ASTM D6732-04(2010)
(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
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 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.
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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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Designation: D6732 − 04(Reapproved 2010)
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 3.2 Definitions of Terms Specific to This Standard:
3.2.1 absorbance, A, n—the logarithm to the base 10 of the
1.1 This test method covers the determination of copper in
ratio of the reciprocal of the transmittance, T:
jet fuels in the range of 5 to 100 µg/kg using graphite furnace
atomic absorption spectrometry. Copper contents above 100 A 5 log 1/T 52log T (1)
~ !
10 10
µg/kg may be determined by sample dilution with kerosine to
3.2.2 integrated absorbance, A,n—the integrated area un-
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bring the copper level into the aforementioned method range.
der the absorbance peak generated by the atomic absorption
When sample dilution is used, the precision statements do not
spectrometer.
apply.
4. Summary of Test Method
1.2 The values stated in SI units are to be regarded as
standard.
4.1 The graphite furnace is aligned in the light path of the
atomic absorption spectrometer equipped with background
1.3 This standard does not purport to address all of the
correction. An aliquot (typically 10 µL) of the sample is
safety concerns, if any, associated with its use. It is the
pipetted onto a platform in the furnace. The furnace is heated
responsibility of the user of this standard to establish appro-
to low temperature to dry the sample completely without
priate safety and health practices and determine the applica-
spattering. The furnace is then heated to a moderate tempera-
bility of regulatory limitations prior to use.
ture to eliminate excess sample matrix. The furnace is further
2. Referenced Documents
heated very rapidly to a temperature high enough to volatilize
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
D4306 Practice for Aviation Fuel Sample Containers for
4.2 The light absorbed is measured over a specified period.
Tests Affected by Trace Contamination
The integrated absorbance A produced by the copper in the
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D6299 Practice for Applying Statistical Quality Assurance
samples is compared to a calibration curve constructed from
and Control Charting Techniques to Evaluate Analytical
measured A values for organo-metallic standards.
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Measurement System Performance
5. Significance and Use
3. Terminology
5.1 At high temperatures aviation turbine fuels can oxidize
3.1 Definitions:
and produce insoluble deposits that are detrimental to aircraft
3.1.1 radiant power, P, n—the rate at which energy is
propulsion systems. Very low copper concentrations (in excess
transported in a beam of radiant energy.
of 50 µg/kg) can significantly accelerate this thermal instability
3.1.2 transmittance, T, n—the ratio of the radiant power
of aviation turbine fuel. Naval shipboard aviation fuel delivery
transmitted by a material to the radiant power incident upon it.
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
This test method is under the jurisdiction of ASTM Committee D02 on
on shipboard, in refineries, and at fuel storage depots.
Petroleum Products and Lubricantsand is the direct responsibility of Subcommittee
D02.03 on Elemental Analysis.
Current edition approved May 1, 2010. Published May 2010. Originally
6. Interferences
approved in 2001. Last previous edition approved in 2004 as D6732–04. DOI:
10.1520/D6732-04R10.
6.1 Interferences most commonly occur due to light that is
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
absorbed by species other than the atomic species of interest.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Generally, this is due to undissociated molecular particles from
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. thesamplematrix.Thecharstepinthefurnaceprogramisused
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6732 − 04 (2010)
to eliminate as much of the matrix as possible before the 9. Sampling
atomization step. Spectrometers are equipped with background
9.1 Samples shall be taken in accordance with procedures
correction capabilities to control further possibilities of erro-
described in Practice D4057.
neous results due to molecular absorption.
9.2 Samples shall be thoroughly mixed in their containers
immediately prior to testing.
7. Apparatus
10. Calibration and Standardization
7.1 AtomicAbsorptionSpectrometer—Anatomicabsorption
spectrometer with the capability of setting the wavelength at
10.1 Preparation of Standards:
324.8 nm, setting the slit width at typically 0.7 nm, and using
10.1.1 Nominal 1 mg/kg Intermediate Stock Standard—
peak area integration for the atomic and background readings
Accurately weigh a nominal 0.50 g of the 100 mg/kg stock
shall be used. The spectrometer shall be equipped with the
organo-metallic standard into a suitable container (capable of
following:
being sealed for mixing). (All masses are measured to the
7.1.1 Copper Hollow Cathode Lamp—as the elemental light nearest 0.0001 g.) Suitable sample containers are described in
source. Practice D4306. Add enough odorless kerosine to bring the
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, and
7.1.3 Graphite FurnaceAtomizer—which uses pyrolytically
100 µg/kg—Accurately weigh a nominal 0.20, 0.40, 0.60, 0.80,
coated graphite tubes with L’vovplatforms.
and 1.00 g of the nominal 1 mg/kg intermediate stock standard
7.2 Autosampler or Manual Pipettor—capable of reproduc-
into five suitable containers. (All masses are measured to the
ibly delivering 10 6 0.5 µLaliquots of samples, standards, and
nearest 0.0001 g.) Add enough odorless kerosine to each
blank to the graphite furnace.
container to bring the total mass to a nominal 10.00 g. Seal
containers and mix well. This produces working standards of
7.3 Analytical Balance—capable of weighing 100 g 6
nominal 20, 40, 60, 80, and 100 µg/kg, respectively. See 12.1.2
0.0001 g.
for calculations of actual concentrations.
8. Reagents and Materials
10.2 Calibration:
10.2.1 Prepare a standard calibration curve by using the
8.1 Purity of Reagents—Reagent grade chemicals shall be
odorless kerosine as a blank and each of the five working
used in all tests. Unless otherwise indicated, it is intended that
standards. The instrument measures the integrated absorbance
all reagents conform to the specifications of the Committee on
A of 10 µL of each working standard and blank. The
i
Analytical Reagents of the American Chemical Society where
3 intermediate stock standard and working standards shall be
such specifications are available. Other grades may be used,
prepared daily.
provided it is first ascertained that the reagent is of sufficiently
10.2.2 The calibration curve is constructed by plotting the
high purity to permit its use without lessening the accuracy of
corrected integrated absorbances (on y-axis) versus the con-
the determination.
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
absorption spectroscopy. Many atomic absorption spectrom-
8.3 100 mg/kg Organo-metallic Standard for Copper, or a
eters have the capability of constructing the calibration curve
multielement standard containing copper at 100 mg/kg.
internally or by way of computer software. Construct the best
8.4 Silica Gel, 100 to 200 mesh.
possible fit of the data with available means.
8.5 Argon Gas, 99.999%, (Warning—Argon is a com-
11. Procedure
pressed gas under high pressure) for graphite furnace gas flow
11.1 Set the spectrometer at a wavelength of 324.8 nm and
system.
a slit width of typically 0.7 nm.Align the hollow cathode lamp
8.6 Quality Control (QC) Samples, preferably are portions
and furnace assembly to obtain maximum transmittance.
of one or more kerosine materials that are stable and represen-
11.2 Condition new (or reinstalled) graphite tube and L’vov
tativeofthesamplesofinterest.TheseQCsamplescanbeused
platform with the temperature program provided by the spec-
to check the validity of the testing process as described in
trometer manufacturer until the baseline shows no peaks.
Section 14. Use a stable QC concentrate, and dilute it on the
day of the QC check to the trace level required. 11.3 Calibrate the graphite furnace temperature controller at
2300°C according to the spectrometer manufacturer’s instruc-
tions.
11.4 Whenanautosamplerisusedwiththegraphitefurnace,
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
use odorless kerosine as the rinse solution. Use only autosam-
lis
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