ASTM D6732-04(2020)
(Test Method)Standard Test Method for Determination of Copper in Jet Fuels by Graphite Furnace Atomic Absorption Spectrometry
Standard Test Method for Determination of Copper in Jet Fuels by Graphite Furnace Atomic Absorption Spectrometry
SIGNIFICANCE AND USE
5.1 At high temperatures aviation turbine fuels can oxidize and produce insoluble deposits that are detrimental to aircraft propulsion systems. Very low copper concentrations (in excess of 50 μg/kg) can significantly accelerate this thermal instability of aviation turbine fuel. Naval shipboard aviation fuel delivery systems contain copper-nickel piping, which can increase copper levels in the fuel. This test method may be used for quality checks of copper levels in aviation fuel samples taken on shipboard, in refineries, and at fuel storage depots.
SCOPE
1.1 This test method covers the determination of copper in jet fuels in the range of 5 μg/kg to 100 μg/kg using graphite furnace atomic absorption spectrometry. Copper contents above 100 μg/kg may be determined by sample dilution with kerosine to bring the copper level into the aforementioned method range. When sample dilution is used, the precision statements do not apply.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 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.
General Information
Relations
Standards Content (Sample)
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: D6732 − 04 (Reapproved 2020)
Standard Test Method for
Determination of Copper in Jet Fuels by Graphite Furnace
Atomic Absorption Spectrometry
This standard is issued under the fixed designation D6732; 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 3. Terminology
1.1 This test method covers the determination of copper in 3.1 Definitions:
jet fuels in the range of 5 µg⁄kg to 100 µg⁄kg using graphite 3.1.1 radiant power, P, n—the rate at which energy is
furnace atomic absorption spectrometry. Copper contents transported in a beam of radiant energy.
above 100 µg⁄kg may be determined by sample dilution with
3.1.2 transmittance, T, n—the ratio of the radiant power
kerosine to bring the copper level into the aforementioned
transmitted by a material to the radiant power incident upon it.
method range. When sample dilution is used, the precision
3.2 Definitions of Terms Specific to This Standard:
statements do not apply.
3.2.1 absorbance, A, n—the logarithm to the base 10 of the
1.2 The values stated in SI units are to be regarded as
ratio of the reciprocal of the transmittance, T:
standard. No other units of measurement are included in this
A 5 log 1/T 52log T (1)
~ !
10 10
standard.
3.2.2 integrated absorbance, A,n—the integrated area un-
i
1.3 This standard does not purport to address all of the
der the absorbance peak generated by the atomic absorption
safety concerns, if any, associated with its use. It is the
spectrometer.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
4.1 The graphite furnace is aligned in the light path of the
1.4 This international standard was developed in accor-
atomic absorption spectrometer equipped with background
dance with internationally recognized principles on standard-
correction. An aliquot (typically 10 µL) of the sample is
ization established in the Decision on Principles for the
pipetted onto a platform in the furnace. The furnace is heated
Development of International Standards, Guides and Recom-
to low temperature to dry the sample completely without
mendations issued by the World Trade Organization Technical
spattering. The furnace is then heated to a moderate tempera-
Barriers to Trade (TBT) Committee.
ture to eliminate excess sample matrix. The furnace is further
heated very rapidly to a temperature high enough to volatilize
2. Referenced Documents
the analyte of interest. It is during this step that the amount of
2.1 ASTM Standards:
light absorbed by the copper atoms is measured by the
D4057 Practice for Manual Sampling of Petroleum and
spectrometer.
Petroleum Products
4.2 The light absorbed is measured over a specified period.
D4306 Practice for Aviation Fuel Sample Containers for
The integrated absorbance A produced by the copper in the
Tests Affected by Trace Contamination i
samples is compared to a calibration curve constructed from
D6299 Practice for Applying Statistical Quality Assurance
measured A values for organo-metallic standards.
and Control Charting Techniques to Evaluate Analytical i
Measurement System Performance
5. Significance and Use
5.1 At high temperatures aviation turbine fuels can oxidize
This test method is under the jurisdiction of ASTM Committee D02 on
and produce insoluble deposits that are detrimental to aircraft
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
propulsion systems. Very low copper concentrations (in excess
Subcommittee D02.03 on Elemental Analysis.
of50 µg⁄kg)cansignificantlyacceleratethisthermalinstability
Current edition approved May 1, 2020. Published June 2020. Originally
of aviation turbine fuel. Naval shipboard aviation fuel delivery
approved in 2001. Last previous edition approved in 2015 as D6732 – 04 (2015).
DOI: 10.1520/D6732-04R20.
systems contain copper-nickel piping, which can increase
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
copper levels in the fuel. This test method may be used for
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
quality checks of copper levels in aviation fuel samples taken
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. on shipboard, in refineries, and at fuel storage depots.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6732 − 04 (2020)
6. Interferences to check the validity of the testing process as described in
Section 14. Use a stable QC concentrate, and dilute it on the
6.1 Interferences most commonly occur due to light that is
day of the QC check to the trace level required.
absorbed by species other than the atomic species of interest.
Generally, this is due to undissociated molecular particles from
9. Sampling
thesamplematrix.Thecharstepinthefurnaceprogramisused
to eliminate as much of the matrix as possible before the 9.1 Samples shall be taken in accordance with procedures
atomization step. Spectrometers are equipped with background
described in Practice D4057.
correction capabilities to control further possibilities of erro-
9.2 Samples shall be thoroughly mixed in their containers
neous results due to molecular absorption.
immediately prior to testing.
7. Apparatus
10. Calibration and Standardization
7.1 AtomicAbsorptionSpectrometer—Anatomicabsorption
10.1 Preparation of Standards:
spectrometer with the capability of setting the wavelength at
10.1.1 Nominal 1 mg⁄kg Intermediate Stock Standard—
324.8 nm, setting the slit width at typically 0.7 nm, and using
Accurately weigh a nominal 0.50 g of the 100 mg⁄kg stock
peak area integration for the atomic and background readings
organo-metallic standard into a suitable container (capable of
shall be used. The spectrometer shall be equipped with the
being sealed for mixing). (All masses are measured to the
following:
nearest 0.0001 g.) Suitable sample containers are described in
7.1.1 Copper Hollow Cathode Lamp—as the elemental light
Practice D4306. Add enough odorless kerosine to bring the
source.
total mass to a nominal 50.00 g. Seal the container and mix
7.1.2 Background Correction Capability—to cover the
well. See 12.1.1 for calculation of actual concentration.
324.8 nm wavelength range.
10.1.2 Working Standards of Nominally (20, 40, 60, 80,
7.1.3 Graphite Furnace Atomizer—which uses pyrolytically
100) µg⁄kg—Accurately weigh a nominal (0.20, 0.40, 0.60,
coated graphite tubes with L’vov platforms.
0.80, 1.00) g of the nominal 1 mg⁄kg intermediate stock
7.2 Autosampler or Manual Pipettor—capable of reproduc-
standardintofivesuitablecontainers.(Allmassesaremeasured
ibly delivering 10 µL 6 0.5 µL aliquots of samples, standards,
to the nearest 0.0001 g.)Add enough odorless kerosine to each
and blank to the graphite furnace.
container to bring the total mass to a nominal 10.00 g. Seal
7.3 Analytical Balance—capable of weighing 100 g 6 containers and mix well. This produces working standards of
0.0001 g.
nominal (20, 40, 60, 80, 100) µg⁄kg, respectively. See 12.1.2
for calculations of actual concentrations.
8. Reagents and Materials
10.2 Calibration:
8.1 Purity of Reagents—Reagent grade chemicals shall be
10.2.1 Prepare a standard calibration curve by using the
used in all tests. Unless otherwise indicated, it is intended that
odorless kerosine as a blank and each of the five working
all reagents conform to the specifications of the Committee on
standards. The instrument measures the integrated absorbance
Analytical Reagents of the American Chemical Society where
A of 10 µL of each working standard and blank. The interme-
i
such specifications are available. Other grades may be used,
diate stock standard and working standards shall be prepared
provided it is first ascertained that the reagent is of sufficiently
daily.
high purity to permit its use without lessening the accuracy of
10.2.2 The calibration curve is constructed by plotting the
the determination.
corrected integrated absorbances (on y-axis) versus the con-
centrations of copper in the working standards in µg/kg (on
8.2 Odorless or Low Odor Kerosine, filtered through silica
x-axis). See 12.2.1 for calculating corrected integrated absor-
gel.
bance. Fig. 1 shows a typical calibration curve for atomic
8.3 100 mg/kg Organo-metallic Standard for Copper, or a
absorption spectroscopy. Many atomic absorption spectrom-
multielement standard containing copper at 100 mg⁄kg.
eters have the capability of constructing the calibration curve
8.4 Silica Gel, 100 mesh to 200 mesh.
internally or by way of computer software. Construct the best
possible fit of the data with available means.
8.5 Argon Gas, 99.999 %, (Warning—Argon is a com-
pressed gas under high pressure) for graphite furnace gas flow
11. Procedure
system.
8.6 Quality Control (QC) Samples, preferably are portions 11.1 Set the spectrometer at a wavelength of 324.8 nm and
a slit width of typically 0.7 nm.Align the hollow cathode lamp
of one or more kerosine materials that are stable and represen-
tativeofthesamplesofinterest.TheseQCsamplescanbeused and furnace assembly to obtain maximum transmittance.
11.2 Condition new (or reinstalled) graphite tube and L’vov
platform with the temperature program provided by the spec-
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
trometer manufacturer until the baseline shows no peaks.
Standard-Grade Reference Materials, American Chemical Society, Washington,
DC. For suggestions on the testing of reagents
...
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