ASTM C1128-01(2008)
(Guide)Standard Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel Cycle Materials
Standard Guide for Preparation of Working Reference Materials for Use in Analysis of Nuclear Fuel Cycle Materials
SIGNIFICANCE AND USE
Certified reference materials (CRMs) prepared from nuclear materials are generally of high purity, possessing chemical stability or reproducible stoichiometry. Usually they are certified using the most unbiased and precise measurement methods available, often with more than one laboratory being involved in making certification measurements. CRMs are generally used on a national or international level, and they are at the top of the metrological hierarchy of reference materials. A graphical representation of a national nuclear measurement system is shown in Fig. 3.
Working reference materials (WRMs) need to have quality characteristics that are similar to CRMs, although the rigor used to achieve those characteristics is not usually as stringent as for CRMs. Where possible, CRMs are often used to calibrate the methods used for establishing the concentration values (reference values) assigned to WRMs, thus providing traceability to CRMs as required by ISO 17025. A WRM is normally prepared for a specific application.
Because of the importance of having highly reliable measurement data from nuclear materials, particularly for control and accountability purposes, CRMs are sometimes used for calibration when available. However, CRMs prepared from nuclear materials are not always available for specific applications. Thus, there may be a need for a laboratory to prepare WRMs from nuclear materials. Also, CRMs are often too expensive, or their supply is too limited for use in the quantities needed for long-term, routine use. When properly prepared, WRMs will serve equally well as CRMs for most applications, and using WRMs will preserve supplies of CRMs.
Difficulties may be encountered in the preparation of RMs from nuclear materials because of the chemical and physical properties of the materials. Chemical instabilities, problems in ensuring stoichiometry, and radioactivity are factors involved, with all three factors being involved with some materials. Those preparing ...
SCOPE
1.1 This guide covers the preparation and characterization of working reference materials (WRM) that are produced by a laboratory for its own use in the analysis of nuclear materials. Guidance is provided for establishing traceability of WRMs to certified reference materials by a defined characterization process. The guidance provided is generic; it is not specific for a given material.
1.2 The information provided by this guide is found in the following sections:
Section Planning 6 Preparation 7 Packaging and Storage 8 Characterization 9 Statistical Analysis10 Documentation11
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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.
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Designation: C1128 − 01(Reapproved 2008)
Standard Guide for
Preparation of Working Reference Materials for Use in
Analysis of Nuclear Fuel Cycle Materials
This standard is issued under the fixed designation C1128; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope a Laboratory Within the Nuclear Industry
C1215Guide for Preparing and Interpreting Precision and
1.1 This guide covers the preparation and characterization
Bias Statements in Test Method Standards Used in the
of working reference materials (WRM) that are produced by a
Nuclear Industry
laboratory for its own use in the analysis of nuclear materials.
2.2 ISO Standards:
Guidance is provided for establishing traceability ofWRMs to
ISO Guide to the Expression of Uncertainty in Measure-
certified reference materials by a defined characterization
ment
process.The guidance provided is generic; it is not specific for
ISO17025General Requirements for the Competence of
a given material.
Calibration and Testing Laboratories
1.2 The information provided by this guide is found in the
ISO Guide30Terms and Definitions Used in Connection
following sections: 3
with Reference Materials
Section
Planning 6
3. Terminology
Preparation 7
3.1 Definitions of Terms Specific to This Standard:
Packaging and Storage 8
Characterization 9
3.1.1 certified reference material (CRM) —a reference ma-
Statistical Analysis 10
terial with one or more property values that are certified by a
Documentation 11
technically valid procedure, accompanied by or traceable to a
1.3 The values stated in SI units are to be regarded as
certificate or other documentation that is issued by a certifying
standard. No other units of measurement are included in this
body (as defined by ISO Guide30). A certifying body is a
standard.
technically competent body (organization or firm, public or
1.4 This standard does not purport to address all of the
private) that issues a reference material certificate (as defined
safety concerns, if any, associated with its use. It is the
by ISO Guide30). A reference material certificate is a docu-
responsibility of the user of this standard to establish appro-
ment certifying one or more property values for a certified
priate safety and health practices and determine the applica-
reference material, stating that the necessary procedures have
bility of regulatory limitations prior to use.
been carried out to establish their validity (as defined by ISO
Guide30).
2. Referenced Documents
3.1.2 reference material (RM) —amaterialorsubstanceone
2.1 ASTM Standards:
or more properties of which are sufficiently well established to
C859Terminology Relating to Nuclear Materials
be used for the calibration of an apparatus, the assessment of a
C1009Guide for Establishing a QualityAssurance Program
measurement method, or assigning values to materials (as
forAnalytical Chemistry Laboratories Within the Nuclear
defined by ISO Guide30). A reference material may be
Industry
referred to in this guide also as a standard, such as calibration
C1068Guide for Qualification of Measurement Methods by
standard or control standard.
3.1.3 working reference material (WRM) —a RM usually
prepared by a single laboratory for its own use as a calibration
This guide is under the jurisdiction ofASTM Committee C26 on Nuclear Fuel
standard, as a control standard, or for the qualification of a
Cycle and is the direct responsibility of Subcommittee C26.08 on Quality
Assurance, Statistical Applications, and Reference Materials.
measurementmethod(seeGuideC1068)asindicatedinFig.1.
CurrenteditionapprovedJune1,2008.PublishedJuly2008.Originallyapproved
in 1989. Last previous edition approved in 2001 as C1128–01. DOI: 10.1520/
C1128-01R08. Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 4th Floor, New York, NY 10036, http://www.ansi.org.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM See C859 for other terms specific to the nuclear fuel cycle.
Standards volume information, refer to the standard’s Document Summary page on It is important that a well defined uncertainty in the stated value(s) be given in
the ASTM website. the certificate.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1128 − 01 (2008)
FIG. 1 Quality Assurance of Analytical Laboratory Data
4. Summary of Guide
4.1 This guide covers the preparation of WRMs from
nuclear fuel cycle materials. These materials are compounds
and metal of uranium and plutonium, absorber materials such
asboroncarbide,andcladdingmaterialssuchaszirconiumand
stainless steel. The criteria governing the preparation of reli-
ableWRMs are identified and discussed. Because this guide is
FIG. 2 Producing a Working Reference Material
generic, requirements and detailed information for specific
nuclear materials are not given.Aflow diagram to illustrate an
from nuclear materials are not always available for specific
approach to producing WRMs is given in Fig. 2.
applications. Thus, there may be a need for a laboratory to
prepare WRMs from nuclear materials. Also, CRMs are often
5. Significance and Use
too expensive, or their supply is too limited for use in the
5.1 Certified reference materials (CRMs) prepared from
quantities needed for long-term, routine use. When properly
nuclear materials are generally of high purity, possessing
prepared, WRMs will serve equally well as CRMs for most
chemical stability or reproducible stoichiometry. Usually they
applications, and using WRMs will preserve supplies of
are certified using the most unbiased and precise measurement
CRMs.
methods available, often with more than one laboratory being
5.4 Difficulties may be encountered in the preparation of
involved in making certification measurements. CRMs are
RMs from nuclear materials because of the chemical and
generallyusedonanationalorinternationallevel,andtheyare
physical properties of the materials. Chemical instabilities,
at the top of the metrological hierarchy of reference materials.
problems in ensuring stoichiometry, and radioactivity are
A graphical representation of a national nuclear measurement
factors involved, with all three factors being involved with
system is shown in Fig. 3.
some materials. Those preparing WRMs from nuclear materi-
5.2 Working reference materials (WRMs) need to have
als must be aware of how these factors affect preparation, as
quality characteristics that are similar to CRMs, although the
well as being aware of the other criteria governing the
rigor used to achieve those characteristics is not usually as
preparation of reliable WRMs.
stringent as for CRMs. Where possible, CRMs are often used
tocalibratethemethodsusedforestablishingtheconcentration 6. Planning
values (reference values) assigned to WRMs, thus providing
6.1 Producing a WRM requires forethought to ensure the
traceability to CRMs as required by ISO 17025. A WRM is
credibility of the completed WRM. Planning also ensures that
normally prepared for a specific application.
the necessary resources are available. Time, funding, and
5.3 Because of the importance of having highly reliable materials can be wasted easily without thorough planning.
measurement data from nuclear materials, particularly for Planning should include developing an outline or general
control and accountability purposes, CRMs are sometimes scheme for preparing the WRM. The intended use of the
used for calibration when available. However, CRMs prepared WRM, the sources available for obtaining needed materials,
C1128 − 01 (2008)
FIG. 3 United States Nuclear Measurement System
and the equipment required are some areas of planning that 6.2 Initial Planning:
should be considered. These considerations and others, i.e., 6.2.1 Application of WRM—AWRM can be prepared for a
initial planning, a production plan, and a statistical plan (see singlemethodofanalysisorforseveralmethods.Forexample,
Fig. 2), are discussed in this section. Initial planning generally one might be prepared for the determination of uranium in
starts with the application or need for aWRM and the quantity uranium dioxide. If a standard is also required for the isotopic
needed. As planning progresses into the actual preparation, a analysis of uranium, it might be possible to prepare and
production plan and a statistical analysis plan will be devel- characterizethatWRMforisotopicanalysisaswell.Duringthe
oped. preparation of a WRM for the determination of a major
C1128 − 01 (2008)
constituent, it might be possible to add desired impurities and Appendix X1). Characterization may include the analysis of
to establish values for those impurities. Careful consideration starting materials for impurities and major constituents. It
should be given to the preparation of multi-purpose WRMs, should include a scheme for establishing the value to be
however, because they tend to be difficult to prepare and assigned (reference value) to each constituent of interest. In
characterize. planning for characterization, consideration must be given to
thedegreeofreliabilityrequiredforareferencevalue.Thiswill
6.2.2 Quantity—The quantity of WRM prepared will de-
involve planning for the statistical collection and analysis of
pend on such factors as the length of time required for its use,
characterization data (see 6.4).
the frequency of use, the amount of material available, and the
6.3.5 Packaging—Packaging of the WRM should be
WRM’santicipatedshelflife.Considerationshouldbegivento
planned.Decisionsneedtobemadeconcerning thedivisionof
the amount of WRM that will be needed for characterization
the WRM into portions, selecting containers, uniquely identi-
and for archival purposes. Needs may develop during the use
of a WRM such as the exchange of materials with another fying containers, sealing containers, and using additional
meanstoprotecttheintegrityoftheWRM.Itmaybenecessary
laboratory for an interlaboratory testing program. For this and
otherpossiblecontingencies,thepreparationofaquantityover to package some WRMs soon after preparation to preserve
integrity; in that case, packaging materials and equipment
the anticipated amount should be planned.
should be readied prior to material preparation. Inadequate
6.3 Production Plan—An outline that specifies how the
packaging may lead to loss of the WRM’s integrity through
WRM will be produced should be prepared during planning.
such consequences as contamination, evaporation, degradation
The subjects discussed in 6.2 and in this section should be
and absorption.
considered and addressed if appropriate. A preparation proce-
6.4 Statistical Plan—A statistical plan for characterization
dure should be written and included as a part of the production
should be developed during planning. Such a plan is necessary
plan(see7.4).Theproductionplanmustbeintegratedwiththe
to allow an uncertainty to be determined for each reference
statistical plan (see 6.4).
value.Thestatisticalplanestablisheshowcharacterizationwill
6.3.1 Materials—The selection of materials is an important
be done. It includes sampling of the WRM, the frequency and
part of planning because proper selection is critical to achiev-
number of measurements to be made of the WRM, any
ingcredibleWRMs.Selectiondependsonavailability(source),
reference material to be measured with the WRM, and the
cost, chemical and physical properties, and stability or repro-
order of measurements (see 9.3 and 9.4). The validation or
ducible stoichiometry. The material selected for a WRM must
calibration of the measurement method to be used for charac-
beassimilaraspossibletothesamplematerialinchemicaland
terization may be addressed in the plan also (see 9.2.3). It is
physical properties, particularly in those that will affect the
essential to have a qualified statistician involved in developing
method of analysis. One way to achieve similarity in compo-
the plan, and the statistician should be brought into the
sition is to prepare the WRM material by the same or similar
planning process early (see Fig. 2). Developing a statistical
processusedtopreparethesamplematerial.Probablythemost
planisaniterativeprocessthatwillgoonthroughoutplanning,
important criterion for selection is stability. The WRM com-
and it must be integrated with the production plan (see 6.3).
position must be sufficiently stable to make the preparation of
the WRM cost effective, and the stability must be known well
7. WRM Preparation
enough to establish a shelf life with a high degree of confi-
7.1 The objective of preparation is to make physical and
dence.Somewhatunstablematerialswhosestoichiometriescan
chemical manipulations so as to produce a homogeneous and
be reproduced easily can be used for WRMs.
stable material in the form required for a WRM. For a given
6.3.2 Equipment—Generally,standardlaboratoryequipment
WRM, the physical and chemical manipulations that will be
will be involved in preparing a WRM. Analytical setups and
used depend on the starting material(s), the WRM form
instrumentation will be required, possibly to analyze starting
required, and the physical and chemical properties of the
materials for impurities and other constituents and certainly to
materials involved. Various aspects of preparation are dis-
analyze the prepared material during final characterization of
cussed in this section.
the WRM. Depending on packaging requirements, equipment
7.2 StartingMaterials—Thestartingmaterialsfortheprepa-
may be required for such things as sealing glass ampoules or
ration of WRMs may be the WRM forms desired or may be
packaging a WRM in a special atmosphere.
other materials that are processed into those forms. In the
6.3.3 Use—The degree of attention given to some steps in
former case, the starting material is process material. For
producing a WRM may vary depending on its planned use.
example, a batch of uranium dioxide pellets, boron carbide
Usually, WRMs are used for calibration and measurement
powder, or plutonium nitrate solution might be taken directly
control.Acommonapproachtoproducingacontrolstandardis
from a process run, treated as necessary, characterized, and
to take material from a batch of production material, treat it as
packaged as aWRM. In the latter case, various approaches are
necessarytoensurehomogeneity,andestablishinitialmeasure-
used to produce the form desired. For ex
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation:C1128–95 Designation:C1128–01 (Reapproved 2008)
Standard Guide for
Preparation of Working Reference Materials for Use in the
Analysis of Nuclear Fuel Cycle Materials
This standard is issued under the fixed designation C1128; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Figure 1 was corrected editorially in February 1997.
1. Scope
1.1 This guide covers the preparation and characterization of working reference materials (WRM) that are produced by a
laboratory for its own use in the analysis of nuclear materials. Guidance is provided for establishing traceability of WRMs to
certified reference materials by a defined characterization process. The guidance provided is generic; it is not specific for a given
material.
1.2 The information provided by this guide is found in the following sections:
Section
Planning 6
Preparation 7
Packaging and Storage 8
Characterization 9
Statistical Analysis 10
Documentation 11
1.3The values stated in SI units are to be regarded as the standard.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
C859 Terminology Relating to Nuclear Materials
C1009 GuideforEstablishingaQualityAssuranceProgramforAnalyticalChemistryLaboratoriesWithintheNuclearIndustry
C1068 Guide for Qualification of Measurement Methods by a Laboratory Within the Nuclear Industry
C1215 Guide for Preparing and Interpreting Precision and Bias Statements in Test Method Standards Used in the Nuclear
Industry
2.2 ISO Standards:
ISO Guide25 General Requirements for the Competence of Calibration and Testing Laboratories
ISO Guide to the Expression of Uncertainty in Measurement
ISO17025 General Requirements for the Competence of Calibration and Testing Laboratories
ISO Guide30 Terms and Definitions Used in Connection with Reference Materials
This guide is under the jurisdiction of ASTM Committee C-26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.8 on Quality Assurance
Applications.
Current edition approved Oct. 10, 1995. Published March 1996. Originally published as C1128–89. Last previous edition C1128–89.
This guide is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.08 on Quality Assurance,
Statistical Applications, and Reference Materials.
Current edition approved June 1, 2008. Published July 2008. Originally approved in 1989. Last previous edition approved in 2001 as C1128–01.
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.ForAnnualBookofASTMStandards
, Vol 12.01.volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute, 11 W. 42nd St., 13th Floor, New York, NY 10036.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 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.
C1128–01 (2008)
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 certified reference material (CRM) —a reference material with one or more property values that are certified by a
technicallyvalidprocedure,accompaniedbyortraceabletoacertificateorotherdocumentationthatisissuedbyacertifyingbody
(asdefinedbyISOGuide30).Acertifyingbodyisatechnicallycompetentbody(organizationorfirm,publicorprivate)thatissues
areferencematerialcertificate(asdefinedbyISOGuide30).SuchanorganizationcouldbetheNationalInstituteofStandardsand
Technology (NIST) or the New Brunswick Laboratory. A reference material certificate is a document certifying one or more
property values for a certified reference material, stating that the necessary procedures have been carried out to establish their
validity (as defined by ISO Guide30).Areference material certificate is a document certifying one or more property values for a
certified reference material, stating that the necessary procedures have been carried out to establish their validity (as defined by
ISO Guide30).
3.1.2 reference material (RM) —a material or substance one or more properties of which are sufficiently well established to be
used for the calibration of an apparatus, the assessment of a measurement method, or assigning values to materials (as defined by
ISO Guide30). A reference material may be referred to in this guide also as a standard, such as calibration standard or control
standard.
3.1.3 working reference material (WRM) —a RM usually prepared by a single laboratory for its own use as a calibration
standard, as a control standard, or for the qualification of a measurement method (see Guide C1068) as indicated in Fig. 1.
4. Summary of Guide
4.1 This guide covers the preparation of WRMs from nuclear fuel cycle materials. These materials are compounds and metal
of uranium and plutonium, absorber materials such as boron carbide, and cladding materials such as zirconium and stainless steel.
The criteria governing the preparation of reliableWRMs are identified and discussed. Because this guide is generic, requirements
anddetailedinformationforspecificnuclearmaterialsarenotgiven.AflowdiagramtoillustrateanapproachtoproducingWRMs
is given in Fig. 2.
5. Significance and Use
5.1 Certified reference materials (CRMs) prepared from nuclear materials are generally of high purity, possessing chemical
stability or reproducible stoichiometry. Usually they are certified using the most unbiased and precise measurement methods
available, often with more than one laboratory being involved in making certification measurements. CRMs are generally used on
It is important that some well defined indication of the uncertainty in the stated values be given in the certificate.
See C859 for other terms specific to the nuclear fuel cycle.
Based on NUREG-0118 (also designated LA-NUREG-6348), Preparation of Working Calibration and Test Materials: Plutonium Nitrate Solution, Nuclear Regulatory
Commission. Available from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402.
It is important that a well defined uncertainty in the stated value(s) be given in the certificate.
FIG. 1 Quality Assurance of Analytical Laboratory Data
C1128–01 (2008)
FIG. 2 Producing a Working Reference Material
a national or international level, and they are at the top of the metrological hierarchy of reference materials. A graphic
descriptiongraphical representation of the United Statesa national nuclear measurement system is shown in Fig. 3.
5.2 Workingreferencematerials(WRMs)needtohavequalitycharacteristicsthataresimilartoCRMs,althoughtherigorused
to achieve those characteristics is not usually as stringent as for CRMs. Where possible, CRMs are often used to calibrate the
methodsusedforestablishingtheconcentrationvalues(referencevalues)assignedtoWRMs,thusprovidingtraceabilitytoCRMs
as required by ISO 17025. A WRM is normally prepared for a specific application.
5.3 Because of the importance of having highly reliable measurement data from nuclear materials, particularly for control and
accountability purposes, CRMs are sometimes used for calibration when available. However, CRMs prepared from nuclear
materials are not always available for specific applications. Thus, there may be a need for a laboratory to prepare WRMs from
nuclearmaterials.Also,CRMsareoftentooexpensive,ortheirsupplyistoolimitedforuseinthequantitiesneededforlong-term,
routine use. When properly prepared, WRMs will serve equally well as CRMs for most applications, and using WRMs will
preserve supplies of CRMs.
5.4 Difficulties may be encountered in the preparation of RMs from nuclear materials because of the chemical and physical
properties of the materials. Chemical instabilities, problems in ensuring stoichiometry, and radioactivity are factors involved, with
all three factors being involved with some materials. Those preparing WRMs from nuclear materials must be aware of how these
factors affect preparation, as well as being aware of the other criteria governing the preparation of reliable WRMs.
6. Planning
6.1 Producing aWRM requires forethought before the work starts to ensure that the credibility of the completedWRM will be
established. WRM. Planning is also important to ensure ensures that the necessary resources are available. Time, funding, and
materials can be wasted easily without thorough planning, whichplanning. Planning should include developing an outline or
general scheme for preparing theWRM.The intended use of theWRM, the sources available for obtaining needed materials, and
the equipment required are some areas of planning that mustshould be considered. These considerations and others are discussed
in this section in terms ofothers, i.e., initial planning, a production plan, and a statistical plan (see Fig. 2), are discussed in this
section. Initial planning generally starts with the application or need for a WRM and the quantity needed.As planning progresses
into the actual preparation, a production plan and a statistical analysis plan will be developed.
C1128–01 (2008)
FIG. 3 United States Nuclear Measurement System
6.2 Initial Planning:
6.2.1 Application of WRM—AWRM can be prepared for a single method of analysis or for several methods. For example, one
might be prepared for the determination of uranium in uranium dioxide. If a standard is also required for the isotopic analysis of
uranium, it might be possible to prepare and characterize that WRM for isotopic analysis as well. In situations involving the
determination of impurities, it may or may not be desirable to prepare WRMs. Often, determinations of impurities do not require
highly reliable results, and the preparation of a WRM might not be cost effective.Areference material lower in the metrological
hierarchy could be adequate. On the other hand, during the preparation of a WRM for the determination of a major constituent,
it might be possible to add desired impurities and to establish values for those impurities.This would give a multi-purposeWRM.
C1128–01 (2008)
Careful consideration should be given to the preparation of multi-purpose WRMs, however, because they tend to be difficult to
prepare and characterize. —A WRM can be prepared for a single method of analysis or for several methods. For example, one
might be prepared for the determination of uranium in uranium dioxide. If a standard is also required for the isotopic analysis of
uranium,itmightbepossibletoprepareandcharacterizethatWRMforisotopicanalysisaswell.DuringthepreparationofaWRM
for the determination of a major constituent, it might be possible to add desired impurities and to establish values for those
impurities. Careful consideration should be given to the preparation of multi-purpose WRMs, however, because they tend to be
difficult to prepare and characterize.
6.2.2 Quantity—The quantity of WRM prepared will depend on such factors as the length of time required for its use, the
frequency of use, the amount of material available, and its theWRM’s anticipated shelf life. Consideration should be given to the
amount of WRM that will be needed for characterization and perhaps for archival purposes. Needs may develop during the use
of a WRM such as the exchange of materials with another laboratory for an interlaboratory testing program. For this and other
possible contingencies, the preparation of a quantity over the anticipated amount should be planned.
6.3 Production Plan—An outline should be prepared during planning that specifies how theWRM will be produced should be
preparedduringplanning.Thesubjectsdiscussedin6.2andinthissectionmustshouldbeconsideredandaddressedifappropriate.
A preparation procedure should be written and included as a part of the production plan (see 7.4). The production plan must be
integrated with the statistical plan (see 6.4).
6.3.1 Materials—The selection of materials is an important part of planning because proper selection is critical to achieving
credible WRMs. Selection depends on availability (source), cost, chemical and physical properties, and stability or reproducible
stoichiometry. The material selected for a WRM must be as similar as possible to the sample material in chemical and physical
properties, particularly in those that will affect the method of analysis. One way to achieve similarity in composition is to prepare
the WRM material by the same or similar process used to prepare the sample material. Probably the most important criterion for
selection is stability. The WRM composition must be sufficiently stable to make the preparation of the WRM cost effective, and
the stability must be known well enough to establish a shelf life with a high degree of confidence. Somewhat unstable materials
whose stoichiometries can be reproduced easily can be used for WRMs.
6.3.2 Equipment—Generally, standard laboratory equipment will be involved in preparing a WRM. Analytical setups and
instrumentationwillberequired,possiblytoanalyzestartingmaterialsforimpuritiesandotherconstituentsandcertainlytoanalyze
the prepared material during final characterization of the WRM. Depending on packaging requirements, equipment may be
required for such things as sealing glass ampoules or packaging a WRM in a special atmosphere.
6.3.3 Use—The degree of attention given to some steps in producing aWRM may vary depending on its planned use. Usually,
WRMs are used for calibration and measurement control.Acommon approach to producing a control standard is to take material
from a batch of production material, treat it as necessary to ensure homogeneity, and establish initial measurement control limits
b
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