1、BRITISH STANDARDGas analysis Investigation and treatment of analytical biasICS 71.040.40g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN ISO 15
2、796:2008This British Standard waspublished under the authorityof the Standards Policy andStrategy Committee on 5 September 2005 BSI 2009National forewordAmendments corrigenda issued since publicationThis British Standard is the UK implementation of EN ISO 15796:2008. It is identical with ISO 15796:2
3、005. It supersedes BS ISO 15796:2005, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee PTI/15, Natural gas and gas analysis.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purpo
4、rt to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations. ISBN 978 0 580 65014 7Date Comments 30 June 2009 This corrigendum renumbers BS ISO 15796:2005 asBS EN ISO 1579
5、6:2008BS EN ISO 15796:2008EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 15796August 2008ICS 71.040.40English VersionGas analysis - Investigation and treatment of analytical bias(ISO 15796:2005)Analyse des gaz - Investigation et traitement des biaisanalytiques (ISO 15796:2005)Gasanalyse - Unt
6、ersuchung und Behandlung vonsystematischen Abweichungen (ISO 15796:2005)This European Standard was approved by CEN on 30 July 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standa
7、rd without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other lan
8、guage made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland
9、,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE F
10、R NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 15796:2008: EEN ISO 15796:2008 (E) Foreword The text of ISO 15796:2005 has been prepared by Technical Committee
11、ISO/TC 158 “Analysis of gases” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 15796:2008 by Technical Committee CEN/SS N21 “Gaseous fuels and combustible gas” the secretariat of which is held by CMC. This European Standard shall be given the status of a
12、 national standard, either by publication of an identical text or by endorsement, at the latest by February 2009, and conflicting national standards shall be withdrawn at the latest by February 2009. Attention is drawn to the possibility that some of the elements of this document may be the subject
13、of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgar
14、ia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text o
15、f ISO 15796:2005 has been approved by CEN as a EN ISO 15796:2008 without any modification. ii EN ISO 15796:2008BSiiiContents Page Foreword iv Introduction v 1 Scope 1 2 Terms and definitions. 1 3 Symbols . 3 4 Bias related to instrumental drift. 4 4.1 Principle . 4 4.2 Stability monitoring 4 4.3 Dri
16、ft correction 6 5 Bias related to effects of sample composition 10 5.1 Principles . 10 5.2 Local bias handling. 11 5.3 Bias handling for an extended measuring range 23 6 Treatment of matrix interferences. 27 Annex A (normative) Critical values for the trend test 29 Annex B (informative) Uncertainty
17、issues . 30 Bibliography . 33 EN ISO 15796:2008 (E) EN ISO 15796:2008BSiv 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 te
18、chnical 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 close
19、ly 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
20、 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. Attention is drawn to the possibility that some of the elements of this docume
21、nt may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 15796 was prepared by Technical Committee ISO/TC 158, Analysis of gases. EN ISO 15796:2008 (E) EN ISO 15796:2008BSvIntroduction Traceability is considered as one of the key it
22、ems of quality assurance in gas analysis. In general, it is defined by the existence of unbroken chains of comparisons, relating the analytical result to acknowledged standards of measurement. More specifically, an analytical result is considered traceable if, by way of these comparisons, it has bee
23、n demonstrated to be free of significant bias, significance referring to the specified uncertainty of the result. As a rule, traceability is not demonstrated individually for a single analytical result but for a defined analytical procedure with specified ranges of analyte concentration and matrix c
24、omposition. An analytical procedure is considered traceable if it has been demonstrated to be free of significant bias, or if significant bias has been corrected, by measurement on representative samples of known traceable composition. These may be samples of appropriate reference gas mixtures. Alte
25、rnatively, other representative samples may be analysed in parallel using an accepted reference procedure. This International Standard provides generic methods for demonstrating, or establishing, traceability of analytical procedures using reference gas mixtures or reference analytical procedures, i
26、mplementing principles laid out in ISO 14111 1and ISO/TS 14167 2, and respecting the principles of the Guide to the Expression of Uncertainty in Measurement (GUM) 3. In this International Standard, the term “concentration” is used for two different purposes: as a general term for quantities measured
27、 in gas composition analysis, replacing the term “content” (see ISO 7504 4); as a generic substitute for any of the specific quantities measured in gas composition analysis such as the mass concentration or the mole fraction of a specified analyte (see ISO 75044). EN ISO 15796:2008 (E) EN ISO 15796:
28、2008BSblank1Gas analysis Investigation and treatment of analytical bias 1 Scope This International Standard specifies generic methods for detecting and correcting bias (systematic errors) of analytical procedures for the analysis of gases, using reference gas mixtures or reference analytical procedu
29、res, as well as for estimating the correction uncertainty. The main sources of (and parameters affecting) bias of analytical procedures are instrumental drift (time) and matrix interferences (matrix composition). Moreover, bias normally varies with analyte concentration. This International Standard
30、therefore establishes protocols for detecting and correcting drift for an analytical system of limited stability, investigating and handling bias of a stable analytical system for a specified range of sample composition, which are intended to be used in method development and method validation studi
31、es, either separately or sequentially. This International Standard specifies procedures for two options, applicable to systematic effects, as follows: a) tracing the observed pattern of deviations and correcting for their effect, b) averaging over their effects and increasing the uncertainty, where
32、normally the first option entails lower uncertainty at the expense of higher effort. For the convenience of the user, the methods specified in this International Standard are described for procedures of composition analysis, i.e. procedures for measuring the concentration of a specified analyte in a
33、 gas mixture. However, they are equally applicable to measurements of physico-chemical properties of a gas or gas mixture relevant to gas analysis, and translation into this subject field is straightforward. 2 Terms and definitions For the purposes of this document, the following terms and definitio
34、ns apply. 2.1 bias estimate of systematic error NOTE Since the true value of a measurand cannot be known exactly, systematic errors cannot be determined exactly but have to be estimated using reference values. 2.2 correction procedure by which the uncorrected result of a measurement is adjusted to c
35、ompensate for systematic error NOTE 1 Since systematic errors cannot be determined exactly, a correction can never be complete. NOTE 2 In the VIM5, the term correction is used with a different meaning. EN ISO 15796:2008 (E) EN ISO 15796:2008BS2 2.3 uncertainty parameter, associated with the result o
36、f a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand GUM:19933, definition 2.3.2 2.4 traceability property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or in
37、ternational standards, through an unbroken chain of comparisons VIM:19935, definition 6.10 NOTE In ISO 141111, the term traceability is defined as the ability to provide evidence of the overall accuracy attributed to measurement results through documented calibrations, using measurement standards of
38、 known accuracy and comparison measurements of known performance. 2.5 reference value estimate of a quantity, with sufficiently well established traceability and specified uncertainty, used as a reference for a specified purpose NOTE In gas analysis, reference values of composition or physico-chemic
39、al properties are most often provided by reference gas mixtures and reference analytical procedures. 2.6 reference gas mixture calibration gas mixture whose composition is sufficiently well established and stable to be used as a reference standard of composition from which other composition data are
40、 derived ISO 7504:20014, definition 4.1.1 2.7 reference analytical procedure analytical procedure which is capable of providing traceable results with sufficiently well established uncertainty for use as reference values 2.8 drift slow change of output, at constant input, of a measuring system 2.9 s
41、tability of a measuring system absence of significant drift 2.10 matrix interference change in analytical response for a specified analyte, caused by variations in matrix composition EN ISO 15796:2008 (E) EN ISO 15796:2008BS33 Symbols A, B specified drift-control mixtures biparameters of a bias corr
42、ection model deviation (from a reference value) I interferent under consideration M gas mixture under consideration m, n, N number of data in a data series p number of correction parameters Q recovery (with respect to a reference value) r number of reference gas mixtures used for bias investigation
43、Rireference gas mixtures used for bias investigation s standard deviation of a data series srrelative standard deviation of a data series (coefficient of variation) s2variance of a data series t time u(x) standard uncertainty of an estimated quantity x u2(x) variance of an estimated quantity x ur(x)
44、 relative standard uncertainty of an estimated quantity x u(x, y) covariance between two estimated quantities x and y x, y quantity under consideration x mean value of several quantities xiX analyte under consideration 2mean-square successive difference of a data series EN ISO 15796:2008 (E) EN ISO
45、15796:2008BS4 4 Bias related to instrumental drift 4.1 Principle This clause specifies procedures for investigating potential drift of an analytical system and taking corrective actions, if significant drift is encountered. If the analytical system is expected to be stable, a “drift-control mixture”
46、 is measured on a regular basis. For each specified analyte, the results are recorded on a control chart, and the time series of control data is examined continuously. As long as these data vary at random within established control limits, the analytical system has been demonstrated to be stable. Mo
47、notonic decrease or increase in control data indicates drift. As an alternative to visual inspection, a statistical test based on successive differences may be used to detect a significant trend. As soon as drift becomes significant, e.g. when data exceed control limits, or when a significant trend
48、is observed, the analytical system is removed from service. After adjustment and re-calibration, the analytical system is returned to service. The “drift-control mixture” should contain all analytes currently being measured. Given sufficient information on the response behaviour of the analytical sy
49、stem, a representative subset of analytes may be used. If the analytical system is known to exhibit significant drift, it can at least be expected that the drift behaviour of the system does not significantly depend upon sample composition, since this would allow for drift correction based on measurements of appropriate “drift-correction mixtures”. This expectation is tested by analysing two mixtures of distinct composition (different concentrations of the analytes under consideration, different matrix compositions) on a regular basis. T
