1、November 2008DEUTSCHE NORM English price group 16No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 71.040.40!$Rg“1476888
2、www.din.deDDIN EN ISO 15796Gas analysis Investigation and treatment of analytical bias (ISO 15796:2005)English version of DIN EN ISO 15796:2008-11Gasanalyse Untersuchung und Behandlung von systematischen Abweichungen (ISO 15796:2005)Englische Fassung DIN EN ISO 15796:2008-11www.beuth.deDocument comp
3、rises 39 pagesDIN EN ISO 15796:2008-11 2 National foreword This standard has been prepared by Technical Committee ISO/TC 158 “Analysis of gases” (Secretariat: NEN, Netherlands) and has been taken over as EN ISO 15796:2008 by Technical Committee CEN/SS N21 “Gaseous fuels and combustible gas” (Secreta
4、riat: CMC). The responsible German body involved in its preparation was the Normenausschuss Materialprfung (Materials Testing Standards Committee), Technical Committee NA 062-05-73 AA Gasanalyse und Gas-beschaffenheit. The DIN Standards corresponding to the International Standards referred to in thi
5、s document are as follows: ISO 14111 DIN EN ISO 14111 ISO 7504 DIN V 51897 ISO 6143 DIN EN ISO 6143 ISO 5725-3 DIN ISO 5725-3 ISO 14956 DIN EN ISO 14596 In addition, it should be noted that the “Guide to the expression of uncertainty in measurement (GUM)” has been published as DIN V ENV 13005. Natio
6、nal Annex NA (informative) Bibliography DIN V 51897, Gas analysis Definitions and explanations DIN V ENV 13005, Guide to the expression of uncertainty in measurement DIN EN ISO 6143, Gas analysis Comparison methods for determining and checking the composition of calibration gas mixtures DIN EN ISO 1
7、4111, Natural gas Guidelines to traceability in analysis DIN EN ISO 14596, Petroleum products Determination of sulfur content Wavelength-dispersive X-ray fluorescence spectrometry DIN EN ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories DIN ISO 5725-3, Ac
8、curacy (trueness and precision) of measurement methods and results Part 3: Intermediate measures of the precision of a standard measurement method EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 15796August 2008ICS 71.040.40English VersionGas analysis - Investigation and treatment of analytica
9、l bias(ISO 15796:2005)Analyse des gaz - Investigation et traitement des biaisanalytiques (ISO 15796:2005)Gasanalyse - Untersuchung 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/CEN
10、ELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard 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
11、CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language 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 m
12、embers are the national standards bodies of Austria, Belgium, Bulgaria, 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,
13、 Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR 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
14、. EN ISO 15796:2008: E2 Contents Page Foreword3 Introduction .4 1 Scope 5 2 Terms and definitions .5 3 Symbols 7 4 Bias related to instrumental drift .8 4.1 Principle8 4.2 Stability monitoring .8 4.3 Drift correction 10 5 Bias related to effects of sample composition 14 5.1 Principles. 14 5.2 Local
15、bias handling 15 5.3 Bias handling for an extended measuring range 27 6 Treatment of matrix interferences. 31 Annex A (normative) Critical values for the trend test 33 Annex B (informative) Uncertainty issues . 34 Bibliography. 37 DIN EN ISO 15796:2008-11 EN ISO 15796:2008 (E) Foreword The text of I
16、SO 15796:2005 has been prepared by Technical Committee 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
17、. This European Standard shall be given the status of a 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 so
18、me of the elements of this document may be the subject 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 imp
19、lement this European Standard: Austria, Belgium, Bulgaria, 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, Switzerlan
20、d and the United Kingdom. Endorsement notice The text of ISO 15796:2005 has been approved by CEN as a EN ISO 15796:2008 without any modification. 3 DIN EN ISO 15796:2008-11 EN ISO 15796:2008 (E) Introduction Traceability is considered as one of the key items of quality assurance in gas analysis. In
21、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 been demonstrated to be free of significant bias
22、, 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 composition. An analytical procedure is consid
23、ered 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. Alternatively, other representative samples may b
24、e 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, implementing principles laid out in ISO 14111
25、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 in gas composition analysis, replacing the t
26、erm “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). 4 DIN EN ISO 15796:2008-11 EN ISO 15796:2008 (E) 1 Scope This International Stan
27、dard 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 procedures, as well as for estimating the correction uncertainty. The main sources of (and parameters affectin
28、g) bias of analytical procedures are instrumental drift (time) and matrix interferences (matrix composition). Moreover, bias normally varies with analyte concentration. This International Standard therefore establishes protocols for detecting and correcting drift for an analytical system of limited
29、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 studies, either separately or sequentially. This International Standard specifies procedures for two options
30、, 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 normally the first option entails lower uncertainty at the expense of higher effort. For the convenienc
31、e 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 gas mixture. However, they are equally applicable to measurements of physico-chemical properties of a
32、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 definitions apply. 2.1 bias estimate of systematic error NOTE Since the true value of a measurand cannot be know
33、n 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 compensate for systematic error NOTE 1 Since systematic errors cannot be determined exactly, a correctio
34、n can never be complete. NOTE 2 In the VIM5, the term correction is used with a different meaning. 5 DIN EN ISO 15796:2008-11 EN ISO 15796:2008 (E) 2.3 uncertainty parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attribu
35、ted 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 international standards, through an unbroken chain of comparisons VIM:19935, definition 6.10 NOTE I
36、n 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 known accuracy and comparison measurements of known performance. 2.5 reference value estimate of
37、 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-chemical properties are most often provided by reference gas mixtures and reference analytical procedur
38、es. 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 derived ISO 7504:20014, definition 4.1.1 2.7 reference analytical procedure analytical procedure
39、 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 stability of a measuring system absence of significant drift 2.10 matrix interference change in an
40、alytical response for a specified analyte, caused by variations in matrix composition 6 DIN EN ISO 15796:2008-11 EN ISO 15796:2008 (E) 3 Symbols A, B specified drift-control mixtures biparameters of a bias correction model deviation (from a reference value) I interferent under consideration M gas mi
41、xture 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 Rireference gas mixtures used for bias investigation s standard deviation of a data series
42、 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) relative standard uncertainty of an estimated quantity x u(x, y) covariance between two e
43、stimated 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 7DIN EN ISO 15796:2008-11 EN ISO 15796:2008 (E) 4 Bias related to instrumental drift 4.1 Principle This clause specifie
44、s 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” is measured on a regular basis. For each specified analyte, the results are recorded
45、 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. Monotonic decrease or increase in control data indicates drift. As an alternative to vi
46、sual 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 is observed, the analytical system is removed from service. After adjustment and re-c
47、alibration, 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 system, a representative subset of analytes may be used. If the analytical system is kn
48、own 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 anal
49、ysing two mixtures of distinct composition (different concentrations of the analytes under consideration, different matrix compositions) on a regular basis. The results are recorded, and for each analyte the two time-series of drift measurement data are compared in order to investigate whether drift behaviour can be expressed in a concentration-invariant manner. Given this for every analyte under consideration, the two time-series for each analyte are pooled to derive a drift correction. In fortunate cases, a joint drift co
