ASTM E2972-15(2019)

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: E2972 − 15 (Reapproved 2019)
Standard Guide for
Production, Testing, and Value Assignment of In-House
Reference Materials for Metals, Ores, and Other Related
Materials
This standard is issued under the fixed designation E2972; 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 Scope Aluminum-Base Alloys (Withdrawn 2017)
E50 Practices for Apparatus, Reagents, and Safety Consid-
1.1 This document provides guidance for the implementa-
erations for Chemical Analysis of Metals, Ores, and
tion of procedures for preparation of in-house reference mate-
Related Materials
rials for analytical testing of metals, ores, slags, and other
E55 Practice for Sampling Wrought Nonferrous Metals and
materials encountered within the metals and mining industries.
Alloys for Determination of Chemical Composition
1.2 This guide is applicable to the production of reference E88 Practice for Sampling Nonferrous Metals and Alloys in
materials only (usually for internal use) and does not apply to Cast Form for Determination of Chemical Composition
the production of certified reference materials (CRMs). Mate- E135 Terminology Relating to Analytical Chemistry for
rialsmayincludemetals,alloys,minerals,geologicalmaterials, Metals, Ores, and Related Materials
manufacturing intermediates, and byproducts. Samples may be E178 Practice for Dealing With Outlying Observations
in a number of physical forms including blocks, disks, rods, E255 Practice for Sampling Copper and Copper Alloys for
wires, chips, granules, powders, and liquids. the Determination of Chemical Composition
E415 Test Method for Analysis of Carbon and Low-Alloy
1.3 This standard does not purport to address all of the
Steel by Spark Atomic Emission Spectrometry
safety concerns, if any, associated with its use. It is the
E716 Practices for Sampling and Sample Preparation of
responsibility of the user of this standard to establish appro-
Aluminum and Aluminum Alloys for Determination of
priate safety, health, and environmental practices and deter-
Chemical Composition by Spark Atomic Emission Spec-
mine the applicability of regulatory limitations prior to use.
trometry
1.4 This international standard was developed in accor-
E826 Practice for Testing Homogeneity of a Metal Lot or
dance with internationally recognized principles on standard-
Batch in Solid Form by Spark Atomic Emission Spec-
ization established in the Decision on Principles for the
trometry
Development of International Standards, Guides and Recom-
E877 Practice for Sampling and Sample Preparation of Iron
mendations issued by the World Trade Organization Technical
Ores and Related Materials for Determination of Chemi-
Barriers to Trade (TBT) Committee.
cal Composition and Physical Properties
E1086 TestMethodforAnalysisofAusteniticStainlessSteel
2. Referenced Documents
by Spark Atomic Emission Spectrometry
E1329 Practice for Verification and Use of Control Charts in
2.1 ASTM Standards:
Spectrochemical Analysis (Withdrawn 2019)
E32 Practices for Sampling Ferroalloys and Steel Additives
E1806 Practice for Sampling Steel and Iron for Determina-
for Determination of Chemical Composition
tion of Chemical Composition
E34 Test Methods for Chemical Analysis of Aluminum and
E2857 Guide for Validating Analytical Methods
2.2 ISO Standards:
ISO Guide 30 Terms and Definitions Used in Connection
This test method is under the jurisdiction of ASTM Committee E01 on
with Reference Materials
Analytical Chemistry for Metals, Ores, and Related Materials and is the direct
responsibility of Subcommittee E01.22 on Laboratory Quality.
ISO Guide 30/Amd. 1 Revision of definitions for reference
Current edition approved Oct. 1, 2019. Published November 2019. Originally
approved in 2015. Last previous edition approved in 2015 as E2972–15. DOI:
10.1520/E2972-15R19.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The last approved version of this historical standard is referenced on
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM www.astm.org.
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2972 − 15 (2019)
material and certified reference material tation of an in-house reference material (hereafter called an
ISO Guide 35 Reference materials—General and statistical iRM) to be used for a number of purposes, enumerated in the
principles for certification following document, associated with development, validation,
ISO Guide 98-3 Guide to the Expression of Uncertainty in and control of chemical and physical measurement processes.
Measurement (GUM: 1995)
4.2 This guide is primarily concerned with characterization
ISO/IEC 17025 General requirements for the competence of
of the chemical compositions of metals, ores, and related
testing and calibration laboratories
materials. For all these materials, there is a continuing, strong
demand for reference materials (RMs) that is difficult for
3. Terminology
metrology institutes and private certified reference material
3.1 Definitions—For definitions of terms used in this guide,
(CRM) developers to meet because CRM development re-
refer to Terminology E135.
quires substantial investments of time and money. The metals
3.2 Definitions of Terms Specific to This Standard:
and mining industries consume RMs and create new product
3.2.1 development report, n—document giving detailed in-
and by-product compositions at high rates. They use analytical
formation on the preparation of an in-house reference material
methods that provide rapid and accurate determinations, and
and the methods of measurement used in obtaining the as-
both quality assurance and quality control can be maintained
signed values.
using efficient procedures provided appropriate iRMs are
available.
3.2.2 in-house reference material, iRM, n—reference mate-
rial with documented homogeneity that is intended for use for
4.3 The user of this guide must recognize that development
quality control purposes, calibration, evaluation of a
of an iRM for any purpose carries with it the responsibility to
calibration, or standardization whose values may have limited
design and execute the development process correctly, and to
traceability and for which rigorously derived uncertainty infor-
document the process thoroughly. In addition, the user of an
mation is not mandatory.
iRM bears the responsibility for correct use of the iRM
3.2.3 method of demonstrated accuracy, n—test method for material within its design limitations.
which proof of accuracy has been published even though it
4.4 This guide contains discussions on material selection
may not fall within the category of a reference method.
and sampling for RMs with some attention given to conversion
3.2.4 metrological traceability, n—property of a measure-
to the final forms.
ment result or the value of a reference material whereby it can
4.5 The use of iRMs is appropriate for control chart proce-
be related, with a stated uncertainty, to stated references
dures to demonstrate that chemical measurement processes are
through an unbroken chain of comparisons.
under statistical control. This function requires demonstration
3.2.5 primary reference method, n—analytical procedure
of sufficient homogeneity of a material, but it does not require
that does not require the use of calibrants to achieve accurate
assignment of chemical and physical property values with
results, rather the result is based on a defined physical constant
associated, exhaustively evaluated uncertainties.
or a derived physical constant.
4.6 The use of iRMs is appropriate for calibration of test
3.2.5.1 Discussion—Examples include gravimetry,
methods and evaluation of calibrations in several ways, includ-
coulometry, specific titrimetric methods, and isotope dilution
ing checking for bias, systematic testing of corrections for
mass spectrometry. Each individual laboratory should validate
matrix effects, and testing of sample preparation procedures.
its performance of such methods with reference materials.
See Section 6. This guide provides explanations of general
3.2.6 reference method, n—thoroughly investigated method,
cases in which an iRM can be used as part of a validation
clearly and exactly describing the necessary conditions and
process (see Guide E2857).
proceduresforthemeasurementofoneormorepropertyvalues
4.7 Becausethisdocumentisastandardguide,itisintended
that has been shown to deliver accuracy and precision com-
to educate those who are involved in laboratory operation,
mensurate with its intended use and can therefore be used to
quality system development and maintenance, and accredita-
assess the accuracy of other methods for the same
tion of laboratory operations within the scope of a quality
measurement, particularly in permitting the characterization of
system. However, this guide does not constitute requirements
an RM (ISO Guide 30).
for assessment and accreditation.
3.2.6.1 Discussion—This includes all national or interna-
tional standard methods, which may not be classified as
primary reference methods because they are calibrated against 5. Hazards
standard solutions of pure chemical substances.
5.1 The preparation of metal RMs can involve hazards
3.2.7 uncertainty, n—defined by ISO Guide 98-3 as a
associated with melting, casting, heat treating, forging,
“parameter associated with the result of a measurement that
atomizing, pickling, shot blasting, machining, and sampling.
characterises the dispersion of the values that could reasonably
5.2 Hazards may be encountered in crushing, grinding, and
be attributed to the measurand.”
sieving particulate and powdered materials such as ores and
related metallurgical materials.
4. Significance and Use
4.1 This document provides guidance for the implementa- 5.3 For precautions related to the analysis of RMs, see
tion of procedures for the preparation, testing, and documen- Practices E50.
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6. Uses of iRMs and Information Requirements Related requirements for homogeneity and stability can be relaxed
to the Applications relative to the calibrants.
6.1 Process Control: 6.4 Evaluation of Matrix Influence or Spectral
Interference—Both of these phenomena involve systematic
6.1.1 Forefficient,highthroughputinalaboratory,chemical
effects of one constituent on another or on itself. To evaluate
measurement processes, namely test methods, must be kept
the magnitude of an effect, a laboratory may require a set of
under statistical control. Perhaps the most convenient way to
materials specially prepared to have known relationships
accomplish this control is to measure one or more materials at
among the values of the subject constituents within the set.
appropriate time intervals. When the material(s) can be treated
That is, the value of ConstituentAin Material X may be twice
as a regular sample and taken through all steps of the process,
thevalueinMaterialYandthreetimesthevalueofConstituent
the measured results easily can be used to demonstrate statis-
A in Material Z. There may be multiple pairs of related
tical control of the entire chemical measurement process.
constituents in a set of materials. The known relationships
6.1.2 A product-based material demonstrated to be suffi-
allow the laboratory to calibrate influence and interference
ciently homogeneous can be prepared in sufficient quantity to
coefficients empirically or to validate coefficients determined
enable its use for a long period of time. A sufficient level of
fromfirstprinciples.AniRMforevaluationofmatrixinfluence
homogeneity is defined as providing repeatability variance low
or spectral interference should have values obtained from an
enough to maintain a process control chart that ensures the
independent test method or multiple methods of analysis.
uncertainty goals of the test method are met on a routine basis.
6.4.1 The materials in the set should be demonstrated to be
6.1.3 The material chosen for this purpose should be dem-
sufficiently homogeneous to be sampled at the appropriate
onstrated to be stable for at least the length of time it will be
quantity and maintain the required ratios of constituent
used for control charts. For most metals and alloys, stability is
amounts with sufficient precision for the uncertainty goals of
known to be measured in years, if not decades. Stability of
the test method.
natural matrix geological and mineral materials may be less
6.4.2 Stability is a less stringent requirement because it is
certain and may require monitoring. However, RM producers
typical that the coefficient(s) need only be determined once,
havedemonstratedthatmineralandgeologicalmaterialscanbe
unless the instrumentation is modified significantly. This is
processed and packaged in ways that provide long-term stabil-
convenient because it is known that some artificial sets of
ity measured in years.
materials, even alloys, of this nature are unstable and may last
6.1.4 For process control, it is not necessary to develop
for months instead of years.
values traceable to the International System of Units (SI) or
anyCRMs.Thelaboratorysimplyrunsthematerialasaroutine
6.5 Calibration—An iRM can be used as a calibrant in
sample at least 20 times to establish a mean and repeatability
much the same way as a CRM. This is a key role because not
standard deviation. These measurements should be carried out
allCRMproducerscankeeppacewiththedevelopmentofnew
over a time period chosen with consideration to other factors
alloys and the development or modification of manufacturing
affecting routine use of the test method. Refer to Practice
specifications.
E1329 for further guidance on the use of control charts.
6.5.1 An iRM used for calibration should have been devel-
opedwithattentiontohomogeneityaswithotherusesofiRMs.
6.2 Drift Correction—The purpose of a drift correction iRM
6.5.2 An iRM for calibration should have values obtained
is to provide stable, high-precision signals for the constituents
of interest. In this case, it is not necessary to know the values from independent test methods or multiple methods of analy-
sis.
of the amounts of the constituents. Homogeneity and stability
should be demonstrated as above, but the calculations can be
6.5.3 If the laboratory requires the same characteristics as
done in units of the measured phenomenon on which the provided by a CRM, the requirements are essentially the same
instrumental or chemical technique is based. One example is
as for development of a CRM by internationally accepted
the count rate of fluorescent X-rays obtained under the chosen practices.
measurement conditions.
6.5.4 If the laboratory chooses to take a less stringent
6.2.1 To satisfy these requirements, it is necessary to have a approach, the laboratory may assign values based on its own
stable, homogeneous material that can be used numerous times analyses, possibly with analyses from additional laboratories.
withoutdegradationandthatgivesastrongmeasuredsignalfor Such approaches may not cover all aspects found in interna-
a high correction point or a low signal for a low correction tional standards and guides for RM development.
point in the case of a two-point drift correction approach.
6.6 Type Standardization—Type standardization is often
6.3 Instrument Conditioning—For certain test methods, the described as a form of drift correction. In fact, it is both a drift
equipment must be stabilized and conditioned for use on a correction and a recalibration of the sensitivity of the calibra-
regular basis, typically daily. It is necessary to use materials tion model. Laboratories use RMs to adjust a general calibra-
similar in chemical and physical properties to the analysis tion for a specific alloy or material type.
samples, but it is not necessary to know accurately the
6.6.1 Forexample,sparkatomicemissionspectrometerscan
compositions of materials used for conditioning.
be calibrated to a range of alloys in a general category such as
6.3.1 Itmaybeusefultohaveconfidencethataconditioning aluminum. There are hundreds of registered alloys whose
material is homogeneous and stable. However, the purpose is compositionsvarysignificantly.Thegeneralcalibrationdefines
to show that the instrument is ready for calibration, and the matrix and spectral influence coefficients and the curve
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x-intercept. However it is difficult to define accurately inter- 7.9 Identify a suitable panel of test methods and analysts
element corrections for each individual alloy given the number and provide instructions for the determinations.
of alloys and possible composition ranges. The laboratory may
7.10 Select samples of the material and of quality assurance
useaRMofasimilarcompositiontoaparticularalloytoadjust
materials and provide them to the analysts, along with instruc-
the sensitivity parameters of the calibration model for as many
tions for reporting results.
elements as are certified for the RM. This approach places
7.11 Receive, tabulate, and perform a technical evaluation
utmost confidence in the certified values for the RM.
of the resultant data. Carry out necessary rework.
6.6.2 This approach is convenient in that it does provide
driftcorrectionbyrecalibratingthesensitivityvalueswhenever
7.12 Write, review, and approve reports for all testing, as
samples of that alloy specification must be analyzed. applicable.
6.6.3 If there is not a CRM available with the required
7.13 Perform a statistical analysis of the data set to ensure it
composition or if a CRM does not contain value(s) for key
is appropriate for the intended purpose of the iRM.
constituents, the laboratory may choose to develop an iRM, or
7.14 Complete and approve all necessary documentation for
it may choose to develop additional values for an available
the iRM, including a development report and a concise
CRM.
summary that provides the information necessary for the
6.6.3.1 Developing additional values for an existing CRM
intended use of the iRM.
from an outside supplier requires the assumption that the
homogeneity of the existing CRM for additional constituents
8. Factors Influencing the Specifications for the Finished
canbeadequatelyassessedusingasmallnumberofunitsofthe
In-house Reference Material
CRM.
6.6.3.2 All such values and uncertainties developed without
8.1 It is appropriate to set aside production materials having
the knowledge or participation of the original developer of the
the same manufacturing specification and metallurgical history
CRM are of lesser quality, assuming the original developer
as the production materials they will subsequently be used to
complied with all international practices.
monitor. The desired composition may already be available in
6.6.4 If the laboratory requires the same characteristics as
semi-finished form, such as an ingot, bar, or slab.
provided by a CRM, the requirements for production of the
8.1.1 For analysis of metals, metallurgical condition is an
iRM should be similar to those for development of a CRM by
importantconsideration.InstrumentaltechniquessuchasX-ray
industry accepted practices.
fluorescence, spark atomic emission, and glow-discharge
6.6.5 If the laboratory chooses to take a less stringent
atomic emission are usually used to measure samples in solid
approach, the laboratory may assign values based on its own
form with minimal sample preparation. These techniques may
analyses, possibly with analyses from additional laboratories.
be subject to analytical bias caused by the metallurgical history
6.6.6 Insomecases,itmaybenecessarytoobtainadditional
of the alloy. It may be necessary to develop separate RMs for
values for an RM or CRM when those values are needed to
each of the metallurgical processes.
enablecorrectionsforinterferencesininstrumentalmethods.In
8.1.2 Cast materials that are rapidly quenched (namely, chill
this case, traceability of the value(s) to the SI is not necessary
cast) may have the advantages of minimal grain size and
because the values will be used only for making minor
improved homogeneity. However, it is necessary to character-
corrections, and the influence of uncertainty is low.
ize the extent (distance) within the material to which the
improved properties extend.
7. Production Sequence
8.2 It may be possible to obtain the desired material in
7.1 Identify the need for an iRM. Confirm that a material of
finished form meeting the physical size requirement from a
iRM quality would be fit for the intended purpose. commercial source.
7.2 Specify the required form and composition, the desired
8.3 If a composition is to be made by a melting process, a
manufacturing method, and the minimum quantity required. detailed understanding of the metallurgical interactions be-
tween the added constituents and the matrix metal may be
7.3 Identify the source for the iRM.
useful. In many cases, the more elements specified, the greater
7.4 Initiate the project documentation process.
the difficulty in achieving the specification in a homogeneous
7.5 Identifytheprocessesrequiredtoconvertthematerialto material.
the desired form for use as an iRM.
8.4 For particulate materials, it will be necessary to choose
7.6 Prepare the candidate iRM, including packaging and the optimum particle size range based on compositional and
identification of all lots and sublots, if appropriate. analytical requirements. Specially designed grinding and siev-
ing may be necessary to obtain the required homogeneity.
7.7 Develop an experimental plan for acceptance and ho-
mogeneity testing, including selection of test samples, desig- 8.5 Mineralogical materials often require specific drying
nation of test methods, and specification of sample quantities instructions or ignition procedures to define adequately the
for each test method. form of the material to be analyzed and the basis for the
assigned values of the constituents or properties.
7.8 Perform acceptance testing, including material homoge-
neity testing and evaluation of other characteristics, possibly 8.6 Sterilization may be necessary for natural matrix mate-
including material stability. rials for the purpose of destroying any microorganisms that
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may use components of the material as a food source or other 10.4.3 For ores, slags and other non-metals, local inhomo-
resource. Bacterial action may convert an element to a volatile geneity can be caused by the presence of metal particles and
ch
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