Trace elemental analysis is used to indicate the level of
Silicon 251.611
contaminationofmiddledistillatefuels.Tracemetalsinturbine
Silver 328.068
Strontium 407.771
fuels can cause corrosion and deposition on turbine compo-
Tin 283.999, 189.991
nents at elevated temperatures. Some diesel fuels have speci-
Titanium 334.940
Vanadium 310.230 fication limit requirements for trace metals to guard against
Zinc 213.857
enginedeposits.Tracelevelcopperinmiddledistillateaviation
turbine fuel can significantly accelerate thermal instability of
the fuel, leading to oxidation and production of detrimental
3.1.3 calibration standard, n—a standard having an ac- insoluble deposits in the engine.
cepted value (reference value) for use in calibrating a measure-
5.2 Gas turbine fuel oil Specification D2880 provides rec-
ment instrument or system.
ommended upper limits for five trace metals (calcium, lead,
3.1.4 detection limit, n—a stated limiting value that desig-
sodium, potassium, and vanadium). Military specification
nates the lowest concentration that can be determined with
MIL-DTL-16884 for naval distillate fuel sets requirements for
confidence and that is specific to the analytical procedure used.
maximum concentrations of the same five metals. Both speci-
fications designate Test Method D3605, an atomic absorption/
3.1.5 emission spectroscopy, n—measurement of the energy
flame emission method, for the quantitative analysis of four of
spectrum emitted by or from an object under some form of
the metals.Test Method D3605 does not cover potassium.This
energeticstimulation;forexample,lightorelectricaldischarge.
test method provides an alternative to Test Method D3605,
3.1.6 inductively coupled plasma, n—a high temperature
covers potassium and a number of additional elements.
discharge generated by passing an ionizable gas through a
magnetic field induced by a radio frequency coil surrounding 5.3 There are several sources of multi-element contamina-
tion of naval distillate fuel. Sea water is pumped into the diesel
the tubes that carry the gas.
fuel tanks (as ballast) to trim ships. Also, some of the oilers
3.1.7 radio frequency, n—the range of frequencies between
(fuel supply ships) have dirty tanks. Corrosion products come
3 kHz and 300 GHz.
from unlined tanks, piping, pumps, and heat exchangers.
3.1.8 standard, n—a physical or chemical reference used as
a basis for comparison or calibration.
6. Interferences
3.2 Definitions of Terms Specific to This Standard:
6.1 Elemental wavelengths listed in Tables 1 and 2 have
3.2.1 detection limit, n—the lowest concentration value for
been found to be free of spectral interferences with all other
an element that can be determined by ICP analysis and that is
elements listed in Tables 1 and 2 in the concentration range of
calculated by multiplying three times the standard deviation of
this test method.
ten repetitive element analyses of the blank solution.
6.2 If a spectral interference does exist, then selecting an
3.2.2 internal standard, n—a chemical standard having an
analytical wavelength other than those listed in Table 1 or
accepted value (and added to the fuel test specimen and
Table 2 may be used as long as the new wavelength possesses
calibration standard) to determine the emission intensity ratio
appropriate sensitivity for the scope of the method.
of an element to the internal standard.
6.3 Alternatively, the ICPspectrometer manufacturer’s soft-
4. Summary of Test Method ware may be used to provide corrections to interferences that
cannot be avoided by wavelength selection and background
4.1 Calibration standards are prepared by mixing organo-
correction.
metallic standard materials in kerosine. An internal standard
material is added to the calibration standards and fuel samples. 6.4 An empirical method for correcting for spectral inter-
The calibration standards and the fuel samples are aspirated ferences is detailed in Test Method D5185, Section 6.1
into the ICP-AES instrument. The concentrations of the ele- (Spectral).
D7111 − 16 (2021)
7. Apparatus 8.5 Argon Gas, 99.995 % minimum purity. (Warning—
Argon may be a compressed gas under high pressure.)
7.1 Inductively-Coupled Plasma Atomic Emission
Spectrometer—Any commercial sequential or simultaneous 8.6 Nitrogen Gas, 99.999 % minimum purity. (Warning—
ICP-AES instrument capable of measuring emission intensities Nitrogen may be a compressed gas under high pressure.)
of the elements of interest (and listed in Table 1).Avacuum or
8.7 Nitric Acid, 10 % aqueous solution. (Warning—Nitric
inert gas optical path is required for analysis of any element at
acid may cause severe burns.)
wavelengths below 190 nm.
8.8 Quality Control (QC) Samples, preferably are portions
7.2 Nebulizer—For samples without particulates, a concen-
of one or more fuel or kerosine materials that are stable and
tric nebulizer is recommended to provide higher sensitivity for
representative of the samples of interest. These QC samples
low concentrations and for low sensitivity elements. For
can be used to check the validity of the testing process as
unknown samples, a Babington-type high solids nebulizer is
described in Section 18. If a suitable QC fuel is not available,
recommended to reduce the possibility of clogging from
obtain a stable QC concentrate, and dilute it with kerosine on
particulate.
thedayoftheQCchecktothetracelevelrequiredasdescribed
7.3 Spray Chamber, suitable for organic materials. in 12.3. Use HDPE plastic bottles to contain concentrated
organometallic solutions and for sodium analysis.
7.4 Peristaltic Pump—A peristaltic pump is required to
provide a constant flow of liquid to the ICP.Viton pump tubing
9. Hazards
is recommended for use with fuels and kerosine.
9.1 Gasesunderhighpressureandcorrosiveacidareusedin
7.5 Membrane Filter, 47 mm diameter, 0.8 µm or 1.0 µm
this method. Wear appropriate personal protective equipment
pore size.
when working with nitric acid. Use only apparatus rated for
7.6 Membrane Filter Holder Assembly, for 47 mm diameter
handling the high gas pressures that occur in this test method.
filters, with filtration flask.
7.7 Pipette, 1000 µL. 10. Sampling and Test Specimens
7.8 Volumetric Flasks, 25 mL and 50 mL, glass. 10.1 Samples shall be taken in accordance with procedures
described in Practice D4057. Suitable sample containers for
7.9 Glass or High Density Polyethylene (HDPE) Bottles,
aviation fuels are described in Practice D4306. Use HDPE
125 mL, round.
plastic containers for sodium analysis.
7.10 Analytical Balance, measuring to 0.0001 g.
10.2 Samples shall be thoroughly mixed in their containers
immediately prior to testing.
8. Reagents and Materials
10.3 If particulate matter is observed in the sample, filter it
8.1 Purity of Reagents—Reagent grade chemicals shall be
through a 0.8 µm or 1.0 µm (nylon, TFE-fluorocarbon, cellu-
used in all tests. Unless otherwise indicated, it is intended that
lose acetate/cellulose nitrate, or other compatible material)
all reagents conform to the specifications of the Committee on
membranefilterintoanacid-cleanedflaskandretainthefiltrate
Analytical Reagents of the American Chemical Society where
4 for analysis. Follow the same filtration procedure for the
such specifications are available. Other grades may be used,
kerosine blank material used for the analysis of these samples.
provided it is first ascertained that the reagent is of sufficiently
high purity to permit its use without lessening the accuracy of
11. Preparation of Apparatus
the determination.
11.1 Spectrometer—PreparetheICPspectrometeraccording
8.2 Organometallic Standards, single element and multiele-
to the manufacturer’s instructions and parameter settings for
ment organometallic standards, nominal 100 mg/kg of each
organic materials and the elements of interest. At least three
element of interest.
integrations should be made for all samples (standards, blank,
8.3 Internal Standard, fuel soluble yttrium, cobalt, scan-
fuels) run. Table 1 provides recommended element wave-
dium or other single element organometallic standard, not a
lengths for fuels; however, other wavelengths may be used due
component of the fuel test specimen or calibration standard,
to possible instrument variations or spectral interferences. The
nominal 5000 mg/kg.
optical path can be purged with argon or another high purity
8.4 Kerosine, with analyte concentrations below the detec- gas(forexample,nitrogen)recommendedbythemanufacturer.
tion limits of the instrument. The kerosine can be screened for
Before igniting the plasma, inspect the quartz torch to make
the presence of analytes as detailed in 12.1 by performing a sure that it is clean. If carbon build-up is observed, replace the
wavelength scan for analyte wavelengths.
torch and make the manufacturer’s recommended adjustments
for this problem. Warm up the instrument while purging the
optics for the time period recommended by the ICP manufac-
turer. If necessary, replace the peristaltic pump tubing and
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington,
adjust the solution uptake to the desired rate. Ignite the torch,
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
then begin aspirating kerosine through the nebulizer and into
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
the spray chamber. Continue plasma warm-up/stabilization for
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD. the duration specified by the ICP manufacturer.
D7111 − 16 (2021)
11.2 Glassware, Plasticware—Acid clean glassware and 12.3.2 Calibration Standard Solution (nominal
plasticware with 10 % nitric acid (trace metal analysis grade) 2.0 mg⁄kg)—Tare on an analytical balance a clean glass or
followedbyseveraldistilledwaterrinses.Donotuseglassware HDPE plastic container (for example, 125 mL bottle, use
and plasticware that has previously contained solutions with HDPE for sodium analysis) sized for the following procedure:
high concentrations of the element(s) of interest. Weigh a nominal 1.0 g (to the nearest 0.0001 g) of the nominal
100 mg⁄kg organometallic standard (for all elements of inter-
est) into the container.Add kerosine to bring the solution mass
12. Preparation of Standards and Test Specimens
to a nominal 50.0 g. Determine the solution mass to the nearest
12.1 Purity of Kerosine—Sources of satisfactory high purity
0.0001 g. Seal the container and mix the solution well.
kerosine are commercially available. For ICP instruments
Calculate the element concentrations as shown in 16.1. Use
which provide a visual profile of emission peaks, a check may
these values for establishing the calibration lines (see Section
be made of the kerosine purity by aspirating the kerosine and
14). The calibration standard solution is to be prepared daily
viewing the spectral regions where the element emissions of
when samples are to be analyzed.
interestaretobefound.Theabsenceofemissionpeaksinthese
12.3.3 Working Standard—The working standard is pre-
regions is evidence that the purity is satisfactory.
pared with the calibration standard solution and the internal
12.2 Internal Standard Stock Solution:
standard stock solution as follows: To a 50 mL volumetric
12.2.1 The analyst’s selection of the single element internal
flask, pipette 1000 µL of the internal standard stock solution.
standard may be influenced by the capabilities (wavelength Fill the volumetric flask to the volume mark with the calibra-
availability, sensitivity) of the ICP instrument available. The
tion standard solution prepared in 12.3.2. Seal the volumetric
single element chosen for the internal standard should not be a flask and mix well. Working standards are to be prepared daily
component of the fuel test specimen or calibration standard.
when samples are to be analyzed.
Organometallic yttrium has performed well as an internal
12.3.3.1 Use of the yttrium internal standard stock solution
standard for this test method and is recommended. Table 2 lists
described in 12.2.3 will provide a nominal 1.0 mg/kg internal
internal standards, their recommended wavelengths, and their
standard in the working standard.
approximate use concentrations for this test method.
12.4 Check Standard—Prepare an instrument check stan-
12.2.2 Prepare a stock solution of the internal standard by
dard in the same manner as the working standard (see 12.3)at
weight from a 5000 mg/kg single element organometallic
element concentrations that are anticipated for the fuel samples
standard material and kerosine. Prepare a concentration that is
to be analyzed. It is advisable to prepare the check standard
approximately 50 times the concentration required in the fuel
from an alternative source of certified organometallic standard.
test specimen and working standard. Prepare a minimum of 50
12.5 Test Specimens—To a 50 mL volumetric flask, add
gramsofinternalstandardstocksolution.Preparefreshinternal
1000 µLof the internal standard stock solution. Fill the flask to
standard stock solution weekly.
the mark with the fuel to be analyzed. This provides a fuel test
12.2.3 The following is an example for preparing a nominal
specimenwithaninternalstandardatthesameconcentrationas
50 mg/kg yttrium internal standard stock solution: Tare on an
provided in the working standard. If insufficient fuel sample is
analytical balance a clean glass or HDPE plastic container (for
available, the flask volume and added internal standard stock
example, 125 mL bottle, use HDPE for sodium analysis) sized
solution volume may be proportionally reduced. Since the
for the following procedure. Weigh a nominal 0.5 g (to the
same amount of internal standard stock solution has been
nearest 0.001 g) of the 5000 mg/kg yttrium organometallic
added to the working standard and the fuel test specimens, no
internal standard into the container. Add kerosine to bring the
dilution factor correction is needed.
solutionmasstoanominal50.0g.Determinethesolutionmass
to the nearest 0.001 g. Seal the container and mix well. The
13. Wavelength Selection and Background Correction
internal standard stock solution concentration is determined in
the same manner as described for the calibration standard in
13.1 Recommended wavelengths for each element to be
16.1.
determined and for internal standards are given in Table 1 and
Table 2, respectively. To accommodate different ICP instru-
12.3 Working Standard:
ments and their performances, other wavelengths not shown in
12.3.1 Preparation of a nominal 2.0 mg/kg elemental work-
these tables may be used. Select wavelengths with best
ing standard is described in this test method as an example.
intensity, peak shape, and lack of interferences. Since analyses
Higher or lower working standard concentrations may be
are for trace levels of elements, background correction is
prepared depending on the sensitivity of the ICP spectrometer
required. Thus, for all elements possible, the baseline for the
(forexample,radialoraxialviewing,detectortype,ageofICP)
emission peak should be set with points as close to both sides
and the elements of interest in the fuel sample. Determine the
of the peak without measuring the element wavelength inten-
suitability of the working standard concentration after calibra-
sity (see Fig. 1).After these baselines are set, a check standard
tion by analyzing a kerosine sample prepared with a known
is used to test the system response and calibration as described
concentration (for example, 1.0 mg/kg) of the elements of
in the next section.
interest. Measured values within 5 % of the prepared concen-
tration are acceptable. Commercially available organometallic 13.2 Appropriate selection of wavelengths for background
standards with certified element concentrations are suitable for corrections is extremely critical for the determination of
this test method. sodium since the predominate sodium emission line
D7111 − 16 (2021)
FIG. 1 Correct (A) and Incorrect (B) Selection of Background
(588.995 nm) resides near a significant argon emission inter- the element signal intensity after the kerosine purge to ensure
ference. During method development it is recommended, if that it has been removed.
possible, that the spectra of samples and standards be com-
14.4 Most ICP spectrometers have software that automati-
pared at the sodium emission wavelength to ensure that signal
cally performs the calculations to establish the calibration
integration occurs accurately.
curve when using an internal standard. Element emission
NOTE 1—Some emission wavelengths occur on a highly structured
intensities are ratioed to the internal standard emission inten-
background(forexample,sodiumemissionat588.995nm);henceasingle
sities. Subsequent references to emission intensities in this
off-peak background measurement may provide inaccurate results. For
section and Section 15 pertain to baseline corrected peak areas.
emission wavelengths on a structured background, background correction
is recommended at both lower and higher wavelengths from the emission
The calibration curve is a plot of the intensity ratio for an
wavelength. In addition, some low-resolution, photomultiplier tube-based
element e in the working standard (R ) versus the concentra-
ws
instruments may require a comprised selection of background points,
tion of element e in the calibration standard (C ), and
cs
which could also provide inaccurate results.
R 5 I 2 I /I (1)
~ !
ws ws b ints
14. Calibration
where:
14.1 A two-point calibration, consisting of the kerosine
I = emission intensity for element e in the working
ws
blank and the working standard, of the instrument is conducted
standard,
within the linear range of the spectrometer. Calibration shall be
I = emission intensity for element e in the kerosine blank,
b
performed each time a new batch of fuel samples is to be
and
analyzed.
I = emission intensity of the internal standard in the
ints
14.2 Analyzethecheckstandardtodetermineifallelements
working standard solution.
are in calibration. Each element must be within 5 % of its
prepared concentration in order to proceed to testing of fuel 15. Analysis
samples. If not, make necessary instrument adjustments and
15.1 Determine the ICP detection limits for all elements of
recalibrate until all elements are within 5 % of check standard
interest as follows: Prepare a kerosine blank with an internal
values.
standard by pipetting 1000 µL of the internal standard stock
14.3 Aspirate kerosine between standard (and fuel test solution into a 50 mL volumetric flask, and fill to the volume
specimen) runs to purge the system of elements prior to the markerwithkerosine.Sealtheflask,andmixwell.Performten
next run. If high element concentrations have been run, check consecutiveanalysesofthissolutionforallelementsofinterest
D7111 − 16 (2021)
under the same conditions/parameters that the two-point cali- C 5 M /M C (4)
...