ISO/TS 4807:2022
(Main)Reference materials for particle size measurement — Specification of requirements
Reference materials for particle size measurement — Specification of requirements
This document is intended to support users of reference materials (RMs) for particle size analysis to identify suitable RMs (certified or not) for their needs. In line with the focus on users, questions on sample preparation that go beyond preparation of the sample as received by the user will not be covered by this document. This document describes the fundamental requirements that RMs (certified or not) for the determination of particle size shall fulfil in order to be fit for a given purpose. The document is limited to a description of the fundamental principles – the discussion whether a certain numerical value is fit for purpose is beyond the scope of this document. The scope of this document is limited to RMs (certified or not) in the form of particles. This document does not deal with any other form of RMs, like calibration grids.
Matériaux de référence pour la mesure de taille de particules — Spécification des exigences
General Information
Standards Content (Sample)
TECHNICAL ISO/TS
SPECIFICATION 4807
First edition
2022-06
Reference materials for particle size
measurement — Specification of
requirements
Matériaux de référence pour la mesure de taille de particules —
Spécification des exigences
Reference number
ISO/TS 4807:2022(E)
© ISO 2022
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ISO/TS 4807:2022(E)
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ISO/TS 4807:2022(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 4
5 Basic principles . 5
5.1 Measurand definitions in particle size analysis . 5
5.1.1 General . 5
5.1.2 Operationally defined measurands in particle characterisation: Equivalent
diameters . 5
5.1.3 Required detail of procedure description for operationally defined
measurands. 7
5.1.4 Conditions for equivalent diameters to coincide with the actual particle
diameter . 7
5.2 Metrological traceability of size measurement results . . 8
5.2.1 General . 8
5.2.2 Establishing versus verifying traceability in particle characterisation . 11
5.3 Types of RMs . 11
5.3.1 Certified and non-certified RMs/certified and non-certified values . 11
5.3.2 Primary/secondary/tertiary CRMs .12
5.3.3 Spherical/non-spherical and monodisperse/polydisperse RMs .13
5.4 Porous/dense RMs . . 14
6 Practical handling .14
7 Requirements for specific uses .14
7.1 General . 14
7.2 Instrument verification/design qualification . 14
7.3 Installation qualification . 14
7.3.1 General . 14
7.3.2 Type of material . 14
7.3.3 Kind of quantity of the assigned value . 15
7.3.4 Degree of homogeneity . 15
7.4 Calibration . 16
7.4.1 General . 16
7.4.2 Type of material . 16
7.4.3 Traceability of the certified values . 16
7.4.4 Kind of quantity of the certified property . 16
7.4.5 Uncertainty of the certified value . 17
7.5 Operational qualification/demonstration of proficiency . 17
7.5.1 General . 17
7.5.2 Type of material . 17
7.5.3 Kind of quantity of the certified property . 18
7.5.4 Uncertainty of certified values . 20
7.6 Statistical quality control/performance qualification . 20
7.6.1 General .20
7.6.2 Type of material .20
7.6.3 Kind of quantity .20
7.6.4 Degree of homogeneity . 21
7.7 Summary . 21
Bibliography .24
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ISO/TS 4807:2022(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 24, Particle characterization including
sieving, Subcommittee SC 4, Particle characterization.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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TECHNICAL SPECIFICATION ISO/TS 4807:2022(E)
Reference materials for particle size measurement —
Specification of requirements
1 Scope
This document is intended to support users of reference materials (RMs) for particle size analysis
to identify suitable RMs (certified or not) for their needs. In line with the focus on users, questions
on sample preparation that go beyond preparation of the sample as received by the user will not be
covered by this document.
This document describes the fundamental requirements that RMs (certified or not) for the
determination of particle size shall fulfil in order to be fit for a given purpose. The document is limited
to a description of the fundamental principles – the discussion whether a certain numerical value is fit
for purpose is beyond the scope of this document.
The scope of this document is limited to RMs (certified or not) in the form of particles. This document
does not deal with any other form of RMs, like calibration grids.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
kind of quantity
aspect common to mutually comparable quantities
Note 1 to entry: The division of ‘quantity’ according to ‘kind of quantity’ is to some extent arbitrary.
EXAMPLE The quantities diameter, circumference, and wavelength are generally considered to be quantities
of the same kind, namely of the kind of quantity called length.
Note 2 to entry: Quantities of the same kind within a given system of quantities have the same quantity dimension.
However, quantities of the same dimension are not necessarily of the same kind.
[SOURCE: ISO/IEC Guide 99:2007, 1.2, modified — Note 3 to entry and EXAMPLES 2 and 3 have been
deleted.]
3.2
measurand
quantity intended to be measured
Note 1 to entry: The specification of a measurand requires knowledge of the kind of quantity (3.1), description of
the state of the phenomenon, body, or substance carrying the quantity, including any relevant component, and
the chemical entities involved.
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ISO/TS 4807:2022(E)
[SOURCE: ISO/IEC Guide 99:2007, 2.3, modified — Notes 2 and 3 to entry and all the EXAMPLES have
been deleted.]
3.3
operationally defined measurand
method-defined measurand
measurand (3.2) that is defined by reference to a documented and widely accepted measurement
procedure to which only results obtained by the same procedure can be compared
Note 1 to entry: A term for measurands that are independent of a procedure does not exist. The term “non-
operationally defined measurand” is used in this document.
[SOURCE: ISO 17034:2016, 3.7, modified — the second term has been added and Note 1 to entry has
been replaced.]
3.4
metrological traceability
property of a measurement result whereby the result can be related to a reference through a
documented unbroken chain of calibrations (3.12), each contributing to the measurement uncertainty
Note 1 to entry: For this definition, a ‘reference’ can be a definition of a measurement unit through its practical
realization, or a measurement procedure including the measurement unit for a non-ordinal quantity, or a
measurement standard.
[SOURCE: ISO/IEC Guide 99:2007, 2.41, modified — Notes 2 to 8 to entries have been deleted.]
3.5
monomodal material
material consisting of particles where the particle size density distribution has only one maximum
Note 1 to entry: A monomodal material is not monodisperse if the width of the distribution is larger than the
limits described for monodisperse mateials (3.6).
3.6
monodisperse material
material consisting of particles with narrow particle size distribution
Note 1 to entry: For this document, a material is considered monodisperse if the width of the distribution of the
number-based diameter expressed as x /x is 1,12 or less (where x is 10 % percentile of the cumulative particle
90 10 10
size distribution and x is 90 % percentile of the cumulative particle size distribution), which corresponds
90
to a relative standard deviation of the distribution of 4,4 %. The limit 1,12 is taken from the requirements for
monodisperse pickets from ISO/TS 14411-1. Such narrow size distributions are typically found in polymer latex
materials.
3.7
spherical particle
particle with an aspect ratio of 0,95 or above in all three dimensions
Note 1 to entry: particles with small outgrows or that are not smooth can nevertheless fulfil this definition of
sphericity.
3.8
reference material
RM
material, sufficiently homogeneous and stable with respect to one or more specified properties, which
has been established to be fit for its intended use in a measurement process
Note 1 to entry: RM is a generic term comprising both certified and non-certified RMs. There is no term explicitly
referring to RMs without any assigned certified value (3.10). In this document, the term “reference material/
RM” is used for the superordinate, i.e. certified and non-certified RMs, whereas “non-certified RM” is used to
explicitly refer to materials without certified values.
Note 2 to entry: Properties can be quantitative or qualitative, e.g. identity of substances or species.
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ISO/TS 4807:2022(E)
Note 3 to entry: Uses may include the calibration (3.12) of a measurement system, assessment of a measurement
procedure, assigning values to other materials, and quality control.
[SOURCE: ISO Guide 30:2015, 2.1.1, modified — Note 1 to entry has been expanded and Note 4 to entry
has been deleted.]
3.9
certified reference material
CRM
reference material (3.8) characterized by a metrologically valid procedure for one or more specified
properties, accompanied by an RM certificate that provides the value of the specified property, its
associated uncertainty, and a statement of metrological traceability (3.4)
Note 1 to entry: The concept of value includes a nominal property or a qualitative attribute such as identity or
sequence. Uncertainties for such attributes may be expressed as probabilities or levels of confidence.
[SOURCE: ISO Guide 30:2015, 2.1.2, modified — Notes 2 to 4 to entry have been deleted.]
3.10
certified value
value, assigned to a property of a reference material (3.8) that is accompanied by an uncertainty
statement and a statement of metrological traceability (3.4), identified as such in the RM certificate
[SOURCE: ISO Guide 30:2015, 2.2.3]
3.11
indicative value
information value
informative value
value of a quantity or property, of a reference material (3.8), which is provided for information only
Note 1 to entry: An indicative value cannot be used as a reference in a metrological traceability (3.4) chain
[SOURCE: ISO Guide 30:2015, 2.2.4]
3.12
calibration
operation that, under specified conditions, in a first step, establishes a relation between the quantity
values with measurement uncertainties provided by measurement standards and corresponding
indications with associated measurement uncertainties and, in a second step, uses this information to
establish a relation for obtaining a measurement result from an indication.
Note 1 to entry: A calibration may be expressed by a statement, calibration function, calibration diagram,
calibration curve, or calibration table. In some cases, it may consist of an additive or multiplicative correction of
the indication with associated measurement uncertainty.
Note 2 to entry: Calibration should not be confused with adjustment of a measuring system, often mistakenly
called “self-calibration”, nor with verification of calibration.
Note 3 to entry: Often, the first step alone in the above definition is perceived as being calibration.
[SOURCE: ISO/IEC Guide 99:2007, 2.39]
3.13
design qualification
DQ
process for verification that the proposed specification for the facility, equipment, or system meets the
expectation for the intended use
[SOURCE: ISO 11139:2018, 3.220.1]
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ISO/TS 4807:2022(E)
3.14
installation qualification
IQ
process of establishing by objective evidence that all key aspects of the process equipment and ancillary
system installation comply with the approved specification
[SOURCE: ISO 11139:2018, 3.220.2]
3.15
performance qualification
PQ
process of establishing by objective evidence that the process, under anticipated conditions, consistently
produces a product which meets all predetermined requirements
[SOURCE: ISO 11139:2018, 3.220.4]
3.16
operational qualification
OQ
process of obtaining and documenting evidence that installed equipment operates within predetermined
limits when used in accordance with its operational procedures
[SOURCE: ISO 11139:2018, 3.220.3]
3.17
proficiency test
evaluation of participant performance against pre-established criteria by means of interlaboratory
comparisons
[SOURCE: ISO/IEC 17043:2010, 3.7, modified — Notes to entry 1 and 2 have been removed.]
3.18
statistical quality control
part of quality control in which statistical methods are used (such as estimation and tests of parameters
and sampling inspection)
EXAMPLE The use of quality control charts.
[SOURCE: ISO 12491:1997, 3.2, modified — the EXAMPLE has been added.]
4 Abbreviated terms
CRM Certified reference material
DLS Dynamic light scattering
DMA Differential mobility analysis
DQ Sesign qualification
ESZ Electric sensing zone
IQ Installation qualification
OQ Operational qualification
PQ Performance qualification
RM Reference material
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ISO/TS 4807:2022(E)
SAXS Small angle X-ray scatteringPQ
SI International system of units
SQC Statistical quality control
5 Basic principles
5.1 Measurand definitions in particle size analysis
5.1.1 General
In general, two kinds of measurands can be distinguished.
— Non-operationally defined measurands are measurands where a physical unit can be directly related
to a property of a particle and where no further information is required in order to interpret the
value of this quantity. Examples for non-operationally defined measurands are a mass of a particle
or a distance between two points.
— Operationally defined measurands are measurands that are the result of a specific set of operations.
The quantity values of operationally defined measurands are only meaningful in connection with
this set of operations. Deviation from the specified set of operations does not only result in a wrong
result, but actually means that a different quantity is measured.
EXAMPLE 1 The impact toughness of a material as determined by for example, ISO 148-1. This is the energy
required to break a sample of specified dimensions (1 cm × 1 cm × 5 cm) that has a notch of specified width
depths with a hammer of specified dimensions. Deviation from the specifications of ISO 148-1 means that a
different procedure was applied and that the values obtained are not comparable to the impact toughness of
ISO 148-1. Note that the results of impact toughness measurements are expressed in joule, an SI unit. This shows
that operationally defined measurands can be expressed in SI units.
Meaningful comparisons of numerical values can only be made for quantities of the same kind. This
is immediately obvious for some non-operationally defined measurands: a comparison of a mass and
a length is meaningless. As indicated in Note 2 to entry of 3.1, expression in the same unit is required
but not sufficient in order to make results comparable. This is especially important for operationally
defined measurands.
EXAMPLE 2 In the example of impact toughness above, the energy required to break a sample of different
dimensions (e.g. 2 cm × 1 cm × 5 cm) is still expressed in J but it is impossible to say if a material with an impact
toughness of 85 J measured on a 2 cm × 1 cm × 5 cm sample is tougher than a material with an impact toughness
of 70 J as measured according to ISO 148-1.
This means that one should not expect that different operationally defined measurands yield the same
value. Samples may exist that give the same result for two unrelated methods, but this may be due
to coincidence. Conflicting values do not mean that one of the values is wrong, but simply reflect the
different response for the sample measured.
As will be explained below, the same principle applies to results from different methods for particle
size determinations: although the results can all be expressed (and traceable to) as metres, they are in
fact different kinds of quantities and not comparable unless very specific conditions are met.
5.1.2 Operationally defined measurands in particle characterisation: Equivalent diameters
None of the methods used for particle sizing actually measures a particle diameter. Doing so requires
applying a caliper to a particle or every individual particle of the sample. This is clearly impractical and
all particle sizing methods actually measure particle properties different from particle diameters and
relate these properties to the particle size. Examples of measured material properties for some particle
characterisation methods are given in Table 1.
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ISO/TS 4807:2022(E)
Table 1 — Selected measurement principles in particle characterisation, their measured
properties and information on how this property is expressed
Method Measured property Result are expressed as distribution of
Diameters of spheres with the same sedimen-
Sedimentation analysis Speed of sedimentation
tation velocity (equivalent Stokes’ diameter)
Diameters of spheres with the same diffusion
Dynamic light scattering,
Speed of diffusion coefficient (equivalent hydrodynamic
particle tracking analysis
diameter)
Differential mobility Electrical mobility of charged aerosol Diameters of spheres with the same electrical
analysis particles mobility
Drop in resistance when a particle passes
Electrical sensing zone Diameters of spheres with the same volume
through an aperture
Diameters of circles with the same circum-
Length (diameter, circumference) or area of a ference or area, also direct measurement
Image analysis
projection or reflection of the particle of maximum and minimum Feret diameter
possible
Light scattering particle Intensity of the light scattered by individual
counters particles
Diameters of spheres of the same light scat-
tering/extinction
Light extinction particle Extinction of light caused by individual
counters particles
Ultrasonic attenuation Frequency-dependent attenuation of Diameters of (usually spherical) particles
spectroscopy ultrasound which give the same attenuation spectrum
Single particle inductively
Diameters of spheres of the same mass of the
coupled plasma mass Mass of the selected element(s) per particle
selected element/compound
spectrometry
Angular distribution of elastically scattered Diameters of (usually spherical) particles
Small angle X-ray scattering
X-rays with the same angular distribution of X-rays
Diameters of spheres with the same angular
Laser diffraction Angular distribution of scattered light
distribution of light
Mass fractions passing sieves of specified
Sieving analysis Mass of material that passes a sieve
aperture size
NOTE Results can also differ in the way they are weighted (intensity, number, area etc.).
These different properties are subsequently expressed as lengths, namely as diameters of spheres
that show the same response, for example, having the same speed of sedimentation. These diameters
are called “equivalent diameters”. Equivalent diameters are operationally defined measurands: they
depend on the property measured (projected area, sedimentation velocity, etc.) and the definition to
which shape the property should be equivalent (e.g. equivalent sphere, cube, tetrahedron).
As none of the methods used for particle sizing actually measure the particle diameter, all results of
particle sizing methods are operationally defined. This also means that one should not expect that
different methods yield the same value unless the particles measured fulfil very specific requirements
(see 5.1.4). This non-comparability is clear when one looks at the properties actually measured, but is
hidden by the expression of these properties in the dimension of length. It is not surprising that the
speed of diffusion differs from the projected area but the fact that both are expressed as lengths of
equivalent spheres falsely suggests otherwise.
Conceptually there is no difference between the determination of the equivalent diameter of a single
particle and the determination of the distribution of equivalent diameters in an ensemble method:
in each case, a property is measured and related to spherical particles that behave the same way for
the chosen property. While relating the measured property to spherical particles is more complex for
ensemble methods, it is conceptually not different from relating the property of a single particle to the
same property of a sphere.
EXAMPLE In laser diffraction, the diffraction pattern of a sample is measured. Applying a chosen theory that
models the diffraction pattern of spherical particles, the particle size distribution of an ensemble of spherical
particles is calculat
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