Final Report of APMP.QM-K46 Ammonia in Nitrogen at 30 µmol/mol Level

Final Report of APMP.QM-K46 Ammonia in Nitrogen at 30 µmol/mol Level Shinji Uehara 1), HAN Qiao 2), Takuya Shimosaka 3)* 1) Chemicals Evaluation and Research Institute, Japan (CERI) 2) National Institute of Metrology (NIM), No.18, Bei-San-Huan Dong Str., Beijing 100029, China 3) National Metrology Institute of Japan (NMIJ), AIST Tsukuba Central 3, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8563, Japan *) Coordinator of this comparison Field Amount of Substance Subject Comparison of 30 µmol/mol ammonia in nitrogen Participants CERI (Japan), NIM (China) Coordinating Laboratory National Metrology Institute of Japan (NMIJ) Organizing Body APMP 1 / 19

Introduction Ammonia is an important compound in the chemical industry. It is widely used and is the basis for producing other compounds containing nitrogen. Ammonia is also very hazardous, and consequently emissions of ammonia need be controlled and monitored. VSL coordinated CCQM-K46 (30 µmol/mol - 50 µmol/mol, NH 3 in nitrogen) in 2006 [1]. CERI participated in the comparison, but NIM did not participate in CCQM-K46. NIM would like to compare the gas standard with CERI through the bilateral comparison. Initially, analytical comparison between CERI and NIM was planned and CERI gravimetrically prepared two primary gas mixtures of NH 3 in N 2 for this comparison. However the cylinder was not able to be transported to NIM. Difficulty of cylinder transport often occurs. Therefore, the protocol of this comparison was changed where NIM will send their cylinder to CERI for analysis. This report describes the results for a bilateral comparison of ammonia in nitrogen gas mixture. The nominal amount-of-substance fraction was 30 µmol/mol. Protocol NIM prepared one gas mixture sample and sent it to CERI for analysis. The amount-of-substance fraction NH 3 in N 2 should be between 30 µmol/mol and 50 µmol/mol. The pressure of the gas mixture should be greater than 10 MPa. A cylinder with an inner volume of 10 dm 3 or larger one should have been used. CERI analyses the sample from NIM against CERI s primary gas mixtures. The sample was returned to NIM after the measurement at CERI. Because CERI participated in CCQM-K46 and the result was consistent with the KCRV, the key comparison reference value, amount-of-substance fraction as obtained from gravimetry at CERI is used as a reference value of this comparison. The participating laboratory is responsible for the calculation of the amount-of-substance fraction ammonia from gravimetric preparation and its uncertainty. For a proper evaluation of the data, it is necessary that purity analysis of raw gases, evaluation of gravimetric preparation process and stability were done properly at each NMI. After transfer of the cylinder to NIM, NIM had to reanalyse the returned cylinder for stability check (pressure at least 5 MPa). The stability data is to be combined into stability data for uncertainty evaluation in the report. Schedule Shipping to CERI : February, 2015 2 / 19

Shipping to NIM : November, 2015 Draft A : March, 2016 Draft B :June, 2016 Analysis and s The gas mixture was analysed by an NDIR calibrated by three standard gas mixtures of ammonia in nitrogen prepared by the gravimetric method according to ISO 6142 and ISO 6143 [2, 3]. The NDIR was a specific model of Shimadzu CGT-7000, modified for ammonia analysis. The measurement method of the ammonia fraction in the APMP.QM-K46 sample is the same as the method that CERI did in CCQM-K46. The experimental conditions for this comparison are summarized in Table 1. The amount-of-substance fractions of the standard gas mixtures, RM1, RM2 and RM3, and their uncertainties are summarized in Table 2. Table 1 Experimental conditions of NDIR for determination of NH 3 in N 2. Condition Analyzer NDIR (CGT-7000, Shimadzu) Sample flow rate 1 L/min Table 2 Standard gas mixtures of ammonia in nitrogen of CERI. amount fraction Standard uncertainty RM1 50.03 0.025 RM2 35.00 0.018 RM3 20.01 0.010 The APMP sample and the primary standard gas mixtures were measured in the following order; RM1 RM2 Sample RM3. This sequence was done 3 times within one day. Tables 3 and 4 show the results of this comparison, where x NIM is the NIM s reported value of amount-of-substance fraction of ammonia in the sample. Table 3 Reported value of NIM Cylinder number x NIM U(x NIM ) Coverage Factor CPE-10086 33.46 0.32 2 3 / 19

Table 4 s of determination of ammonia in the sample Ammonia molar fraction Cylinder number 1 2 3 4 Average Standard uncertainty CPE-10086 33.446 33.494 33.494 33.447 33.470 0.0851 The results shown in Table 4 are determined by the same method used in CCQM.K46 and the standard gas mixtures of ammonia in nitrogen prepared by the gravimetric method, and therefore the averaged value can be considered as a KCRV of this comparison. A degree of equivalence (D APMP ) is defined as the difference between NIM s reported value and the KCRV. Δx = D APMP = x NIM x KCRV U(D APMP ) 2 = U 2 (x NIM ) + U 2 (x KCRV ) Table 5 and Figure 1 show the result of this comparison. Table 5 Reuslts of this comparison x NIM U(x NIM ) x KCRV U(x KCRV ) D APMP U(D APMP ) (k = 2) NMI NIM 33.46 0.32 33.47 0.17-0.01 0.36 0.4 Degree of Equivalence 0.3 0.2 0.1 0-0.1-0.2-0.3-0.4-0.5 NIM CERI Figure 1 Degree of equivalence of APMP.QM-K46. 4 / 19

Linking APMP.QM-K46 to CCQM-K46 The results of the CCQM-K46 key comparison are summarized in Table 6. The degree of equivalence and its uncertainty of APMP.QM-K46 are transferred to the CCQM key comparison with the equations given as D i = D APMP + D CCQM, U(D i ) = U(D APMP ), where D CCQM is the degree of equivalence for CERI s result of CCQM-K46. The result of this comparison is added to Table 6, and Figure 2 shows the degree of equivalence of CCQM-K46 and APMP.QM-K46. Table 6 Summary of results of CCQM-K46 and APMP.QM-K46 Laboratory x prep u(x prep ) x lab U(x lab ) D i U(D i ) µmol/ mol µmol/mol µmol/mol VSL 34.028 0.201 33.8 0.7 0.79 0.757 NPL 34.104 0.201 34.52 0.99 1.434 1.031 VNIIM 33.983 0.201 33.7 0.5 0.735 0.577 METAS 34.057 0.201 32.27 0.36-0.769 0.513 NIST 33.929 0.201 32.37 0.28-0.541 0.460 KRISS 34.113 0.201 32.91 0.62-0.185 0.689 CERI 34.091 0.201 32.81 0.38-0.263 0.484 x prep u(x prep ) x KCRV U(x KCRV ) D i U(D i ) NIM 33.46 0.32 33.470 0.17-0.27 0.36 5 / 19

3 2.5 Degree of Equivalence 2 1.5 1 0.5 0-0.5-1 -1.5 CCQM-K46 APMP.QM- K46-2 VSL NPL VNIIM METAS NIST KRISS CERI NIM CERI Participants Figure 2 s of CCQM-K46 and APMP.QM-K46. Conclusion This bilateral comparison was carried out to support NIM s capability for the measurement of ammonia in nitrogen at a level of 30µmol/mol. In this key comparison, the result of the participant, NIM is consistent with the KCRV within the uncertainty. Therefore, this key comparison supports the capability of ammonia in nitrogen or air in the range of 30 to 100. Reference [1] Adriaan M.H. van der Veen et al, International comparison CCQM-K46: Ammonia in nitrogen, Metrologia, 47, Tech. Suppl. 08023 (2010). [2] International Organization for Standardization, ISO 6142:2001 Gas analysis - Preparation of calibration gas mixtures - Gravimetric methods, 2nd edition. [3] International Organization for Standardization, ISO 6143:2001 Gas analysis Comparison methods for determining and checking the composition of calibration gas mixtures. 6 / 19

Annex A Report Form APMP.QM-K46 Ammonia in nitrogen Laboratory name: Chemicals Evaluation and Research Institute, Japan Cylinder number: CPE-10086 Measurement #1 Component (dd/mm/yy) Standard deviation number of replicates NH3 3/6/2015 33.446 0.06001 3 Measurement #2 Component (dd/mm/yy) Standard deviation number of replicates NH 3 4/6/2015 33.494 0.05437 3 Measurement #3 Component (dd/mm/yy) Standard deviation number of replicates NH 3 5/6/2015 33.494 0.02108 3 Measurement #4 Component (dd/mm/yy) Standard deviation number of replicates NH 3 8/6/2015 33.447 0.1667 3 s Component Expanded Uncertainty Coverage factor 1 NH 3 33.47 0.17 2 1 The coverage factor shall be based on approximately 95% confidence. 7 / 19

Reference Method: Instruments for NH 3 measurement Principles : NDIR (Type:CGT-7000, Make : Shimadzu corporation) Data collection : integrator Calibration Standards: Preparation : Gravimetric method Purity analysis ; NH 3, N 2 : Impurities in NH 3 and N 2 are determined by analyses and the amount of the major component is conventionally determined by, N X pure = 1 x i i= 1 where: x I = mole fraction of impurity i, determined by analysis N = number of impurities X pure = mole fraction purity of the pure parent gas Instrument Calibration: Component Table 1 Composition of PSMs amount-of-substance fraction ( µmol/mol ) R 1 R 2 R 3 NH 3 50.03 35.00 20.01 Calibration method Analytical scheme was, R 1 R 2 APMP Sample R 3. This scheme was repeated 3-times in a day. These measurements were carried out for 4-days. 8 / 19

Uncertainty: Uncertainty source Measurement R 1 R 2 R 3 Round off total Value +/- 0.08328 0.02502 0.01750 0.01000 0.005 Method of evaluation (type A or typeb) Assumed probability distribution Divisor A 1 A 1 A 1 A 1 B rectangular 3 Standard uncertainty u(x i ) 0.08328 0.02502 0.01750 0.01000 0.002887 Sensitivity coefficient c i 1 0.04569 0.9902 0.05550 1 Contribution u ⅰ (y) 0.08328 0.001143 0.01733 0.0005550 0.002887 0.08512 Coverage factor: 2 Expanded uncertainty: 0.17 µmol/mol Authorship Shinji UEHARA 9 / 19

National Institute of Metrology (NIM), China Transmission of International Comparison s The title of international comparison: Ammonia in nitrogen Serial number for international comparison: APMP.QM-K46 Comparison experiment period: Jan 2015~Aug 2015 Experiment reporter: HAN Qiao Phone number of experiment reporter: +86-10-84252300 E-mail: hanqiao@nim.ac.cn NIM address: No.18, Bei-San-Huan Dong Str., Beijing 100029, China Phone/Fax number of Department of Metrology Services: +86-10-64213104 Phone/Fax number of Department of R&D and Planning (International Cooperation): +86-10-64218565 E-mail: yw@nim.ac.cn Transmission date: December 4, 2015 10 / 19

Key Comparison APMP.QM-K46 Ammonia in nitrogen 1. General information Institute Address Contact person National Institute of Metrology (NIM), China No.18, Bei-San-Huan Dong Str., Beijing 100029, China Mr. Qiao Han, Mr. Defa Wang Telephone +86-10-6452 5336 Fax +86-10-8425 2306 Email SN of cylinders Cylinder pressure wangdf@nim.ac.cn CPE-10086 8Mpa 2. s Cylinder No. Methane mole fraction x NH 3 /µmol/mol Expanded uncertainty U ( x NH 3) /µmol/mol Coverage factor CPE 10086 33.46 0.32 2 3. Purity data of parent gases Table 1. Purity table of parent gas N2, pure, A655029# fraction Std. u Technique Ar(Argon) 0.000050000 0.000005000 GC-PDHID CH 4 (Methane) 0.000000100 0.000000050 GC-FID-Cat.** CO(Carbon monoxide) 0.000000200 0.000000050 GC-FID-Cat.** CO 2 (Carbon dioxide) 0.000000500 0.000000050 GC-FID-Cat.** H 2 (Hydrogen) 0.000000100 0.000000058 GC-PDHID H 2 O(Water) 0.000000250 0.000000144 CRDS O 2 (Oxygen) 0.000000130 0.000000075 Oxygen analyzer N 2 (Nitrogen) 0.999948720 0.000005004 NH3, pure, MK-20385# fraction Std. u Technique Ar(Argon) 0.000000350 0.000000035 GC-PDHID CH 4 (Methane) 0.000000010 0.000000006 GC-PDHID H 2 O(Water) 0.000001000 0.000000577 Product Spec.* O 2 (Oxygen) 0.000000790 0.000000080 GC-PDHID N 2 (Nitrogen) 0.000001700 0.000000500 GC-PDHID 11 / 19

NH 3 (Ammonia) 0.999996150 0.000000769 * Product Spec., data was from the product specification provided by the manufacturer. ** GC-FID-Cat., GC-FID with methanator catalyst. 4. Gravimetric preparation of gas mixtures The standard gas mixtures of ammonia in nitrogen were prepared by using gravimetric method according to ISO6142:2001, and the parent gases were nitrogen, and ammonia of high purity. Figure 1 showed the dilution chart from pure gases to the final gas mixtures of NH 3 /N 2. Pure NH3 Pure N2 3.954g, u=0.005g CPE 10083 NH3=6.11072E-03 mol/mol 1057.9936g, u=0.020g 5.9246g, u=0.005g CPE 10086 NH3=3.37628E-05 mol/mol 1068.9272g, u=0.020g Figure 1. Dilution scheme from pure gases to NH 3 /N 2 Mass comparator with capacity of 26kg and resolution of 1mg is provided by Mettler Toledo. Temperature and relative humidity in balance room were controlled at 20 C±1 C and 50%RH±10%RH, respectively. Tare cylinder and substitution method were used during weighing of cylinder, by automatic weighing system, in order to cancel buoyancy effect. Fig.1 showed that standard uncertainty to the mass of parent gas added into the target cylinder was estimated as 0.005g when the added gas was around 3g~6g. By 2-step dilutions, around 33ppm ammonia in nitrogen could be achieved from the pure gases. 5. Measurement The new sample cylinder was verified against our PRM cylinder by using a photoacoustic infrared spectra ammonia analyzer. The gas pressure from each sample cylinders was reduced by a regulator, and then the sample gas was introduced into analyzer by using a pump installed inside the instrument. Sample gas flow rate was around 500mL/min. 12 / 19

Measurement repeatability is about 0.05ppm. PRMs used in measurement are listed in table 2. These gas mixtures were prepared by gravimetric method in our lab, which was described in 4. Gravimetric preparation of gas mixtures. The certified value and uncertainty of PRMs included the contribution from gravimetric method and short time stability. Table 2. Certified value and uncertainty of PRMs Cylinder Number Certified value µmol/mol Standard uncertainty µmol/mol CPE 10081 33.809 0.088 CPE 10085 33.869 0.088 Single point calibration method was used to calculate the concentration of ammonia in sample cylinder. The sample gas and reference gases were measured in the order of Reference Sample Reference alternatively. The sample gas mixture was prepared in 18/12/2014 and measured against our calibration reference mixtures 4 days after the preparation, for the first time. Half month later the second measurement was carried out. The results are in table 3 and table 4. Table 3. s of first measurement Relative standard Number of repeat (dd/mm/yy) deviation 22/12/2014 33.61 0.22% 6 23/12/2014 33.60 0.24% 6 24/12/2014 33.66 0.18% 6 Average 33.62 Table 4. s of second measurement Relative standard Number of repeat (dd/mm/yy) deviation 5/1/2015 33.68 0.23% 6 6/1/2015 33.63 0.19% 6 7/1/2015 33.62 0.23% 6 Average 33.64 The uncertainty of each measurement was evaluated according to the following equation: 2 uu mmmmmm = uu rrrrrr + uu2 aaaaaa Where, u mea is the standard uncertainty of each measurement, u ref is the uncertainty contribution from PRMs, u ana is the uncertainty contribution from analysis method. The uncertainty sources of analysis method are listed in table 5. 13 / 19

Table 5. Uncertainty sources of analysis method Uncertainty sources Relative standard uncertainty Distribution Analyzer reading repeatability of 0.16% Normal sample gas mixture Analyzer reading repeatability of reference gas mixture 0.16% Normal Repeatability of measurement 0.12% Normal results The relative standard uncertainty contribution of this analysis method was 0.256%, which led to u ana =0.086 µmol/mol for this sample gas mixture. Table 2 shows u ref =0.088 µmol/mol. So, the standard uncertainty of each measurement was about 0.123 µmol/mol and the expanded uncertainty was about 0.25 µmol/mol (k=2). 6. Stability In order to study the stability of sample gas mixture, it was re-analyzed when arriving at NIM after the measurement in CERI, the coordinating laboratory. The re-analyzed results were listed in table 6. Table 7 and figure 2 are the summary of stability study, which shows about 0.32 µmol/mol decreasing happened during about 12 months period. Table 6. s of re-analysis Relative standard Number of repeat (dd/mm/yy) deviation 26/11/2015 33.33 0.32% 6 27/11/2015 33.28 0.31% 4 1/12/2015 33.29 0.16% 5 Average 33.30 Table 7. Summary of stability test Time of test Test result Expanded uncertainty (k=2) December of 2014 33.62 0.25 January of 2015 33.64 0.25 November of 2015 33.30 0.25 14 / 19

Test results µmol/mol 34 33.9 33.8 33.7 33.6 33.5 33.4 33.3 33.2 33.1 33-1 1 3 5 7 9 11 13 Month after preparation Figure2. Stability test during 12 month 7. Certified value and uncertainty of sample gas mixture The certified value of ammonia in sample cylinder CPE 10086 was determined according to the following equation: XX = XX 0 + XX Where, X is the certified value, X 0 is the measurement result (=33.62 µmol/mol) after the sample gas mixture preparation in December of 2014 and X is the average variation of ammonia concentration in 12 months. The stability study showed that the variation of ammonia concentration was from 33.62 µmol/mol to 33.30 µmol/mol. According to rectangular distribution, X =-0.16 µmol/mol and u( X) was 0.10 µmol/mol. So, the certified value of sample gas mixture was 33.46 µmol/mol. The standard uncertainty and expanded uncertainty of X were estimated by following equations: uu(xx) = uu 2 (XX 0 ) + uu 2 ( XX) UU(XX) = kk uu(xx), kk = 2 So, the expanded uncertainty of certified value was 0.32 µmol/mol. 15 / 19

Annex B APMP.QM-K46 Protocol for Bilateral Comparison on Ammonia in Nitrogen between NIM and CERI coordinated by NMIJ Introduction Ammonia is an important compound in the chemical industry. It is widely used and is the basis for producing other compounds containing nitrogen. Ammonia is also very hazardous, and consequently emissions of ammonia need be controlled and monitored. VSL coordinated CCQM-K46 (30 µmol/mol - 50 µmol/mol, NH 3 in N 2 ) in 2006. CERI participated in the comparison, but NIM did not participate in CCQM-K46. NIM would like to compare the gas standard with CERI through the bilateral comparison. Initially, analytical comparison between CERI and NIM was planned and CERI prepared two primary gas mixtures of NH 3 in N 2 for this comparison, but the cylinder was not transported to NIM. Difficulty of cylinder transport often occurs. Therefore, the protocol of this comparison was changed where NIM will send their cylinder to CERI. Participants CERI (Chemicals Evaluation and Research Institute, Japan) and NIM (National Institute of Metrology, China). Method of the Bilateral Comparison NIM will prepare one gas mixture sample and send it to CERI. Concentration of NH 3 in N 2 should be between 30 µmol/mol and 50 µmol/mol. The pressure in the cylinders should be more than 10 MPa. Cylinder of 10 dm 3 nominal or larger one should be used. CERI will measure the cylinder from NIM against CERI s primary gas mixtures. The cylinder will be sent back to NIM after the measurement at CERI. CERI participated in CCQM-K46 and the result was consistent with the KCRV, key comparison reference value. The amount-of-substance fractions as obtained from gravimetry at CERI will be used as reference value. Each cylinder will have its own reference value. Each participating laboratory will be responsible for the calculation of the gravimetric concentration and its uncertainty. For a proper evaluation of the data, it is necessary that purity analysis of raw gases, evaluation of gravimetric preparation process and stability 16 / 19

are done properly at each NMI. After the transfer of cylinder to NIM, NIM has to measure the returned cylinder for stability check (pressure at least 5 MPa), the stability data is to be combined into stability data for uncertainty evaluation in the report. NIM will bear cost for all transportations. Transport of the cylinder from NIM to CERI and CERI to NIM will be arranged by NIM. Schedule (original) February 2011 April 2011 June 2011 July 2011 August 2011 September 2011 Preparation and verification of gas mixture in CERI Transport to NIM (8MPa or more) Measurement of gas mixture in NIM Return of cylinder to CERI (5 MPa or more) Verification of gas mixture in CERI Report to NMIJ Draft A Report Draft B Report Coordinator Dr. Kenji Kato National Metrology Institute of Japan (NMIJ) AIST Tsukuba Central 3, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8563, Japan Phone : +81 29 861 4841 Fax : +81 29 861 6857 Email : k.kato@aist.go.jp Contact person of CERI Mr. UEHARA Shinji Chemicals Evaluation and Research Institute, Japan (CERI) 1600 Shimotakano, Sugito-machi, Kitakatsushika-gun, Saitama 345-0043, Japan Phone : +81 480 37 2601 Fax : +81 480 37 2521 17 / 19

Report Form APMP.QM-K46 Ammonia in nitrogen Laboratory name: Cylinder number: Purity analysis of NH 3 Component Standard deviation number of replicates (dd/mm/yy) (mol/mol) (% relative) Ammonia Purity analysis of N 2 Component Standard deviation number of replicates (dd/mm/yy) (mol/mol) (% relative) Ammonia Gravimetric concentration of NH 3 in N 2 Component Standard deviation number of replicates (dd/mm/yy) (mol/mol) (% relative) Ammonia 18 / 19

Assigned concentration and uncertainty of the sample Component Expanded Uncertainty Coverage factor 2 (mol/mol) Purity of NH 3 Purity of N 2 Gravimetry Stability 2 The coverage factor shall be based on approximately 95% confidence. 19 / 19