CEN/TS 14793:2005

SLOVENSKI STANDARD
01-september-2005
(PLVLMHQHSUHPLþQLKYLURY±1RWUDQMLODERUDWRULMVNLSRVWRSNLYDOLGDFLMHDOWHUQDWLYQH
PHWRGHYSULPHUMDYL]UHIHUHQþQRPHWRGR
Stationary source emission - Intralaboratory validation procedure for an alternative
method compared to a reference method
Emissionen aus stationären Quellen - Laborinterne Validierung von Alternativverfahren
durch Vergleich mit einem Referenzverfahren
Emissions de sources fixes - Méthode de validation intralaboratoire d'une méthode
'alternative' comparée a une méthode de référence
Ta slovenski standard je istoveten z: CEN/TS 14793:2005
ICS:
13.040.40 (PLVLMHQHSUHPLþQLKYLURY Stationary source emissions
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION
CEN/TS 14793
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
March 2005
ICS 13.040.40
English version
Stationary source emission - Intralaboratory validation procedure
for an alternative method compared to a reference method
Emissions de sources fixes - Méthode de validation Emissionen aus stationären Quellen -
intralaboratoire d'une méthode 'alternative' comparée à une Intralaborvalidierverfahren für ein Alternativverfahren
méthode de référence verglichen mit einem Referenzverfahren
This Technical Specification (CEN/TS) was approved by CEN on 1 March 2004 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, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 14793:2005: E
worldwide for CEN national Members.

page
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions .5
3.1 General Vocabulary .6
3.2 Symbols .9
4 Contents of the validation.11
4.1 General.11
4.2 Description of the alternative method .11
4.3 Determination of performance characteristics.12
4.3.1 General.12
4.3.2 Manual method.12
4.3.3 Automatic method .12
4.4 Calculation of the overall uncertainty.13
4.5 In field validation.13
4.5.1 Coverage of in field validation.13
4.5.2 Evaluation of repeatability and non systematic deviation in relation to the reference
method .14
5 Summary of experiments performed.18
Annex A (informative)  Example of measurement of repeatability and trueness of Thorin method
compared to Ion chromatography for SO measurement in stack.20
Annex B (informative)  Statistical tables.27
B.1 Distribution of the Student probability function.27
B.2 Critical values for Grubbs test .29
Bibliography .30

Foreword
This document CEN/TS 14793:2005 has been prepared by Technical Committee CEN/TC 264 “Air quality”,
the secretariat of which is held by DIN.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, Czech Republic, Denmark,
Finland, France, Germany, Greece, Hungary Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway,
Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom.
Annexes A and B are informative.
Introduction
Much has been published in the literature concerning method validation by collaborative study. CEN TC264
working groups try to follow these method validations when a new standard is prepared and the collaborative
study is probably the preferred way of carrying out the validation. However, it is not always a suitable option
for accredited laboratories. The application for which the method is required may be esoteric to the extent that
no other laboratories would be interested in collaboration. Those that might be interested can be competitors.
The present Technical Specification provides one of the possible methods of testing the equivalence of an
alternative method with a reference method.
1 Scope
The purpose of this Technical Specification is to specify a validation procedure to show if an Alternative
Method (AM) can be used as an alternative to the Standard Reference Method (SRM), both implemented to
determine the same measurand. This document has been drawn up for laboratories working in air pollution
measurements (and consequently examples taken from this sector are included in the appendices).
In particular, this Technical Specification provides the statistical tools and different criteria to evaluate the
alternative method; this does not release the person responsible for this validation from bearing technical and
analytical judgement on the evaluation of the different criteria.
Three steps are described in the validation procedure:
 description of the AM and setting of the field of equivalence (range and type of gas matrix);
 determination of the performance characteristics of the AM and calculation of the overall uncertainty
where appropriate and check of compliance of the maximum overall uncertainty allowed for the SRM;
 check of repeatability and lack of systematic deviation of the AM in the field in comparison with the SRM
for the type of matrix defined in the field of equivalence.
NOTE Some parts of the second step of the validation of the alternative method should be performed by a
recognised test-house.
If the AM fulfils the requirement of the procedure, then the laboratory that carried out the whole validation
process is allowed to use it as a SRM in the field application where the equivalence has been demonstrated.
However, if the validation process involves at least 4 different accredited laboratories performing
simultaneously parallel measurements in the field, and if the AM passes with success all the tests of the
procedure, then this method could be proposed to CEN, who can decide to consider this AM as a new
reference method (ARM).
The use of this procedure implies that a reference method has been defined by the regulator or in a contract
and has been validated.
This Technical Specification only considers the case of linear quantitative methods.
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.

ENV 13005, Guide to the expression of uncertainly in measurement.
EN ISO 14956, Air quality – Evaluation of suitability of a measurement procedure by comparison with a
required measurement uncertainty (ISO 14956:2002).
ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results – Part 2: Basic method
for the determination of repeatability and reproducibility of a standard measurement method.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 General Vocabulary
3.1.1
accepted reference value (see ENV 13005)
value which serves as an accepted reference value (or conventionally true value) of the sample, provided by
the arithmetic mean of the measurement values repeated according to the standard reference method (see
3.1.19)
3.1.2
alternative method (AM)
measurement method (3.1.15) which complies with the criteria given by this Technical Specification with
respect to the reference method (SRM)
NOTE An alternative analysis method can consist of a simplification of the reference method.
3.1.3
automatic measuring system (AMS)
measuring system interacting with one or several air quality characteristics and which returns an output signal
giving the measurement result expressed in the physical unit of such air quality characteristics
3.1.4
calibration
set of operations that establishes, under specified conditions, the systematic difference that may exist
between values of a measurand indicated by a measuring system and the corresponding values given by a
"reference" system represented by the reference materials and their accepted values (derived from VIM 6.11
and from ISO 11095:1996, clause 4)
NOTE 1 The result of a calibration permits either the assignment of values of the measurand to the indications or the
determination of corrections with respect to indications.
NOTE 2 A calibration may also determine other metrological properties such as the effect of influence quantities.
3.1.5
field of application of the measurement method
combination of the different types of matrix (3.1.12) and the range of concentrations of the measurand (3.1.14)
covered, to which the measurement method (3.1.15) is applied
NOTE As well as being an indication of all the satisfactory performance conditions for each factor, the field of
application of the measurement method can also include warnings concerning known interferences caused by other
components, or the inapplicability of certain matrices or conditions.
WARNING 1 The field of application of an alternative method can partially or completely cover the field of
application of the reference method. However, if it covers the fields of application of several reference
methods (horizontal method), several evaluations of each reference method shall be performed (e.g. Multi-
component measurement methods like FTIR).
WARNING 2 The definition of the field of application depends entirely upon the laboratory responsible for
the validation study and the knowledge acquired during the development of the method. It is sometimes
preferable to segment a field of application rather than to attempt to validate an overly general method. In this
case, a validation file for each field of application shall be compiled.
3.1.6
field repeatability conditions
the conditions in which independent test results are obtained by one laboratory using the same method
carried out through two measurement systems set up according a written procedure and measuring
simultaneously the concentration of the measurand
[ISO 5725-1:1994]
3.1.7
field reproducibility conditions
the conditions in which independent test results are obtained by at least two laboratories using the same
method carried out through two measurement systems set up according a written procedure and measuring
simultaneously the concentration of the measurand
[ISO 5725-1:1994]
3.1.8
lack of fit
systematic deviation within the range of application between the measurement result obtained by applying the
linear model equation to the observed response of the measuring system measuring reference materials and
the corresponding accepted value of such reference materials
NOTE 1 Lack of fit may be a function of the measurement result.
NOTE 2 Since bias is considered as too specific and to difficult to be determined experimentally, the concept of lack of
fit is selected for this Technical Specification.
3.1.9
limit of detection (L )
D
smallest measurand (3.1.14) concentration which can be detected, but not quantified, in the experiment
conditions described for the method
3.1.10
limit of quantification (L )
Q
smallest measurand (3.1.14) concentration which can be quantified, in the experiment conditions described for
the method
3.1.11
linearity
capacity of a measurement method (3.1.15), within certain limits, to provide an instrument response or results
proportional to the quantity of the measurand (3.1.14) to be determined in the sample
This proportionality is expressed through a defined a priori mathematical expression.
The linearity limits are the concentration limits in the experiment between which a linear calibration model can
be applied with a known level of confidence.
3.1.12
matrix
all the components of the sample other than the measurand (3.1.14) that could influence the measurement
3.1.13
maximum permissible errors
extreme values of the error permitted by specifications, regulations, etc. for the given measuring system
(VIM:1994, 5.21)
3.1.14
measurand
subject that is characterised by a measurement method (3.1.15)
3.1.15
measurement method
method described in a written procedure containing all the means and procedures required to sample and
analyse, namely: field of application, principle and/or reactions, definitions, reagents, equipment, procedures,
presentation of results, repeatability (3.1.16) and other requirements, test report
3.1.16
repeatability
the closeness of agreement between independent test results obtained in the stipulated conditions
NOTE 1 Repeatability depends exclusively upon the distribution of random errors and has no relation with the true or
specified value.
NOTE 2 The measurement of repeatability is calculated from the standard deviation of test results. A lower level of
repeatability is reflected by a greater standard deviation.
NOTE 3 The term "independent test results" signifies results obtained in such a way as not to be influenced by a
previous result on the same or similar testing equipment. Quantitative measurements of repeatability depend critically
upon the stipulated conditions. Repeatability and reproducibility conditions are specific groups of extreme conditions.
[ISO 5725-1:1994]
3.1.17
standard deviation of field repeatability
standard repeatability of numerous repetitions obtained by a laboratory in field repeatability conditions (see
3.1.6)
3.1.18
standard deviation of field reproducibility
standard reproducibility of numerous repetitions obtained by at least two laboratories in field reproducibility
conditions (see 3.1.7)
3.1.19
standardised reference method (SRM)
measurement method (3.1.15) recognised by experts and taken as a reference by convention, which gives, or
is presumed to give, the accepted reference value of the concentration of the measurand (3.1.14) to be
measured
3.1.20
trueness
closeness of agreement between the mean value obtained from a large series of test results and an accepted
reference value
[ISO 5725-1:1994]
NOTE 1 The measurement of trueness is generally expressed in terms of a bias or a systematic deviation.
3.1.21
validation of a measurement method
act of subjecting a measurement method (3.1.15) to a study, which is based on a standardised and/or
recognised protocol and which provides proof that, for its field of application, the measurement method
satisfies pre-established performance criteria
NOTE In the framework of this Technical Specification, the validation of a method is mainly based on an “in
field” study that includes comparison to a reference method.
3.2 Symbols
For the requirements of this Technical Specification, the symbols and notations defined in Table 1 are
applicable.
Table 1 – Symbols
Symbol Description
Intercept of the orthogonal regression line between AM and SRM values
C
Slope of the orthogonal regression line between AM and SRM values
C
Difference between and for each value of i
dx x x
i i1 i2
Relative value e of ratio between and for each value of i,
i
e dx x
i i iav
G Ratio between ( − e) and
i
e s
i ei
Limit of detection
L
D
Limit of quantification
L
Q
Number of trials
p
n Number of parallel measurement for the alternative method
i
Number of parallel measurement for the reference method
m
i
Standard deviation of the population of the
s e
ei i
Standard deviation of repeatability for the alternative method
s (x)
r
Standard deviation of repeatability for the reference method
s (z)
r
Maximum allowable standard deviation of repeatability for the reference method
S (z)
r limit
Standard deviation of reproducibility for the alternative method
s (x)
R
Standard deviation of reproducibility for the reference method
s (z)
R
u Maximum combined standard uncertainty given in the SRM standard
cSRM
Measurement of the concentration obtained by the alternative method for a trial i and
x
ij
repetition j
Outlier
x
p
Average value for each value of i
x
iav
Measurement of the concentration obtained by the reference method for a trial i and
z
ij
repetition j
Table 1 (concluded)
Symbol Description Formula
ni
Arithmetic mean of a variable x for which  n
x
i
j
x
∑
measurements have been taken
ij
i=1
x =
j
n
i
p n
i
Grand average of a variable x for which
x N
x
∑∑
measurements have been taken
ij
i==11j
x =
N
p
Total number of measurements for AM
N(x)
N(x) = n
∑
i
i=1
Total number of measurements for SRM p
N(z)
N( z) = m
∑
i
i=1
Sum of the squares of the mean deviations for
SSD(x)
p
 
a variable x
∑ 
x
 i
p
2 i=1
 
SSD()x = −
∑
x
i
p
i=1
SSD(x)
(x) Variance of a variable x
s
(x) =
s
p −1
Repeatability variance of the alternative method p n
i
s (x) 2
r
()x - x
∑∑
ij i
i1==1 j
s (x) =
r
N(x) − p
Coefficient of the orthogonal regression line
k
1−
r
k =
t
1−α / 2
n − 2
Regression coefficient
r
SPD(x, z)
r =
SSD(x).SSD(z)
p p
Sum of the products of the deviations for two
SPD(x, z)
x y
i
∑ ∑
i
p
variables x and z
i=1 i=1
SPD()x, z = x y −
i
∑
i
p
i=1
4 Contents of the validation
4.1 General
The user of an alternative method is responsible for ensuring that it is adequately validated. This validation
shall include the following items:
 description of the alternative method (see 4.2);
 determination of performance characteristics (see 4.3);
 calculation of the overall uncertainty of the method (see 4.4);
 in field validation (see 4.5).
4.2 Description of the alternative method
The description shall permit all competent persons to use it (including the procedure and the calculations).
The following items should be addressed:
 title;
 warnings and safety precautions (where relevant);
 introduction;
 purpose and field of application;
 standard references;
 definitions;
 principle (sampling and analysis);
 reagents and products (where relevant);
 equipment (e.g.: description of the sampling line and measuring device);
 procedures for quality checks;
 presentation of results and performance characteristics;
 specific cases;
 remarks;
 test report;
 annexes;
 bibliography.
The field of application of the alternative method shall be clearly defined in terms of:
 gas matrixes;
 concentration range (the limit of quantification (3.1.10) and the upper limit of the claimed concentration
range shall be given);
 external conditions (e.g. ambient temperature).
NOTE Some of the above items might not be applicable to a specific method.
4.3 Determination of performance characteristics
4.3.1 General
Identify all potentially important sources of uncertainty in accordance with relevant standards. Any
performance characteristic that is not able to create a standard uncertainty of more than 20 % of the highest
standard uncertainty of the others may be excluded from the selection.
4.3.2 Manual method
Main sources of uncertainty are attached to:
 absorption efficiency of the absorption bottles;
 calibration of the gas volume meter;
 effect of temperature variation in the gas meter;
 effect of ambient pressure variation in the gas meter;
 humidity after the drying cartridge;
 leakage of the sampling line;
 absorption in the sampling system;
 preparation of sample for analysis;
 analysis;
 limit of detection and quantification;
 lack of fit;
 repeatability;
 interferences;
 absorption in the sampling system;
 reference material.
4.3.3 Automatic method
Main sources of uncertainty are attached to the performance characteristics of the method, which shall be
determined according to relevant test procedures recognised by CEN:
 response time;
 limit of detection and quantification;
 lack of fit;
 short term drift;
 long term drift;
 repeatability;
 dependence on sampling gas pressure;
 dependence on ambient temperature;
 dependence on voltage;
 interferences;
 leakage of the sampling line;
 absorption in the sampling system;
 adjustment of the analyser;
 reference material (e.g. calibration gas).
4.4 Calculation of the overall uncertainty
The overall uncertainty of the alternative method shall be calculated by building an uncertainty budget
according to EN ISO 14956 or ENV 13005. The maximum overall uncertainty of the alternative method shall
be compared with the reference’s and shall be lower or equal to the maximum overall uncertainty specified by
the standard reference method at the Emission Limit Value.
4.5 In field validation
4.5.1 Coverage of in field validation
4.5.1.1 Gas matrixes
The “in field validation” covers the field
...