ASTM D8371-20

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: D8371 − 20
Standard Test Method for
Trace Metal Content Analysis in Carbon Black
This standard is issued under the fixed designation D8371; 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 Spectrometry (ICP-AES) for ElementalAnalysis of Petro-
leum Products and Lubricants
1.1 This test method covers the determination of metal
content in carbon black with ICP-OES or ICP-MS after
3. Terminology
adequate digestion. See 3.1.5 – 3.1.7 for definitions.
3.1 Definitions:
1.2 The concentration ranges covered by these test methods
3.1.1 calibration, n—the process by which the relationship
are determined by the sensitivity of the instruments, the
between signal intensity and element concentration is deter-
amount of sample taken for analysis and the dilution volume.
mined for a specific element analysis.
1.3 Detection limits, sensitivity and optimum ranges of the
3.1.2 calibration curve, n—the plot of signal intensity (on
metals will vary with the matrices and model of spectrometer.
the ‘y’ axis) versus element concentration (on the ‘x’ axis)
1.4 Elements present at concentrations above the linear
using data obtained from standards that contain certified trace
response range of the calibration curve can be determined with
metal concentrations (calibration solutions), known with high
additional appropriate dilutions.
accuracy.
1.5 The values stated in SI units are to be regarded as
3.1.3 calibration solution, n—solution containing mixture
standard. No other units of measurement are included in this
of elements of known concentrations (multi element certified
standard.
standard solution).
1.6 This standard does not purport to address all of the
3.1.4 detection limit, n—the concentration of an analyte that
safety concerns, if any, associated with its use. It is the
results in a signal intensity that is some multiple (typically
responsibility of the user of this standard to establish appro-
three) times the standard deviation of the background intensity
priate safety, health, and environmental practices and deter-
of the blank.
mine the applicability of regulatory limitations prior to use.
3.1.5 ICP-MS, n—inductively coupled plasma – mass spec-
1.7 This international standard was developed in accor-
trometry.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the 3.1.6 ICP-OES, n—inductively coupled plasma – optical
emission spectrometry.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.1.7 inductively coupled plasma (ICP), n—a high tempera-
Barriers to Trade (TBT) Committee.
ture discharge generated by flowing an ionizable gas through a
magnetic field induced by a load coil that surrounds the tubes
2. Referenced Documents
carrying the gas.
2.1 ASTM Standards:
3.1.8 linear response range, n—the elemental concentration
D1193 Specification for Reagent Water
range over which the calibration curve is a straight line, within
D1506 Test Methods for Carbon Black—Ash Content
the precision of the test method.
D7260 Practice for Optimization, Calibration, and Valida-
3.1.9 secondary solution, n—calibration solution from a
tion of Inductively Coupled Plasma-Atomic Emission
second source.
4. Summary of Test Method
This test method is under the jurisdiction ofASTM Committee D24 on Carbon
Black and is the direct responsibility of Subcommittee D24.66 on Environment,
4.1 A sample of carbon black is digested either with strong
Health, and Safety.
acid under high temperature and pressure or after incineration
Current edition approved Dec. 1, 2020. Published January 2021. DOI: 10.1520/
D8371-20.
of the sample and acid treatment of the ash. By digestion, the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
trace metals are transferred into their soluble salts, and most of
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
the interfering matrix components, that is, carbon black, are
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. removed.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8371 − 20
4.2 The digestion solution is measured with an ICP-OES or 6.10 Crucibles, made of porcelain, quartz or platinum,
ICP-MS to quantify the trace metals of interest, after a high-form, for example, size O, rim 35 mm, height 29 mm,
calibration with a mix of elements in a certified standard capacity 15 cm , with cover. Other size crucibles may be used.
reference solution. The concentrations of elements in the test
6.11 Desiccator.
specimen are calculated by comparing emission intensities of
6.12 Oven, gravity-convection type, capable of temperature
elements in the test specimen with emission intensities mea-
regulation within 61°C at 125°C and temperature uniformity
sured in the standards.
within 65°C.
4.3 The ICP-MS is typically one or more orders of magni-
6.13 Filter Paper, for example, Whatman #41.
tude more sensitive and has a wider dynamic range than
ICP-OES. The quantitative reporting limits of the instruments
7. Reagents and Solutions
in terms of ug/g sample varies with specific element, sample
7.1 Argon, purity 5.0.
weight, final solution volume, specific instrument, and other
factors. For example, for a 0.3 g sample weight into a final 7.2 Nitrogen, purity 5.0.
volume of 25 cm , ICP-MS for some transition elements can
7.3 Water, ultra-pure with a conductivity according to
measure down to the 10’s of ppb concentrations or possibly
Specification D1193 Type I.
less, while both ICP-OES and ICP-MS can be used for
7.4 Nitricacid(HNO )67to69%,suprapureortracemetal
measurements in the ppm range.
grade.
4.4 The instrument manufacturers recommendations should
7.5 Hydrochloric acid (HCl), concentrated, trace metal
be followed when operating the ICP-OES or ICP-MS. Addi-
grade or equivalent.
tional information and other general considerations on the
7.6 Multi-Element certified standard solutions.
ICP-OES technique are given in Practice D7260.
7.7 Desiccant.
5. Significance and Use
NOTE 1—All reagents should be of sufficiently high purity to permit
their use without negatively impacting the accuracy of the determination.
5.1 This test covers the quantitation of trace metals in
carbon black. The quantitation of heavy metals may help to
8. Procedure
estimate their contribution to a final finished article. Metal
8.1 Sample Preparation/Digestion—The parameters de-
components may impact application properties of final prod-
scribed in 8.2.1 – 8.2.5 provide appropriate microwave diges-
ucts or may be a regulatory issue. It is the responsibility of the
tion. Other microwave parameters can be used that shall
user of the material to consider the impact of the elements
provide adequate digestion of the trace metals. Ideally the
when designing a final product.
obtained solution should be clear by visual observation. In
5.2 Elements which cannot be digested with nitric acid,
somecases,asmallamountofvisiblecarbonblackmayremain
such as silicon, cannot be quantified by this test method. This
after the microwave step and it would not be possible to
standard describes two digestion methods; microwave acid
determine visually if any undissolved metals are remaining. In
digestion and furnace ashing. The furnace ashing method may
those cases, the adequacy of the digestion shall be verified by
not be appropriate for certain more volatile elements which can
comparing to the furnace ashing method (for non-volatile
be lost during incineration.
metals) and by achieving appropriate recoveries on a spiked
sample.
6. Apparatus
8.2 Method A – Microwave Digestion:
6.1 Balance, analytical, with 0.1 mg sensitivity.
NOTE 2—Microwave digestion of carbon black is a hazardous operation
involving concentrated acids under high pressure and heat, generation of
6.2 Microwave, capable of producing 285°C and pressure of
toxic vapors such as NOx, and other hazards. Follow the safety instruc-
16 MPa (160 bar). Microwaves with lower temperatures and
tions by the manufacturer.
pressures can be used provided the sample is adequately
8.2.1 A sample amount of 0.3 to 0.4 g carbon black is
digested.
weighed to the nearest 0.1 mg in a quartz digestion vessel,
6.3 Microwave Digestion Vessels with Lid (made of quartz).
mixed with 10 cm of nitric acid and covered with a lid.
8.2.2 Fill the reactor vessel with 120 cm wa
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