Preparation of nitrous oxide in air standard (320 nmol/mol) for CCQM-K68

Transcription

1 Preparation of nitrous oxide in air standard (320 nmol/mol) for CCQM-K68 8th APMP/TCQM Gas CRM Workshop June 10 th, 2010 Tukuba, Ibaraki, Japan Nobuyuki Aoki, Takuya Shimosaka, Nobuhiro Matsumoto, Kenji Kato (National Metrology Institute of Japan, AIST)

2 Table of contents Background of CCQM-K68 Outline of CCQM-K68 Preparation procedure Purity analysis of parent gas Weighing process of filling gas Result of CCQM-K68 Summary

3 Background 300 times GWP of CO %/yr(0.8ppb/yr) It is necessary to harmonize calibration scale

4 Outline of CCQM-K68 Pilot laboratory Component KRISS Nitrous Oxide in synthetic air Concentration Target uncertainty 0.1 % Supported claims Participants objective 320 nmol/mol N 2 O in synthetic air at atmospheric level with the uncertainty within calibration scale of global monitoring division NMIJ, VSL, NIST, VNIM, NIM, KRISS, NOAA* 1, IMK-IFU* 2 Comparison of the measurement capability of N 2 O at a trace level of 320 nmol/mol * 1 NOAA is the Central Calibration Laboratory to maintain WMO scale * 2 IMK-IFU is a World Calibration Centre for N 2 O to take over Quality Assurance and Quality Control (QA/QC) to combine N 2 O measurements from different sites and different monitoring programs responsibility.

5 Preparation procedure Gravimetric value x i = P i, A A n n A= 1 A= 1 x j, A M j x j= 1 m P j= 1 x m A j, A M j x j,a : mol fraction of the component Purity of parent gas SI Amount of substance (mol) Impurity analysis with primary standards m A : mass of parent gas Amount of parent gas Mass (kg) Weighing with balance calibrated by the mass piece M j : Molar mass IUPAC Atomic weight Relative mass

6 Purity analysis of raw materials Purity table of N 2 Purity table of N 2 O Components Applied concentration (μmol/mol) Standard uncertainty (μmol/mol) Analytical method N Micro GC O Micro GC CO GC-FID with methanizer CH GC-FID CO H 2 O N 2 O GC-FID with methanizer Capacitance-type moisture meter Components Components Applied concentration (μmol/mol) Applied concentration (μmol/mol) Standard uncertainty (μmol/mol) Analytical method N GC-TCD Ar GC-TCD CO FT-IR CH FT-IR CO FT-IR H 2 O Capacitance-type moisture meter N 2 O Clyo. conc. /GC/MS O Standard uncertainty (μmol/mol) Analytical method O Micro GC CO FT-IR CH FT-IR CO FT-IR H 2 O Capacitance-type moisture meter N 2 O Clyo. conc. /GC/MS N Purity table of O 2

7 Analytical system for impurity N 2 O in N 2, O 2 pump Module 1 Module 2 Module 1 Module 2 Module 3 Tenax Glass bead Module 3 Precolum forcouser -120 C -150 C -180 C 20 C 150 C 70 C GC-MS Column: Pora PLOT Q 0.32mm 25m Oven: 50 Time: 12min Carrier gas: He 2.0ml/min Mode: SIM(mass:30)

8 N 2 O concentration in O 2 and N N 2 O was not detected! Area The value was determined from detection limit Concentration (nmol/mol)) N 2 O in He (gravimetric method) He (nmol/mol) Concentration(x d ) = Detection limit 2 Standard uncertainty(u xd ) Detection limit = 3 N 2 O value in dilution gases are 0.02±0.02 nmol/mol The uncertainty is expanded uncertainty with the coverage factor of 2

9 Weighing process Main source of uncertainty Balance Buoyancy effect Absorption and adsorption to external cylinder surface.etc Comparative Weighing Weighing room 25 C, 50% Filling room 24 C, 20~80% Mixture Reference kg Alternately-measured an hour after filling parent gas five hours after filling dilution gases N 2 O or N 2 O in N 2 N 2 or O 2

10 Weighing system of NMIJ Mixture cylinder Reference cylinder Electric mass comparator Max=15kg, d=1mg Automatic cylinder exchanger Standard uncertainty of balance system : 2.6 mg!

11 Preparation protocol N 2 O, N 2 CPB16182 CPB16250 CPC00878 CPB16181 CPB step %mol/mol Expanded uncertainty: 0.04 % N 2 CPB16174 CPB16178 CPC00871 CPB16176 CPB step μmol/mol Expanded uncertainty: 0.05 % N 2 CPB16185 CPB16184 CPB16187 CPB16186 CPB step μmol/mol Expanded uncertainty: 0.06 % N 2, O 2 CPB16463 CPB31362 CPC00877 CPC00415 CPB step nmol/mol Expanded uncertainty: 0.06 % Five standards were independently prepared!

12 Verification of parent gases 1 step Deviation between five values < ± 0.15 % Internal consistency test check that gravimetric value is consistent with analytical value highlight significant errors in the preparation process FT-IR 3 step 2 step Deviation between five values < ± 0.08 % FT-IR Deviation between five values < ± 0.06 % GC-ECD

13 N 2 O standards of NMIJ Cylinder number Gravimetric Value (nmol/mol) Expanded uncertainty (nmol/mol) [k=2] Calculated Value (nmol/mol) Deviation (nmol/mol) CPB CPB CPB CPC CPB

14 Analytical system

15 Chromatogram Column: Porapak-Q(80/100), 1.2m(1/8inch) Oven: 30 C ECD: 345 C Carrier gas: N 2 (10ml/min) Make up gas: ArCH 4 (10ml/min) A good chromatogram was obtained!

16 Draft A report of CCQM-K68 Draft of CCQM-K68 Relative deviation (%) NMIJ Laboratory Y axis =(Analysis value)-(kcrv) Reported value of NMIJ is in excellent agreement with key comparison reference value (KCRV)

17 Summary N 2 O concentration in N 2 and O 2 is estimated by preconcentration GC-MS N 2 O standards traceable to SI have been prepared Analysis result of is in excellent agreement with KCRV in CCQM-K68

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19 This study NMIJ Preparation of N 2 O standard traceable to SI Evaluation of NIES standards NIES Measurement of NMIJ standards by GC-ECD of NIES Evaluation of NMIJ standards NMIJ (Japan) NMis International comparison (CCQM-K68) Pilot laboratory KRISS ( KRISS ) WMO IMK-IFU NOAA NMi-VSL (Netherlands) NIST (USA) NMi (China) VNIIM (Rossia)