SIST-TS ISO/TS 13530:2013
Water quality - Guidance on analytical quality control for chemical and physicochemical water analysis
Water quality - Guidance on analytical quality control for chemical and physicochemical water analysis
This Technical Specification provides comprehensive guidance on within-laboratory and between-laboratory quality control for ensuring the production of results with a known level of accuracy in the analysis of waters. This Technical Specification is applicable to the chemical and physicochemical analysis of all types of waters. It is not intended for application to the analysis of sludges and sediments (although many of its general principles are applicable to such analysis) and it does not address the biological or microbiological examination of water. Whilst sampling is an important aspect, this is only briefly considered. Analytical quality control, as described in this Technical Specification, is intended for application to water analysis carried out within a quality-assurance programme. This Technical Specification does not address the detailed requirements of quality assurance for water analysis, which can be found in the EURACHEM/CITACGuide (2002) [20]. The recommendations of this Technical Specification are in agreement with the requirements of established
quality-assurance documentation (e.g. ISO/IEC 17025). This Technical Specification is applicable to the use of all analytical methods within its field of application, although its detailed recommendations may require interpretation and adaptation to deal with certain types of determinands (for example, non-specific determinands, such as suspended solids or biochemical oxygen demand, BOD). In the event of any disparity between the recommendations of this Technical Specification
and the requirements of a standard method of analysis, the requirements of the method should prevail.
Qualité de l'eau - Lignes directrices pour le contrôle de qualité analytique pour l'analyse chimique et physicochimique de l'eau
L'ISO/TS 13530:2009 fournit des lignes directrices d�taill�es relatives au contr�le qualit� intralaboratoire et interlaboratoires afin de s'assurer que les r�sultats de l'analyse des eaux sont obtenus avec un niveau d'exactitude connue.
L'ISO/TS 13530:2009 est applicable � l'analyse chimique et physicochimique de tous les types d'eaux. Elle ne s'applique pas � l'analyse des boues et s�diments (m�me si la plupart de ses principes g�n�raux s'appliquent � de telles analyses) et ne concerne pas l'examen biologique ou microbiologique de l'eau. Bien que l'�chantillonnage soit un aspect important, celui-ci n'est que bri�vement abord�.
Kakovost vode - Navodilo za kontrolo kakovosti za kemijske in fizikalno-kemijske analize vode
To tehnično poročilo podaja celostne smernice za nadzor laboratorijske in medlaboratorijske kakovosti za pridobivanje rezultatov analiz vode z znano ravnjo natančnosti. To tehnično poročilo velja za kemijske in fizikalno-kemijske analize vseh vrst vode. Ni namenjeno uporabi za analizo blat in sedimentov (čeprav številna splošna načela iz tega poročila veljajo za takšno analizo) ter ne obravnava biološkega ali mikrobiološkega preučevanja vode. Čeprav je vzorčenje pomemben vidik, je upoštevan le bežno. Kontrola kakovosti analize, kot je opisana v tem tehničnem poročilu, je namenjena uporabi analize vode, ki se izvaja v okviru programa zagotavljanja kakovosti. To tehnično poročilo ne obravnava podrobnih zahtev za zagotavljanje kakovosti analize vode, ki je opisano v smernicah EURACHEM/CITAC (2002) [20]. Priporočila iz tega tehničnega poročila so skladna z zahtevami uveljavljene dokumentacije glede zagotavljanja kakovosti (npr. ISO/IEC 17025). To tehnično poročilo velja za uporabo vseh analitičnih metod na področju uporabe, vendar je za podrobna priporočila v njem potrebna interpretacija in prilagoditev, ki omogoča obravnavanje določenih vrst analitov (npr. nespecifičnih analitov, kot so neraztopljene trdne snovi ali biokemijska potreba po kisiku, BPK). V primeru neskladnosti med priporočili iz tega tehničnega poročila in zahtevami standardnih metod analize prevladajo zahteve metode.
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TECHNICAL ISO/TS
SPECIFICATION 13530
First edition
2009-03-15
Water quality — Guidance on analytical
quality control for chemical and
physicochemical water analysis
Qualité de l'eau — Lignes directrices pour le contrôle de qualité
analytique pour l'analyse chimique et physicochimique de l'eau
Reference number
ISO/TS 13530:2009(E)
©
ISO 2009
---------------------- Page: 1 ----------------------
ISO/TS 13530:2009(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
COPYRIGHT PROTECTED DOCUMENT
© ISO 2009
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2009 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 13530:2009(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
3.1 Terms related to measurement methods . 2
3.2 Terms related to measurement results. 3
3.3 Terms related to uncertainty . 5
4 Performance characteristics of analytical systems . 5
4.1 Introduction . 5
4.2 Scope of the method . 6
4.3 Calibration . 6
4.4 Limit of detection, limit of quantification . 10
4.5 Interferences and matrix effects . 12
4.6 Accuracy (trueness and precision) and uncertainty of measurement. 14
4.7 Robustness . 14
4.8 Fitness for purpose . 15
5 Choosing analytical systems . 15
5.1 General considerations. 15
5.2 Practical considerations . 16
6 Intralaboratory quality control. 16
6.1 General. 16
6.2 Terms relating to within-laboratory quality control . 17
6.3 Control of accuracy . 17
6.4 Control of trueness. 18
6.5 Control of precision. 19
6.6 Principles of applying control charts . 21
6.7 Conclusions . 25
6.8 Control charts with fixed quality criterions (target control charts). 27
7 Quality control in sampling . 27
8 Interlaboratory quality control. 28
9 Quality control for lengthy analytical procedures or analysis undertaken infrequently or
at an ad hoc basis. 28
9.1 Quality control for lengthy analytical procedures. 28
9.2 Analysis undertaken infrequently or on an ad hoc basis. 29
Annex A (informative) Verification of the limit of detection and the limit of quantification . 30
Annex B (informative) The nature and sources of analytical errors . 32
Annex C (informative) Estimating the measurement uncertainty . 35
Annex D (informative) Example for performing quality control for lengthy analytical procedures. 37
Bibliography . 38
© ISO 2009 – All rights reserved iii
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ISO/TS 13530:2009(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of document:
⎯ an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
⎯ an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
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.
ISO/TS 13530 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2,
Physical, chemical and biochemical methods.
This first edition of ISO/TS 13530 cancels and replaces ISO/TR 13530:1997, which has been technically
revised.
iv © ISO 2009 – All rights reserved
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TECHNICAL SPECIFICATION ISO/TS 13530:2009(E)
Water quality — Guidance on analytical quality control for
chemical and physicochemical water analysis
1 Scope
This Technical Specification provides comprehensive guidance on within-laboratory and between-laboratory
quality control for ensuring the production of results with a known level of accuracy in the analysis of waters.
This Technical Specification is applicable to the chemical and physicochemical analysis of all types of waters.
It is not intended for application to the analysis of sludges and sediments (although many of its general
principles are applicable to such analysis) and it does not address the biological or microbiological
examination of water. Whilst sampling is an important aspect, this is only briefly considered.
Analytical quality control, as described in this Technical Specification, is intended for application to water
analysis carried out within a quality-assurance programme. This Technical Specification does not address the
detailed requirements of quality assurance for water analysis, which can be found in the EURACHEM/CITAC
[20]
Guide (2002) .
The recommendations of this Technical Specification are in agreement with the requirements of established
quality-assurance documentation (e.g. ISO/IEC 17025).
This Technical Specification is applicable to the use of all analytical methods within its field of application,
although its detailed recommendations may require interpretation and adaptation to deal with certain types of
determinands (for example, non-specific determinands, such as suspended solids or biochemical oxygen
demand, BOD). In the event of any disparity between the recommendations of this Technical Specification
and the requirements of a standard method of analysis, the requirements of the method should prevail.
2 Normative references
The following referenced documents are indispensable for the application 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 3534-2:2006, Statistics — Vocabulary and symbols — Part 2: Applied statistics
ISO 5725 (all parts), Accuracy (trueness and precision) of measurement methods and results
ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 1: Statistical evaluation of the linear calibration function
ISO 8466-2, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 2: Calibration strategy for non-linear second-order calibration functions
ISO 13528:2005, Statistical methods for use in proficiency testing by interlaboratory comparisons
ISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories
ISO Guide 35, Reference materials — General and statistical principles for certification
© ISO 2009 – All rights reserved 1
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ISO/TS 13530:2009(E)
ISO/IEC Guide 43-1, Proficiency testing by interlaboratory comparisons — Part 1: Development and operation
of proficiency testing schemes
ISO/IEC Guide 43-2, Proficiency testing by interlaboratory comparisons — Part 2: Selection and use of
proficiency testing schemes by laboratory accreditation bodies
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Terms related to measurement methods
3.1.1
validation
confirmation by examination and the provision of objective evidence that the particular requirements for the
specific intended use are fulfilled
[ISO/IEC 17025:2005]
3.1.2
accuracy
closeness of agreement between a test result or measurement result and the true value
NOTE 1 In practice, the accepted reference value (3.2.6) is substituted for the true value.
NOTE 2 The term “accuracy”, when applied to a set of test or measurement results, involves a combination of random
components and a common systematic error or bias component.
NOTE 3 Accuracy refers to a combination of trueness and precision.
[ISO 3534-2:2006]
3.1.3
bias
difference between the expectation of a test result or measurement result and a true value
[ISO 3534-2:2006]
3.1.4
trueness
closeness of agreement between the expectation of a test result or a measurement result and a true value
NOTE 1 The measure of trueness is usually expressed in terms of bias.
NOTE 2 Trueness is sometimes referred to as “accuracy of the mean”. This usage is not recommended.
NOTE 3 In practice, the accepted reference value is substituted for the true value.
[ISO 3534-2:2006]
3.1.5
precision
closeness of agreement between independent test/measurement results obtained under stipulated conditions
NOTE 1 Precision depends only on the distribution of random errors and does not relate to the true value or the
specified value.
NOTE 2 The measure of precision is usually expressed in terms of imprecision and computed as a standard deviation
of the test results or measurement results. Less precision is reflected by a larger standard deviation.
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ISO/TS 13530:2009(E)
NOTE 3 Quantitative measures of precision depend critically on the stipulated conditions. Repeatability conditions and
reproducibility conditions are particular sets of extreme stipulated conditions.
[ISO 3534-2:2006]
3.1.6
limit of detection
output signal or value above which it can be affirmed with a stated level of confidence, for example 95 %, that
a sample is different from a blank sample containing no determinand of interest
[ISO 6107-2:2006]
3.1.7
limit of quantification
stated multiple of the limit of detection, for example, two or three times the limit of detection, at a concentration
of the determinand that can reasonably be determined with an acceptable level of accuracy and precision
NOTE Limit of quantification can be calculated using an appropriate standard or sample, and may be obtained from
the lowest calibration point on the calibration curve (excluding the blank).
[ISO 6107-2:2006]
3.1.8
analytical run
group of measurements or observations carried out together, either simultaneously or sequentially, without
interruption, on the same instrument by the same analyst using the same reagents
NOTE 1 An analytical run may consist of more than one batch of analyses. During an analytical run, the accuracy and
precision of the measuring system is expected to be stable.
NOTE 2 Definition taken from Reference [33] in the Bibliography.
3.1.9
batch of analyses
group of measurements or observations of standards, samples and/or control solutions which have been
performed together in respect of all procedures, either simultaneously or sequentially, by the same analysts
using the same reagents, equipment and calibration
3.2 Terms related to measurement results
3.2.1
error of measurement
test result or measurement result minus the true value
NOTE 1 In practice, the accepted reference value is substituted for the true value.
NOTE 2 Error is the sum of random errors and systematic errors.
NOTE 3 Adapted from ISO 3534-2:2006.
3.2.2
systematic error of result
component of the error of result which, in the course of a number of test results or measurement results, for
the same characteristic or quantity, remains constant or varies in a predictable manner
NOTE Systematic errors and their causes can be known or unknown.
[ISO 3534-2:2006]
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ISO/TS 13530:2009(E)
3.2.3
random error of result
component of the error of result which, in the course of a number of test results or measurement results, for
the same characteristic or quantity, varies in an unpredictable manner
NOTE It is not possible to correct for random error.
[ISO 3534-2:2006]
3.2.4
true value
value which characterizes a quantity or quantitative characteristic perfectly defined in the conditions which
exist when that quantity or quantitative characteristic is considered
NOTE The true value of a quantity or quantitative characteristic is a theoretical concept and, in general, cannot be
known exactly.
[ISO 3534-2:2006]
3.2.5
conventional true value
value of a quantity or quantitative characteristic which, for a given purpose, may be substituted for a true value
NOTE A conventional true value is, in general, regarded as being sufficiently close to the true value for the difference
to be insignificant for the given purpose.
[ISO 3534-2:2006]
3.2.6
accepted reference value
value that serves as an agreed-upon reference for comparison
NOTE The accepted reference value is derived as:
a) a theoretical or established value, based on scientific principles;
b) an assigned or certified value, based on experimental work of some national or international organization;
c) a consensus or certified value, based on collaborative experimental work under the auspices of a scientific or
technical group;
d) the expectation, i.e. the mean of a specified set of measurements, when a), b) and c) are not available.
[ISO 3534-2:2006]
3.2.7
certified reference material
reference material, accompanied by a certificate, one or more of whose property values are certified by a
procedure which establishes traceability to an accurate realization of the unit in which the property values are
expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence
NOTE Definition taken from Reference [36] in the Bibliography.
3.2.8
metrological traceability
property of a measurement result relating the result to a stated metrological reference through an unbroken
chain of calibrations of a measuring system or comparisons, each contributing to the stated measurement
uncertainty
[ISO/IEC Guide 99:2007]
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ISO/TS 13530:2009(E)
3.3 Terms related to uncertainty
3.3.1
uncertainty of measurement
non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand,
based on the information used
[ISO/IEC Guide 99:2007]
3.3.2
standard uncertainty
u(x )
i
uncertainty of the result x of a measurement expressed as a standard deviation
i
[ISO/IEC Guide 98-3:2008]
3.3.3
combined standard uncertainty
u (y)
c
standard measurement uncertainty that is obtained using the individual standard measurement uncertainties
associated with the input quantities in a measurement model
[ISO/IEC Guide 99:2007]
3.3.4
expanded uncertainty
U
product of a combined standard measurement uncertainty and a factor larger than the number one
NOTE 1 The factor depends upon the type of probability distribution of the output quantity in a measurement model
and on the selected coverage probability.
NOTE 2 The term “factor” in this definition refers to a coverage factor.
[ISO/IEC Guide 99:2007]
3.3.5
coverage factor
k
numerical factor used as a multiplier of the combined standard uncertainty in order to obtain an expanded
uncertainty
NOTE A coverage factor is typically in the range from 2 to 3.
[ISO/IEC Guide 98-3:2008]
4 Performance characteristics of analytical systems
4.1 Introduction
ISO/IEC 17025 requires the validation of methods; the validation process is described in detail in EURACHEM
[18]
Guide (1998) . Primary validation is part of the development of a new analytical method, and is performed
during the standardization of the method. Important points to be considered for the primary validation of an
analytical method are the following:
⎯ scope of the method;
⎯ calibration;
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ISO/TS 13530:2009(E)
⎯ limit of detection/limit of quantification;
⎯ interferences;
⎯ estimation of accuracy (trueness and precision);
⎯ uncertainty of measurement;
⎯ robustness;
⎯ fitness for purpose.
According to ISO/IEC 17025, the laboratory shall confirm that it can correctly operate standard methods
before applying these methods. This procedure is called secondary validation, where emphasis is laid on
calibration and interferences, as well as the laboratory limit of quantitation and measurement uncertainty. In
4.2 to 4.8, the topics calibration and quantification, matrix effects and measurement uncertainty are dealt with
especially.
4.2 Scope of the method
A clear definition should be given of the forms of the substance that are determined by the procedure and also,
when necessary to avoid ambiguity, those forms that are not capable of determination. At this point, it is worth
emphasizing that the analyst's selection of an analytical method should meet the user's definition of the
determinand. Non-specific determinands need the use of rigorously stipulated analytical methods in order to
obtain reliable and comparable results.
Many substances exist in water in a variety of forms or “species”, and many analytical systems provide a
differential response to the various forms. For example, when a separation of “dissolved” and “particulate”
material is required, special care is necessary to define precisely the nature and pore-size of the filter to be
used.
A precise description of the types and natures of samples is important before the analytical system can be
chosen. The precautions to be taken when a sample is analysed will depend to a high degree on the sample.
The analyst needs information that is as complete as possible on sample types, concentration levels and
possible interferences. The scope should contain a clear statement of the types of sample and sample
matrices for which the procedure is suitable. If necessary, a statement should also be made of important
sample types and matrices for which the procedure is not suitable.
The range of application corresponds to the lowest and highest concentrations for which tests of precision and
bias have been carried out using the system without modification. Where an extension can be used to enable
the examination of samples containing concentrations greater than the upper limit, such as by analysis after
dilution, then it should be regarded as a different procedure but whose performance characteristics may be
inferred from the values quoted for the original.
The concentration range of interest can have a marked effect on the choice of analytical technique; of primary
concern is the smallest concentration of interest.
4.3 Calibration
4.3.1 Basics of calibration and quantification
A calibration function is determined from information values y , obtained by measuring given standard
i
concentrations x . The resulting standard deviation of the method s or confidence interval is a performance
i xo
characteristic of this calibration, not a performance characteristic of the quantification. Quantification of the
analyte content of samples using a calibration function is based on interpolation. The most important
performance characteristic for quantification is the estimation of measurement uncertainty (see 4.6) where the
uncertainty of calibration is one of the contributions.
6 © ISO 2009 – All rights reserved
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ISO/TS 13530:2009(E)
Depending on the kind of the functional relationship between the analyte concentration and the measurement
response, different mathematical or statistical tools can be used. Mathematical and statistical models are
subject to different assumptions; therefore, not only is the performance of the analytical equipment essential
but also the kind of mathematical approach. The models should help the analyst to find a clear and reliable
functional relationship for calibration. The models should not limit the capabilities of the analytical equipment.
Therefore, the selection of the calibration model should be undertaken carefully, taking into consideration the
fitness for purpose and the measurement uncertainty required.
⎯ Model of linear regression (ISO 8466-1): the classical model for calibration with the limitations of normal
distribution of the responses and a homogeneity of variances over the working range. Normally, this
homogeneity of variances is only given in a working range of one or at maximum two decades of
concentration. This fact limits the applicability.
⎯ Model of non-linear second-order calibration functions (ISO 8466-2): after discovering a significant non-
linearity. This model has the same limitations as linear regression: normal distribution of the responses
and homogeneity of variances over the working range.
⎯ Model of weighted regression, weighting the information value with the reciprocal variance, calibration
over more than a decade of concentration range is possible.
⎯ Calibration over more than one decade of concentration with at least two concentrations, e.g. for
inductively coupled plasma/mass spectrometry (ICP/MS). Linearity must have been checked beforehand
with a minimum of five concentrations, e.g. by graphical presentation.
NOTE Detailed instructions on calibration procedures are given in References [26] and [28] in the Bibliography.
All these kinds of calibration should be tested for their contribution to measurement uncertainty. For example,
analyse N times, as a minimum in triplicate, an independent standard or a certified reference material within
the concentration range of interest, and calculate the results in accordance with the applied calibration method.
The standard uncertainty component, s , representing the deviation of the single results, ρ , from the reference
p i
value, ρ, is calculated as follows:
N
2
ρρ−
()
∑ i
i=1
s = (1)
p
N−1
where
s is the standard uncertainty component from calibration;
p
N is the number of replicate measurements.
N should be chosen with respect to the confidence required. s should be compared with the respective target
p
measurement uncertainty to set the tolerable amount.
4.3.2 Calibration strategies
4.3.2.1 Basic or instrument calibration
This type of calibration is carried out without matrix components and without sample preparation; for
calibration, pure standard solutions are used. This is inexpensive and directly suited for quantification, if matrix
components do not change the slope and the intercept of the calibration function significantly. Normally this
calibration is more precise than a calibration including all sample preparation steps.
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ISO/TS 13530:2009(E)
4.3.2.2 Calibration with matrix material
This kind of calibration is comparable with basic calibration (4.3.2.1). No sample preparation steps are carried
out. Instead of the pure solutions of the standards, solutions of the standard substances in analyte-free matrix
or artificial matrix are used.
4.3.2.3 Calibration over the total procedure
This type of calibration includes all sample preparation steps, and the calibration solutions are prepared with a
representative matrix material. It is suitable to show whether matrix components or sample preparation steps
do or do not change the slope and intercept of the calibration function compared to the basic calibration
function. Frequently, it is not easy to find a representative matrix material to use it as a basis of calibration
solutions. In water
...
SLOVENSKI STANDARD
SIST-TS ISO/TS 13530:2013
01-september-2013
1DGRPHãþD
SIST ENV ISO 13530:2000
Kakovost vode - Navodilo za kontrolo kakovosti za kemijske in fizikalno-kemijske
analize vode
Water quality - Guidance on analytical quality control for chemical and physicochemical
water analysis
Qualité de l'eau - Lignes directrices pour le contrôle de qualité analytique pour l'analyse
chimique et physicochimique de l'eau
Ta slovenski standard je istoveten z: ISO/TS 13530:2009
ICS:
13.060.45 Preiskava vode na splošno Examination of water in
general
SIST-TS ISO/TS 13530:2013 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST-TS ISO/TS 13530:2013
---------------------- Page: 2 ----------------------
SIST-TS ISO/TS 13530:2013
TECHNICAL ISO/TS
SPECIFICATION 13530
First edition
2009-03-15
Water quality — Guidance on analytical
quality control for chemical and
physicochemical water analysis
Qualité de l'eau — Lignes directrices pour le contrôle de qualité
analytique pour l'analyse chimique et physicochimique de l'eau
Reference number
ISO/TS 13530:2009(E)
©
ISO 2009
---------------------- Page: 3 ----------------------
SIST-TS ISO/TS 13530:2013
ISO/TS 13530:2009(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
COPYRIGHT PROTECTED DOCUMENT
© ISO 2009
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2009 – All rights reserved
---------------------- Page: 4 ----------------------
SIST-TS ISO/TS 13530:2013
ISO/TS 13530:2009(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
3.1 Terms related to measurement methods . 2
3.2 Terms related to measurement results. 3
3.3 Terms related to uncertainty . 5
4 Performance characteristics of analytical systems . 5
4.1 Introduction . 5
4.2 Scope of the method . 6
4.3 Calibration . 6
4.4 Limit of detection, limit of quantification . 10
4.5 Interferences and matrix effects . 12
4.6 Accuracy (trueness and precision) and uncertainty of measurement. 14
4.7 Robustness . 14
4.8 Fitness for purpose . 15
5 Choosing analytical systems . 15
5.1 General considerations. 15
5.2 Practical considerations . 16
6 Intralaboratory quality control. 16
6.1 General. 16
6.2 Terms relating to within-laboratory quality control . 17
6.3 Control of accuracy . 17
6.4 Control of trueness. 18
6.5 Control of precision. 19
6.6 Principles of applying control charts . 21
6.7 Conclusions . 25
6.8 Control charts with fixed quality criterions (target control charts). 27
7 Quality control in sampling . 27
8 Interlaboratory quality control. 28
9 Quality control for lengthy analytical procedures or analysis undertaken infrequently or
at an ad hoc basis. 28
9.1 Quality control for lengthy analytical procedures. 28
9.2 Analysis undertaken infrequently or on an ad hoc basis. 29
Annex A (informative) Verification of the limit of detection and the limit of quantification . 30
Annex B (informative) The nature and sources of analytical errors . 32
Annex C (informative) Estimating the measurement uncertainty . 35
Annex D (informative) Example for performing quality control for lengthy analytical procedures. 37
Bibliography . 38
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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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of document:
⎯ an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
⎯ an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
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.
ISO/TS 13530 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2,
Physical, chemical and biochemical methods.
This first edition of ISO/TS 13530 cancels and replaces ISO/TR 13530:1997, which has been technically
revised.
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SIST-TS ISO/TS 13530:2013
TECHNICAL SPECIFICATION ISO/TS 13530:2009(E)
Water quality — Guidance on analytical quality control for
chemical and physicochemical water analysis
1 Scope
This Technical Specification provides comprehensive guidance on within-laboratory and between-laboratory
quality control for ensuring the production of results with a known level of accuracy in the analysis of waters.
This Technical Specification is applicable to the chemical and physicochemical analysis of all types of waters.
It is not intended for application to the analysis of sludges and sediments (although many of its general
principles are applicable to such analysis) and it does not address the biological or microbiological
examination of water. Whilst sampling is an important aspect, this is only briefly considered.
Analytical quality control, as described in this Technical Specification, is intended for application to water
analysis carried out within a quality-assurance programme. This Technical Specification does not address the
detailed requirements of quality assurance for water analysis, which can be found in the EURACHEM/CITAC
[20]
Guide (2002) .
The recommendations of this Technical Specification are in agreement with the requirements of established
quality-assurance documentation (e.g. ISO/IEC 17025).
This Technical Specification is applicable to the use of all analytical methods within its field of application,
although its detailed recommendations may require interpretation and adaptation to deal with certain types of
determinands (for example, non-specific determinands, such as suspended solids or biochemical oxygen
demand, BOD). In the event of any disparity between the recommendations of this Technical Specification
and the requirements of a standard method of analysis, the requirements of the method should prevail.
2 Normative references
The following referenced documents are indispensable for the application 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 3534-2:2006, Statistics — Vocabulary and symbols — Part 2: Applied statistics
ISO 5725 (all parts), Accuracy (trueness and precision) of measurement methods and results
ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 1: Statistical evaluation of the linear calibration function
ISO 8466-2, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 2: Calibration strategy for non-linear second-order calibration functions
ISO 13528:2005, Statistical methods for use in proficiency testing by interlaboratory comparisons
ISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories
ISO Guide 35, Reference materials — General and statistical principles for certification
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SIST-TS ISO/TS 13530:2013
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ISO/IEC Guide 43-1, Proficiency testing by interlaboratory comparisons — Part 1: Development and operation
of proficiency testing schemes
ISO/IEC Guide 43-2, Proficiency testing by interlaboratory comparisons — Part 2: Selection and use of
proficiency testing schemes by laboratory accreditation bodies
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Terms related to measurement methods
3.1.1
validation
confirmation by examination and the provision of objective evidence that the particular requirements for the
specific intended use are fulfilled
[ISO/IEC 17025:2005]
3.1.2
accuracy
closeness of agreement between a test result or measurement result and the true value
NOTE 1 In practice, the accepted reference value (3.2.6) is substituted for the true value.
NOTE 2 The term “accuracy”, when applied to a set of test or measurement results, involves a combination of random
components and a common systematic error or bias component.
NOTE 3 Accuracy refers to a combination of trueness and precision.
[ISO 3534-2:2006]
3.1.3
bias
difference between the expectation of a test result or measurement result and a true value
[ISO 3534-2:2006]
3.1.4
trueness
closeness of agreement between the expectation of a test result or a measurement result and a true value
NOTE 1 The measure of trueness is usually expressed in terms of bias.
NOTE 2 Trueness is sometimes referred to as “accuracy of the mean”. This usage is not recommended.
NOTE 3 In practice, the accepted reference value is substituted for the true value.
[ISO 3534-2:2006]
3.1.5
precision
closeness of agreement between independent test/measurement results obtained under stipulated conditions
NOTE 1 Precision depends only on the distribution of random errors and does not relate to the true value or the
specified value.
NOTE 2 The measure of precision is usually expressed in terms of imprecision and computed as a standard deviation
of the test results or measurement results. Less precision is reflected by a larger standard deviation.
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NOTE 3 Quantitative measures of precision depend critically on the stipulated conditions. Repeatability conditions and
reproducibility conditions are particular sets of extreme stipulated conditions.
[ISO 3534-2:2006]
3.1.6
limit of detection
output signal or value above which it can be affirmed with a stated level of confidence, for example 95 %, that
a sample is different from a blank sample containing no determinand of interest
[ISO 6107-2:2006]
3.1.7
limit of quantification
stated multiple of the limit of detection, for example, two or three times the limit of detection, at a concentration
of the determinand that can reasonably be determined with an acceptable level of accuracy and precision
NOTE Limit of quantification can be calculated using an appropriate standard or sample, and may be obtained from
the lowest calibration point on the calibration curve (excluding the blank).
[ISO 6107-2:2006]
3.1.8
analytical run
group of measurements or observations carried out together, either simultaneously or sequentially, without
interruption, on the same instrument by the same analyst using the same reagents
NOTE 1 An analytical run may consist of more than one batch of analyses. During an analytical run, the accuracy and
precision of the measuring system is expected to be stable.
NOTE 2 Definition taken from Reference [33] in the Bibliography.
3.1.9
batch of analyses
group of measurements or observations of standards, samples and/or control solutions which have been
performed together in respect of all procedures, either simultaneously or sequentially, by the same analysts
using the same reagents, equipment and calibration
3.2 Terms related to measurement results
3.2.1
error of measurement
test result or measurement result minus the true value
NOTE 1 In practice, the accepted reference value is substituted for the true value.
NOTE 2 Error is the sum of random errors and systematic errors.
NOTE 3 Adapted from ISO 3534-2:2006.
3.2.2
systematic error of result
component of the error of result which, in the course of a number of test results or measurement results, for
the same characteristic or quantity, remains constant or varies in a predictable manner
NOTE Systematic errors and their causes can be known or unknown.
[ISO 3534-2:2006]
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3.2.3
random error of result
component of the error of result which, in the course of a number of test results or measurement results, for
the same characteristic or quantity, varies in an unpredictable manner
NOTE It is not possible to correct for random error.
[ISO 3534-2:2006]
3.2.4
true value
value which characterizes a quantity or quantitative characteristic perfectly defined in the conditions which
exist when that quantity or quantitative characteristic is considered
NOTE The true value of a quantity or quantitative characteristic is a theoretical concept and, in general, cannot be
known exactly.
[ISO 3534-2:2006]
3.2.5
conventional true value
value of a quantity or quantitative characteristic which, for a given purpose, may be substituted for a true value
NOTE A conventional true value is, in general, regarded as being sufficiently close to the true value for the difference
to be insignificant for the given purpose.
[ISO 3534-2:2006]
3.2.6
accepted reference value
value that serves as an agreed-upon reference for comparison
NOTE The accepted reference value is derived as:
a) a theoretical or established value, based on scientific principles;
b) an assigned or certified value, based on experimental work of some national or international organization;
c) a consensus or certified value, based on collaborative experimental work under the auspices of a scientific or
technical group;
d) the expectation, i.e. the mean of a specified set of measurements, when a), b) and c) are not available.
[ISO 3534-2:2006]
3.2.7
certified reference material
reference material, accompanied by a certificate, one or more of whose property values are certified by a
procedure which establishes traceability to an accurate realization of the unit in which the property values are
expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence
NOTE Definition taken from Reference [36] in the Bibliography.
3.2.8
metrological traceability
property of a measurement result relating the result to a stated metrological reference through an unbroken
chain of calibrations of a measuring system or comparisons, each contributing to the stated measurement
uncertainty
[ISO/IEC Guide 99:2007]
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3.3 Terms related to uncertainty
3.3.1
uncertainty of measurement
non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand,
based on the information used
[ISO/IEC Guide 99:2007]
3.3.2
standard uncertainty
u(x )
i
uncertainty of the result x of a measurement expressed as a standard deviation
i
[ISO/IEC Guide 98-3:2008]
3.3.3
combined standard uncertainty
u (y)
c
standard measurement uncertainty that is obtained using the individual standard measurement uncertainties
associated with the input quantities in a measurement model
[ISO/IEC Guide 99:2007]
3.3.4
expanded uncertainty
U
product of a combined standard measurement uncertainty and a factor larger than the number one
NOTE 1 The factor depends upon the type of probability distribution of the output quantity in a measurement model
and on the selected coverage probability.
NOTE 2 The term “factor” in this definition refers to a coverage factor.
[ISO/IEC Guide 99:2007]
3.3.5
coverage factor
k
numerical factor used as a multiplier of the combined standard uncertainty in order to obtain an expanded
uncertainty
NOTE A coverage factor is typically in the range from 2 to 3.
[ISO/IEC Guide 98-3:2008]
4 Performance characteristics of analytical systems
4.1 Introduction
ISO/IEC 17025 requires the validation of methods; the validation process is described in detail in EURACHEM
[18]
Guide (1998) . Primary validation is part of the development of a new analytical method, and is performed
during the standardization of the method. Important points to be considered for the primary validation of an
analytical method are the following:
⎯ scope of the method;
⎯ calibration;
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SIST-TS ISO/TS 13530:2013
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⎯ limit of detection/limit of quantification;
⎯ interferences;
⎯ estimation of accuracy (trueness and precision);
⎯ uncertainty of measurement;
⎯ robustness;
⎯ fitness for purpose.
According to ISO/IEC 17025, the laboratory shall confirm that it can correctly operate standard methods
before applying these methods. This procedure is called secondary validation, where emphasis is laid on
calibration and interferences, as well as the laboratory limit of quantitation and measurement uncertainty. In
4.2 to 4.8, the topics calibration and quantification, matrix effects and measurement uncertainty are dealt with
especially.
4.2 Scope of the method
A clear definition should be given of the forms of the substance that are determined by the procedure and also,
when necessary to avoid ambiguity, those forms that are not capable of determination. At this point, it is worth
emphasizing that the analyst's selection of an analytical method should meet the user's definition of the
determinand. Non-specific determinands need the use of rigorously stipulated analytical methods in order to
obtain reliable and comparable results.
Many substances exist in water in a variety of forms or “species”, and many analytical systems provide a
differential response to the various forms. For example, when a separation of “dissolved” and “particulate”
material is required, special care is necessary to define precisely the nature and pore-size of the filter to be
used.
A precise description of the types and natures of samples is important before the analytical system can be
chosen. The precautions to be taken when a sample is analysed will depend to a high degree on the sample.
The analyst needs information that is as complete as possible on sample types, concentration levels and
possible interferences. The scope should contain a clear statement of the types of sample and sample
matrices for which the procedure is suitable. If necessary, a statement should also be made of important
sample types and matrices for which the procedure is not suitable.
The range of application corresponds to the lowest and highest concentrations for which tests of precision and
bias have been carried out using the system without modification. Where an extension can be used to enable
the examination of samples containing concentrations greater than the upper limit, such as by analysis after
dilution, then it should be regarded as a different procedure but whose performance characteristics may be
inferred from the values quoted for the original.
The concentration range of interest can have a marked effect on the choice of analytical technique; of primary
concern is the smallest concentration of interest.
4.3 Calibration
4.3.1 Basics of calibration and quantification
A calibration function is determined from information values y , obtained by measuring given standard
i
concentrations x . The resulting standard deviation of the method s or confidence interval is a performance
i xo
characteristic of this calibration, not a performance characteristic of the quantification. Quantification of the
analyte content of samples using a calibration function is based on interpolation. The most important
performance characteristic for quantification is the estimation of measurement uncertainty (see 4.6) where the
uncertainty of calibration is one of the contributions.
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Depending on the kind of the functional relationship between the analyte concentration and the measurement
response, different mathematical or statistical tools can be used. Mathematical and statistical models are
subject to different assumptions; therefore, not only is the performance of the analytical equipment essential
but also the kind of mathematical approach. The models should help the analyst to find a clear and reliable
functional relationship for calibration. The models should not limit the capabilities of the analytical equipment.
Therefore, the selection of the calibration model should be undertaken carefully, taking into consideration the
fitness for purpose and the measurement uncertainty required.
⎯ Model of linear regression (ISO 8466-1): the classical model for calibration with the limitations of normal
distribution of the responses and a homogeneity of variances over the working range. Normally, this
homogeneity of variances is only given in a working range of one or at maximum two decades of
concentration. This fact limits the applicability.
⎯ Model of non-linear second-order calibration functions (ISO 8466-2): after discovering a significant non-
linearity. This model has the same limitations as linear regression: normal distribution of the responses
and homogeneity of variances over the working range.
⎯ Model of weighted regression, weighting the information value with the reciprocal variance, calibration
over more than a decade of concentration range is possible.
⎯ Calibration over more than one decade of concentration with at least two concentrations, e.g. for
inductively coupled plasma/mass spectrometry (ICP/MS). Linearity must have been checked beforehand
with a minimum of five concentrations, e.g. by graphical presentation.
NOTE Detailed instructions on calibration procedures are given in References [26] and [28] in the Bibliography.
All these kinds of calibration should be tested for their contribution to measurement uncertainty. For example,
analyse N times, as a minimum in triplicate, an independent standard or a certified reference material within
the concentration range of interest, and calculate the results in accordance with the applied calibration method.
The standard uncertainty component, s , representing the deviation of the single results, ρ , from the reference
p i
value, ρ, is calculated as follows:
N
2
ρρ−
()
∑ i
i=1
s = (1)
p
N−1
where
s is the standard uncertainty component from calibration;
p
N is the number of replicate measurements.
N should be chosen with respect to the confidence required. s should be compared with the respective target
p
measurement uncertainty to set the tolerable amount.
4.3.2 Calibration strategies
4.3.2.1 Basic or instrument calibration
This type of calibration is carried out without matrix components and without sample preparation; for
calibration, pure standard solutions are used. This is inexpensive and directly suited for quant
...
SPÉCIFICATION ISO/TS
TECHNIQUE 13530
Première édition
2009-03-15
Qualité de l'eau — Lignes directrices
pour le contrôle de qualité analytique
pour l'analyse chimique et
physicochimique de l'eau
Water quality — Guidance on analytical quality control for chemical and
physicochemical water analysis
Numéro de référence
ISO/TS 13530:2009(F)
©
ISO 2009
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ISO/TS 13530:2009(F)
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ii © ISO 2009 – Tous droits réservés
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ISO/TS 13530:2009(F)
Sommaire Page
Avant-propos .iv
1 Domaine d'application .1
2 Références normatives.1
3 Termes et définitions .2
3.1 Termes liés aux méthodes de mesurage .2
3.2 Termes liés aux résultats de mesure .3
3.3 Termes liés à l'incertitude .5
4 Caractéristiques de performance des systèmes analytiques.6
4.1 Introduction.6
4.2 Domaine d'application de la méthode.6
4.3 Étalonnage .7
4.4 Limite de détection et limite de quantification .11
4.5 Interférences et effets de matrice .13
4.6 Exactitude (justesse et fidélité) et incertitude de mesure.14
4.7 Robustesse .15
4.8 Aptitude à l'emploi.16
5 Choix des systèmes analytiques .16
5.1 Considérations générales.16
5.2 Considérations d'ordre pratique.17
6 Contrôle qualité intralaboratoire.17
6.1 Généralités .17
6.2 Termes relatifs au contrôle qualité intralaboratoire .17
6.3 Contrôle de l'exactitude.18
6.4 Contrôle de la justesse .19
6.5 Contrôle de la fidélité .20
6.6 Principes d'application des cartes de contrôle.22
6.7 Conclusions .26
6.8 Cartes de contrôle ayant des critères de qualité fixés (cartes de contrôle cibles) .28
7 Contrôle qualité de l'échantillonnage.29
8 Contrôle qualité interlaboratoires.29
9 Contrôle qualité pour des modes opératoires analytiques longs ou analyses effectuées
peu fréquemment ou ponctuellement .30
9.1 Contrôle qualité pour des modes opératoires analytiques longs.30
9.2 Analyses effectuées peu fréquemment ou ponctuellement .30
Annexe A (informative) Vérification de la limite de détection et de la limite de quantification .32
Annexe B (informative) Nature et sources des erreurs analytiques.34
Annexe C (informative) Estimation de l'incertitude de mesure.37
Annexe D (informative) Exemple de contrôle qualité pour des modes opératoires analytiques
longs .39
Bibliographie.40
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ISO/TS 13530:2009(F)
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux de
normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général confiée
aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire partie du
comité technique créé à cet effet. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l'ISO participent également aux travaux. L'ISO collabore étroitement avec
la Commission électrotechnique internationale (CEI) en ce qui concerne la normalisation électrotechnique.
Les Normes internationales sont rédigées conformément aux règles données dans les Directives ISO/CEI,
Partie 2.
La tâche principale des comités techniques est d'élaborer les Normes internationales. Les projets de Normes
internationales adoptés par les comités techniques sont soumis aux comités membres pour vote. Leur
publication comme Normes internationales requiert l'approbation de 75 % au moins des comités membres
votants.
Dans d'autres circonstances, en particulier lorsqu'il existe une demande urgente du marché, un comité
technique peut décider de publier d'autres types de documents:
— une Spécification publiquement disponible ISO (ISO/PAS) représente un accord entre les experts dans
un groupe de travail ISO et est acceptée pour publication si elle est approuvée par plus de 50 % des
membres votants du comité dont relève le groupe de travail;
— une Spécification technique ISO (ISO/TS) représente un accord entre les membres d'un comité technique
et est acceptée pour publication si elle est approuvée par 2/3 des membres votants du comité.
Une ISO/PAS ou ISO/TS fait l'objet d'un examen après trois ans afin de décider si elle est confirmée pour trois
nouvelles années, révisée pour devenir une Norme internationale, ou annulée. Lorsqu'une ISO/PAS ou
ISO/TS a été confirmée, elle fait l'objet d'un nouvel examen après trois ans qui décidera soit de sa
transformation en Norme internationale soit de son annulation.
L'attention est appelée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable de ne
pas avoir identifié de tels droits de propriété et averti de leur existence.
L'ISO/TS 13530 a été élaborée par le comité technique ISO/TC 147, Qualité de l'eau, sous-comité SC 2,
Méthodes physiques, chimiques et biochimiques.
Cette première édition de l'ISO/TS 13530 annule et remplace l'ISO/TR 13530:1997, qui a fait l'objet d'une
révision technique.
iv © ISO 2009 – Tous droits réservés
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SPÉCIFICATION TECHNIQUE ISO/TS 13530:2009(F)
Qualité de l'eau — Lignes directrices pour le contrôle de qualité
analytique pour l'analyse chimique et physicochimique de l'eau
1 Domaine d'application
La présente Spécification technique fournit des lignes directrices détaillées relatives au contrôle qualité
intralaboratoire et interlaboratoires afin de s'assurer que les résultats de l'analyse des eaux sont obtenus avec
un niveau d'exactitude connue.
La présente Spécification technique est applicable à l'analyse chimique et physicochimique de tous les types
d'eaux. Elle ne s'applique pas à l'analyse des boues et sédiments (même si la plupart de ses principes
généraux s'appliquent à de telles analyses) et ne concerne pas l'examen biologique ou microbiologique de
l'eau. Bien que l'échantillonnage soit un aspect important, celui-ci n'est que brièvement abordé.
Le contrôle qualité analytique décrit dans la présente Spécification technique s'applique à l'analyse de l'eau
effectuée dans le cadre d'un programme d'assurance de la qualité. La présente Spécification technique ne
traite pas des exigences détaillées d'assurance qualité pour l'analyse des eaux, consultables dans le guide
[20]
EURACHEM/CITAC (2002) .
Les recommandations de la présente Spécification technique sont en accord avec les exigences relatives à la
documentation d'assurance qualité établie (par exemple l'ISO/CEI 17025).
La présente Spécification technique s'applique à l'utilisation de toute méthode analytique employée dans son
domaine d'application, même s'il est admis que ses recommandations détaillées peuvent nécessiter une
interprétation et une adaptation afin de traiter de certains types de paramètres (par exemple paramètres non
spécifiques tels que les matières en suspension ou la demande biochimique en oxygène, DBO). En cas de
divergence entre les recommandations de la présente Spécification technique et les exigences d'une méthode
d'analyse normalisée, il convient de donner la priorité aux exigences de la méthode concernée.
2 Références normatives
Les documents de référence suivants sont indispensables pour l'application du présent document. Pour les
références datées, seule l'édition citée s'applique. Pour les références non datées, la dernière édition du
document de référence s'applique (y compris les éventuels amendements).
ISO 3534-2:2006, Statistique — Vocabulaire et symboles — Partie 2: Statistique appliquée
ISO 5725 (toutes les parties), Exactitude (justesse et fidélité) des résultats et méthodes de mesure
ISO 8466-1, Qualité de l'eau — Étalonnage et évaluation des méthodes d'analyse et estimation des
caractères de performance — Partie 1: Évaluation statistique de la fonction linéaire d'étalonnage
ISO 8466-2, Qualité de l'eau — Étalonnage et évaluation des méthodes d'analyse et estimation des
caractères de performance — Partie 2: Stratégie d'étalonnage pour fonctions d'étalonnage non linéaires du
second degré
ISO 13528:2005, Méthodes statistiques utilisées dans les essais d'aptitude par comparaisons
interlaboratoires
© ISO 2009 – Tous droits réservés 1
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ISO/TS 13530:2009(F)
ISO/CEI 17025:2005, Exigences générales concernant la compétence des laboratoires d'étalonnages et
d'essais
Guide ISO 35, Matériaux de référence — Principes généraux et statistiques pour la certification
Guide ISO/CEI 43-1, Essais d'aptitude des laboratoires par intercomparaison — Partie 1: Développement et
mise en œuvre de systèmes d'essais d'aptitude
Guide ISO/CEI 43-2, Essais d'aptitude des laboratoires par intercomparaison — Partie 2: Sélection et
utilisation de systèmes d'essais d'aptitude par des organismes d'accréditation de laboratoires
3 Termes et définitions
Pour les besoins du présent document, les termes et définitions suivants s'appliquent.
3.1 Termes liés aux méthodes de mesurage
3.1.1
validation
confirmation par examen et apport de preuves objectives du fait que les exigences particulières en vue d'une
utilisation prévue déterminée sont remplies
[ISO/CEI 17025:2005]
3.1.2
exactitude
étroitesse de l'accord entre un résultat d'essai ou résultat de mesure et la valeur vraie
NOTE 1 Dans la pratique, la valeur de référence acceptée (3.2.6) remplace la valeur vraie.
NOTE 2 Le terme «exactitude», appliqué à un ensemble de résultats d'essai ou de mesure, implique une combinaison
de composés aléatoires et d'une erreur systématique commune ou d'une composante de biais.
NOTE 3 L'exactitude fait référence à une combinaison de justesse et de fidélité.
[ISO 3534-2:2006]
3.1.3
biais
différence entre l'espérance mathématique d'un résultat d'essai ou résultat de mesure et une valeur vraie
[ISO 3534-2:2006]
3.1.4
justesse
étroitesse de l'accord entre l'espérance mathématique d'un résultat d'essai ou d'un résultat de mesure et une
valeur vraie
NOTE 1 La mesure de la justesse est généralement exprimée en termes de biais.
NOTE 2 La justesse a été également appelée «exactitude de la moyenne». Cet usage n'est pas recommandé.
NOTE 3 Dans la pratique, la valeur de référence acceptée remplace la valeur vraie.
[ISO 3534-2:2006]
2 © ISO 2009 – Tous droits réservés
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ISO/TS 13530:2009(F)
3.1.5
fidélité
étroitesse d'accord entre des résultats d'essai/de mesure indépendants obtenus sous des conditions stipulées
NOTE 1 La fidélité dépend uniquement de la distribution des erreurs aléatoires et n'a aucune relation avec la valeur
vraie ou la valeur spécifiée.
NOTE 2 La mesure de la fidélité est généralement exprimée en termes d'infidélité et est calculée à partir de l'écart-type
des résultats d'essai ou des résultats de mesure. Une fidélité faible est reflétée par un grand écart-type.
NOTE 3 Les mesures quantitatives de la fidélité dépendent de façon critique des conditions stipulées. Les conditions
de répétabilité et de reproductibilité sont des ensembles particuliers de conditions extrêmes stipulées.
[ISO 3534-2:2006]
3.1.6
limite de détection
valeur ou signal de sortie au-delà desquels on peut affirmer avec un certain niveau de confiance, par exemple
95 %, qu'un échantillon est différent d'un blanc ne contenant pas d'élément à déterminer
[ISO 6107-2:2006]
3.1.7
limite de quantification
valeur ou signal de sortie calculé à partir de la limite de détection, par exemple deux ou trois fois la limite de
détection à une concentration de l'élément à déterminer qui puisse raisonnablement être établie avec un
niveau acceptable de justesse et de fidélité
NOTE La limite de quantification peut être obtenue à l'aide d'un échantillon ou d'un étalon approprié comme étant le
plus petit point d'étalonnage sur la courbe d'étalonnage (à l'exclusion du blanc).
[ISO 6107-2:2006]
3.1.8
regroupement analytique
groupe de mesurages ou d'observations réalisés ensemble, soit simultanément, soit séquentiellement sans
interruption sur le même instrument par le même analyste, au moyen des mêmes réactifs
NOTE 1 Un regroupement analytique peut comporter plus d'une série d'analyses. Au cours d'un regroupement
analytique, il est attendu que l'exactitude et la fidélité du système de mesurage soient stables.
NOTE 2 Définition tirée de la Référence [33].
3.1.9
série d'analyses
groupe de mesurages ou d'observations d'étalons, d'échantillons et/ou de solutions témoins, qui ont été
effectués ensemble selon tous les modes opératoires définis, soit simultanément, soit séquentiellement, par
les mêmes analystes, au moyen des mêmes réactifs, du même équipement et de la même fonction
d'étalonnage
3.2 Termes liés aux résultats de mesure
3.2.1
erreur de mesure
résultat d'essai ou résultat de mesure moins la valeur vraie
NOTE 1 Dans la pratique, la valeur de référence acceptée remplace la valeur vraie.
NOTE 2 L'erreur est la somme des erreurs aléatoires et des erreurs systématiques.
NOTE 3 Adapté de l'ISO 3534-2:2006.
© ISO 2009 – Tous droits réservés 3
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ISO/TS 13530:2009(F)
3.2.2
erreur systématique de résultat
composante de l'erreur d'un résultat qui, lors d'un certain nombre de résultats d'essai ou résultats de mesure,
pour la même caractéristique ou grandeur, demeure constante ou varie de façon prévisible
NOTE Les erreurs systématiques et leurs causes peuvent être connues ou inconnues.
[ISO 3534-2:2006]
3.2.3
erreur aléatoire de résultat
composante de l'erreur d'un résultat qui, lors d'un certain nombre de résultats d'essai ou résultats de mesure,
pour la même caractéristique ou grandeur, varie de façon imprévisible
NOTE Il n'est pas possible de corriger une erreur aléatoire.
[ISO 3534-2:2006]
3.2.4
valeur vraie
valeur qui caractérise une grandeur ou une caractéristique quantitative parfaitement définie dans les
conditions qui existent lorsque cette grandeur ou caractéristique quantitative est considérée
NOTE La valeur vraie d'une grandeur ou d'une caractéristique quantitative est une notion théorique et, en général,
ne peut pas être connue exactement.
[ISO 3534-2:2006]
3.2.5
valeur conventionnellement vraie
valeur d'une grandeur ou d'une caractéristique quantitative qui peut être substituée à une valeur vraie dans un
but déterminé
NOTE Une valeur conventionnellement vraie est, en général, considérée comme suffisamment proche de la valeur
vraie pour que la différence puisse être non significative pour le but donné.
[ISO 3534-2:2006]
3.2.6
valeur de référence acceptée
valeur qui sert de référence consensuelle pour une comparaison
NOTE La valeur de référence acceptée résulte:
a) d'une valeur théorique ou établie, fondée sur des principes scientifiques;
b) d'une valeur assignée ou certifiée, fondée sur les travaux d'une organisation nationale ou internationale;
c) d'une valeur de consensus ou certifiée, fondée sur un travail expérimental en collaboration et placé sous les auspices
d'un groupe scientifique ou technique;
d) de l'espérance, c'est-à-dire la moyenne de la population spécifiée de mesures, dans les cas où a), b) et c) ne sont
pas applicables.
[ISO 3534-2:2006]
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ISO/TS 13530:2009(F)
3.2.7
matériau de référence certifié
matériau de référence, accompagné d'un certificat, dont une ou plusieurs valeurs des propriétés sont
certifiées par un mode opératoire qui établit son raccordement à une réalisation exacte de l'unité dans
laquelle les valeurs de propriété sont exprimées, et pour lequel chaque valeur certifiée est accompagnée
d'une incertitude à un niveau de confiance indiqué
NOTE Définition tirée de la Référence [36].
3.2.8
traçabilité métrologique
propriété d'un résultat de mesure selon laquelle ce résultat peut être relié à une référence par l'intermédiaire
d'une chaîne ininterrompue et documentée d'étalonnages dont chacun contribue à l'incertitude de mesure
[Guide ISO/CEI 99:2007]
3.3 Termes liés à l'incertitude
3.3.1
incertitude de mesure
paramètre non négatif qui caractérise la dispersion des valeurs attribuées à un mesurande, à partir des
informations utilisées
[Guide ISO/CEI 99:2007]
3.3.2
incertitude-type
u(x )
i
incertitude du résultat x d'une mesure exprimée en tant qu'écart-type
i
[Guide ISO/CEI 98-3:2008]
3.3.3
incertitude-type composée
u (y)
c
incertitude-type obtenue en utilisant les incertitudes-types individuelles associées aux grandeurs d'entrée
dans un modèle de mesure
[Guide ISO/CEI 99:2007]
3.3.4
incertitude élargie
U
produit d'une incertitude-type composée et d'un facteur supérieur au nombre un
NOTE 1 Le facteur dépend du type de la loi de probabilité de la grandeur de sortie dans un modèle de mesure et de la
probabilité de couverture choisie.
NOTE 2 Le facteur qui intervient dans la définition est un facteur d'élargissement.
[Guide ISO/CEI 99:2007]
3.3.5
facteur d'élargissement
k
facteur numérique utilisé comme multiplicateur de l'incertitude-type composée pour obtenir l'incertitude élargie
NOTE Un facteur d'élargissement est généralement compris entre 2 et 3.
[Guide ISO/CEI 98-3:2008]
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ISO/TS 13530:2009(F)
4 Caractéristiques de performance des systèmes analytiques
4.1 Introduction
L'ISO/CEI 17025 exige la validation des méthodes; le processus de validation est décrit en détail dans le
[18]
guide EURACHEM (1998) . Le développement d'une nouvelle méthode analytique comprend une étape de
validation primaire, qui est réalisée au cours de la normalisation de la méthode. Les points importants à
prendre en compte lors de la validation primaire d'une méthode analytique sont les suivants:
⎯ domaine d'application de la méthode;
⎯ étalonnage;
⎯ limite de détection/limite de quantification;
⎯ interférences;
⎯ estimation de l'exactitude (justesse et fidélité);
⎯ incertitude de mesure;
⎯ robustesse;
⎯ aptitude à l'emploi.
Conformément à l'ISO/CEI 17025, le laboratoire doit confirmer qu'il peut utiliser correctement les méthodes
normalisées avant de les appliquer. Ce mode opératoire est appelé validation secondaire, et met l'accent sur
l'étalonnage et les interférences, ainsi que sur la limite de quantification et l'incertitude de mesure du
laboratoire. L'étalonnage et la quantification, les effets de matrice et l'incertitude de mesure sont abordés de
façon spécifique de 4.2 à 4.8.
4.2 Domaine d'application de la méthode
Il convient de donner une définition claire des formes des substances qui sont déterminées par la méthode et
également, pour éviter d'éventuelles ambiguïtés, des formes qui ne peuvent être déterminées. Il est bon de
souligner ici qu'il est recommandé que l'analyste choisisse une méthode analytique répondant à la définition
que l'utilisateur donne du paramètre à déterminer. Des paramètres non spécifiques nécessitent l'utilisation de
méthodes analytiques rigoureusement décrites en vue d'obtenir des résultats fiables et comparables.
De nombreuses substances existent dans l'eau sous diverses formes ou «espèces» et de nombreux
systèmes analytiques fournissent une réponse différente à ces diverses formes. Par exemple, lorsqu'il est
nécessaire de séparer les fractions «dissoutes» et «particulaires», il est important de définir avec précision la
nature ainsi que la porosité du filtre à utiliser.
Il est important de disposer d'une description précise du type et de la nature des échantillons avant de choisir
le système analytique. Les précautions à prendre lors de l'analyse de l'échantillon dépendent dans une large
mesure de l'échantillon. Il est nécessaire que l'analyste dispose d'informations aussi complètes que possible
sur les types d'échantillons, les niveaux de concentration ainsi que les interférences éventuelles. Il convient
que le domaine d'application contienne une déclaration claire des types d'échantillons et des matrices
d'échantillons pour lesquels la méthode est appropriée. Si besoin, il convient de signaler également les
principaux types d'échantillons et matrices pour lesquels la méthode ne convient pas.
Le domaine d'application correspond aux concentrations la plus faible et la plus élevée pour lesquelles des
essais de fidélité et de biais ont été effectués au moyen du système sans modification. Lorsqu'une extension
peut être utilisée pour permettre l'examen d'échantillons contenant des concentrations plus importantes que la
limite supérieure, par exemple par analyse après dilution, il convient de considérer cet examen comme une
méthode différente, mais dont les caractéristiques de performance peuvent être déduites à partir des valeurs
mentionnées pour le domaine initial.
La gamme de concentration concernée peut avoir un effet marqué sur le choix de la technique analytique; la
plus faible concentration concernée joue un rôle primordial.
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ISO/TS 13530:2009(F)
4.3 Étalonnage
4.3.1 Bases de l'étalonnage et de la quantification
Une fonction d'étalonnage est déterminée à partir des valeurs d'information y, obtenues en mesurant des
i
concentrations étalons données x. L'écart-type de la méthode s qui en résulte ou l'intervalle de confiance
i xo
est une caractéristique de performance de cet étalonnage, et non une caractéristique de performance de la
quantification. La quantification de la teneur en analyte des échantillons à l'aide d'une fonction d'étalonnage
est fondée sur l'interpolation. La caractéristique de performance la plus importante pour la quantification est
l'estimation de l'incertitude de mesure (voir 4.6), dont l'une des composantes est l'incertitude d'étalonnage.
En fonction du type de relation fonctionnelle entre la concentration en analyte et la réponse de mesure,
différents outils mathématiques ou statistiques peuvent être utilisés. Les modèles mathématiques et
statistiques sont soumis à différentes hypothèses; par conséquent, si les performances de l'équipement
analytique sont essentielles, le type d'approche mathématique l'est également. Il convient que les modèles
aident l'analyste à trouver une relation fonctionnelle claire et fiable pour l'étalonnage. Il convient que les
modèles ne limitent pas les capacités de l'équipement analytique. En conséquence, il convient de consacrer
une attention particulière au choix du modèle d'étalonnage, en tenant compte de l'aptitude à l'emploi et de
l'incertitude de mesure requise.
⎯ Le modèle de régression linéaire (ISO 8466-1): le modèle classique pour l'étalonnage, avec pour limites
la distribution normale des réponses et une homogénéité des variances sur le domaine d'analyse.
Normalement, cette homogénéité des variances est obtenue uniquement dans un domaine d'analyse
d'une ou au maximum de deux décades de concentration. L'applicabilité s'en trouve donc limitée.
⎯ Le modèle de fonctions d'étalonnage non linéaires du second degré (ISO 8466-2): après la mise en
évidence d'une absence significative de linéarité. Ce modèle présente les mêmes limites que la
régression linéaire: distribution normale des réponses et homogénéité des variances sur le domaine
d'analyse.
⎯ Le modèle de régression pondérée: la valeur d'information étant pondérée de la variance réciproque, il
est possible d'effectuer un étalonnage sur plus d'une décade de gamme de concentration.
⎯ L'étalonnage sur plus d'une décade de concentration avec au moins deux concentrations, par exemple
pour la spectrométrie de masse à plasma inductif (ICP/MS). Il faut vérifier la linéarité au préalable avec
au moins cinq concentrations, par exemple au moyen d'une représentation graphique.
NOTE Des instructions détaillées sur les modes opératoires d'étalonnage sont données dans les Références [26]
et [28].
Il convient d'évaluer la contribution de tous ces types d'étalonnage à l'incertitude de mesure. Par exemple,
analyser à N reprises, au moins trois réplicats, un étalon indépendant ou un matériau de référence certifié
dans la gamme de concent
...
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