International Comparison COOMET.QM-K111 Propane in nitrogen

Transcription

1 International Comparison COOMET.QM-K111 Propane in nitrogen Final Report L.A. Konopelko 1, Y.A. Kustikov 1, A.V. Kolobova 1,V.V. Pankratov 1, A.A. Pankov 1, O.V. Efremova 1, M.S. Rozhnov 2, D.M. Melnyk 2, P.V. Petryshyn 2, O.S. Levbarg 2, S.P. Kisel 2, S.A. Shpilnyi 2, S.Ye. Yakubov 2, N.V. Bakovec 3, A.M. Mironchik 3, V.V. Aleksandrov 4. 1 D.I. Mendeleyev Institute for Metrology (VNIIM), Research Department for the State Standard in the Field of Physical-Chemical Measurements; address: , Russia, St.- Petersburg, Moskovsky pr All Ukrainian State Research-Industrial Center of Standardization, Metrology, Certification and Protection of Consumers (Ukrmetrteststandart); address: 03143, Ukraine, Kiev, Metrologhichna str.4. 3 Belorussian State Institute for Metrology (BelGIM), Department of Physical-Chemical and Optical Measurement, Sector of Standards and Gas Mixtures; address: , Belarus, Minsk, Starovilenskiy pr Kazakhstan Institute of Metrology (KazInMetr), Karaganda branch, Kazakhstan; address: , Kazakhstan, Karaganda, Angerskayast. 22/2. Field Amount of substance Subject Comparison of propane in nitrogen (track A core competences) Table of contents Field... 1 Subject... 1 Table of contents Introduction Design and organisation of the comparison Participants Measurement standards Measurement protocol Schedule Measurement equation Measurement methods Degrees of equivalence Results Supported CMC claims Discussion and conclusions... 7 References... 7 Coordinator... 8 Completion date

2 1 Introduction The regional key comparison COOMET.QM-K111 is linking to the appropriate CCQM comparison - CCQM-K111 Propane in nitrogen 1000 [1] which was carried out in ССQM -K111 was one of a series of key comparisons in the gas analysis area assessing core competences (track A key comparisons). Such competences include, among others, the capabilities to prepare Primary Standard gas Mixtures (PSMs) [2], perform the necessary purity analysis on the materials used in the gas mixture preparation, the verification of the composition of newly prepared PSMs against existing ones, and the capability of calibrating a gas mixture. VNIIM showed a consistent result in CCQM-K111 comparison [1]. Therefore, the results of COOMET.QM-K111could be related with CCQM-K111 through the results of VNIIM and could be used to support CMCs of NMIs of COOMET member countries. 2 Design and organisation of the comparison 2.1 Participants Table 1 lists the participants in this key comparison. Table 1: List of participants Acronym Country Institute VNIIM RU D.I. Mendeleyev Institute for Metrology Ukrmetrteststandard UA All Ukrainian State Research-Industrial Center of Standardization, Metrology, Certification and Protection of Consumers BelGIM BY Belorussian State Institute for Metrology KazInMetr KZ Kazakhstan Institute of Metrology 2.2 Measurement standards A set of mixtures were prepared gravimetrically by VNIIM. For the preparation was used high purity propane (from SIAD, Italy), and nitrogen (from Air Liquide, Russia), grade 5.0, which was further purified with the help of gas purifier Gatekeeper (from Entegris, US). The mixtures were verified against a set of VNIIM PSMs. The filling pressure in the cylinders was approximately 10 MPa. Aluminium cylinders having 5 dm 3 water volume from Luxfer UK were used. The mixture composition and its associated uncertainty was calculated in accordance with ISO 6142 [3]. The amount-of-substance fractions as obtained from gravimetry and purity verification of the parent gases were used as key comparison reference values (KCRVs). Each cylinder had its own reference value. The nominal propane amount-of-substance fraction was Measurement protocol The measurement protocol requested each laboratory to perform at least 3 measurements, with independent calibrations. The replicates, leading to a measurement, were to be carried out under repeatability conditions. The protocol informed the participants about the nominal 2

3 concentration ranges. The laboratories were also requested to submit a summary of their uncertainty evaluation used for estimating the uncertainty of their result. 2.4 Schedule The schedule of this key comparison was as follows (table 2). Table 2: Key comparison schedule January 2016 February 2016 March 2016 March 2016 April June 2016 July 2015 August 2016 September 2016 Осtober 2016 December 2016 Stage Preparation of the technical protocol and review of protocol by GAWG Preparation of gas mixtures Verification of mixtures Distribution of mixtures Study of the mixtures by participants Reports arrive at VNIIM Cylinder arrive at VNIIM Re-verification of the mixtures Draft A report available Draft B report available 2.5 Measurement equation The key comparison reference values are based on the weighing data from gravimetry, and the purity verification of the parent gases. All mixtures underwent first verification before shipping them to the participants. After returning of the cylinders, they went through second verification to reconfirm the stability of the mixtures. In the preparation, the following four groups of uncertainty components have been considered: 1. gravimetric preparation (weighing process) (x i,grav ) 2. purity of the parent gases ( x i,purity ) 3. stability of the gas mixture ( x i,stab ) 4. correction due to partial recovery of a component ( x i,nr ) Previous experience has indicated that there are no stability issues and no correction is needed for the partial recovery of a component. These terms are zero, and so are their associated standard uncertainties. The amount of substance fraction x i,prep of a particular component in mixture i, as it appears during use of the cylinder, can now be expressed as x x x, (1) i, prep i, grav i, purity The equation for calculating the associated standard uncertainty reads as 2 ( x ) u ( Δx ). 2 2 ui, prep = u i,grav + i, purity (2) The validity of the mixtures has been demonstrated by verifying the composition as calculated from the preparation data with that obtained from (analytical chemical) 3

4 Propane amount of substance fraction, measurement. In order to have a positive demonstration of the preparation data (including uncertainty, the following condition should be met [4] x 2 2 x 2 u u. (3) i, prep i, ver i, prep i, ver The factor 2 is a coverage factor (based on the normal distribution, 95% level of confidence). The assumption must be made that both preparation and verification are unbiased. Such bias has never been observed. The uncertainty associated with the verification highly depends on the experimental design followed. In this particular key comparison, an approach has been chosen which is consistent with CCQM-K3 [5] and takes advantage of the work done in the gravimetry study CCQM-P41 [6]. The verification experiments have demonstrated that within the uncertainty of these measurements, the gravimetric values of the key comparison mixtures agreed with older measurement standards. The expression for the standard uncertainty of the key comparison reference value is u = u + u (4) 2 i,ref 2 i,prep 2 i,ver The values for comparison. u i, prep, i, ver u and u i, ref are given in the tables containing the results of this key 1006 COOMET.QM-K111 preparation 1 verification 2 verification Figure 1: Preparation and verification data of the transfer standards used in this key comparison 4

5 The preparation and verification data (see figure 1) agree well differencies between preparation and verification values of amount of substance fraction do not exceed 0.35 ppm (0.035 %). 2.6 Measurement methods The measurement methods used by the participants are described in each participant report. A summary of the calibration methods, dates of measurement and reporting, and the way in which metrological traceability is established is given in table 3. Table 3: Summary of calibration methods and metrological traceability Laboratory code Measurements Calibration Traceabili ty BelGIM Calibration curve, 3 points KazInMetr Calibration curve, 3 points Ukrmetrteststandart Calibration curve, 3 points VNIIM One-point calibration Own standards Own standards Own standards Own standards Matrix standard s Nitrogen Nitrogen Nitrogen Nitrogen Measurement technique GC-FID GC-FID GC-FID NDIR 2.7 Degrees of equivalence A unilateral degree of equivalence in key comparisons is defined as Δx = d = x x, (5) i i i,lab - i, KCRV and the uncertainty of the difference d i at 95% level of confidence. Here x i,ref denotes the key comparison reference value, and x i,lab the result of laboratory i. 1 Appreciating the special conditions in gas analysis, it can be expressed as Δx = d = x x. (6) i i i,lab - i,ref The standard uncertainty of d i can be expressed as u ( d ) u + u + u, i = (7) i,lab i,prep i,ver assuming that the aggregated error terms are uncorrelated. As discussed, the combined standard uncertainty of the reference value comprises that from preparation and that from verification for the mixture involved. 3 Results In this section, the results of the key comparison are summarised. In the tables, the following data is presented x i,prep - amount of substance fraction from preparation for cylinder i () u i,prep - standard uncertainty of x i,prep () u i,ver - standard uncertainty from verification for cylinder i () u i,ref - standard uncertainty of reference value () for cylinder i x i,lab - result of laboratory i () 1 Each laboratory receives one cylinder, so that the same index can be used for both a laboratory and a cylinder. 5

6 U i,lab - stated uncertainty of laboratory, at 95 % level of confidence () k i,,lab - stated coverage factor d i - difference between laboratory result and reference value () k - assigned coverage factor for degree of equivalence U(d i )- Expanded uncertainty of difference d i, at 95 % level of confidence 2 () Table 4: Results of COOMET.QM-K111 Laboratory Cylinder x i,ref u i. prep u i,ver u i,ref x i,lab U i,lab k i,lab d i k U(d i ) BelGIM D KazInMetr D Ukrmetrtest D standart VNIIM D In the figure 2 the degrees of equivalence for all participating laboratories are given. The uncertainties are given as 95% confidence intervals as required by the MRA [7]. For the evaluation of uncertainty of the degrees of equivalence, the normal distribution has been assumed, and a coverage factor k = 2 was used. For obtaining the standard uncertainty of the laboratory results, the expanded uncertainty (stated at a confidence level of 95%) from the laboratory was divided by the reported coverage factor. 4 Supported CMC claims The support of CMC claims is described in the final report of CCQM-K111 [1]. 2 As defined in the MRA [6], a degree of equivalence is given by d i and U(d i ). 6

7 Figure 2: Degrees of equivalence 5 Discussion and conclusions The results of this Track A key comparison are satisfactory. All results are within ± 0.4 % of the KCRV. References [1] Van der Veen A.M.H., Van der Hout J.W., Ziel P.R., Oudwater R.J., Fioravante A.L., Augusto C.R., Brum M.C., Uehara S., Akima D., Bae H.K., Kang N., Woo J.C., Liaskos C.E., Roderick G.C., Brewer P.H., Brown A.S., Bartlett S., Downey M.L., Konopelko L.A., Kolobova A.V., Pankov A.A., Orshanskaya A.A., Efremova O.V., International Comparison CCQM-K111 Propane in nitrogen, Final Report, Metrologia Technical Supplement, to be published [2] Alink A., The first key comparison on Primary Standard gas Mixtures, Metrologia 37 (2000), pp [3] International Organization for Standardization, ISO 6142:2001 Gas analysis - Preparation of calibration gas mixtures - Gravimetric methods, 2 nd edition [4] Alink A., Van der Veen A.M.H., Uncertainty calculations for the preparation of primary gas mixtures. 1. Gravimetry, Metrologia 37 (2000), pp [5] Van der Veen A.M.H, De Leer E.W.B., Perrochet J.-F., Wang Lin Zhen, Heine H.-J., Knopf D., Richter W., Barbe J., Marschal A., Vargha G., Deák E., Takahashi C., Kim 7

8 J.S., Kim Y.D., Kim B.M., Kustikov Y.A., Khatskevitch E.A., Pankratov V.V., Popova T.A., Konopelko L., Musil S., Holland P., Milton M.J.T., Miller W.R., Guenther F.R., International Comparison CCQM-K3, Final Report, 2000 [6] Van der Veen A.M.H., Brinkmann F.N.C., Arnautovic M., Besley L., Heine H.-J., Lopez Esteban T., Sega M., Kato K., Kim J.S., Perez Castorena A., Rakowska A., Milton M.J.T., Guenther F.R., Francy R., Dlugokencky E., International comparison CCQM-P41 Greenhouse gases. 2. Direct comparison of primary standard gas mixtures, Metrologia 44 (2007), Techn. Suppl [7] CIPM, Mutual recognition of national measurement standards and of calibration and measurement certificates issued by national metrology institutes, Sèvres (F), October 1999 Coordinator VNIIM, Research department for the State Standards in the field of physical-chemical measurements L.A.Konopelko 19 Moskovskiy pr., Saint-Petersburg, Russia, Phone: Completion date: October

9 Annex A Reports submitted by participating laboratories 9

10 COOMET.QM-K111 (COOMET 678/RU/15) KEY COMPARISON OF STANDART GAS MIXTURES: PROPANE IN NITROGEN, 1000 REPORT ON RESULTS OF THE STUDY I. Results of experimental study Laboratory: Belarus, BelGIM, Section for physicochemical and optical measurements, sector for standards and gas mixtures, 8, Serova st., Minsk. Cylinder No: D Component Result, Standart deviation, % rel. No of observations n Propane Propane Propane Propane Propane Final results: Component Result, μmol/mol Coverage factor Expanded uncertainty, μmol/mol Propane II. Description of study Equipment Measurements were performed on a gas chromatographer (GC) "Crystal 5000" (company "Chromatek Analytic", Russia) fitted with FID. Gas-carrier is helium. Computers and software "Chromatech Analytic", version 2.5 were used to control chromatograph and collect and process chromatographical data. For the purpose of measurements the following auxiliary devices and materials were used: 1. Capillary column HP PLOT/Q 30m х 0,53mm. 2. Helium gas, grade "6.0", high purity hydrogen and compressed air for FID. 3 Multicomponent calibration gas mixtures - Calibration Standards produced and certified by gravimetric method. 4. Gas flow former for creation and maintenance of constant pressure in doses. 10

11 Calibration Standards (CS). The quantitative composition of CS was determined by a gravimetric method according to ISO 6142:2001. The contents of components in CS are expressed in molar fractions. The uncertainty of CS composition is expressed as a standard uncertainty. Molar masses of components and their associated uncertainties are derived from ISO 14912:2003 (E). The purity analysis of initial gases is based on the information provided by the supplier or on the results of determination of impurity in pure gases using measurement procedure developed inside BelGIM. In order to prepare mixtures nitrogen (specification "6.0") was used. Final mixtures are obtained by using 2-time dilution: 100 % 2 % final mixture. GC calibration and standard reference materials measuring 1. When carrying out GC calibration, CS were used the composition of which was identical to the composition of the sample being analyzed. Each CS component contents with associated standard uncertainties are given in Table. Cylinder No, date of preparation cylinder material: aluminum cylinder volume: 4 dm 3 valve material: stainless steel Content, x, Standart uncertainty, u(x), 4211, , , Number of observations for each calibration sample Analytical function (subsequently referred to as AF) used to determine the content of components in a sample being analyzed is written as follows: x (y) =b 1 y+b o, (1) where: x - certain content, mole/mole, %; y - value of the chromatographer response for this component, V*s; b 1 - slope coefficient; b 0 - intercept coefficient. 4. Upon completion of calibration calculations of analytical function coefficients were made according to ISO 6143:2001, and also uncertainties of values of angular coefficients and their covariation were calculated using the program recommended in the abovementioned standard. Uncertainty calculation Generally, the total standard uncertainty related to results of 4 individual measurements, is evaluated by following formula: 2 2 u( x) u А u B, (2) where u A -uncertainty associated with results of individual measurements; u B - uncertainty due to GC calibration and to the uncertainty of CS component contents. A-type uncertainty evaluation 11

12 The A-type uncertainty u A of the results of n=5 measurement series is evaluated by the formula: (3) u n 2 ( xi x) i 1 A, n( n 1) where x i - result of i measurement series; x - arithmetic mean for five (n=5) measurement series. A-type uncertainty evaluation results, mol/mol,. Component Meas. 1 Meas. 2 Meas. 3 Meas. 4 Meas. 5 Mean u A Propane B-type uncertainty evaluation B-type uncertainty u B due to the uncertainty of CS component contents and to the uncertainty of the chromatographer response to these contents during its calibration was evaluated on the basis of results of calibration measurements for each measurement series. Generally, the uncertainty of results of component determination for each series of measurements is evaluated by the following formula: (4) u x) ( b ) u ( y) u ( b ) y u ( b ) 2 y u( b, ), ( b0 where u(y) - standard uncertainty of the chromatographer response y; u (b 1 ) - standard uncertainty of the AF slope coefficient; u (b 0 ) - standard uncertainty of the AF intercept; u (b 1,b 0 ) - covariation of the AF arguments b 0 and b 1. Taking y(u)=0 we obtain the uncertainty associated with the GC calibration. B-type uncertainty evaluation results,. Component Meas. 1 Meas. 2 Meas. 3 Meas. 4 Meas. 5 Max Propane Total standard uncertainty evaluation results. x, u Component A, u B, u(x), Propane

13 International Key Comparison COOMET.QM-K111 (COOMET project 678/RU/15) Key comparison of standard gas mixtures Propane in nitrogen, 1000 Laboratory: Karaganda branch of RSE "Kazakhstan Institute of Metrology" Republic of Kazakhstan Cylinder number: D I. Measurement Measurement #1 Result, Standart deviation (% relative) Number of replicates Propane Measurement #2 Result, Standart deviation (% relative) Number of replicates Propane Measurement #3 Result, Standart deviation (% relative) Number of replicates Propane Measurement #4 Result, Standart deviation (% relative) Number of replicates Propane Measurement #5 Result, Standart deviation (% relative) Number of replicates Propane

14 Result Component Result, Coverage factor*) Expanded Uncertainty, Propane *) The coverage factor based on 95% confidence. II. Measurement Details for COOMET.QM-K111 Instruments Measurements were carried out using gas chromatograph "Crystal 5000" combined with flame-ionization detector. Carrier gas: helium. Volume size: 1 ml. Chromatographic column: Hayesep N 80/100 mesh, 2m х 2mm. Computers and software "Chromatech Analytic were used to control chromatograph and collect and process chromatographic data. Calibration standards 1. The calibration gas standards were prepared by gravimetric method multiple dilutions, according to ISO An electronic mass-comparator (Mettler Toledo model XP10003S, capacity 10,1 kg, readability 1 mg) was used for preparation of all calibration gas standards. Manufacturer, type and metrological characteristics of the equipment used for the preparation of the gravimetric gas mixtures are given in Table 1. Table 1. Type Manufacturer Metrological characteristics Model XP10003S Gas mixing plant, GSU-3 «Mettler- Toledo», Swizerland OOO «PGS- Servise», Russian Federation The maximum limit weighing g Resolution 1 mg The standard deviation of 10 mg The maximum change in temperature for 1 h. ± 0.5 C Pressure measuring range: from to 16.0 MPa Residual pressure cylinders before filling 10 Pa. Диапазон измерения давления: от 0,001 до 16,0 МПа Остаточное давление баллонов перед наполнением 10 Па. For the production of calibration gas mixtures were used aluminum cylinders with a capacity of 4 dm3 complete with brass diaphragm valve type VBM-1. The internal surface of the cylinders was coated by paraffin grade P2. 2. Analysis of the purity of the clean gases. Analysis of the purity of the original pure gases was based on information provided by the suppliers of pure gases (passports, certificates), as well as on the results of the measurement of impurities in pure gases using measurement techniques developed and approved by the RSE "KazInMetr". In cases where the analytical method can not determine the content of the alleged impurities molar fraction of the expected impurity was assumed to be half the 14

15 detection limit of the analytical method. The content of impurities unmeasured assumes a rectangular probability distribution, whereby the standard uncertainty is calculated as half the detection limit. Determination of impurities in the starting pure gases (propane, nitrogen) used to prepare calibration samples was conducted by gas chromatography using a flame ionization, thermal chemical and thermal conductivity detector. The content of impurities in the pure gas used for preparing the calibration gas mixtures shown in Table 2. Table 2. The metrological characteristics of pure gases. Clean gas Component Content mole The standard fraction, % uncertainty, mole Propane The cylinder capacity of 10 dm3 Manufacturer: - Certified in the Federal State Unitary Enterprise "VNIIM" them. D.I. Mendeleev Nitrogen The cylinder capacity of 40 dm3 Manufacturer: The Republic of Kazakhstan fraction,% C 3 H N In measuring the mass of gas filled and comparative cylinder identical volume being weighed according to the scheme and the method of substitution RMMR. Based on previous studies RMS measurement result is taken to be 30 mg (standard uncertainty evaluated by type A). 3. After making the balloon with the calibration gas mixture was placed in a laboratory, where the at least 72 hours. Before the measurement tanks rolled the calibration gas mixtures for 10 minutes. Calibration of instrument 1. Calibration was performed using GC calibration gas mixtures are identical in composition to sample comparisons. The content of each component and its expanded uncertainty (k = 2) is shown in Table 3. Table 3 - Calibration gas mixtures Cylinder number, passport number, size, material, date of manufacture PV-172, 4dm 3, г. PV-173, 4dm 3, г. PV-174, 4dm 3, г. Component Content, x () The standard uncertainty of the calibration samples (rel.), U (x),% C 3 H N 2 - C 3 H N 2 - C 3 H N

16 The total content of components standard uncertainty in calibration gas mixtures are calculated according to the formula: u total = u m + u p u m standard uncertainty weighing, %; u p standard uncertainty of frequency source gases, %. The standard uncertainty of the molar mass of gases, as well as uncertainty due to air buoyancy, with the pressure and volume of a cylinder is filled not taken into account in connection with a minor contribution. 2. The measurements were carried out under repeatability conditions. Before each measurement was conducted by the chromatograph calibration of 3 models (PV- 172, PV-173, PV-174). Each measurement includes 3 observations. 3. Analytical function used to determine the components in the sample is as follows: x(y) = b 1 y + b 0 were, x measured content, ; y chromatographic response of the analyte; b 1 coefficient of linear dependence; b 0 offset coefficient. Sample preparation The sample with the sample and the calibration sample was stored prior to measurement for 24 hours in the laboratory. The change in temperature in the laboratory at the time of measurement is ± 2 C, the change in pressure within ± 0,5 kpa. Calculation of measurement uncertainty Uncertainty value u(x) was calculated in accordance with ISO 6143 taking into account the uncertainties of the calibration standards and instrument response variability during calibration and measurements under reproducibility conditions: u(x) = u 2 (x, x cs ) + u 2 (x, y) were u(x, x cs ) the standard uncertainty associated with the amount-of-substance fractions of the calibration standards; u(x, x cs ) = 16 n ( u(x cs i i=1 n )2, where u(x csi ) uncertainty of the calibration standards; n - number of the calibration standards; u(x, y) uncertainty associated with the instrument response,

17 u(x, y) = u2 (y)+x 2 u 2 (a 1 )+2x cov(a 0,a 1 )+u 2 (a 0 ) a2, 1 where u(y) uncertainty of instrument response during measurements; a 0, a 1, u(a 0 ), u(a 1 ), cov(a 0, a 1 ) calibration function parameters obtained from B_Least for linear function. The calibration function parameters of all measurements are given in Table 4. Table 4 - Calibration function parameters. Parameter Regression coefficient a 0 Regression coefficient a 1 Regression coefficient a 0 uncertainty u(a 0 ) Regression coefficient a 1 uncertainty u(a 1 ) Covariance cov(a 0, a 1 ) 1 st 2 nd 3 rd measurement measurement measurement measurement measurement E E E E E E E E E E E E E E E E E E E E E E E E E+04 4 rd 5 rd Table 5 Uncertainty table Uncertainty source X i Uncertainty associated with the amount-of substance fract ions of the calibration standards Uncertainty associated with the instrument response Coverage factor: k = 2. Esti mate x i Assumed distributio n Expanded uncertainty: 14,5. Standart uncertaint y u(x i ) - Normal Normal 6.7 Sensitivity coefficient c i Contribution to standard uncertainty u i (y)

18 COOMET 678/RU/15 Key comparison of standard gas mixtures: propane in nitrogen, 1000 MEASUREMENT REPORT I. Results of the study Laboratory: Ukrmetrteststandart, Kiev, Ukraine Cylinder number: D Measurement 1 dd/mm/yy Result () Standard deviation (% relative) Number of sub measurements n Propane 17/05/ Measurement 2 dd/mm/yy Result () Standard deviation (% relative) Number of sub measurements n Propane 20/05/ Measurement 3 dd/mm/yy Result () Standard deviation (% relative) Number of sub measurements n Propane 24/05/ Final results: Result Assigned expanded Gas mixture (assigned value) Coverage factor uncertainty Propane in Nitrogen

19 Component Instrument(s) II. Description of study Balance used for primary standard gas mixtures (PSGM) preparation by gravimetric method: Mettler Toledo XP26003L electronic balance (max. load 26,1 kg; min. 0,2 g; standard deviation 0,003 g). Measurement data were collected automatically. Instruments for purity analysis of parent gases: Agilent 6890N gas chromatographs with helium ionization detector, flame ionization detector, thermal conductivity detector and mass spectrometric detector. Measurement data were collected automatically. Calibration Standards Composition of the calibration standards primary standard gas mixtures (PSGM) used for measurements by comparison method is given in the table below: PSGM-1 Cylinder D PSGM-2 Cylinder M PSGM-3 Cylinder D x, % u(x), % x, % u(x), % x, % u(x), % С 3 Н N 2 balance balance balance Note: x mole fraction, u(x) absolute standard uncertainty Purity tables for parent gases used for PSGM preparation for are given below. Purity table for propane Component Mole fraction, Standard uncertainty, C 3 H C 2 H N O Purity table for nitrogen Component Mole fraction, Standard uncertainty, N O CO Ar H 2 O

20 Calibration and Measurement Gas chromatograph was calibrated with the PSGMs. Linear analysis functions for each analyte were calculated from the calibration data using regression analysis. Calculations were made with B_LEAST software recommended in ISO Measurement sequence: PSGM -1 х 5 (Cylinder D757196); PSGM -2 х 5 (Cylinder M937267); COOMET gas mixture х 5 (Cylinder D158027); PSGM -3 х 5 (Cylinder D757204). Three independent measurements were performed. Sample Handling Gas mixtures were handled in accordance with ISO The cylinders had been kept for 24 hrs at the room where the measurements were made. The room was thermostatted at t = (20 ± 2) ºС. Uncertainty evaluation Uncertainty table: Uncertainty source X i Calibration standards Typical relative standard deviation in measurements by comparison method Estimate x i Assumed distribution Standard uncertainty u(x i ) Sensitivity coefficient Contribution to standard uncertainty, 1000 normal ,18 - normal (relative) 1000 Combined standard uncertainty 0.52 Expanded uncertainty with coverage factor k= ,5 Note 1. Typical relative standard deviation in measurements by comparison method was taken for uncertainty evaluation as it is more representative than smaller deviations obtained in this comparison. Note 2. Usually uncertainty evaluation is performed using B_LEAST software taking into account the uncertainties of measuring system response, analysis function and calibration standards. 20

21 COOMET.QM-K111 (COOMET 678/RU/15) Key comparison of standard gas mixtures: propane in nitrogen, 1000 MEASUREMENT REPORT I. Results of the study Laboratory: D.I.Mendeleyev Institute for Metrology (VNIIM) Cylinder number: D Measurement 1 dd/mm/yy Result () Standard deviation (% relative) Number of sub measurements n Propane 17/02/ Measurement 2 dd/mm/yy Result () Standard deviation (% relative) Number of sub measurements n Propane 19/02/ Measurement 3 dd/mm/yy Result () Standard deviation (% relative) Number of sub measurements n Propane 29/08/ Final result: Result Assigned expanded Gas mixture (assigned value) Coverage factor uncertainty Propane

22 Calibration standards Primary Standard Gas Mixtures, prepared by the gravimetric method from pure substances, according to ISO 6142:2001 Gas analysis - Preparation of calibration gas mixtures - Gravimetric method were used as calibration standards. For the preparation was used high purity propane (from SIAD, Italy), and nitrogen (from Air Liquide, Russia), grade 5.0, which was additionaly purified with the help of gas purifier Gatekeeper (from Entegris, US). Characteristics of pure substances used for preparation of the calibration standards are shown in the tables 1 and 2. Table1 Purity table for Propane (cylinder 020) Component Mole fraction () Standard uncertainty () C 3 H N O C 2 H C 3 H i-c 4 H n-c 4 H C 4 H 8 [1-бутен] n-c 6 H Table 2 Purity table for Nitrogen Component Mole fraction () N H 2 O Ar CO O CH CO H Standard uncertainty () Preparation from pure substances was carried out in 2 stages. On the first stage 3 C 3 H 8 /N 2 gas mixtures were prepared on the concentration level of 2.5 %. On the second stage these mixtures were diluted to the target concentration level. 4 gas mixtures on the level of 1000 were prepared.the exact values of propane amount of substance fraction in the calibration gas mixtures and their standard uncertainties are shown in the table 3. Table 3 Cylinder number Component Mole fraction () Standard uncertainty due to weighing and purity () D C 3 H D C 3 H D C 3 H D158048* C 3 H

23 * - the cylinder was used as calibration gas mixture in CCQM-K111, others are newly prepared. All standard gas mixtures were prepared in aluminum cylinders (Luxfer), V=5 dm 3. Instrumentation All the measurements were carried out by NDIR method on the gas analyzer AERONICA (VNIIM, Russia). Verification measurements for pre-mixtures (2.5 %) were performed using cuvette with optical path 1.5 mm. Standard deviation for each measurement series was not more than %. Verification of the target calibration gas mixtures and measurements for investigated gas mixture (cylinder number: D158053) were performed using cuvette with optical path 1000 мм. Standard deviation for each measurement series was not more than %. Calibration method and value assignment Single point calibration method was used to determine propane mole fraction in the investigated gas mixture. Measurement sequence was in the order: zero gas - standard - zero gas - sample - zero gas standard - zero gas. Temperature corrections were not applied due to use of above-mentioned measurement sequence. Three independent measurement series were carried out under repeatability conditions. The amount of substance fraction of propane for a single measurement was calculated Ax according to the formula С x Cst, ( Ast Ast ) / 2 where C x and C st amount of substance fractions of propane in the investigated and standard mixtures; A x analytical signal of propane in the investigated gas mixture (minus zero gas signal) A st and A st analytical signals of propane in the standard gas mixture before and after measurement for the investigated mixture (minus zero gas signals). Uncertainty evaluation Uncertainty table: Uncertainty source Xi Calibration standards (weighing + purity) Estimate xi, mol/mol Assumed distribution Standard uncertainty u(xi) mol/mol Normal 0.13 Sensitivity coefficient ci Contribution to standard uncertainty ui(y), mol/mol 0.13 verification Normal within and between day measurements Normal Combined standard uncertainty: mol/mol Coverage factor: k=2 Expanded uncertainty: 0.96 mol/mol 1.0 mol/mol Relative expanded uncertainty: % 0.10 % 23