Metrology Infrastructure in Gas Analysis
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Metrology Infrastructurein Gas Analysis
Ed W.B. de Leer
NMi Van Swinden Laboratorium
MiC Symposium, Beijing 18-22 October 2004
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Importance of Gas Analysis
Economic Value• Natural Gas (calorific value)• Chemical process industry (ethylene,etc.)• Electronic industry (reactive gases, H2O)• Food industry and health care (purity, composition)
Environmental regulations• Industrial stack emissions (NOx, SO2, HCl, etc.)• Automotive gases (CO, CO2, C3H8, NO)• Occupational hygiene (VOC, particles)• Ambient air quality (Benzene, O3, CH4, N2O, VOC,
etc.)
Legislation• Breath Analysis (ethanol)• Odor Control (n-butanol)
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Traceability to SI ISO TC 158
Laboratory Accreditation
Infrastructure for Gas Analysis
Instrument Manufacturers Reference Gas Producers
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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.
nB = amount of substance of entity B
i
iB
B
i
BB
Mm
M
m
n
ny
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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 (uc ≈ 0.001-0.1%)
Impurity analysis of the parent gases/liquids
Analytical verification of the composition against a coherent set of primary standards (uc ≈ 0.05-1%)
Stability testing
Problems: low amount fractions (nmol/mol) for reactive gases, sorption on cylinder wall, isotopic variation, phase separation
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Stability of PSMs
Stability 600 mmol/mol NO in N2
-0,2
-0,1
0
0,1
0,2
0,3
0 5 10 15
Time (0,5 a)
%
av= +0.004 s.d. = 0.105
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Start of Traceability Chain (II)
For dynamically generated gas mixtures, the traceability chain starts with a primary realisation for amount concentration (mol/m3) for a specified chemical entity.
B
BBB VM
m
V
nc
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.
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Key Comparison of National Standards
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Experimental Set-up KCs (I)
Pilot NMI Participating NMI
Pure gases
PRM
gravimetry
Pure gases*
PSM*comparison
secondary methods(NDIR, GC, FTIR, ….)
gravimetry
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CCQM-K3 – Automotive gases
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CCQM-K4 Ethanol in air
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CCQM GAWG Key Comparisons
Key comparison identifier
Description Status Pilot
CCQM-K1aCCQM-K1bCCQM-K1cCCQM-K1dCCQM-K1eCCQM-K1fCCQM-K1gCCQM-K3CCQM-K4CCQM-K7CCQM-K10
CO in nitrogen (3 concentrations)CO2 in nitrogen (3 concentrations)NO in nitrogen (2 concentrations)SO2 in nitrogen (2 concentrations)Natural gas Type INatural gas Type IINatural gas Type IIIAutomotive gases (CO, CO2, C3H8)Ethanol in airBTEX in air (50 nmol/mol)BTEX in air (5 nmol/mol)
In KCDBIn KCDBIn KCDBIn KCDBIn KCDBIn KCDBIn KCDBIn KCDBIn KCDBIn KCDBIn KCDB
NMi VSLNMi VSLNMi VSLNMi VSLNMi VSLNMi VSLNMi VSLNMi VSLNPLNISTNIST
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CCQM GAWG Key comparisons (II)
Key comparison identifier
Description Status Pilot
CCQM-K15CCQM-K16aCCQM-K16bCCQM-K22CCQM-K23CCQM-K26aCCQM-K26bCCQM-K41CCQM-K46CCQM-K51CCQM-K52CCQM-K53CCQM-Kxx
SF6 and CF4 in nitrogenNatural gas Type IVNatural gas Type VVOC in airNatural gas K1e,f,g repeatNO in nitrogen (ambient level)SO2 in nitrogen (ambient level)H2S in air/nitrogenNH3 in nitrogen
CO in nitrogen (5μmol/mol)CO2 in air (380-400 μmol/mol)Preparative capabilities (O2 in N2)Prep. Capabilities (n-hexane in CH4)
CompletedIn KCDBIn KCDBDraft BDraft ADraft ADraft ADraft APlannedPlannedPlannedPlannedPlanned
KRISSNMi VSLNMi VSLNMIJNMi VSLNPLNPLNISTNMi VSLCSIR-NMLNMi VSLKRISSNMi VSL
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New Set-up CCQM-P23
Pilot NMI Participating NMIs
Pure gases
Series of PRMs
GravimetryAnalytical comparison under repeatabilty
conditions
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“High Accuracy” comparisons
All laboratories send a standard to the pilot laboratory
Preparation errors can now be Preparation errors can now be “randomised”“randomised”
Author: Martin Milton
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Gravimetry: 1000 mol/mol CO
1000 mmol/mol CO in Nitrogen
8100
8200
8300
8400
8500
8600
8700
8800
8900
940 960 980 1000 1020 1040 1060
grav. mol fraction (mmol/mol)
Co
rrec
ted
res
po
nse
(m
V)
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CCQM-P23
• CCQM-P23 used mixtures of CO/N2 at three amount fractions 50,000 1,000 and 10 mmol/mol.
• In the first phase these were all analysed by NDIR at NMi (The Netherlands)
• Evidence was found for 13C/12C variations in pure CO and for an influence of the 13C/12C 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 mmol/mol by NIST (USA) using GC/TCD – 1,000 mmol/mol by Metas (Switzerland) using GC/FID
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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
1,03
47000 47500 48000 48500 49000 49500 50000 50500 51000 51500 52000 52500
Concentration (umol/mol)
Rat
io t
o C
on
tro
l
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GLS for GC-TCD versus Gravimetry
• Conclusions for 50,000 mmol/mol– Std dev of residuals is 1mmol/mol (0.002% rel)-
after excluding two outliers– At 50,000 mmol/mol, the gravimetric values are
very consistent within their stated uncertainties.
-80
-60
-40
-20
0
20
40
60
BAM CENAM CSIRO IPQ KRISS LNE NIST NMIJ NPL
Re
sd
iua
l De
via
tio
n (
um
ol/m
ol)
k=2k=2
Author: Martin Milton
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GLS for 1,000 mmol/mol
• Conclusions– Std dev of residuals is 1.7 mmol/mol (0.17%relative)– At 1,000 mmol/mol , five (out of nine) of the gravimetric
values are not consistent within their stated uncertainties.
-4
-2
0
2
4
6
8
BAM LNE SMIJ NPL IPQ KRISS NIST Metas CSIRO
Resid
ual
Devia
tio
n (
um
ol/
mo
l)
k=2k=2
Author: Martin Milton
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Greenhouse gases: CH4
Author: Adriaan van der Veen
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GLS for CH4 Greenhouse gas
Conclusion:
The std dev of residuals in x-direction is 0.012 μmol/mol (0.6% rel)The uncertainty of two gravimetric standards is not compliant with the regression
Residuals (x-direction)
-0.060
-0.040
-0.020
0.000
0.020
0.040
0.060
1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2
amount-of-substance fraction (µmol/mol)
Resid
ual (x
, µ
mol/m
ol)
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CCQM GAWG Pilot Studies
Key comparison identifier
Description Status Pilot
CCQM-P23
CCQM-P24CCQM-P28CCQM-P41
CCQM-P51CCQM-P71CCQM-P87
Gravimetry (CO, 3 amount fractions) + additional studiesDynamic mixing of gasesAmbient ozone concentrationsGreenhouse gases (CO2 and CH4)Analysis and gravimetryCF4 and SF6 in nitrogenVOC’s in nitrogenGravimetry (natural gas)
Completed
In progressDraft BCompleted
CompletedDraft BPlanned
NMi, NPL, NIST, KRISSLNEBIPMNMi VSL
KRISSNMIJNPL
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Gas CMCs in KCDB
12
480
33
13
3
13
0 100 200 300 400 500 600
4.1 High purity
4.2 Environmental
4.3 Fuel
4.4 Forensic
4.5 Medical
4.6 OthersAugust 9, 2004
18 Countries554 CMC entries146 Measurands 12 Gas Matrices
August 9, 2004
18 Countries554 CMC entries146 Measurands 12 Gas Matrices
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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
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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
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Standardisation
• ISO/TC 146 Air Quality
• ISO/TC 158 Gas Analysis
• ISO/TC 193 Natural Gas
• ISO/TAG 4 Metrological Issues
• OIML Recommendations
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Conclusion
• The metrological concepts of traceability and measurement uncertainty are widely accepted in the field of gas analysis
• Cooperation between NMI’s, Standardization bodies, and Industry is essential for continued development