1 Metrology Infrastructure in Gas Analysis Ed W.B. de Leer NMi Van Swinden Laboratorium MiC Symposium, Beijing October 2004

2 Importance of Gas Analysis Economic Value Natural Gas (calorific value) Chemical process industry (ethylene,etc.) Electronic industry (reactive gases, H 2 O) Food industry and health care (purity, composition) Environmental regulations Industrial stack emissions (NO x, SO 2, HCl, etc.) Automotive gases (CO, CO 2, C 3 H 8, NO) Occupational hygiene (VOC, particles) Ambient air quality (Benzene, O 3, CH 4, N 2 O, VOC, etc.) Legislation Breath Analysis (ethanol) Odor Control (n-butanol)

3 Traceability to SI ISO TC 158 Laboratory Accreditation Infrastructure for Gas Analysis Instrument Manufacturers Reference Gas Producers

4 Start of Traceability Chain (I) For static gas mixtures, the traceability chain starts with a primary realisation of the definition of the mole fraction or amount of substance fraction for a specified chemical entity. n B = amount of substance of entity B

5 Primary Realisation of mol/mol A primary realisation (PSM) of the amount fraction in a static gas mixture involves (ISO 6142:2001): accurate weighing (incl. buoyancy correction) of pure parent gases (or liquids) in a clean high pressure cylinder (u c %) Impurity analysis of the parent gases/liquids Analytical verification of the composition against a coherent set of primary standards (u c %) Stability testing Problems: low amount fractions (nmol/mol) for reactive gases, sorption on cylinder wall, isotopic variation, phase separation

6 Stability of PSMs av = s.d. = 0.105

7 Start of Traceability Chain (II) For dynamically generated gas mixtures, the traceability chain starts with a primary realisation for amount concentration (mol/m 3 ) for a specified chemical entity. N.B. Pressure and temperature need to be defined as well! Usually, permeation, diffusion or injection of a pure gas in a flowing gas stream produces the primary realisation.

Key Comparison of National Standards

9 Experimental Set-up KCs (I) Pilot NMI Participating NMI Pure gases PRM gravimetry Pure gases* PSM* comparison secondary methods (NDIR, GC, FTIR, ….) gravimetry

10 CCQM-K3 – Automotive gases

11 CCQM-K4Ethanol in air

12 CCQM GAWG Key Comparisons Key comparison identifier DescriptionStatusPilot CCQM-K1a CCQM-K1b CCQM-K1c CCQM-K1d CCQM-K1e CCQM-K1f CCQM-K1g CCQM-K3 CCQM-K4 CCQM-K7 CCQM-K10 CO in nitrogen (3 concentrations) CO2 in nitrogen (3 concentrations) NO in nitrogen (2 concentrations) SO2 in nitrogen (2 concentrations) Natural gas Type I Natural gas Type II Natural gas Type III Automotive gases (CO, CO2, C3H8) Ethanol in air BTEX in air (50 nmol/mol) BTEX in air (5 nmol/mol) In KCDB NMi VSL NPL NIST

13 CCQM GAWG Key comparisons (II) Key comparison identifier DescriptionStatusPilot CCQM-K15 CCQM-K16a CCQM-K16b CCQM-K22 CCQM-K23 CCQM-K26a CCQM-K26b CCQM-K41 CCQM-K46 CCQM-K51 CCQM-K52 CCQM-K53 CCQM-Kxx SF6 and CF4 in nitrogen Natural gas Type IV Natural gas Type V VOC in air Natural gas K1e,f,g repeat NO in nitrogen (ambient level) SO2 in nitrogen (ambient level) H2S in air/nitrogen NH 3 in nitrogen CO in nitrogen (5μmol/mol) CO2 in air ( μmol/mol) Preparative capabilities (O2 in N2) Prep. Capabilities (n-hexane in CH4) Completed In KCDB Draft B Draft A Planned KRISS NMi VSL NMIJ NMi VSL NPL NIST NMi VSL CSIR-NML NMi VSL KRISS NMi VSL

14 New Set-up CCQM-P23 Pilot NMI Participating NMIs Pure gases Series of PRMs Gravimetry Analytical comparison under repeatabilty conditions

15 High Accuracy comparisons All laboratories send a standard to the pilot laboratory Preparation errors can now be randomised Preparation errors can now be randomised Author: Martin Milton

16 Gravimetry: 1000 mmol/mol CO

17 CCQM-P23 CCQM-P23 used mixtures of CO/N2 at three amount fractions 50,000 1,000 and 10 mol/mol. In the first phase these were all analysed by NDIR at NMi (The Netherlands) Evidence was found for 13 C/ 12 C variations in pure CO and for an influence of the 13 C/ 12 C ratio on the NDIR signal. Extreme outliers from KRISS (Korea) and NIST (USA) In the second phase two sets of mixtures were re-analysed: –50,000 mol/mol by NIST (USA) using GC/TCD –1,000 mol/mol by Metas (Switzerland) using GC/FID

18 GC-TCD results GC-TCD Results for 50,000 umol/mol CO in nitrogen 0,93 0,94 0,95 0,96 0,97 0,98 0,99 1,00 1,01 1,02 1, Concentration (umol/mol) Ratio to Control

19 GLS for GC-TCD versus Gravimetry Conclusions for 50,000 mol/mol –Std dev of residuals is 1 mol/mol (0.002% rel)- after excluding two outliers –At 50,000 mol/mol, the gravimetric values are very consistent within their stated uncertainties. k=2 Author: Martin Milton

20 GLS for 1,000 mol/mol Conclusions –Std dev of residuals is 1.7 mol/mol (0.17%relative) –At 1,000 mol/mol, five (out of nine) of the gravimetric values are not consistent within their stated uncertainties. k=2 Author: Martin Milton

21 Greenhouse gases: CH 4 Author: Adriaan van der Veen

22 GLS for CH 4 Greenhouse gas Conclusion: The std dev of residuals in x-direction is μmol/mol (0.6% rel) The uncertainty of two gravimetric standards is not compliant with the regression

23 CCQM GAWG Pilot Studies Key comparison identifier DescriptionStatusPilot CCQM-P23 CCQM-P24 CCQM-P28 CCQM-P41 CCQM-P51 CCQM-P71 CCQM-P87 Gravimetry (CO, 3 amount fractions) + additional studies Dynamic mixing of gases Ambient ozone concentrations Greenhouse gases (CO2 and CH4) Analysis and gravimetry CF4 and SF6 in nitrogen VOCs in nitrogen Gravimetry (natural gas) Completed In progress Draft B Completed Draft B Planned NMi, NPL, NIST, KRISS LNE BIPM NMi VSL KRISS NMIJ NPL

24 Gas CMCs in KCDB August 9, Countries 554CMC entries 146Measurands 12 Gas Matrices August 9, Countries 554CMC entries 146Measurands 12 Gas Matrices

25 Function of NMI gas Standards Primary realization of gas composition standards Production of traceable gas transfer standards Calibration of secondary gas standards, instruments, etc Production of pure gases Cylinder treatment Production of traceable calibration gases for field applications NMI Industry Workfloor applications in gas analysis e.g. testing automotive exhaust gases, natural gas composition SI traceable measurement results Workfloor

26 Accreditation of Gas RM Producers Accredited as Calibration Laboratory (ISO/IEC 17025) –Belgium (1)France (2, incl. LNE) –Germany (2)Italy (2) –Netherlands (2, incl. NMi)Spain (6) –Sweden (1)Switzerland (3) –United Kingdom (7, incl. NPL) Accredited as Test Laboratory (ISO/IEC 17025) –Mexico (1) Accredited as Reference Material Producer (ISO Guide 34) –Australia (2)Japan (2, incl. NMIJ) Accredited by Jcss Japan (3) Legal Metrology Systems e.g. China, Russia

27 Standardisation ISO/TC 146Air Quality ISO/TC 158Gas Analysis ISO/TC 193Natural Gas ISO/TAG 4Metrological Issues OIML Recommendations

28 Conclusion The metrological concepts of traceability and measurement uncertainty are widely accepted in the field of gas analysis Cooperation between NMIs, Standardization bodies, and Industry is essential for continued development