ISO/DIS 22176

SLOVENSKI STANDARD
01-februar-2026
Kozmetika - Analizne metode - Validacija kvantitativnih analiznih metod z uporabo
celostnega pristopa
Cosmetics - Analytical methods - Validation of quantitative analytical methods using an
integrated approach
Titre manque
Ta slovenski standard je istoveten z: ISO/DIS 22176
ICS:
71.100.70 Kozmetika. Toaletni Cosmetics. Toiletries
pripomočki
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 22176
ISO/TC 217
Cosmetics — Analytical methods —
Secretariat: INSO
Validation of quantitative analytical
Voting begins on:
methods using an integrated
2026-01-07
approach
Voting terminates on:
ICS: 71.100.70
2026-04-01
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
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Reference number
DRAFT
International
Standard
ISO/DIS 22176
ISO/TC 217
Cosmetics — Analytical methods —
Secretariat: INSO
Validation of quantitative analytical
Voting begins on:
methods using an integrated
approach
Voting terminates on:
ICS: 71.100.70
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
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Published in Switzerland Reference number
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions .1
3.2 Symbols .5
4 General principles . 6
4.1 Reminder .6
4.2 Various conditions for the estimation of precision .6
4.3 Accuracy profile .7
5 Procedure . 9
5.1 Definition of the measured quantity .9
5.2 Definition of objectives .9
5.2.1 Choice of the scope of validation .9
5.2.2 Choice of acceptance limits .9
5.2.3 Choice of the β proportion .10
5.3 Selection of validation samples .10
5.3.1 Choice of the type of matrix or types of matrices .10
5.3.2 Methods for establishing reference values .10
5.4 Characterization plan for validation .11
5.4.1 Organization . . .11
5.4.2 Choice of the number of series, repetitions and concentration levels for the
characterization plan for validation . 12
5.5 Calibration plan for the indirect methods . 12
5.5.1 Organization . . . 12
5.5.2 Choice of the number of repetitions and concentration levels for the calibration
plan . 13
5.6 Testing .14
5.7 Calculation of predicted inverse concentrations for indirect methods . 15
5.7.1 Calculation of the calibration models . 15
5.7.2 Calculation of back-calculated concentrations by inverse prediction .16
5.8 Calculation of the validation criteria by concentration level .16
5.8.1 General .16
5.8.2 Trueness criteria by series .16
5.8.3 Trueness and precision criteria by concentration level .17
5.8.4 Calculation of the tolerance intervals.18
5.9 Construction of the accuracy profile .19
5.10 Interpretation of the accuracy profile for validation .21
5.10.1 General .21
5.10.2 Decision rules .21
5.10.3 Definition of the scope of validity . 23
5.10.4 Choice of a calibration procedure for the routine . 23
5.10.5 Influence and significance of the β proportion . 23
5.10.6 Identification of outliers .24
6 Conclusion of the validation .24
7 Management of the outcomes during routine use .24
Annex A (normative) Calculation of repeatability, intermediate precision and reproducibility
standard deviations .25
Annex B (normative) Contents of the validation file .27

iii
Annex C (informative) Setting-up an assay for determining the accuracy profile in the case of
NDELA in cosmetic samples .29
Annex D (informative) Influence of the value of β on the tolerance interval (R = 3 and s = 1) .39
IP
Annex E (informative) Contribution to the uncertainty calculation .40
Annex F (informative) Choice of acceptance limits. 41
Annex G (informative) Link to other guidelines based on ISO 5725-2 .42
Bibliography .43

iv
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
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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 217, Cosmetics.
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.

v
Introduction
The purpose of this document is to propose a characterization protocol for the validation of a quantitative
analysis method in the cosmetic field and thus responds to the requirements of ISO/IEC 17025, which
advocates a performance goal-based approach. The theoretical principles of this approach can be found in
[1] [2]
Bibliographic References and NF V 03 110:2010 .
Analytical methods for analyses of cosmetics need to be validated. Validation has been long considered as a
process consisting in individually verifying several different criteria, i.e. selectivity, repeatability, linearity,
[1]
trueness, etc. The integrated approach, also known as the global approach, as proposed since 2003 , is
based on the total error concept and the term ‘’global” means that only a single criterion has to be checked
to validate a method: the agreement between a future experimental result and the true value. This approach
[1],[3] [2]
has already been applied in the domains of pharmacy , agricultural chemistry NF V 03 110:2010 , and
[4]
is in agreement with quality assurance guidelines such as GLP or ISO/IEC 17025:2017 . This validation
process applies generally to already developed methods and integrates evaluations of the following criteria:
precision, trueness, linearity of the method, lower and upper limits of quantification, stability, ruggedness.
NOTE 1 This approach is also known as “combined approach” in the International Council for Harmonisation
[5]
Q2(R2) guideline regarding pharmaceuticals.
NOTE 2 Since this document deals with the validation of a quantitative analytical method, it does not propose a
specific approach for the limit of detection calculation. For this purpose, other standards and guidelines already exist.
The large number of cosmetic products and the variety of matrices present a challenge for an analytical
laboratory requiring that standardized methods be adapted for each type of sample. Additional difficulties
are linked to the very low concentrations to be measured, typically in the range of milligrams per kilogram
(mg/kg) or micrograms per kilogram (µg/kg). In such a context, criteria such as accuracy and uncertainty
of measurement of the analytical results are of the utmost importance.
When the concentration of a substance is determined by an analytical laboratory, it is important to evaluate
the gap between the measured value and the known true value. This difference indicates the trueness of
the analysis. If cosmetic samples are analysed several times in different conditions (laboratory, instrument,
operator), the individual results will present a dispersal around the average value which represents the
precision of the measurement. As for the individual measurement, it represents an error with the average
value and an inaccuracy with regard to the reference value (i.e. the true value).
Figure 1 — Illustration of the concepts of accuracy, precision and trueness
When a laboratory measures the concentration of a given substance in a cosmetic product sample, the value
which is obtained is thus characterized by a given accuracy which includes at the same time the notion of
trueness and precision (see Figure 1). It can also be considered as total error. The assurance that the accuracy
of a result is below acceptable limits, is thus one of the ways to make sure of the validity of a measurement.

vi
The accuracy profile (plot of accuracy versus concentration), such as it is developed in numerous domains
[3],[6],[7],[8],[9],[10],[11]
, is thus the way to know the accuracy on a result obtained with a given method applied
to a type of sample in the environment of a given laboratory.
To reach this accuracy profile, it is necessary to undergo a specific assay allowing to demonstrate the
validity of the analytical method, as well as the accuracy of the measurement for a given substance. In this
[12]
approach, it is necessary to determine a tolerance interval which contains a given proportion (β) of
future measured values inside (in average). If this tolerance interval is located inside a limit of acceptability
defined a priori, taking into consideration several parameters such as the type and concentration of analyte,
type of matrix, of analysis and conditions of the experiments, in this case, the method will be considered
as valid, and if it goes outside this limit of acceptability, the method will be considered as non-valid (see
Figure 2).
Key
mean value
true value
Figure 2 — Illustration of the validation principle

vii
DRAFT International Standard ISO/DIS 22176:2026(en)
Cosmetics — Analytical methods — Validation of quantitative
analytical methods using an integrated approach
1 Scope
This document defines an integrated approach for the validation of a quantitative analytical method, based
on the construction and interpretation of an accuracy profile, and specifies its characterization procedure.
This procedure is particularly applicable for internal validation in a cosmetic testing laboratory, but
its scope can be extended to the interpretation of data collected for an interlaboratory study designed
according to the recommendations of the ISO 5725-1. It does not apply to microbiological trials. The present
approach is particularly suited to handle the wide diversity of matrices in cosmetics. This document only
applies to already fully-developed and finalized methods for which selectivity/specificity have already been
studied and the scope of the method to be validated has already been defined, in terms of matrix types and
measurand (for example analyte) concentrations.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 5725-2:2019, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic
method for the determination of repeatability and reproducibility of a standard measurement method
ISO 11095:1996, Linear calibration using reference materials
ISO 13528:2022, Statistical methods for use in proficiency testing by interlaboratory comparison
ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and associated
terms (VIM)
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC Guide 99 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1.1
measurement
process of experimentally obtaining one or more quantity values that can reasonably be attributed to a
quantity
[SOURCE: ISO/IEC Guide 99:2007, 2.1, modified — Notes to entry have been excluded.]

3.1.2
measurand
quantity intended to be measured
Note 1 to entry: The term “analyte”, employed in chemistry, is a synonym of measurand, and is used more generally.
[SOURCE: ISO/IEC Guide 99:2007, 2.3, modified — Original notes to entry have been excluded and a new
note to entry has been added.]
3.1.3
measurement trueness
trueness
closeness of agreement between the average of values obtained by replicate measurements of the same or
similar objects under specified conditions and a reference quantity value
[SOURCE: ISO/IEC Guide 99:2007, 2.14, modified — Notes to entry have been excluded.]
3.1.4
measurement precision
precision
closeness of agreement between indications or measured quantity values obtained by replicate
measurements on the same or similar objects under specified conditions
[SOURCE: ISO/IEC Guide 99:2007, 2.15, modified — Notes to entry have been excluded.]
3.1.5
repeatability condition
condition of measurement, out of a set of conditions that includes the same measurement procedure, same
operator, same measuring system, same operating conditions and same location, and replicate measurements
on the same or similar objects over a short period of time
[SOURCE: ISO/IEC Guide 99:2007, 2.20, modified — Notes to entry have been excluded.]
3.1.6
measurement repeatability
repeatability
measurement precision under a set of repeatability conditions (3.1.5) of measurement
[SOURCE: ISO/IEC Guide 99:2007, 2.21]
3.1.7
intermediate precision condition
condition of measurement, out of a set of conditions that includes the same measurement procedure, same
location, and replicate measurements on the same or similar objects over an extended period of time, but
may include other conditions involving changes
[SOURCE: ISO/IEC Guide 99:2007, 2.22, modified — Notes to entry have been excluded.]
3.1.8
intermediate measurement precision
intermediate precision
measurement precision under a set of intermediate precision conditions (3.1.7) of measurement
[SOURCE: ISO/IEC Guide 99:2007, 2.23, modified — Notes to entry have been excluded.]
3.1.9
reproducibility condition of measurement
reproducibility condition
condition of measurement, out of a set of conditions that includes different locations, operators, measuring
systems, and replicate measurements on the same or similar objects
[SOURCE: ISO/IEC Guide 99:2007, 2.24, modified — Note to entry has been excluded.]

3.1.10
measurement reproducibility
reproducibility
measurement precision under reproducibility conditions of measurement (3.1.9)
[SOURCE: ISO/IEC Guide 99:2007, 2.25, modified — Note to entry has been excluded.]
3.1.11
measurement accuracy
accuracy
closeness of agreement between a measured quantity value and a true quantity value of a measurand
[SOURCE: ISO/IEC Guide 99:2007, 2.13, modified — Notes to entry have been excluded.]
3.1.12
verification
provision of objective evidence that a given item fulfils specified requirements, taking into account any
measurement uncertainty
[SOURCE: ISO/IEC Guide 99:2007, 2.44, modified — Notes to entry have been excluded.]
3.1.13
validation
verification, where the specified requirements are adequate for an intended use
Note 1 to entry: The term “characterization” applies to the method, whereas the term “verification” applies to the
outcomes. Validation of the method therefore consists of checking if the results are adequate for an intended use.
[SOURCE: ISO/IEC Guide 99:2007, 2.45, modified — Example has been excluded and a Note to entry has
been added.]
3.1.14
selectivity
property of a measuring system, used with a specified measurement procedure, whereby it provides
measured quantity values for one or more measurands such that the values of each measurand are
independent of other measurands or other quantities in the measuring system
Note 1 to entry: The IUPAC considers specificity as the final stage of selectivity.
[SOURCE: ISO/IEC Guide 99:2007, 4.13, modified — Examples and original notes to entry have been excluded.
A new note to entry has been added.]
3.1.15
reference value
quantity value whose associated measurement uncertainty is generally considered small enough so that the
value may be used as a basis for comparison with quantity values of the same kind
[SOURCE: ISO/IEC Guide 99:2007, 5.18, modified — Notes to entry have been excluded.]
3.1.16
scope
all of the types of matrix (3.1.22) to which the method applies, taking into account the range
of concentrations involved in validation
3.1.17
scope of validation
all of the types of matrix (3.1.22) to which the method and range of concentrations involved in validation applies
3.1.18
scope of validity
all of the types of matrix (3.1.22) to which the method and range of concentrations involved in validation
applies, and for which future outcomes obtained via the method will be considered valid

3.1.19
quantitative method
method of analysis which determines the quantity or weight fraction of an analyte so that it may be
expressed as a numeric value in the appropriate units
3.1.20
reference method
method of analysis recognized by experts or used as a reference by agreement between parties, which gives,
or is supposed to give the accepted reference value of the measurand
3.1.21
alternative method
method of analysis used by the laboratory instead of one or several reference methods (3.1.20)
3.1.22
matrix
set of properties of the sample and its components other than the analyte
Note 1 to entry: The matrix effect reflects the possible influence that these properties or components can have on the
instrumental response. For practical reasons, since the matrix effect can vary in the different stages of analysis, a type
of matrix is defined as a group of materials or products recognized by the analyst as having consistent behaviour with
regard to the method of analysis used.
3.1.23
series
set of measurements carried out under a set of repeatability conditions
Note 1 to entry: For example, a series includes measurements carried out on the same day and/or by the same operator.
3.1.24
accuracy profile
combination, in a graphic form, of one or several β-expectation tolerance intervals (3.1.25) calculated at
different concentrations, and of one or several acceptance intervals (3.1.26)
3.1.25
β-expectation tolerance interval
tolerance interval
interval which contains, on average, a defined proportion, β %, of future measurements, obtained according
to a given procedure and for a given concentration
Note 1 to entry: The limits of the interval are calculated based on trials conducted for the purpose of validation.
Note 2 to entry: A value of 80 % for β % means that, on average, one out of five results will be outside the limits of the
tolerance interval. See 5.10.
3.1.26
acceptance interval
specification of the performance required for the method, expressed as an acceptable deviation around the
reference value
Note 1 to entry: The limits of the interval are set by the client or by statutory requirements, sometimes according to
the concentration. They are expressed as ±λ as absolute values and in the units of the measurand, or (1 ± λ) × 100 as
relative values.
3.1.27
linearity
establishment of a linear relationship between the deduced (or quantified) quantities in the
samples and their reference values
Note 1 to entry: Linearity of the method is different from linearity of the response function of the measuring apparatus,
which only characterizes the instrumental response during calibration and is not essential for accurate quantitation.

3.1.28
validation sample
control sample
material to which the reference value may be assigned, either because it is a reference material (certified or
uncertified), or because the molecule to be assayed has been subjected to standard addition
3.1.29
limit of quantitation
the lowest and/or highest concentration of analyte that may be quantified under the experimental conditions
of the method. It corresponds to the lowest and/or highest concentration of the scope of validity (3.1.18)
Note 1 to entry: According to the SFSTP (French society for pharmaceutical sciences and technology), the lower limit
of quantitation is the smallest quantity of analyte in a sample that may be assayed under the experimental conditions
described with a defined level of accuracy.
3.1.30
limit of detection
measured quantity value, obtained by a given measurement procedure, for which the probability of falsely
claiming the absence of a component in a material is b, given a probability, α, of falsely claiming its presence
Note 1 to entry: The notation b used in this definition incurs a risk of type II error.
Note 2 to entry: IUPAC recommends default values for α and b equal to 0.05.
[SOURCE: ISO/IEC Guide 99:2007, 4.18, modified — Original notes to entry have been omitted and a new
note to entry has been added.]
3.2 Symbols
i series of measurements (i varying from 1 to I), includes k concentration levels (k varying from 1 to K), for
which j repetitions have been performed (j varying from 1 to J). The subscripts are written in the following
order: i,j,k. The random variables are written in upper case letters and their values in lower case letters.
Description of abbreviations used in formulae is given in Table 1.
Table 1 — Meaning of the different abbreviations used in formulae
Symbol Description
Reference value assigned to a calibration standard for series i (1 ≤ i ≤ I), repetition j (1 ≤ j ≤ J) and con-
centration k (1 ≤ k ≤ K)
x
ijk
or
Reference value assigned to a validation sample for series i, repetition j and concentration k.
Measurement of the instrumental or experimental response observed for a calibration standard or vali-
y
ijk
dation sample for series i, repetition j and concentration k.
Deduced value for a validation sample for series i, repetition j and concentration k, obtained either by
z
ijk
inverse prediction using a calibration model or by direct measurement.
Bias expressing the trueness error for a validation sample between the deduced value and its reference
b
ijk
value b = z − x
ijk ijk ijk
4 General principles
4.1 Reminder
The accuracy profile allows a statistical approach to validation. Formula (1) is used to describe a
measurement, z, of a measurand, Z, from a laboratory:
z = m + B + e (1)
where
m is the overall average for the homogeneous sample sent to the laboratories;
B is the bias component of the laboratory under conditions of repeatability;
e is the random error occurring in each measurement, under conditions of repeatability.
As part of an interlaboratory study, the bias component B comes from the laboratory, but it may also come
from any other source of uncertainty in an intralaboratory study, such as the day, operator, instrument, etc.
In addition to the statistical methods for calculating the accuracy criteria, the present document also
provides details of the organization of data collection and precautions to be taken.
4.2 Various conditions for the estimation of precision
According to its definition, precision can be estimated under various conditions. In any case, precision
is quantified based on a standard deviation, be this for repeatability s , intermediate precision s or
r IP
reproducibility s . A complexity scale may be established between these different standard deviations,
R
according to the number of sources of variation. Figure 3 illustrates this gradation, from conditions of
repeatability where there is no identified variation factor and/or systematic variation component for
calculating the deviation between repetitions, to the various possibilities for estimating intermediate
precision and, finally, conditions of reproducibility for which the number of sources is not known.
To simplify presentation, the notion of series refers to a set of repetitions performed under conditions of
repeatability: a series groups together all of the measurements made under the same conditions, e.g. the
same day, the same operator or a short period of time. For certain methods applying to samples that are
highly unstable over time, the chosen series effect should be the operator rather than the day; the series will
thus include repetitions performed by the same operator:

Figure 3 — Various estimations of the precision of a method according to the sources of variation
involved
More complicated models can be used, as in the following example, in which different laboratories, days,
operators and instruments are combined to give four series in a multi-factorial design with four factors.
Series Laboratories Days Operators Instruments
1 Laboratory 1 Day 1 Operator 1 Instrument 1
2 Laboratory 1 Day 2 Operator 1 Instrument 2
3 Laboratory 2 Day 3 Operator 2 Instrument 3
4 Laboratory 2 Day 4 Operator 2 Instrument 4
In general, the choice of sources of variation for the measurement series shall reflect as best possible the
components of variability that are likely to arise upon routine application of the method to be validated.
NOTE For the purposes described in this document, it is essential to collect data in several series and to control
the sources of variation. Otherwise, it will not be possible to construct an accuracy profile.
4.3 Accuracy profile
From the intermediate precision or reproducibility standard deviation, calculated according to the
calculations described in Annex A, the β-expectation tolerance interval can be obtained, which includes a
proportion, β, of future outcomes.
All calculations are performed separately for each level of concentration k, allowing k precision standard
deviations and then k tolerance intervals to be obtained, which are brought together to construct the
accuracy profile. Figure 4 shows an example of an accuracy profile constructed using three concentrations,
0,4 mg/kg, 2,0 mg/kg and 4,0 mg/kg, which defines the scope of validation of the method to be validated.
The accuracy profile includes the following graphic elements:
— on the horizontal axis: the theoretical concentrations (the concentration reference values);
— on the vertical axis (simultaneously):
— the limits of the β−expectation tolerance intervals, calculated from the deduced concentrations and
expressed as percentages (recovery rate or relative accuracy);

— the acceptance intervals, defined according to the method's objective and expressed in the same way
as the tolerance intervals.
The interpretation strategy for this graph is described in detail in 5.10. Nevertheless, both the acceptance
limits and the proportion β, which is used to calculate the tolerance intervals, are strictly dependent on the
method's context of use and shall be adapted to each individual case. In Figure 4, in the area between the
vertical dashed lines, the method is capable of producing a mean proportion, β, of outcomes that lies within
the acceptance limits: the method is therefore valid within this scope. The scope of validation of the method
is the scope that was initially chosen for validation.
Key
1 mean recovery rate (%)
2 upper tolerance limit
3 upper acceptance limit
4 lower tolerance limit
5 lower acceptance limit
6 lower limit of quantitation
7 scope of validity
8 scope of validation
Y recovery (%)
X known concentration (mg/kg)
Figure 4 — Accuracy profile created using three concentrations
Each grey circle represents the ratio of the mean deduced concentration for the level, expressed as a mean
recovery rate (%) for the concentration, and quantifies the trueness. The horizontal dashed lines delimit
the acceptance interval, and the solid lines delimit the tolerance interval, calculated from the intermediate
precision standard deviations for each concentration. The vertical dashed lines delimit the scope of validity,
within which the method is capable of producing a high and known percentage of acceptable results.
Generally speaking, in order to comply with the statistical models used, repetitions shall be performed
under intermediate precision or reproducibility conditions, using homogeneous validation samples.

5 Procedure
5.1 Definition of the measured quantity
Define the measured quantity according to the procedure for the method, specifying the formulae used to
calculate the final result and the method used to reach this result. In the field of cosmetics, we are often in
the case of indirect methods, which require prior calibration to calculate the concentration of the unknown
samples. These methods involve a two-step approach: firstly, the calibration curve shall be plotted, using
the same physicochemical principle used for the samples; measurements are then made using the unknown
samples, and their concentrations are calculated using the calibration model. In case of direct methods,
which do not require calibration, the situation is even simpler as there is no need of a calibration curve and
the measurement on the unknown samples provides the concentration directly.
It is essential that the quantity measured during the trial corresponds to that which will be routinely
measured. In particular, if the procedure dictates that the final outcome be expressed following a single
measurement, the result of a validation trial shall not be expressed as the mean value of several repetitions.
5.2 Definition of objectives
5.2.1 Choice of the scope of validation
Define the scope of validation of the method in the form of a range of absolute or relative concentrations,
e.g. between 1 g and 60 g or between 1 µg/L and 500 µg/L. Practically speaking, it is through the choices
made — in terms of the range of concentrations for one or several types of matrix — when developing the
experimental design that it is possible to demonstrate the scope within which the method is effectively
valid and whether it is able to provide acceptable outcomes (5.4 and 5.5). The scope concerned by this
demonstration is called the scope of validity and may be smaller than the previously defined scope of
validation of the method.
The choice of the method's scope may correspond to a legal requirement.
If samples are encountered during routine use of the method with concentrations that do not lie within the
scope of validity, extrapolation is not permitted. In case a dilution of the sample is performed prior to the
application of the method, the related uncertainty of this additional step must be taken into account, unless
it can be proved insignificant. Or else a complementary study shall be carried out to extend the scope.
Poor definition of the scope of the method can have significant consequences on validity, especially in terms
of specificity, interference and cross-reactivity.
5.2.2 Choice of acceptance limits
Acceptance limits reflect the practical objectives of users, in terms of maximum allowable total error. They
delimit an interval on both sides of the reference value, and are expressed either as ± λ, when expressed as
absolute values in the same unit as the measurand, or (1 ± λ) × 100 as relative values.
Wherever possible, the acceptance limits must be defined by referring to a regulatory requirement, a client's
requirement, a professional practice or to the performances of a standard method which deals with the
considered measurand.
If there is no specified requirement, the final users’ expectations must be considered. For example,
acceptance limits can be defined according to the presumed measurement uncertainty which is expected at
the end of the validation process.
It is beyond the scope of this document to set requirements for λ, but indicative values can be found in Annex F.
Acceptance limits can be constant within the scope of validation or variable according to the concentration
levels. For instance, acceptance limits are usually set hig
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