Key comparison automotive gas mixtures Euramet.QM-S4 Final Report

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1 Blad 1 van 41 Key comparison automotive gas mixtures Euramet.QM-S4 Final Report

2 Page of 41 VSL Van Swinden Laboratorium B.V., Thijsseweg 11, 69 JA Delft, Nederland INMETRO Instituto Nacional de Metrologia, Normalização e Qualidade Industrial, Av. Nossa Senhora das Graças, 50 Xerém - cep: Prédio 4 - Duque de Caxias - RJ Brasil IPQ Instituto Português da Qualidade, Rua António Gião, Caparica, Portugal NMISA National Metrology Institute of South Africa, Building 5, Meiring Naudé Road, Brummeria, Pretoria, 0184, South Africa SMU Slovak Institute of Metrology, Karloveska 63, SK Bratislava, Slovak Republic This work has been carried out by: Adriaan M.H. van der Veen Rutger Oudwater Paul R. Ziel Janneke I.T. van Wijk VSL VSL VSL VSL With contributions from: Cristiane Rodrigues Augusto Andreia de Lima Fioravante Claudia Cipriano Ribeiro Denise Cristine Gonçalves Sobrinho Valnei Cunha Florbela Dias Gonçalo Baptista Angelique Botha Miroslava Valkova Zuzana Durisova On request of: Euramet e.v. Project number: Euramet 1113 INMETRO INMETRO INMETRO INMETRO INMETRO IPQ IPQ NMISA SMU SMU

3 Page 3 of 41 Summary The capabilities for the preparation of certified reference materials of carbon monoxide, carbon dioxide, and propane in nitrogen have been compared. The participating national metrology institutes submitted each a gravimetrically prepared gas mixture of a specified target composition typical for the automotive industry to the coordinating laboratory. All mixtures were analysed by the coordinating laboratory using a gas chromatograph equipped with a thermal conductivity detector in three runs under repeatability conditions. Based on the calibration curve, reference values were assigned to the amount fractions of carbon monoxide, carbon dioxide, and propane. The degrees of equivalence were established as difference between the gas composition as calculated from preparation and the measured one, and its associated uncertainty. All participants obtained satisfactory results.

4 Page 4 of 41 Table of contents Summary 3 Table of contents 4 List of figures 5 List of tables 6 1 Introduction 7 Design of the key comparison 8.1 Field of measurement 8. Subject 8.3 Participants 8.4 Measurement standards 8.5 Measurement protocol 8.6 Measurement equation 8.7 Degrees of equivalence 9 3 Results Carbon monoxide Carbon dioxide Propane 1 4 Conclusions 15 References 16 Measurement report of INMETRO 17 Measurement report of IPQ 1 Measurement report of NMISA 5 Measurement report of SMU 8 Measurement report of VSL 3 Measurement verification of INMETRO PSM reevaluation of declated certification uncertainty 37

5 Page 5 of 41 List of figures Figure 1: Degrees of equivalence for carbon monoxide Figure : Degrees of equivalence for carbon dioxde... 1 Figure 3: Degrees of equivalence for propane... 14

6 Page 6 of 41 List of tables Table 1: Participants... 8 Table : Calibration mixtures for carbon monoxide Table 3: Regression coefficients for carbon monoxide Table 4: Reference values for carbon monoxide Table 5: Degrees of equivalence for carbon monoxide (mmol mol -1 ) Table 6: Calibration mixtures for carbon dioxide Table 7: Regression coefficients for carbon dioxide Table 8: Reference values for carbon dioxide... 1 Table 9: Degrees of equivalence for carbon dioxide (mmol mol -1 )... 1 Table 10: Calibration mixtures for propane Table 11: Regression coefficients for propane Table 1: Reference values for propane Table 13: Degrees of equivalence for propane (µmol mol -1 )... 13

7 Page 7 of 41 1 Introduction The measurement of carbon monoxide, carbon dioxide, and propane in nitrogen is relevant for implementing regulations with regard to car exhaust gas measurements. This report describes the key comparison on PSMs (primary standard gas mixtures) for automotive gas mixtures between national metrology institutes under auspices of the Euramet. Unlike in EUROMET.QM-K3, in this key comparison the participants submitted a PSM to the coordinating laboratory.

8 Page 8 of 41 Design of the key comparison.1 Field of measurement Amount of substance. Subject Gas mixtures for car exhaust measurements (automotive mixtures): carbon monoxide, carbon dioxide, and propane in nitrogen.3 Participants The following national metrology institutes participated (table 1). Table 1: Participants Country Brasil Portugal the Netherlands Slovakia South Africa Laboratory Instituto Nacional de Metrologia, Normalização e Qualidade Industrial (INMETRO) Instituto Português da Qualidade (IPQ) Van Swinden Laboratorium (VSL) Slovak Institute of Metrology (SMU) National Metrology Institute of South Africa (NMISA).4 Measurement standards The laboratories were requested to prepare an automotive mixture with the following nominal composition 0 mmol mol -1 carbon monoxide, 10 mmol mol -1 carbon dioxide, and 1000 µmol mol -1 propane in nitrogen. The calculation of the gas composition and associated uncertainty evaluation should be done in accordance with ISO 614 [1]..5 Measurement protocol The submitted reference gas mixtures were measured three times against VSL PSMs (primary standard gas mixtures) on three different days. The reference values for the amount of substance fractions are obtained by interpolation using the calibration curve. The measurements were taken on an Agilent 6890N gas chromatograph equipped with a 10ft Porapak N and a 3ft Molsieve 13x column, and two detectors (flame ionisation detector (FID) and thermal conductivity detector (TCD)). The column temperature is 35 C and the carrier gas flow is 5 ml min -1. Helium (5.0) is used as carrier gas. For all components, the TCD signal was used..6 Measurement equation The results from the gas chromatographic measurements have been fitted using a quadratic function in accordance with ISO 6143 []. The amount of substance fractions of the components are computed using the calibration functions. This function reads for each component as follows ( x; ) = a + a x a x y = f a Given a response y 0 for a component in one of the submitted mixtures, the associated x value (x 0 ) is to be calculated. This calculation can be done iteratively, using for example the bisection algorithm [3, p. 7]. An

9 Page 9 of 41 implementation of the bisection algorithm is given in [4, pp ]. The idea behind the method is that the solution is bracketed by two guesses. At convergence, ( ) y 0 = f x 0 ;a (1) The uncertainty associated with x 0 is computed from [5] u [ ] f 0 0; a a a x T ( x ) = ( x a) u ( y ) + ( f ( x ; a) ) V ( f ( x ; a) ) 1 () where T m ( f ( x ; a )) ( 1 x K x ) a 0 = V a denotes the covariance matrix associated with the parameter vector a. For a quadratic polynomial, m =..7 Degrees of equivalence A degree of equivalence is defined as the difference of a measurement result with respect to the key comparison reference value (KCRV) [6,7] d = x (3) i i x KCRV and its associated uncertainty. In previous key comparisons where the participating laboratories submitted a mixture, the KCRV was calculated from the consensus straight line obtained from calibrating the analyser with the submitted mixtures [8,9]. This approach is in this key comparison not possible, because of the very limited ranges of the components. As alternative approach the analyser is calibrated with the PSMs (Primary Standard gas Mixtures) from the coordinating laboratory. In this case the analysed value of the amount of substance fraction is adopted as KCRV x KCRV = x 0 (4) for each component in each mixture. The uncertainty of the degree of equivalence defined by equations (3) and (4) is given by u ( d ) u ( x ) u ( x ) = (5) i i + KCRV which follows directly from the application of the law of propagation of uncertainty to equation (3).

10 Page 10 of 41 3 Results 3.1 Carbon monoxide The results used for calibrating the GC (see section.5) for carbon monoxide are shown in table. These data can be fitted with a quadratic polynomial. The coefficients are given in table 3. The residuals satisfy the consistency criteria of ISO 6143 []. Table : Calibration mixtures for carbon monoxide y u(y) Mixture x u(x) mol mol -1 mol mol -1 VSL VSL VSL VSL VSL VSL Table 3: Regression coefficients for carbon monoxide Coefficient value u a[0] a[1] a[] Using the calibration curve, the reference values have been obtained by analysing the mixtures. The expression for the key comparison reference value (KCRV), x 0, and its associated standard uncertainty are given in section.6. The results are given in table 4. Table 4: Reference values for carbon monoxide x u(x ) u(x )/x Δx/x Mixture y u(y) x i Δx mmol mol -1 0 mmol mol -1 0 mmol mol % relative mmol mol -1 0 % relative IP IN VSL NM SM The degrees of equivalence have been computed as described in section.7 and are given in table 5. The degrees of equivalence are shown in figure 1. All laboratories have satisfactory results for carbon monoxide. Table 5: Degrees of equivalence for carbon monoxide (mmol mol -1 ) 1 Mixture x i u(x i ) x KCRV u(x KCRV ) d i u(d i ) IP IN VSL NM SM After disclosure of the measurement results by the coordinator, Inmetro realised that the calculation of the given uncertainty was not correctly propagated. The amended measurement report for Inmetro is annexed to this report (after the measurement reports).

11 Page 11 of Degree of equivalence (mmol mol -1 ) IPQ INMETRO VSL Laboratory NMISA SMU Figure 1: Degrees of equivalence for carbon monoxide 3. Carbon dioxide The results used for calibrating the GC (see section.5) for carbon dioxide are shown in table 6. These data can be fitted with a quadratic polynomial. The coefficients are given in table 7. The residuals satisfy the consistency criteria of ISO 6143 []. Table 6: Calibration mixtures for carbon dioxide y u(y) Mixture x u(x) mol mol -1 mol mol -1 VSL VSL VSL VSL VSL VSL Table 7: Regression coefficients for carbon dioxide Coefficient value u a[0] a[1] a[] Using the calibration curve, the reference values have been obtained by analysing the mixtures. The expression for the KCRV, x 0, and its associated standard uncertainty are given in section.6.the results are given in table 8.

12 Page 1 of 41 Table 8: Reference values for carbon dioxide x u(x ) u(x )/x Δx/x Mixture y u(y) x i Δx mmol mol -1 0 mmol mol -1 0 mmol mol % relative mmol mol -1 0 % relative IN VSL NM IP SM The degrees of equivalence have been computed as described in section.7 and are given in table 9. The degrees of equivalence are shown in figure. All laboratories have satisfactory results for carbon dioxide. Table 9: Degrees of equivalence for carbon dioxide (mmol mol -1 ) Mixture x i u(x i ) x KCRV u(x KCRV ) d i u(d i ) IN VSL NM IP SM Degree of equivalence (mmol mol -1 ) INMETRO VSL NMISA Laboratory IPQ SMU Figure : Degrees of equivalence for carbon dioxde 3.3 Propane The results used for calibrating the GC (see section.5) for propane (TCD signal) are shown in table 10. These data can be fitted with a quadratic polynomial. The coefficients are given in table 11. The residuals satisfy the consistency criteria of ISO 6143 [].

13 Page 13 of 41 Table 10: Calibration mixtures for propane y u(y) Mixture x u(x) µmol mol -1 µmol mol -1 VSL VSL VSL VSL VSL VSL Table 11: Regression coefficients for propane Coefficient value u a[0] a[1] a[] Using the calibration curve, the reference values have been obtained by analysing the mixtures. The expression for the KCRV, x 0, and its associated standard uncertainty are given in section.6. The results are given in table 1. Table 1: Reference values for propane x u(x ) u(x )/x Δx/x Mixture y u(y) x i Δx µmol mol -1 0 µmol mol -1 0 µmol mol % relative µmol mol -1 0 % relative IP VSL IN NM SM The degrees of equivalence have been computed as described in section.7 and are given in table 13. The degrees of equivalence are shown in figure 3. All laboratories have satisfactory results for carbon dioxide. Table 13: Degrees of equivalence for propane (µmol mol -1 ) Mixture x i u(x i ) x KCRV u(x KCRV ) d i u(d i ) IP VSL IN NM SM

14 Page 14 of Degree of equivalence (µmol mol -1 ) IPQ VSL INMETRO Laboratory NMISA SMU Figure 3: Degrees of equivalence for propane

15 Page 15 of 41 4 Conclusions All mixtures submitted are consistent with respect to the key comparison reference value (KCRV) for all components (carbon monoxide, carbon dioxide and propane in nitrogen). Participating laboratories have therefore successfully validated their preparation capabilities for this 4-component gas mixture.

16 Page 16 of 41 References [1] International Organization for Standardization, ISO 614:001 Gas analysis - Preparation of calibration gas mixtures - Gravimetric methods, nd edition [] International Organization for Standardization, ISO 6143 Gas analysis -- Comparison methods for determining and checking the composition of calibration gas mixtures, ISO Geneva, 001 [3] Cox M.G., Forbes A.B., Harris P.M., Smith I.M., The classification and solution of regression problems for calibration, NPL Report CMSC 4/03, National Physical Laboratory, Teddington (UK), March 003 [4] Press W.H., Teukolsky S.A., Vetterling W.T., Flannery B.P., Numerical Recipes in C the art of scientific computing, nd edition, Cambridge University Press, 199 [5] Milton M.J.T., Harris P.M., Smith I.M., Brown A.S., Goody B.A., Implementation of a generalised leastsquares method for determining calibration curves from data with general uncertainty structures, Metrologia 43 (006), pp. S91-S98 [6] Cox M.G., The evaluation of key comparison data: An introduction, Metrologia 39 (00), pp [7] Cox M.G., The evaluation of key comparison data, Metrologia 39 (00), pp [8] Jeongsoon Lee, Jin Bok Lee, Dong Min Moon, Jin Seog Kim, Van der Veen A.M.H., Besley L., Heine H.J., Martin B., Konopelko L.A., Kato K., Shimosaka T., Perez Castorena A., Macé T., Milton M.J.T., Kelley M., Guenther F., Botha A., Final report on international key comparison CCQM-K53: Oxygen in nitrogen, Metrologia 47 (010), Tech. Suppl., [9] Van der Veen A.M.H., Chander H., Ziel P.R., Wessel R.M., de Leer E.W.B., Smeulders D., Besley L., Kato K., Watanabe T., Seog Kim J., Woo J-C., Kil Bae H., Doo Kim Y., Pérez Castorena A., Rangel Murillo F., Serrano Caballero V.M., Ramírez Nambo C., Avila Salas M.d.J., Konopelko L.A., Popova T.A., Pankratov V.V., Kovrizhnih M.A., Kuzmina T.A., Efremova O.V., Kustikov Y.A., M.J.T.Milton, Vargha G., Guenther F.R. and Rhoderick G.C., International comparison CCQM-K54: Primary standard gas mixtures of hexane in methane, Metrologia 47 (010), Tech. Suppl., 08019

17 Page 17 of 41 Measurement report of INMETRO 1. CYLINDER DETAILS Date of mixture preparation 0/08/009 Volume (L) 5 Total Pressure (bar) 10 Connection type (e.g. DIN1, BS14 etc.) DIN1. SOURCE OF CO VSL PRM PURITY TABLE FOR NOMINALLY PURE CO Component Method Mole Fraction Ar Supplier purity table CH 4 Supplier purity table CO Supplier purity table CO Supplier purity table C x H y Supplier purity table H Supplier purity table H O Supplier purity table N Supplier purity table O Supplier purity table

18 Page 18 of PURITY TABLE FOR NOMINALLY PURE N Component Method Mole Fraction N CO H O O C x H y ISO 614 purity estimation ISO 614 purity estimation ISO 614 purity estimation ISO 614 purity estimation ISO 614 purity estimation SOURCE OF CO White Martins WM PURITY TABLE FOR NOMINALLY PURE CO Component Method Mole Fraction N CO CO H H O O C x H y ISO 614 purity estimation ISO 614 purity estimation ISO 614 purity estimation ISO 614 purity estimation ISO 614 purity estimation ISO 614 purity estimation ISO 614 purity estimation SOURCE OF PROPANE VSL MY967

19 Page 19 of PURITY TABLE FOR NOMINALLY PURE PROPANE Component Method Mole Fraction Ar Supplier purity table CH 4 Supplier purity table CO Supplier purity table CO Supplier purity table C H 6 Supplier purity table C 3 H 6 Supplier purity table C 3 H 8 Supplier purity table H Supplier purity table H O Supplier purity table N Supplier purity table O Supplier purity table PREPARATION OF FINAL MIXTURE Parent gases x (grav+pur) u(x) CO x x 10-6 CO x x 10-6 C 3 H x x 10-6 N x PURITY TABLE FOR FINAL MIXTURE Component x (grav+pur) u(x) CH N C 3 H Ar CO CO C H H H O

20 Page 0 of 41 Component x (grav+pur) u(x) O C x H y C 3 H RESULTS The results are presented in following table with data: x prep amount of substance fraction, from preparation (mol.mol -1 ) u prep uncertainty of x prep from gravimetrical preparation and purity (mol.mol -1 ) u ver uncertainty from verification (mol.mol -1 ) u st uncertainty of stability (mol.mol -1 ) u cert final uncertainty of x (mol.mol -1 ) U(k=) stated uncertainty of x, at 95% level of confidence (mol.mol -1 ) Standard uncertainty of the mixture was calculated with following formula: u = u + u + u cert prep ver st Component x prep u prep u ver u st u cert x U(k=) CO x x x x x x 10 - CO x x x x x x 10 - propane x x x x x x 10-6

21 Page 1 of 41 Measurement report of IPQ 1. CYLINDER DETAILS Date of mixture preparation Volume (L) 5 Total Pressure (bar) 100 Connection type (e.g. DIN1, BS14 etc.) DIN 477 nº 1. SOURCE OF CO Ar Liquido 3. PURITY TABLE FOR NOMINALLY PURE CO Component Method mole fraction CO specifications ,0 x ,0 x 10-6 N specifications 10,0 x ,0 x 10-6 Ar specifications 10,0 x ,0 x 10-6 CO specifications 1,0 x ,5 x 10-6 H O specifications 3,0 x ,5 x 10-6 H specifications 1,0 x ,5 x 10-6 O specifications 3,0 x ,5 x 10-6 CH 4 specifications 1,0 x ,5 x 10-6 C n H m specifications,0 x ,0 x 10-6

22 Page of PURITY TABLE FOR NOMINALLY PURE N Component Method mole fraction N specifications ,4 x ,5 x 10-7 CO specifications,5 x ,4 x 10-7 CO specifications,5 x ,4 x 10-7 H O specifications 0,10 x ,06 x 10-7 H specifications 5,0 x 10-7,9 x 10-7 O specifications 0,05 x ,03 x 10-7 C n H m specifications 0,5 x ,3 x SOURCE OF CO Gasin 6. PURITY TABLE FOR NOMINALLY PURE CO Component Method mole Fraction CO specifications ,0 x ,9 x 10-6 N specifications,5 x ,4 x 10-6 CO specifications 0,5 x ,3 x 10-6 H O specifications 1,5 x ,9 x 10-6 O specifications 1,5 x ,9 x 10-6 C n H m specifications 0,5 x ,3 x SOURCE OF PROPANE Ar Liquido 8. PURITY TABLE FOR NOMINALLY PURE PROPANE Component Method Mole Fraction C 3 H 8 specifications x x 10-6 N specifications 0 x x 10-6 CO specifications,5 x ,4 x 10-6 H O specifications,5 x ,4 x 10-6

23 Page 3 of 41 Component Method Mole Fraction H specifications 0 x x 10-6 O specifications 5,0 x 10-6,9 x 10-6 C 3 H 6 specifications 100 x x 10-6 C n H m specifications 100 x x PREPARATION OF FINAL MIXTURE Parent gases x (grav+pur) u(x) CO 98,657 x ,005 x 10-3 C 3 H 8 49,951 x ,007 x PURITY TABLE FOR FINAL MIXTURE Component x (grav+pur) u(x) Ar 0,0 x ,10 x 10-6 CO 1,996 x 10-0,0001 x 10 - CO 1,0533 x 10-0,0003 x 10 - H O 0,37 x ,1 x 10-6 H 0,41 x ,19 x 10-6 O 0,7 x ,11 x 10-6 N 85,8504 x 10-0,0003 x 10 - CH 4 0,05 x ,0 x 10-6 C 3 H 6 0,0 x ,10 x 10-6 C 3 H 8 998,8 x , x 10-6 C n H m 0,6 x ,11 x RESULTS The results are presented in following table with data: x prep amount of substance fraction, from preparation (mol.mol -1 ) u prep uncertainty of x prep from gravimetrical preparation and purity (mol.mol -1 ) u ver uncertainty from verification (mol.mol -1 ) u st uncertainty of stability (mol.mol -1 ) u cert final uncertainty of x (mol.mol -1 ) U(k=) stated uncertainty of x, at 95% level of confidence (mol.mol -1 ) Standard uncertainty of the mixture was calculated with following formula:

24 Page 4 of 41 u = u + u + u cert prep ver st Component x prep u prep u ver u st u cert x cert U(k=) CO 1,996 x 10-0,0001 x 10-0,0054 x ,0054 x 10-1,997 x 10-0,011 x 10 - CO 1,0533 x 10-0,0003 x 10-0,0168 x ,0168 x 10-1,070 x 10-0,034 x 10 - propane 998,8 x , x ,0 x ,0 x ,6 x ,0 x 10-6 Note: These gases are stable for a long period so we consider u st negligible.

25 Page 5 of 41 Measurement report of NMISA 1. CYLINDER DETAILS Date of mixture preparation 17 August 009 Volume (L) 5 Total Pressure (bar) 10 Connection type (e.g. DIN1, BS14 etc.) BS 341 no.4. SOURCE OF CO CO 4.7 from Air Liquide 3. PURITY TABLE FOR NOMINALLY PURE CO Component Method Mole Fraction (x 10-6 mol/mol) (x 10-6 mol/mol) Ar Specification CO 100-X H Specification H O Hydrocarbons Specification Specification N Specification O Specification PURITY TABLE FOR NOMINALLY PURE N Component Method Mole Fraction (x 10-6 mol/mol) (x 10-6 mol/mol) CH 4 GC-FID CO GC-FID CO GC-FID H Specification H O Specification N 100-X O Specification

26 Page 6 of SOURCE OF CO CO 4.5 from Air Products 6. PURITY TABLE FOR NOMINALLY PURE CO Component Method Mole Fraction (x 10-6 mol/mol) (x 10-6 mol/mol) CO 100-X H O Specification.0.7 Hydrocarbons Specification O Specification SOURCE OF PROPANE Propane 3.5 from Air Liquide 8. PURITY TABLE FOR NOMINALLY PURE PROPANE Component Method Mole Fraction (x 10-6 mol/mol) (x 10-6 mol/mol) C 3 H X CO Specification H O Specification.5.9 Hydrocarbons Specification N GC-PDHID O Specification PREPARATION OF FINAL MIXTURE Parent gases x (grav+pur) (x 10-6 mol/mol) u(x) (x 10-6 mol/mol) CO NML NML BIP

27 Page 7 of PURITY TABLE FOR FINAL MIXTURE Component x (grav+pur) u(x) Ar C 3 H CH CO CO H H O Hydrocarbons N O RESULTS The results are presented in following table with data: x prep amount of substance fraction, from preparation (x 10-6 mol.mol -1 ) u prep uncertainty of x prep from gravimetrical preparation and purity (x 10-6 mol.mol -1 ) u ver uncertainty from verification (x 10-6 mol.mol -1 ) u st uncertainty of stability (x 10-6 mol.mol -1 ) u cert final uncertainty of x (x 10-6 mol.mol -1 ) U(k=) stated uncertainty of x, at 95% level of confidence (x 10-6 mol.mol -1 ) Standard uncertainty of the mixture was calculated with following formula: u = u + u + u cert prep ver st Component x prep u prep u ver u st u cert x U(k=) CO CO propane

28 Page 8 of 41 Measurement report of SMU 1. CYLINDER DETAILS Date of mixture preparation 11.VI.009 Volume (L) 5 Total Pressure (bar) 100 Connection type (e.g. DIN1, BS14 etc.) DIN1. SOURCE OF CO The source of nominally pure CO gas was CO 4.7 Messer. The gas was diluted in one step to the concentration 0. mol/mol with BIP N. Calculation of purity table was made automatically by.0 version ISO 614 software with inputs from gravimetric preparation and purity measurements. Purity measurements were made using following analytical instruments: GC FID- methaniser, GC TCD, FTIR and Dew-point meter. Mole fraction of undetected, but analysed component was calculated from detection limit of used method. Specifications of the manufacturer were used for Ar, H and O. Uncertainties in purity table are in unextended form. 3. PURITY TABLE FOR NOMINALLY PURE CO Messer 4.7 CO Component Method Mole Fraction CO rest Ar specifications CO FTIR H specifications O specifications N GC-TCD H O Dew-point meter CH 4 FTIR-DL PURITY TABLE FOR NOMINALLY PURE N N BIP 6.0 (AIR Products) Component Method Mole Fraction N rest

29 Page 9 of 41 Component Method Mole Fraction CO GC-FID (methaniser) CO GC-FID (methaniser) H specifications O specifications H O Dew-point meter DL CH 4 C 3 H 8 GC-FID (methaniser) DL GC-FID (methaniser) DL SOURCE OF CO The source of nominally pure CO gas was CO 5.5 Air Liquid gas. Calculation of the purity table was made automatically by.0 version ISO 614 software with inputs from purity measurements. Purity measurements were made using following analytical instruments: GC FID- methaniser, GC TCD and Dew-point meter. Specifications of the manufacturer were used for O. Uncertainties in purity table are in unextended form. 6. PURITY TABLE FOR NOMINALLY PURE CO CO 5.5 Air Liquid Component Method Mole Fraction CO rest CO GC-FID (methaniser) O specifications N GC-TCD H O Dew-point meter CH 4 GC-FID (methaniser) SOURCE OF PROPANE The source of nominally pure propane gas was propane 3.5 Messer. The gas was diluted in one step to the concentration mol/mol with BIP Plus N. Calculation of purity table was made automatically by.0 version ISO 614 software with inputs from gravimetric preparation and purity measurements. Purity measurements were made using following analytical instruments: GC FID- methaniser, GC TCD and Dew-point meter. Mole fraction of undetected, but analysed component was calculated from detection limit of used method. Specification of the manufacturer was used for O. Uncertainties in purity table are in unextended form.

30 Page 30 of PURITY TABLE FOR NOMINALLY PURE PROPANE Propane 3.5 Messer Component Method Mole Fraction propane rest CO GC-FID (methaniser) DL CO GC-FID (methaniser) O specifications N GC-TCD H O Dew-point meter CH 4 GC-FID (methaniser) DL C H 6 GC-FID Iso-butane GC-FID N-butane GC-FID PREPARATION OF FINAL MIXTURE Parent gases x (grav+pur) u(x) 0045F_3 (Propane) F_ (CO) B (CO ) (N BIP) PURITY TABLE FOR FINAL 0066F_3 MIXTURE Component x (grav+pur) u(x) Ar CO CO H O N H O

31 Page 31 of 41 Component x (grav+pur) u(x) CH C H C 3 H Iso-butane N-butane VERIFICATION The mixture was verified on GC Varian using Porapack and molsieve packed columns, x 1mL sample loops, TCD (for CO, CO ) and FID (for propane) detectors, oven temperature 95 C, method time 9 min, carrier gas Helium. All measurements were done in automatic way using selector gas valve. Before entering sample loops all gas mixtures went through a mass flow controller and pressure controller for regulation. 7 PSM calibration standards used for verification were made gravimetrically according to ISO 614 and ISO 6143 in SMU. Measurement method with 7 automated runs was used. All runs in first, third, fifth, seventh measurement sequence had rising molar fraction, second, fourth, sixth processed in reverse order. From each run was made one calibration curve with sample signals. Data were subjected to the b_least program (weighted least square regression). The result of the measurement sequence was the average of molar fractions. 11. RESULTS The results are presented in following table with data: x prep amount of substance fraction, from preparation (mol.mol -1 ) u prep uncertainty of x prep from gravimetrical preparation and purity (mol.mol -1 ) u ver uncertainty from verification (mol.mol -1 ) u st uncertainty of stability (mol.mol -1 ) u cert final uncertainty of x (mol.mol -1 ) U(k=) stated uncertainty of x, at 95% level of confidence (mol.mol -1 ) Standard uncertainty of the mixture was calculated with following formula: u = u + u + u cert prep ver st Component x prep u prep u ver u st u cert x U(k=) CO CO propane

32 Page 3 of 41 Measurement report of VSL 1. CYLINDER DETAILS Date of mixture preparation Volume (L) 5 Total Pressure (bar) 10 Connection type (e.g. DIN1, BS14 etc.) DIN1. SOURCE OF CO CO 4.7 from Air Liquide Belgium 3. PURITY TABLE FOR NOMINALLY PURE CO AL8811 Component Method Mole Fraction CO rest Ar GC-PDHID CO GC-TCD H specifications N GC-TCD H O specifications C x H y specifications PURITY TABLE FOR NOMINALLY PURE N N BIP 6.0 (AIR Products) APN6B Component Method Mole Fraction N rest CH 4 FT-IR CO FT-IR CO FT-IR H specifications

33 Page 33 of 41 Component Method Mole Fraction O specifications H O CRDS SOURCE OF CO Air Products Belgium 6. PURITY TABLE FOR NOMINALLY PURE CO Complete data for all components considered: AP Component Method Mole Fraction CO rest CO specifications O CG-PDHID N GC-PDHID H O CRDS CH 4 specifications SOURCE OF PROPANE Air Liquide Belgium 8. PURITY TABLE FOR NOMINALLY PURE PROPANE Complete data for all components considered: AL Component Method Mole Fraction propane rest C H 6 GC-FID N GC-PDHID O GC-PDHID PREPARATION OF FINAL MIXTURE Parent gases x (grav+pur) u(x) (Propane) VSL (CO) VSL

34 Page 34 of 41 Parent gases x (grav+pur) u(x) (CO ) See purity table pure CO (N BIP) See purity table pure N 10. PURITY TABLE FOR FINAL MIXTURE (VSL49709) Complete data for all components considered: Component x (grav+pur) u(x) Ar CH CO CO C 3 H C x H y H H O N O VERIFICATION The final mixture was verified using a GC method. An Agilent 6890 GC equipped with FID and TCD detectors and with a molsieve and porapak column was operated at optimised conditions for automotive mixture analyses. A set of 7 multicomponent PSM mixtures was used to construct a calibration line for both CO, CO and propane. Calibration curve were constructed in accordance with ISO 6143, a quadratic fit was made in all cases. The verification was repeated 3 times to calculate a standard deviation under repeatability conditions. 11. RESULTS The results are presented in following table with data: x prep amount of substance fraction, from preparation (mol.mol -1 ) u prep uncertainty of x prep from gravimetrical preparation and purity (mol.mol -1 ) u ver uncertainty from verification (mol.mol -1 ) u st uncertainty of stability (mol.mol -1 ) u cert final uncertainty of x (mol.mol -1 ) U(k=) stated uncertainty of x, at 95% level of confidence (mol.mol -1 ) Standard uncertainty of the mixture was calculated with following formula: u = u + u + u cert prep ver st

35 Page 35 of 41 Component x prep u prep u ver u st u cert x U(k=) CO CO propane

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37 Page 37 of 41 Measurement verification of INMETRO PSM reevaluation of declared certification uncertainty The prepared reference gas mixture was measured against PRMs on three different days. The reference values for the amount-of-substance fractions are obtained by interpolation using a calibration curve. The results that follow are presenting the uncertainty of the area, with 07 (seven) repetitions, for each day, during 03 (three) days. The results from the gas chromatographic measurements have been fitted using a quadratic polynomial function, instead of the cubic one used previously, in accordance with ISO 6143, using the software b-least. The quadratic function reads for each component as follows: y = f ( x, a) = a + a x + a x 0 1 A. CARBON MONOXIDE Table A1 Calibration mixtures for carbon monoxide* y u(y) Mixture x u(x) mmol mol -1 mmol mol -1 ML ML NPL ML ML *average of the 3 (three) days of analysis. Table A Regression coefficients for carbon monoxide Coefficient Day 1 Day Day 3 value u value u value u a E E E E E E-03 a 1.664E E E E-08.79E E-07 a 8.781E E E E E E-13 Table A3 Reference values for carbon monoxide u(x calib ) Mixture y u(y) x calib u(x calib )/x calib X prep x x/x prep mmol mol -1 mmol mol -1 % rel mmol mol -1 mmol mol -1 % rel IN Standard uncertainty of the mixture was calculated with following formula: u = u + u + u cert prep ver st Table A4 Results for carbon monoxide (mmol mol -1 ) Component x prep u prep u ver u st u cert x U(k=) CO

38 Page 38 of 41 Table A5 Differences in the DOE uncertainty for carbon monoxide for Inmetro (mmol mol -1 ) Calibration curve x KCVR u(x KCVR ) x lab u(x lab ) d u(d) Observation Cubic Considering standard deviation of area measurements (previous results) Quadratic revised results, considering uncertainty of the area Figure 1A Degree-of-equivalence for carbon monoxide B. CARBON DIOXIDE Table B1 Calibration mixtures for carbon dioxide* y u(y) Mixture x u(x) mmol mol -1 mmol mol -1 ML NPL NPL ML ML ML NPL *average of the 3 (three) days of analysis. Coefficient Table B Regression coefficients for carbon dioxide Day 1 Day Day 3 value u value u value u a E E E E E-03.58E-0 a 1.451E E E E-07.53E E-07

39 Page 39 of 41 a E-13.18E E E E-13.75E-13 Table B3 Reference values for carbon dioxide u(x calib ) Mixture y u(y) x calib u(x calib )/x calib X prep x x/x prep mmol mol -1 mmol mol -1 % rel mmol mol -1 mmol mol -1 % rel IN Standard uncertainty of the mixture was calculated with following formula: u = u + u + u cert prep ver st Table B4 Results for carbon dioxide (mmol mol -1 ) Component x prep u prep u ver u st u cert x U(k=) CO Table B5 Differences in the DOE uncertainty for carbon dioxide for Inmetro (mmol mol -1 ) Calibration x KCVR u(x KCVR ) x lab u(x lab ) d u(d) Observation curve Cubic Considering standard deviation of area measurements (previous results) Quadratic Revised results, considering uncertainty of the area Figure 1B Degree-of-equivalence for carbon dioxide

40 Page 40 of 41 C. PROPANE Table C1 Calibration mixtures for propane* y u(y) Mixture x u(x) μmol mol -1 μmol mol -1 ML ML NPL ML NPL ML NPL *average of the 3 (three) days of analysis. Table C Regression coefficients for propane Coefficient Day 1 Day Day 3 value u value u value u a 0.680E E E E E E+00 a 1.75E E-05.83E E-05.77E E-06 a E E E E E E-1 Table C3 Reference values for propane u(x ) Mixture y u(y) x calib u(x calib )/x calib X prep x x/x prep μmol mol -1 calib μmol mol -1 % rel μmol mol -1 μmol mol -1 % rel IN Standard uncertainty of the mixture was calculated with following formula: u = u + u + u cert prep ver st Table C4 Results for propane (μmol mol -1 ) Component x prep u prep u ver u st u cert x U(k=) C 3 H Table C5 Differences in the DOE uncertainty for propane for Inmetro (μmol mol -1 ) Calibration x KCVR u(x KCVR ) x lab u(x lab ) d u(d) Observation curve Cubic Considering standard deviation of area measurements (previous results) Quadratic Revised results, considering uncertainty of the area

41 Page 41 of 41 Figure 1C Degree-of-equivalence for propane As presented above, the results from Inmetro were revised, as it was observed that the verification uncertainties were higher than the average uncertainties from verification from the other laboratories. Re-evaluating our results, we observed that the reason that our verification uncertainty was higher for all the three gases was because we committed a mistake when calculating this uncertainty, as we used the standard deviation of the repeated areas. When we use the uncertainty of the areas, the results improved. It should be observed that the laboratory hasn t measured the mixtures again, and what was made was a correction and a reanalysis of the results previously obtained. So, using the same repetitions (7), same days of analysis (3), and same PRM standards, we tested some new models to better adjust the calibration curve. We noticed that using the quadratic function, instead of the cubic function we previously used, with 7 calibration PRMs for CO and C 3 H 8, and 5 calibration PRMs (straighter range) for CO, the uncertainties obtained in calibration step were much better than the previous results we reported.