SIST-TS CEN/TS 17174:2018
(Main)Animal feeding stuffs: Methods of sampling and analysis - Performance criteria for single laboratory validated and ring-trial validated methods of analysis for the determination of heavy metals
Animal feeding stuffs: Methods of sampling and analysis - Performance criteria for single laboratory validated and ring-trial validated methods of analysis for the determination of heavy metals
This document specifies performance criteria for the selection of single-laboratory validated or collaborative-trial validated methods of analysis of elements and their chemical species in feed. The terms and definition of the relevant parameters for method validation are included. The performance requirements and characteristics are provided. This document may serve as a guide:
- to assess the quality of new European Standard methods under validation;
- to review the quality of previous collaborative trials;
- to confirm the extension of the scope of an already published European Standard applied to other analyte concentrations or matrices; or
- to evaluate the fitness-for-purpose of single-validated methods.
The performance criteria can apply to methods dedicated to the determination of heavy metals, trace elements, major elements and minerals.
Futtermittel - Probenahme- und Untersuchungsverfahren - Leistungskriterien für laborintern validierte und Ringversuch validierte Analysemethoden zur Bestimmung von Schwermetallen
Dieses Dokument legt Leistungskriterien für die Auswahl von in Einzellaboratorien validierten oder in Laborvergleichsuntersuchungen validierten Analyseverfahren für Elemente und ihren Verbindungen in Futtermitteln fest. Enthalten sind die Begriffe der relevanten Parameter für die Verfahrensvalidierung. Die Leistungsanforderungen und merkmale werden zur Verfügung gestellt. Dieses Dokument darf als Orientierung dienen für:
- die Beurteilung der Qualität neuer Europäischer Normverfahren während ihrer Validierung;
- die Überprüfung der Qualität vorangegangener Laborvergleichsuntersuchungen;
- die Bestätigung der Erweiterung des Anwendungsbereichs einer bereits veröffentlichten Europäischen Norm, die für andere Analytkonzentrationen oder Matrices angewendet wurde; oder
- die Evaluierung der Gebrauchseignung einfach validierter Verfahren.
Die Leistungskriterien können bei Verfahren zur Bestimmung von Schwermetallen, Spurenelementen, Hauptelementen und Mineralien verwendet werden.
Aliments des animaux : Méthodes d'échantillonnage et d'analyse - Critères de performance pour les méthodes d'analyse validées par un ou plusieurs laboratoires pour le dosage des métaux lourds
Le présent document spécifie les critères de performance pour la sélection de méthodes validées par un ou plusieurs laboratoires pour l’analyse des éléments minéraux et de leurs espèces chimiques dans les aliments composés pour animaux. Les termes et définitions de paramètres pertinents pour la validation des méthodes sont inclus. Les exigences de performance et les caractéristiques sont fournies. Le présent document peut servir de guide :
- pour évaluer la qualité des nouvelles méthodes de Norme européenne en cours de validation ;
- pour examiner la qualité de précédents essais interlaboratoires ;
- pour confirmer l’extension du domaine d’application d’une Norme européenne déjà publiée appliquée à d’autres concentrations ou matrices d’analytes ; ou
- pour évaluer l’adaptation à l’objectif de méthodes validées par un seul laboratoire.
Les critères de performance peuvent s’appliquer aux méthodes dédiées au dosage des métaux lourds, des éléments trace, des éléments majeurs et des minéraux.
Krma: metode vzorčenja in analize - Izvedbena merila v posameznem laboratoriju in v primerjalnem preskusu validirane metode analiz za določanje težkih kovin
Ta dokument določa izvedbena merila za izbiro v posameznem laboratoriju ali primerjalnem preskusu validiranih metod analiz elementov in njihovih kemičnih vrst v krmi. Vključeni so izrazi in opredelitve ustreznih parametrov v zvezi za validacijo metode. Podane so tudi zahteve za izvedbo in lastnosti. Ta dokument se lahko uporablja kot vodnik za:
– ocenjevanje kakovosti metod novih evropskih standardov v postopku validacije;
– pregled kakovosti prejšnjih primerjalnih preskusov;
– potrditev razširitve področja uporabe že objavljenega evropskega standarda, ki se uporablja za druge koncentracije ali matrice analita; ali
– vrednotenje primernosti za namen v posameznem laboratoriju validiranih metod.
Izvedbena merila je mogoče uporabljati za metode, ki so namenjene določanju težkih kovin, elementov v sledovih ter glavnih elementov in mineralov.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TS CEN/TS 17174:2018
01-oktober-2018
.UPD PHWRGHY]RUþHQMDLQDQDOL]H,]YHGEHQDPHULODYSRVDPH]QHPODERUDWRULMX
LQYSULPHUMDOQHPSUHVNXVXYDOLGLUDQHPHWRGHDQDOL]]DGRORþDQMHWHåNLKNRYLQ
Animal feeding stuffs: Methods of sampling and analysis - Performance criteria for single
laboratory validated and ring-trial validated methods of analysis for the determination of
heavy metals
Futtermittel - Probenahme- und Untersuchungsverfahren - Leistungskriterien für
laborintern validierte und Ringversuch validierte Analysemethoden zur Bestimmung von
Schwermetallen
Aliments des animaux : Méthodes d'échantillonnage et d'analyse - Critères de
performance pour les méthodes d'analyse validées par un ou plusieurs laboratoires pour
le dosage des métaux lourds
Ta slovenski standard je istoveten z: CEN/TS 17174:2018
ICS:
65.120 Krmila Animal feeding stuffs
SIST-TS CEN/TS 17174:2018 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TS CEN/TS 17174:2018
CEN/TS 17174
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
August 2018
TECHNISCHE SPEZIFIKATION
ICS 65.120
English Version
Animal feeding stuffs: Methods of sampling and analysis -
Performance criteria for single laboratory validated and
ring-trial validated methods of analysis for the
determination of heavy metals
Aliments des animaux : Méthodes d'échantillonnage et Futtermittel - Probenahme- und
d'analyse - Critères de performance pour les méthodes Untersuchungsverfahren - Leistungskriterien für
d'analyse validées par un ou plusieurs laboratoires laborintern validierte und Ringversuch validierte
pour le dosage des métaux lourds Analysemethoden zur Bestimmung von
Schwermetallen
This Technical Specification (CEN/TS) was approved by CEN on 8 February 2018 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 17174:2018 E
worldwide for CEN national Members.
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CEN/TS 17174:2018 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Criteria for analytical methods for heavy metals . 13
4.1 Overall concepts . 13
4.2 Horwitz/Thompson equation . 13
4.3 Horwitz ratio . 14
4.4 Precision . 14
4.5 Trueness . 15
4.6 Minimum applicability range . 15
4.7 Limit of detection (LOD) and limit of quantification (LOQ) . 16
Annex A (normative) Review of the repeatability and reproducibility relative standard
deviations reported in the EN 15510 standard and EN 15621 technical specifications . 17
Annex B (informative) R and RSD versus mass fractions . 21
rec
Annex C (informative) Assessment of method compliance. 23
Bibliography . 25
2
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CEN/TS 17174:2018 (E)
European foreword
This document (CEN/TS 17174:2018) has been prepared by Technical Committee CEN/TC 327 “Animal
feeding stuffs: Methods of sampling and analysis”, the secretariat of which is held by NEN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom
3
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Introduction
The working group, CEN/TC 327 “Animal feeding stuffs - Methods of sampling and analysis” WG 4
“Elements and their chemical species” selects and elaborates methods of analysis of elements and their
chemical species in feedstuffs.
There are many methods of analysis for the determination of elements in feedstuffs, which have been
validated and published. It is often required to make a choice between several established methods
applicable to the same measurand (analyte/matrix combination).
The Working Group was mandated by the European Commission [1] to establish specific criteria to
guide the analyst in the selection between several methods of analysis. As a general rule, analysts
should give preference to methods of analysis which comply with the provisions given in Clauses 1 and
2 of Annex III to the Regulation (EU) 2017/625 [2], in the Directive 2002/32/EC [3], with the
Commission Regulation (EC) No 152/2009 [4], or with the General Principles for Methods of Analysis of
the Codex Alimentarius Commission (CAC), as defined in the CAC Procedural Manual [5] and further
developed in the “criteria approach” to the methods of analysis developed by the Codex Committee of
Methods of Analysis and Sampling (CCMAS) [6].
The performance criteria laid down in this document are based on published guidance documents (such
as the AOAC guidelines [7]; the IUPAC Harmonized Protocol [8] and the SANCO document [9]) or data
collected from official reports on European collaborative studies (e.g. EN 15510 [10] or EN 15621 [11]).
When such performance characteristics are not available, the criteria were established based on the
experience and opinions of the CEN/TC 327/WG 4.
The criteria included in this document have also been used as guidance in the Working Group for the
selection of specific methods of analysis of trace elements to be further standardized, for the evaluation
of on-going collaborative trials and for the review of previously published standards of analytical
methods.
NOTE All the criteria provided in this document refer to concentrations (mass fractions) greater than or
equal to 0,1 mg/kg, related to the lowest maximum level (ML) set for mercury in feed.
4
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1 Scope
This document specifies performance criteria for the selection of single-laboratory validated or
collaborative-trial validated methods of analysis of elements and their chemical species in feed. The
terms and definition of the relevant parameters for method validation are included. The performance
requirements and characteristics are provided. This document may serve as a guide:
— to assess the quality of new European Standard methods under validation;
— to review the quality of previous collaborative trials;
— to confirm the extension of the scope of an already published European Standard applied to other
analyte concentrations or matrices; or
— to evaluate the fitness-for-purpose of single-validated methods.
The performance criteria can apply to methods dedicated to the determination of heavy metals, trace
elements, major elements and minerals.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
accuracy
closeness of agreement between a test result and the accepted reference value
[SOURCE: ISO 5725-1, see [12]]
Note 1 to entry: The term accuracy, when applied to a set of test results, involves a combination of random
components and a common systematic error or bias component.
Note 2 to entry: It is assessed by determining trueness and precision.
[SOURCE: 2002/657/EEC, see [13]]
3.2
applicability
scope of the analytical method; description of the analytes, matrices, and concentration ranges (mass
fractions) for which a method of analysis may be used satisfactorily to determine compliance with a
given standard (i.e. CEN, ISO, CODEX)
Note 1 to entry: In addition to a statement of the range of capability of satisfactory performance for each factor,
the statement of applicability (scope) also includes warnings as to known interference by other analytes, or
inapplicability to certain matrices and situations.
3.3
bias
difference between the expectation of the test results (x) and an accepted reference value (x )
ref
[SOURCE: ISO 5725-1, see [12]]
5
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Note 1 to entry: The bias can be expressed in absolute or relative terms (b or b(%), respectively) as:
b xx− (1)
ref
xx−
ref
b(%) × 100 (2)
x
ref
[SOURCE: Eurachem 2014, see [14]]
3.4
inter-laboratory comparison
organisation, performance and evaluation of measurements or tests on the same or similar items by
two or more laboratories in accordance with predetermined conditions
[SOURCE: ISO/IEC 17043:2010, see [15]]
Note 1 to entry: The larger the number of participating laboratories, the greater the confidence that can be
placed in the resulting statistical parameters.
3.4.1
collaborative trials
inter-laboratory comparison aiming at the evaluation of the performance characteristics of a method –
often described as ring-test or ring-trial
[SOURCE: ISO/IEC 17043:2010, see [15]]
Note 1 to entry: It means analysing the same sample by the same method to determine the performance
characteristics of the method.
Note 2 to entry: The study covers random measurement error and laboratory bias.
[SOURCE: 2002/657/EEC, see [13]]
Note 3 to entry: The reported results are used to estimate the performance characteristics of the method, such
as precision. When necessary and possible, other pertinent characteristics such as systematic error and/or
recovery may be reported.
3.4.2
proficiency testing
inter-laboratory comparison aiming at the evaluation of participant performance against pre-
established criteria
[SOURCE: ISO/IEC 17043:2010, see [15]]
Note 1 to entry: The reported results are compared with those from other laboratories or with the known or
assigned reference value, usually with the objective of evaluating or improving laboratory performance.
Note 2 to entry: Proficiency testing means analysing the same sample allowing laboratories to choose their own
methods, provided these methods are used under routine conditions.
[SOURCE: 2002/657/EEC, see [13]]
6
=
=
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3.4.3
reference material characterisation
inter-laboratory comparison aiming at the assignment of values to reference materials and assessment
of their suitability for use in specific test or measurement procedures
[SOURCE: ISO/IEC 17043:2010, see [15]]
3.5
limit of detection
x
LOD
concentration (mass fraction) derived from the smallest measure that can be detected with reasonable
certainty for a given analytical procedure
[SOURCE: ISO 11843, see [16]]
Note 1 to entry: For analytical systems where the validation range does not include or approach it, the detection
limit does not need to be part of a validation.
[SOURCE: IUPAC 2002, see [8]]
Note 2 to entry: The various conceptual approaches to the subject depend on the estimate of precision at or
near zero concentration (mass fraction) under repeatability or reproducibility conditions.
3.6
limit of quantification
x
LOQ
lowest concentration (mass fraction) determined with satisfactory measurement uncertainty
[SOURCE: ISO 11843, see [16]]
Note 1 to entry: It is useful to state a concentration (mass fraction) below which the analytical method cannot
operate with an acceptable precision. Such precision is arbitrarily defined as relative standard deviation of 10 %.
Note 2 to entry: Usually the limit is set as a fixed multiple (e.g. 3,3) of the detection limit.
Note 3 to entry: Measurements below LOQ are not devoid of information content and are fit for purpose.
[SOURCE: IUPAC 2002, see [8]]
3.7
linearity
ability (within a given range) of an analytical procedure to obtain test results which are directly
proportional to the concentration (mass fraction) of analyte in the sample
3.8
lowest validated Ievel
lowest concentration (mass fraction) investigated in the frame of a collaborative trial or a single-
laboratory validation
7
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3.9
measurement uncertainty
parameter associated with the result of a measurement, that characterises the dispersion of the values
that could reasonably be attributed to the measurand
[SOURCE: GUM, see [17]]
Note 1 to entry: Uncertainty should be distinguished from an estimate attached to a test result which
characterizes the range of values within which the expectation is asserted to lie. This latter estimate is a measure
of precision rather than of accuracy and should be used only when the true value is not defined.
Note 2 to entry: The measurand is a description of the specific quantity intended to be measured. In chemical
and biochemical analysis the specification of the measurand requires at least the description of the quantity (e.g.
mass fraction or amount of substance concentration), the analyte and where relevant the matrix.
Note 3 to entry: Uncertainty of measurement comprises, in general, many components. Some of these
components may be estimated on the basis of the statistical distribution of the results of a series of measurements
and can be characterized by standard deviations. Estimates or other components can only be based on experience
or other information.
[SOURCE: TAM, see [18]]
3.10
precision
closeness of agreement between independent test results obtained under stipulated conditions
[SOURCE: ISO 5725-1, see [12]]
Note 1 to entry: Precision depends only on the distribution of random errors and does not relate to the true
value, conventional true value or specified value.
Note 2 to entry: The measure of precision is usually expressed in terms of imprecision and computed as a
standard deviation of the test results. Less precision is reflected by a larger standard deviation.
Note 3 to entry: “Independent test results” means results obtained in a manner not influenced by any previous
result on the same or similar test object. Quantitative measure of precision depends critically on the stipulated
conditions. Repeatability and reproducibility conditions are particular sets of extreme conditions.
3.10.1
repeatability
precision under repeatability conditions
[SOURCE: ISO 5725-1, see [12]]
3.10.1.1
repeatability conditions
conditions where independent test results are obtained with the same method on identical test items in
the same laboratory by the same operator using the same equipment within short intervals of time
[SOURCE: ISO 5725-1, see [12]]
8
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3.10.1.2
repeatability standard deviation
s
r
standard deviation of test results obtained under repeatability conditions
Note 1 to entry: It is a measure of the dispersion of the distribution of test results under repeatability
conditions.
Note 2 to entry: Similarly “repeatability variance” and “repeatability coefficient of variation” could be defined
and used as measures of the dispersion of the test results under repeatability conditions.
3.10.1.3
repeatability relative standard deviation
RSDr
relative standard deviation of test results obtained under repeatability conditions
Note 1 to entry: The repeatability relative standard deviation (RSD ) can be expressed as follows:
r
s
r
RSD (%) × 100 (3)
r
c
mean
where
c is the mean concentration (mass fraction)
mean
3.10.1.4
repeatability limit
r
value less than or equal to which the absolute difference between two test results obtained under
repeatability conditions may be expected to be within a probability of 95 %
Note 1 to entry The repeatability limit (r) can be expressed as follows:
rs22× (4)
r
[SOURCE: ISO 3534-1, see [19]]
[SOURCE: ISO 5725-6, see [20]]
3.10.2
within-laboratory reproducibility (intermediate precision)
precision under within-laboratory reproducibility conditions
3.10.2.1
within-laboratory reproducibility conditions
conditions where test results are obtained with the same method on identical test items on different
days with different operators using different equipment
[SOURCE: ISO 5725-1, see [12]]
9
=
=
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3.10.2.2
within-laboratory reproducibility standard deviation
s
WLR
standard deviation of test results obtained under within-laboratory reproducibility conditions
Note 1 to entry It is a measure of the dispersion of the distribution of test results under within-laboratory
reproducibility conditions
3.10.2.3
within-laboratory reproducibility relative standard deviation
RSD
WLR
relative standard deviation of test results obtained under within-laboratory reproducibility conditions
Note 1 to entry: The within-laboratory reproducibility relative standard deviation (RSDWLR) can be expressed as
follows:
s
WLR
RSD (%) × 100 (5)
WLR
c
mean
where
c is the mean concentration (mass fraction).
mean
3.10.3
reproducibility
precision under reproducibility conditions
[SOURCE: ISO 5725-1, see [12]]
3.10.3.1
reproducibility conditions
conditions where test results are obtained with the same method on identical test items in different
laboratories with different operators using different equipment
[SOURCE: ISO 5725-1, see [12]]
3.10.3.2
reproducibility standard deviation
s
R
standard deviation of test results obtained under reproducibility conditions
[SOURCE: ISO 5725-1, see [12]]
Note 1 to entry: It is a measure of the dispersion of the distribution of test results under reproducibility
co
...
SLOVENSKI STANDARD
kSIST-TS FprCEN/TS 17174:2017
01-november-2017
.UPD PHWRGHY]RUþHQMDLQDQDOL]H,]YHGEHQDPHULODYSRVDPH]QHPODERUDWRULMX
LQYSULPHUMDOQHPSUHVNXVXYDOLGLUDQHPHWRGHDQDOL]]DGRORþDQMHWHåNLKNRYLQ
Animal feeding stuffs: Methods of sampling and analysis - Performance criteria for single
laboratory validated and ring-trial validated methods of analysis for the determination of
heavy metals
Futtermittel - Probenahme- und Untersuchungsverfahren - Leistungskriterien für
laborintern validierte und Ringversuch validierte Analysemethoden zur Bestimmung von
Schwermetallen
Aliments des animaux : Méthodes d'échantillonnage et d'analyse - Critères de
performance pour les méthodes d'analyse validées par un ou plusieurs laboratoires pour
le dosage des métaux lourds
Ta slovenski standard je istoveten z: FprCEN/TS 17174
ICS:
65.120 Krmila Animal feeding stuffs
kSIST-TS FprCEN/TS 17174:2017 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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kSIST-TS FprCEN/TS 17174:2017
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kSIST-TS FprCEN/TS 17174:2017
FINAL DRAFT
TECHNICAL SPECIFICATION
FprCEN/TS 17174
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
October 2017
ICS
English Version
Animal feeding stuffs: Methods of sampling and analysis -
Performance criteria for single laboratory validated and
ring-trial validated methods of analysis for the
determination of heavy metals
Aliments des animaux : Méthodes d'échantillonnage et Futtermittel - Probenahme- und
d'analyse - Critères de performance pour les méthodes Untersuchungsverfahren - Leistungskriterien für
d'analyse validées par un ou plusieurs laboratoires laborintern validierte und Ringversuch validierte
pour le dosage des métaux lourds Analysemethoden zur Bestimmung von
Schwermetallen
This draft Technical Specification is submitted to CEN members for Vote. It has been drawn up by the Technical Committee
CEN/TC 327.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a Technical Specification. It is distributed for review and comments. It is subject to change
without notice and shall not be referred to as a Technical Specification.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TS 17174:2017 E
worldwide for CEN national Members.
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kSIST-TS FprCEN/TS 17174:2017
FprCEN/TS 17174:2017 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Criteria for analytical methods for heavy metals . 12
4.1 Overall concepts . 12
4.2 Horwitz/Thompson equation . 13
4.3 Horwitz ratio . 13
4.4 Precision . 13
4.5 Trueness . 14
4.6 Minimum applicability range . 14
4.7 Limit of detection (LOD) and limit of quantification (LOQ) . 15
Annex A (normative) Review of the repeatability and reproducibility relative standard
deviations reported in the EN 15510 standard and CEN/TS 15620 technical
specifications . 16
Annex B (informative) Rrec and RSD versus mass fractions . 20
Annex C (informative) Assessment of method compliance . 22
Bibliography . 25
2
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FprCEN/TS 17174:2017 (E)
European foreword
This document (FprCEN/TS 17174:2017) has been prepared by Technical Committee CEN/TC 327
“Animal feeding stuffs: Methods of sampling and analysis”, the secretariat of which is held by NEN.
This document is currently submitted to the Formal Vote.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
3
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FprCEN/TS 17174:2017 (E)
Introduction
The working group, CEN/TC 327 “Animal feeding stuffs” WG 4 “Methods of sampling and analysis”
selects and elaborates methods of analysis of elements and their chemical species in feedstuffs.
There are many methods of analysis for the determination of elements in feedstuffs, which have been
validated and published. It is often required to make a choice between several established methods
applicable to the same measurand (analyte/matrix combination).
The Working Group was mandated by the European Commission [1] to establish specific criteria to
guide the analyst in the selection between several methods of analysis. As a general rule, analysts
should give preference to methods of analysis which comply with the provisions given in Clauses 1 and
2 of the Annex to the Regulation (EC) No 882/2004 [2], with the Decision in the Directive 2002/32/EC
[3], with the Commission Regulation (EC) No 152/2009 [4], or with the General Principles for Methods
of Analysis of the Codex Alimentarius Commission (CAC), as defined in the CAC Procedural Manual [5]
and further developed in the “criteria approach” to the methods of analysis developed by the Codex
Committee of Methods of Analysis and Sampling (CCMAS) [6].
The performance criteria laid down in this document are based on published guidance documents (such
as the AOAC guidelines [7]; the IUPAC Harmonized Protocol [8] and the SANCO document [9]) or data
collected from official reports on European collaborative studies (e.g. EN 15510 [10] or CEN/TS 15620
[11]). When such performance characteristics are not available, the criteria were established based on
the experience and opinions of the CEN/TC 327/WG 4.
The criteria included in this document have also been used as guidance in the Working Group for the
selection of specific methods of analysis of trace elements to be further standardized, for the evaluation
of on-going collaborative trials and for the review of previously published standards of analytical
methods.
NOTE All the criteria provided in this document refer to concentrations (mass fractions) greater than or
equal to 0,1 mg/kg, related to the lowest maximum level (ML) set for mercury in feed.
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1 Scope
This document specifies performance criteria for the selection of single-laboratory validated or
collaborative-trial validated methods of analysis of elements and their chemical species in feed. The
terms and definition of the relevant parameters for method validation are included. The performance
requirements and characteristics are provided. This document may serve as a guide:
— to assess the quality of new European Standard methods under validation;
— to review the quality of previous collaborative trials;
— to confirm the extension of the scope of an already published European Standard applied to other
analyte concentrations or matrices; or
— to evaluate the fitness-for-purpose of single-validated methods.
The performance criteria can apply to methods dedicated to the determination of heavy metals, trace
elements, major elements and minerals.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
accuracy
closeness of agreement between a test result and the accepted reference value
[SOURCE: ISO 5725-1, see [12]]
Note 1 to entry: The term accuracy, when applied to a set of test results, involves a combination of random
components and a common systematic error or bias component.
Note 2 to entry: It is assessed by determining trueness and precision.
[SOURCE: 2002/657/EEC, see [13]]
3.2
applicability
scope of the analytical method; description of the analytes, matrices, and concentration ranges (mass
fractions) for which a method of analysis may be used satisfactorily to determine compliance with a
given standard (i.e. CEN, ISO, CODEX)
Note 1 to entry: In addition to a statement of the range of capability of satisfactory performance for each factor,
the statement of applicability (scope) also includes warnings as to known interference by other analytes, or
inapplicability to certain matrices and situations.
3.3
bias
difference between the expectation of the test results (x) and an accepted reference value (x )
ref
[SOURCE: ISO 5725-1, see [12]]
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Note 1 to entry: The bias can be expressed in absolute or relative terms (b or b(%), respectively) as:
b xx− (1)
ref
xx−
ref
b(%) × 100 (2)
x
ref
[SOURCE: Eurachem 2014, see [14]]
3.4
inter-laboratory comparison
organisation, performance and evaluation of measurements or tests on the same or similar items by
two or more laboratories in accordance with predetermined conditions
[SOURCE: ISO/ISO 17043:2010, see [15]]
Note 1 to entry: The larger the number of participating laboratories, the greater the confidence that can be
placed in the resulting statistical parameters.
3.4.1
collaborative trials
inter-laboratory comparison aiming at the evaluation of the performance characteristics of a method –
often described as ring-test or ring-trial
[SOURCE: ISO/ISO 17043:2010, see [15]]
Note 1 to entry: It means analysing the same sample by the same method to determine the performance
characteristics of the method.
Note 2 to entry: The study covers random measurement error and laboratory bias.
[SOURCE: 2002/657/EEC, see [13]]
Note 3 to entry: The reported results are used to estimate the performance characteristics of the method, such
as precision. When necessary and possible, other pertinent characteristics such as systematic error and/or
recovery may be reported.
3.4.2
proficiency testing
inter-laboratory comparison aiming at the evaluation of participant performance against pre-
established criteria
[SOURCE: ISO/IEC 17043:2010, see [15]]
Note 1 to entry: The reported results are compared with those from other laboratories or with the known or
assigned reference value, usually with the objective of evaluating or improving laboratory performance.
Note 2 to entry: Proficiency testing means analysing the same sample allowing laboratories to choose their own
methods, provided these methods are used under routine conditions.
[SOURCE: 2002/657/EEC, see [13]]
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3.4.3
reference material characterisation
inter-laboratory comparison aiming at the assignment of values to reference materials and assessment
of their suitability for use in specific test or measurement procedures
[SOURCE: ISO/IEC 17043:2010, see [15]]
3.5
limit of detection
x
LOD
concentration (mass fraction) derived from the smallest measure that can be detected with reasonable
certainty for a given analytical procedure
[SOURCE: ISO 11843, see [16]]
Note 1 to entry: For analytical systems where the validation range does not include or approach it, the detection
limit does not need to be part of a validation.
[SOURCE: IUPAC 2002, see [8]]
Note 2 to entry: The various conceptual approaches to the subject depend on the estimate of precision at or
near zero concentration (mass fraction) under repeatability or reproducibility conditions.
3.6
limit of quantification
x
LOQ
lowest concentration (mass fraction) determined with satisfactory measurement uncertainty
[SOURCE: ISO 11843, see [16]]
Note 1 to entry: It is useful to state a concentration (mass fraction) below which the analytical method cannot
operate with an acceptable precision. Such precision is arbitrarily defined as relative standard deviation of 10 %.
Note 2 to entry: Usually the limit is set as a fixed multiple (e.g. 3,3) of the detection limit.
Note 3 to entry: Measurements below LOQ are not devoid of information content and are fit for purpose.
[SOURCE: IUPAC 2002, see [8]]
3.7
linearity
ability (within a given range) of an analytical procedure to obtain test results which are directly
proportional to the concentration (mass fraction) of analyte in the sample
3.8
lowest validated Ievel
lowest concentration (mass fraction) investigated in the frame of a collaborative trial or a single-
laboratory validation
3.9
measurement uncertainty
parameter associated with the result of a measurement, that characterises the dispersion of the values
that could reasonably be attributed to the measurand
[SOURCE: GUM, see [17]]
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Note 1 to entry: Uncertainty should be distinguished from an estimate attached to a test result which
characterizes the range of values within which the expectation is asserted to lie. This latter estimate is a measure
of precision rather than of accuracy and should be used only when the true value is not defined.
Note 2 to entry: The measurand is a description of the specific quantity intended to be measured. In chemical
and biochemical analysis the specification of the measurand requires at least the description of the quantity (e.g.
mass fraction or amount of substance concentration), the analyte and where relevant the matrix.
Note 3 to entry: Uncertainty of measurement comprises, in general, many components. Some of these
components may be estimated on the basis of the statistical distribution of the results of a series of measurements
and can be characterized by standard deviations. Estimates or other components can only be based on experience
or other information.
[SOURCE: TAM, see [18]]
3.10
precision
closeness of agreement between independent test results obtained under stipulated conditions
[SOURCE: ISO 5725-1, see [12]]
Note 1 to entry: Precision depends only on the distribution of random errors and does not relate to the true
value, conventional true value or specified value.
Note 2 to entry: The measure of precision is usually expressed in terms of imprecision and computed as a
standard deviation of the test results. Less precision is reflected by a larger standard deviation.
Note 3 to entry: “Independent test results” means results obtained in a manner not influenced by any previous
result on the same or similar test object. Quantitative measure of precision depends critically on the stipulated
conditions. Repeatability and reproducibility conditions are particular sets of extreme conditions.
3.10.1
repeatability
precision under repeatability conditions
[SOURCE: ISO 5725-1, see [12]]
3.10.1.1
repeatability conditions
conditions where independent test results are obtained with the same method on identical test items in
the same laboratory by the same operator using the same equipment within short intervals of time
[SOURCE: ISO 5725-1, see [12]]
3.10.1.2
repeatability standard deviation
s
r
standard deviation of test results obtained under repeatability conditions
Note 1 to entry: It is a measure of the dispersion of the distribution of test results under repeatability
conditions.
Note 2 to entry: Similarly “repeatability variance” and “repeatability coefficient of variation” could be defined
and used as measures of the dispersion of the test results under repeatability conditions.
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3.10.1.3
repeatability relative standard deviation
RSD
r
relative standard deviation of test results obtained under repeatability conditions
Note 1 to entry: The repeatability relative standard deviation (RSDr) can be expressed as follows:
s
r
RSD (%) × 100 (3)
r
c
mean
where
c is the mean concentration (mass fraction)
mean
3.10.1.4
repeatability limit
r
value less than or equal to which the absolute difference between two test results obtained under
repeatability conditions may be expected to be within a probability of 95 %
Note 1 to entry The repeatability limit (r) can be expressed as follows:
rs22× (4)
r
[SOURCE: ISO 3534-1, see [19]]
[SOURCE: ISO 5725-6, see [20]]
3.10.2
within-laboratory reproducibility (intermediate precision)
precision under within-laboratory reproducibility conditions
3.10.2.1
within-laboratory reproducibility conditions
conditions where test results are obtained with the same method on identical test items on different
days with different operators using different equipment
[SOURCE: ISO 5725-1, see [12]]
3.10.2.2
within-laboratory reproducibility standard deviation
s
WLR
standard deviation of test results obtained under within-laboratory reproducibility conditions
Note 1 to entry It is a measure of the dispersion of the distribution of test results under within-laboratory
reproducibility conditions
3.10.2.3
within-laboratory reproducibility relative standard deviation
RSD
WLR
relative standard deviation of test results obtained under within-laboratory reproducibility conditions
Note 1 to entry: The within-laboratory reproducibility relative standard deviation (RSD ) can be expressed as
WLR
follows:
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s
WLR
RSD (%) × 100 (5)
WLR
c
mean
where
c is the mean concentration (mass fraction).
mean
3.10.3
reproducibility
precision under reproducibility conditions
[SOURCE: ISO 5725-1, see [12]]
3.10.3.1
reproducibility conditions
conditions where test results are obtained with the same method on identical test items in different
laboratories with different operators using different equipment
[SOURCE: ISO 5725-1, see [12]]
3.10.3.2
reproducibility standard deviation
s
R
standard deviation of test results obtained under repeatability conditions
[SOURCE: ISO 5725-1, see [12]]
Note 1 to entry: It is a measure of the dispersion of the distribution of test results under reproducibility
conditions.
Note 2 to entry: Sim
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