international comparison ccqm-k101:oxygen in nitrogen10national metrology institute of south...
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CCQM K101
1
CCQM K101 Final Report
International Comparison CCQM-K101:Oxygen in Nitrogen _ a
Track B Comparison and That the Matrix Contains Argon
Zeyi Zhou1,Qiao Han
1, Defa Wang
1, Tatiana Macé
2,Heinrich Kipphardt3, Michael
Maiwald3,Dirk Tuma
3, Shinj Uehara 4
, Dai Akima4, Takuya Shimosaka
5,Jinsang
Jung6,Sang-Hyub Oh
6, Adriaan van der Veen
7,Janneke I.T. van Wijk7,Paul R. Ziel
7,Leonid Konopelko
8,Miroslava Valkova9,David M Mogale
10, Angelique Botha
10,Paul
Brewer11
, Arul Murugan11
, Marta Doval Minnaro11
, Michael Miller11 , Frank
Guenther12
, Michael E. Kelly12
1National Institute of Metrology(NIM),Beijing Beisanhuan East road Nop.18,
Beijing 100029, China. 2Laboratoire National de Metrologie et D'essais(LNE),1, rue Gaston Boissier, 75 724
Paris Cedex 15, France. 3BAM Federal Institute for Materials Research and Testing(BAM),Division 1.4, Gas
Analysis/Gasanalytik 40/423, Unter den Eichen 87, 12205 Berlin, Germany. 4Chemicals Evaluation and Research Institute (CERI),1600 Shimotakano,
Sugito-machi, Kitakatsushika-gun, Saitama 345-0043, Japan. 5National Metrology Institute of Japan(NMIJ),1-1-1 Umezono, Tsukuba, Ibaraki,
305-8563, Japan. 6Korea Research Institute of Standards and Science(KRISS),267 Gajeong-ro
Yuseong-gu Daejeon, 305-340, the Republic of Korea. 7 Netherlands Meetinstituut Van Swinden Laboratory(VSL),Thijsseweg 11, 2629 JA
Delft, The Netherlands. 8D.I. Mendeleyev Institute for Metrology(VNIIM), 19 Moskovsky pr., St. Petersburg,
190005, Russia. 9Slovak Institute of Metrology(SMU), Karloveska 63, SK-842 55 Bratislava,
Slovakia. 10
National Metrology Institute of South Africa(NMISA), CSIR Campus, Meiring
Naudé Road, Brummeria, Pretoria, South Africa
.11
National Physical Laboratory(NPL), Hampton Road, Teddington, Middlesex,
TW11 0LW. 12
National Institute of Standards and Technology(NIST) , 100 Bureau Drive,
Gaithersburg, MD 20899-8393.
CCQM K101
2
Coordinating Laboratory: National Institute of Metrology (NIM)
Study Coordinator: Zeyi Zhou
Field: Amount of substance
Subject: Oxygen in Nitrogen at 10 mol/mol
Organizing Body: CCQM
Schedule of comparison:
Protocol issued April 2012, Paris
June 2012 Preparation cylinder and verification
Oct.2012 ~Feb. 2013 Cylinders shipped to participating labs
Sept. ~ Nov. 2013 Reports and Cylinders back to NIM for verification
Nov. 2013~April 2014 Prepare report of K101
April 2014 Draft A report issued
Sept. 2014 Draft B report issued
1. Introduction
This key comparison aims to assess the capabilities of the participants to determine
the amount-of-substance fraction oxygen in nitrogen. The GAWG has classified this
as a Track B comparison, due to the unexpected 50 mol/mol Argon mole fraction
content of the transfer standards, which effects the achievable performance of some
measurement techniques such a GC-TCD. The separation of oxygen and argon is a
challenging, and not all systems in use are equally well designed for it. As this
analytical challenge due to a substantial fraction of Argon in the transfer standards
became a reality, the Gas Analysis Working Group (GAWG) decided to qualify this
key comparison as a regular key comparison and not as a core comparison, which
may be used to support calibration and measurement capabilities (CMCs) for oxygen
in nitrogen, or for oxygen in nitrogen mixtures containing argon only (see also the
section on support to CMCs).
Support to CMCs
This key comparison provides evidence in support of CMCs for oxygen in the
amount-of-substance fraction range from 5mol/mol to 50 %, in a matrix of nitrogen
or helium.
Laboratories that have an analytical system that is sensitive to the presence of
substantial levels of argon in such mixtures, can continue to use CCQM-K53 [1] to
underpin their CMCs. They can use this key comparison to underpin measurement
capabilities for determining the oxygen fraction in gas mixtures in nitrogen or helium
in the presence of argon.
CCQM K101
3
2. Participants
Participants are listed in table 1
Table 1 Participants
ACRONYM COUNTRY INSTITUTE
LNE France Laboratoire national de metrologie et d'essais
BAM Germany BAM Federal Institute for Materials Research and Testing
CERI Japan Chemicals Evaluation and Research Institute
NMIJ Japan National Metrology Institute of Japan
NIM China National Institute of Metrology
KRISS Korea Korea Research Institute of Standards and Science
VSL Netherlands Van Swinden Laboratory
VNIIM Russia D.I. Mendeleyev Institute for Metrology
SMU Slovak Slovak Institute of Metrology
NMISA South Africa National Metrology Institute of South Africa
NPL UK National Physical Laboratory
NIST USA National Institute of Standards and Technology
3. Preparation of Parent Mix Cylinder
4.1 Specification of balance
METTLER TOLEDO XP10003S, Repeatability, 2 mg, capacity, 10.1 kg, resolution, 1
mg.
4.2 Weighing method
Substitution method, reference cylinder (A-B-A)
Amount-of-substance fraction can be calculated according to ISO 6142 with equation
(1):
(1)
Amount-of-substance fraction uncertainties are calculated with equation (2):
(2)
P
jn
i
iij
j
P
jn
i
iij
jkj
k
Mx
m
Mx
mx
y
1
1
1
1
)(
)(
)()()()( 2
1
2
1
2
2
1
2
2
1
2
ij
P
j
q
i ij
k
j
p
j j
k
i
q
i i
k
k xux
ymu
m
yMu
M
yyu
CCQM K101
4
Two aluminum compressed gas cylinders (cylinder 608583 and cylinder 610357) with
an internal volume of approximately 4 L were used as the parent mixture at last step.
They were filled and verified in a manner that meet or exceed the guidelines outlined
in ISO 6142 and ISO 6143. Table 2 below lists the dilution steps of the gravimetric
method for preparation of cylinder 608583 and cylinder 610357 respectively.
Table 2 Gravimetric hereditary
pure O2: 34.0414 g(0.006g)
pure N2: 344.7445g (0.015g)
Step 1
cylinder# 608519: 25.5377g (0.006g)
cylinder# (pure N2): 424.6296g (0.015g)
Step 2
cylinder# 608572: 24.8424g (0.006g)
Cylinder # (pure N2):394.4840g (0.015g)
Step 3
cylinder# 608583: 264.436 (0.094) mol/mol*
pure O2: 30.5643g (0.006g)
pure N2: 395.3078g (0.015g)
Step 1
cylinder# 610735: 25.2692g (0.006g)
cylinder# (pure N2): 427.7141g (0.015g)
Step 2
cylinder#608482: 31.7808g (0.006g)
cylinder # (pure N2): 395.5329 (0.015g)
Step 3
cylinder# 610357: 260.687 (0.088) mol/mol
Cylinder 608583 and Cylinder 610357 preparation information are listed in table 3.
The purity of nitrogen and oxygen listed in table 4.
Table 3 Parent mixtures information
Cylinder 618583 preparation information
Uncertainty source
Component
Estimate xi
(mol/mol)
Standard uncertainty u(xi)
(mol/mol)
CO 5.2910-8
3.1810-8
CO2 1.3210-7
0.7710-7
CH4 1.0410-8
1.0210-8
H2 3.0810-7
0.4810-7
H2O 1.2010-8
0.9510-8
Ar 4.9010-5
0.1210-5
N2 9.9995010-1
0.0000210-1
O2 2.6443610-4
0.0009410-4
Cylinder 610357 preparation information
Uncertainty source
Component
Estimate xi
(mol/mol)
Standard uncertainty u(xi)
(mol/mol)
CO 5.2910-8
3.1310-8
CCQM K101
5
CO2 1.3110-7
0.7610-8
CH4 1.0510-8
1.0210-8
H2 3.0810-7
0.4710-7
H2O 1.2010-8
0.9310-8
Ar 4.9010-5
0.1210-5
N2 9.9994910-1
0.0000210-1
O2 2.6068710-4
0.0008810-4
Table 4 Assay of the pure nitrogen and pure oxygen
Component Purity of N2
(mol/mol)
Standard uncertainty
(mol/mol)
H2O 1.210-8 1.010
-8
O2 1.410-8 0.510
-8
H2 3.010-7 1.010
-7
CO 5.310-8 3.010
-8
CO2 1.310-7 1.010
-7
CH4 1.010-8 1.010
-8
Ar 4.9010-5 0.1210
-5
N2 0.999970 0.000002
Component Purity of O2
(mol/mol)
Standard uncertainty
(mol/mol)
H2O 4.910-9 5.010
-9
N2 3.010-6 1.510
-6
H2 3.010-7 1.510
-7
CO 2.010-8 2.010
-8
CO2 5.010-7 3.010
-7
CH4 1.010-7 1.010
-7
Ar 2.010-6 1.010
-6
O2 0.999994 0.000002
4.3 Preparation of Comparison Cylinders
About twenty five aluminum compressed gas cylinders with internal volume of
approximately 5.9 L were purchased from a specialty gas company and were used to
prepare the sample mixtures. They were filled in a manner that meet the guideline
outlined ISO 6142.
These comparison cylinders were prepared from different parent mixtures but all with
the same source of balance gas (nitrogen). The table 5 below gives an assay of the
pure nitrogen used to prepare these cylinders:.
CCQM K101
6
Table 5 Assay of the pure nitrogen
Component Purity of N2
(mol/mol)
Standard uncertainty
(mol/mol)
H2O 1.910-8 1.010
-8
O2 1.4010-8 0.0510
-8
H2 1.010-7 1.010
-7
CO 2.010-8 2.010
-8
CO2 1.010-7 1.010
-7
CH4 1.010-7 1.010
-7
Ar 4.9010-5 0.1210
-5
N2 0.9999951 0.000001
Candidate cylinders gravimetric preparation results listed in table 6:
Table 6 Gravimetric preparation results for candidate cylinders
Cylinder
number
Gravimetric Value
mol/mol
Standard uncertainty
ugrv
mol/mol
FB03480 10.0204 0.0041
FB03481 9.8935 0.0040
FB03484 9.9840 0.0041
FB03488 10.0005 0.0041
FB03490 10.0199 0.0041
FB03494 10.0243 0.0041
FB03496 10.0212 0.0041
FB03497 10.0158 0.0039
FB03498 10.0041 0.0041
FB03506 10.0199 0.0041
FB03508 10.0248 0.0041
FB03510 10.0277 0.0041
FB03482 10.0114 0.0039
FB03485 10.0153 0.0039
FB03492 10.0198 0.0039
FB03493 10.0146 0.0039
FB03507 10.0018 0.0039
FB03509 10.0159 0.0039
CAL017795 10.0012 0.0042
CAL017814 10.0150 0.0042
CAL017787 10.0354 0.0042
CAL017827 10.0022 0.0041
CAL017846 10.0343 0.0041
CAL017852 10.0301 0.0042
CCQM K101
7
CAL017804 10.0484 0.0043
3.4 Verification of Candidate Comparison Cylinder
The oxygen content of each comparison cylinder was verified prior to shipment to the
participants using a Delta-F 310 analyzer. This analyzer utilizes an electrical cell and
is capable of making oxygen measurement at the 10 nmol/mol level. Its upper range is
0-50 µmol/mol, and in order to display at a response with a resolution of less than 1
nmol/mol, a digital signal transfer was used to connect with the Delta-F 310ɛ analyzer.
A gas sampling system was used to indicate a manual switchover from the NIM
standards or CCQM cylinders to the Control cylinder (FB03513). The CCQM
cylinders and the PRMs listed below were measured against the Control cylinder two
times during an analytical period.
Calibration Standards:
Three NIM’s gravimetrically prepared primary reference materials ranging in
concentration from 9.5 µmol/mol to 10.0 µmol/mol oxygen/nitrogen were used in this
analysis. The PRMs and their expanded uncertainties are listed in table 7.
Table 7 Calibration cylinders information
Cylinder Number
Concentration
(µmol/mol)
Gravimetric Uncertainty
k=2, (µmol/mol)
FB03502
FB03487
CAL017807
FB03513(Control cylinder)
10.0253
9.9923
9.5644
10.0290
0.0076
0.0081
0.0085
0.0080
Instrument Calibration:
The Delta-F 310 analyzer was calibrated using three gravimetrically prepared PRMs.
The CCQM comparison cylinders were included in the analysis with the PRMs. They
were all compared to the Control cylinder a minimum of two times during each of the
analytical days. The analytical scheme used for each primary standard and the CCQM
cylinders on each analytical day was:
Control cylinder
PRMs Standard
CCQM cylinder
Control cylinder
Sample Handling:
This analysis is to verify the O2 in CCQM-K101 cylinders. The sample was fitted
with a low dead-volume, stainless steel regulator (no pressure gauges) with a
CGA-590 fitting. Sample selection was achieved manually using a stainless steel six
way valve and 1/8” stainless steel lines. Gas mixtures Flow rate is about 500 ml/min.
The procedure called for each cylinder to have 8.0 minutes period of equilibration and
CCQM K101
8
3.0 minute data collection period. Table 8 below lists the calibration results and figure
1and table 9 show the general least squares (GLS) fitting results.
Table 8 Calibration results
PRMs:
Cylinder
Concens.
(mol/mol)
Uncertainties
(mol/mol)
k=2
Read responds
of Delta F 310
(transfer signal)
Uncertainties
(mV)
k=2
FB03513
(control
cylinder)
10.0290 0.0076 2.0742 0.005
FB03502 10.0253 0.0081 2.0734 0.005
FB03487 9.9923 0.0085 2.0668 0.005
CAL017807 9.5644 0.0080 1.9757 0.005
Figure 1: The general least squares (GLS) fitting
Table 9 Polynomial fit results: GLS, DEGREE 1
Root mean square residual error: 0.0432
Maximum absolute weighted residual: 0.0481
Gradient m: 4.7121
Uncertainty associated with um: 0.300
Intercept with y-axis c: 0.254
Uncertainty associated with uc: 0.613
9.4
9.5
9.6
9.7
9.8
9.9
10
10.1
10.2
1.94 1.96 1.98 2 2.02 2.04 2.06 2.08 2.1
Fitted curve Measurement data
Read respons of Delta F 310 e
Co
ncern
s, m
ol/m
ol
CCQM K101
9
Covariance associated with m and c: -0.1834
Intercept with x-axis x0: -0.0540
Uncertainty associated with x0 0.134
The verification results were obtained from the analyses conducted on the shipment
cylinders in July 2013 and Nov. 2013 respectively. The verification uncertainty is a
combination of the analytical uncertainty and the primary standard suite uncertainty
calculated according to ISO 6143 with equation (3).
uver = ua2 + u𝑃𝑅𝑀
2 (3)
Where,
uver is the verification standard uncertainty.
ua is the analytical standard uncertainty (which was estimated by combination of
standard deviation of measurement results and instrument stability.).
uPRM is the gravimetric standard uncertainty of PRMs (see report part of Calibration
Standards).
The first verification results listed in table 10 below:
Table 10 First verification results
Cylinder
number
Gravimetric values
xigrav
First Verification (07/2013)
xiver
Response of Delta
F 310 (transfer
signal)
FB03488 10.0005 10.0014 2.0653
FB03490 10.0199 10.0415 2.0738
FB03506 10.0199 10.0160 2.0684
FB03508 10.0248 10.0491 2.0754
FB03496 10.0212 10.0481 2.0752
FB03510 10.0277 10.0311 2.0751
FB03484 9.9840 9.9877 2.0624
FB03498 10.0041 10.0264 2.0706
FB03507 10.0018 10.0250 2.0703
FB03494 10.0243 10.0472 2.0750
FB03480 10.0204 10.0297 2.0713
FB03481 9.8935 9.9118 2.0463
Verification of Returned Comparison Cylinder
The oxygen content of each comparison cylinder was verified after the participants
returned their cylinder using a Delta-F 310 analyzer.
The calibration standard, instrument calibration, sample handing and analysis method
are same as that of before shipment used for verification the comparison cylinders.
CCQM K101
10
The second verification results listed in table 11:
Table 11 Second verification results
Cylinder
number
Gravimetric values
xigrav
Second Verification (11/2013)
xiver
FB03488 10.0005 10.0004
FB03490 10.0199 10.0202
FB03506 10.0199 10.0184
FB03508 10.0248 Empty*
FB03496 10.0212 10.0212
FB03510 10.0277 10.0269
FB03484 9.9840 9.9872
FB03498 10.0041 10.0058
FB03507 10.0018 10.0285*
FB03494 10.0243 10.0262
FB03480 10.0204 10.0231
FB03481 9.8935 9.8902
*:Cylinder FB03508 second verification was not done due the empty of the cylinder after returned
in NIM.
* Cylinder FB03507 second verification was finished in April of 2014 due to the comparison
cylinder was delayed sending back.
The verification results were demonstrated by verifying the composition as calculated
from preparation data with that obtained from verification measurement, and the
following criterion (equation (4)) was met:
xigrav − xiver ≤ 2 uigrav2 + uiver
2 (4)
Where,
xigrav is the gravimetric value of comparison cylinder i.
xiver is the verification result of comparison cylinder i.
uigrav is the standard uncertainty of xigrav .
uiver is the standard uncertainty of. xiver .
Figure 2 shows the results of verification of comparison cylinder in July 2013 and
November 2013.
CCQM K101
11
Figure 2: Verification of comparison cylinder in July 2013 and November 2013.
9.8
9.85
9.9
9.95
10
10.05
10.1
10.15
10.2
First verification
Second verification
veri
fica
tio
nva
lue
s w
ith
co
mb
ine
d u
nce
rtai
nty
,k=2
u
mo
l/m
ol
Cylinder verification analysis
FB0
34
81
FB0
34
80
FB0
34
94
FB0
35
07
FB0
34
98
FB0
34
84
FB0
35
10
FB0
34
96
FB0
35
08
FB0
35
06
FB0
34
90
FB0
34
88
CCQM K101
12
4. Key Comparison Reference Value
All of the comparison cylinders passed the verification in November of 2013 after
return from the participants except NMIJ cylinder (FB03508) empty (due to testing
too long time in sample handing in NMIJ) and SMU (FB03507) delayed to shipment
back due to Custom problems (which was passed the verification in April of 2014).
Therefore, the NIM gravimetrically calculated value and uncertainty is used within
this report as the Key Comparison Reference Value (KCRV).
Participant Results:
Participants’ reports are appended to this report. The reported instrumental method
and calibration standards used are summarized in Table 12. A total of six participants
used GC-TCD(3),GC-PDHID(2) and GC-HDID(1) instrument, one use Sevomex
Xenra 4100C with measurement cell Zr 704 O2 traces analyzer, one use GC-MS
(Quadruplet) ,and the remaining three participants used Delta F analyzers. There was
no correlation between the degrees of equivalence and the method used, or the source
of the primary standards. The analyzer results reported by each participant are listed
in Table 13.
Table 14 presents the comparison results in tabular form:
Standard uncertainty of verification uver is the combined standard uncertainty of the
analytical uncertainty ua and the primary standard suite uncertainty uPRM, uver2 = ua
2 +
uPRM2
Δi is the difference of the verification result and the gravimetric value of comparison
cylinder i, Δi = xiver - xigrav
Standard uncertainty of reference value uiref is the combined standard uncertainty of
uver and the standard uncertainty of gravimetric method ugrva, uiref2 = uver
2 + ugrav2
Standard uncertainty of degree equivalence ui is the combined standard uncertainty of
standard uncertainty of reference value uiref and standard uncertainty of participated
lab reported uLabi, ui2 = uiref
2 + uLabi2
Degree of equivalence Di is calculated in the normal manner, Di = xlabi - xiref, and the
results for each participant are presented in table 14 and also displayed in Figure 3.
At last, results of this comparison are presented in Table 15 and Table 16, formatted
for submission to the Key Comparison Database.
5. Conclusion
The results of all participants in this key comparison, except for one, are consistent
with their KCRV. The one participant which is outside the KCRV interval is SMU.
CCQM K101
13
Table 12 Method used by participating laboratories
Labs Standards Instrumentation Measurements
LNE One primary standard prepared
according to ISO 6142.
A Delta F analyzer 4 measurements, each with 3
sub-measurements
BAM Three primary standards prepared
according to ISO 6142.
Sevomex Xenra 4100C O2
traces analyzer
5 measurements, each with 6
sub-measurements
CERI One primary standard prepared
according to ISO 6142.
GC-MS (Quadruplet) 8 measurements, each with 8
sub-measurements
NMIJ Four primary standards prepared
according to ISO 6142.
GC-TCD 3 measurements, each with 4
sub-measurements
NIM Three primary standards prepared
according to ISO 6142.
Delta F 310ɛ analyzer 3 measurements, each with 3
sub-measurements
KRISS Four primary standards prepared
according to ISO 6142.
GC-TCD 4 measurements, each with 3
sub-measurements
VSL One primary standard prepared
according to ISO 6142.
GC-PDHID 5 measurements, each with 7
sub-measurements
VNIIM Three primary standard prepared
according to ISO 6142.
Delta F 310 6 measurements, each with
2-4 sub-measurements
SMU Three primary standards prepared
according to ISO 6142.
GC-TCD 3 measurements, each with 6
sub-measurements
NMISA Five primary standards prepared
according to ISO 6142.
GC-PDHID 3 measurements, each with
10 sub-measurements
NPL NPL PRGMs standard prepared
according to ISO 6142.
GC-HDID/CRDS 5 measurements, each with
2-4 sub-measurements
NIST Five primary standard prepared
according to ISO 6142.
Delta F Nano Trace II™
analyzer
3 measurements, each with 3
sub-measurements
Table 13 Oxygen measurement results reported by participated laboratories
Labs
Comparison
Cylinder
No.
Reported Value
(mol/mol)
Reported Expanded
Uncertainty, k=2
(mol/mol)
LNE FB03488 9.973 0.044
BAM FB03490 9.96 0.15
CERI FB03506 9.84 0.27
NMIJ FB03508 9.977 0.079
NIM FB03496 10.025 0.048
KRISS FB03510 10.021 0.063
VSL FB03484 10.04 0.07
VNIIM FB03498 10.01 0.07
SMU FB03507 9.80 0.15
NMISA FB03494 9.86 0.19
NPL FB03480 9.96 0.08
NIST FB03481 9.912 0.048
CCQM K101
14
Table 14 Comparison results with Degrees of Equivalence
Cylinder
# Lab i
Gravimetric
xigrav/xiref
Uncert.
ugrav
Ver.
xiver
Δ i uver uiref
Labs
results
xlabi
Uncert.
(labs)
uLabi
Di ui Ui
k=2 %rel.
FB03488 LNE 10.0005 0.0041 10.0014 0.0009 0.0175 0.0180 9.973 0.022 -0.0275 0.028 0.057 -0.27
FB03490 BAM 10.0199 0.0041 10.0415 0.0216 0.0175 0.0180 9.96 0.075 -0.0599 0.077 0.155 -0.60
FB03506 CERI 10.0199 0.0041 10.0160 -0.0039 0.0175 0.0180 9.84 0.135 -0.1799 0.141 0.283 -1.80
FB03508 NMIJ 10.0248 0.0041 10.0491 0.0243 0.0175 0.0180 9.977 0.040 -0.0478 0.043 0.088 -0.48
FB03496 NIM 10.0212 0.0041 10.0481 0.0269 0.0175 0.0180 10.025 0.024 0.0038 0.030 0.060 0.04
FB03510 KRISS 10.0277 0.0041 10.0311 0.0034 0.0175 0.0180 10.021 0.032 -0.0067 0.037 0.074 -0.07
FB03484 VSL 9.9840 0.0041 9.9877 0.0037 0.0175 0.0180 10.04 0.035 0.0560 0.039 0.079 0.56
FB03498 VNIIM 10.0041 0.0041 10.0264 0.0223 0.0175 0.0180 10.01 0.035 0.0059 0.039 0.079 0.06
FB03507 SMU 10.0018 0.0039 10.0250 0.0232 0.0175 0.0179 9.80 0.075 -0.2018 0.077 0.155 -2.02
FB03494 NMISA 10.0243 0.0041 10.0472 0.0229 0.0175 0.0180 9.86 0.095 -0.1643 0.097 0.194 -1.64
FB03480 NPL 10.0204 0.0040 10.0297 0.0093 0.0175 0.0180 9.96 0.040 -0.0604 0.044 0.088 -0.60
FB03481 NIST 9.8935 0.0040 9.9118 0.0183 0.0175 0.0179 9.912 0.024 0.0185 0.030 0.060 0.19
Note:
Standard uncertainty of verification uver is the combined standard uncertainty of ua and uPRM, uver2 = ua
2 + uPRM2
Δ i = xiver - xigrav.
Standard uncertainty of reference value uiref is the combined standard uncertainty of uiver and ugrva, uiref2 = uver
2 + ugrav2
Standard uncertainty of degree equivalence ui is the combined standard uncertainty of uiref and uLabi, ui2 = uiref
2 + uLabi2
Degree of equivalence: Di = xlabi - xiref
CCQM K101
15
Figure 3: Calculated Degrees of Equivalence of CCQM K101
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0 1 2 3 4 5 6 7 8 9 10 11 12
Degrees of Equivalence
Di (umol/mol)
Di, u
mo
l/m
ol
NIS
T
NP
L
NM
ISA
SM
U
VN
IIM
VS
L
KR
ISS
NIM
NM
IJ
CE
RI
BA
M
LN
E
CCQM K101
16
Table 15
Key comparison CCQM-K101
MEASRAND: Amount-of-substance fraction of Oxygen in Nitrogen
NORMINAL VALUE: 10 mol/mol
xLabi result of measurement carried out by laboratory i(see table 14)
uLabi combined standard uncertainty of xlabi (see table 14)
xiref reference value for the cylinder sent to laboratory i(see table 14)
uiref combined standard uncertainty of xiref (see table 14)
Labi Cylinder
number
xLabi
/
mol/mol
ulabi
/
mol/mol
xiref
/
mol/mol
uiref
/
mol/mol
LNE FB03488 9.973 0.022 10.0005 0.0180
BAM FB03490 9.96 0.075 10.0199 0.0180
CERI FB03506 9.84 0.135 10.0199 0.0180
NMIJ FB03508 9.977 0.040 10.0248 0.0180
NIM FB03496 10.025 0.024 10.0212 0.0180
KRISS FB03510 10.021 0.032 10.0277 0.0180
VSL FB03484 10.04 0.035 9.9840 0.0180
VNIIM FB03498 10.01 0.035 10.0041 0.0180
SMU FB03507 9.80 0.075 10.0018 0.0179
NMISA FB03494 9.86 0.095 10.0243 0.0180
NPL FB03480 9.96 0.04 10.0204 0.0180
NIST FB03481 9.912 0.024 9.8935 0.0179
CCQM K101
17
Table 16
Key comparison CCQM-K101
MEASRAND: Amount-of-substance fraction of Oxygen in Nitrogen
NORMINAL VALUE: 10 mol/mol.
Key comparison reference of each laboratory i with respect to the reference value is
given by a pair of terms:
Di = (xLabi - xiref), and its associated expanded uncertainty (k=2) Ui, both expressed in
mol/mol.
No pair-wise degrees of equivalence are computed for this key comparison.
Labi Di
mol/mol
Ui
mol/mol
LNE -0.0275 0.057
BAM -0.0599 0.155
CERI -0.1799 0.283
NMIJ -0.0478 0.088
NIM 0.0038 0.060
KRISS -0.0067 0.074
VSL 0.0560 0.079
VNIIM 0.0059 0.079
SMU -0.2018 0.155
NMISA -0.1643 0.194
NPL -0.0604 0.088
NIST 0.0185 0.060
References
1. International Key Comparison CCQM K53-Oxygen 100 mol/mol level in
Nitrogen. Final report.
2. International Key Comparison CCQM K74-Nitrogen dioxide 10mol/mol level in
Nitrogen. Final report.
CCQM K101
18
Appendix
CCQM K101 Comparison Measurement Reports from participants
Appendix A
Report Form oxygen in nitrogen
Laboratory name: LNE
Cylinder number: FB03488
Measurement 1#
Component Date (dd/mm/yy)
Result
(mol/mol)
Standard deviation (% relative)
Number of replicates
O2 21/12/2012 9.969 0.16 3
Measurement 2#
Component Date (dd/mm/yy)
Result
(mol/mol)
Standard deviation (% relative)
Number of replicates
O2 03/01/2012 9.984 0.16 3
Measurement 3#
Component Date (dd/mm/yy)
Result
(mol/mol)
Standard deviation (% relative)
Number of replicates
O2 04/01/2012 9.974 0.12 3
Measurement 4#
Component Date (dd/mm/yy)
Result
(mol/mol)
Standard deviation (% relative)
Number of replicates
O2 05/01/2012 9.965 0.19 3
Results
Component Result
(mol/mol)
Expanded uncertainty
(mol/mol)
Coverage factor
O2 9.973 0.044 2
Method description forms
Details of the measurement method used:
Reference Method:
An electrochemical analyzer DELTA F has been used to analyze oxygen.
Calibration standard:
LNE has prepared a gas mixture of oxygen at about 10 µmol/mol in nitrogen by gravimetric method: it
has been prepared in 3 steps. The oxygen in pure nitrogen has been determined for each gravimetric
gas mixture.
Instrument calibration:
The analyzer is calibrated at 2 points : at zero point with pure nitrogen and at scale point with the
gravimetric gas mixture at 10 µmol/mol.
Then the gas mixture inside the cylinder n°FB03488 is injected inside the analyzer. The oxygen
concentration of the unknown gas mixture (CO2) is equal to :
)(
)(
tan
tan
Odards
Osampledards
OLL
LLCC
2
With :
Cstandard the concentration of the gravimetric gas mixture
Lsample the reading for the unknown gas mixture
L0 the reading at zero
Lstandard the reading for the gravimetric gas mixture
Sampling handing:
Cylinders were maintained inside a laboratory at a nominal temperature of (212)°C for all the
period.
Samples were introduced into the analyzer using a low volume gas regulator.
Uncertainty:
1) Gravimetric gas mixtures uncertainties:
As explained before the preparation of the gravimetric gas mixture at about 10 µmol/mol needed the
preparation of 3 gravimetric gas mixtures.
Pure oxygen Air
Liquide Alphagaz 2
n°20026895
Pure nitrogen Air
Products N2 BIP +
n°49270
Pure nitrogen Air
Products N2 BIP +
n°48786
Pure nitrogen Air
Products N2 BIP +
n°283016
Gas Mixture n° O2/N2 0019
C=1.7715 %mol/mol
U (k=2)=0.0015 %mol/mol
Gas Mixture n° O2/N2 0020
C=448.75 µmol/mol
U (k=2)=0.48 µmol/mol
Gas Mixture n° O2/N2 0021
C=10.105 µmol/mol
U (k=2)=0.029 µmol/mol
m=31.274g
u=0.013g
m=1518.132g
u=0.017g
m=35.678g
u=0.013g
m=1369.157g
u=0.016g
m=34.180g
u=0.012g
m=1484.148g
u=0.016g
Purity tables of each component
Component Concentration (mol/mol) Uncertainty (mol/mol)
N2 0.000002000 0.0000011547
O2 0.999997842 0.000001155
H2O 0.000000000 0.000000001
methane 0.0000000015 0.000000001
CO2 0.000000139 0.000000005
CO 0.00000000283 0.0000000008
NO2 0.000000015 0.0000000087
Purity table of pure oxygen (Air Liquide Alphagaz 2 n°20026895)
Component Concentration (mol/mol) Uncertainty (mol/mol)
N2 0.99999964 0.000000123
O2 0.0000000034 0.000000013
H2O 0.000000010 0.0000000058
methane 0.000000025 0.0000000144
CO2 0.0000000125 0.000000072
CO 0.0000000125 0.000000072
H2 0.000000025 0.0000000144
Ar 0.0000002715 0.000000120
Purity table of nitrogen (BIP+ n°49270)
Component Concentration (mol/mol) Uncertainty (mol/mol)
N2 0.999999648 0.000000037
O2 0.000000007 0.000000013
H2O 0.000000010 0.0000000058
methane 0.000000025 0.0000000144
CO2 0.0000000125 0.000000072
CO 0.0000000125 0.000000072
H2 0.000000025 0.0000000144
Ar 0.0000002603 0.000000025
Purity table of nitrogen (BIP+ n°48786)
Component Concentration (mol/mol) Uncertainty (mol/mol)
N2 0.999999615 0.000000108
O2 0.000000002 0.000000013
H2O 0.000000010 0.0000000058
methane 0.000000025 0.0000000144
CO2 0.0000000125 0.000000072
CO 0.0000000125 0.000000072
H2 0.000000025 0.0000000144
Ar 0.000000298 0.000000025
Purity table of nitrogen (BIP+ n°283016)
Composition of the gravimetric gas mixture O2/N2 0021 used for the comparison
Component Concentration (µmol/mol) Uncertainty (µmol/mol)
Oxygen 10.105 0.0145
Argon 0.297 0.025
Nitrogen and other impurities - -
2) Detailed uncertainty budget:
Typical evaluation of the measurement uncertainty of O2:
Uncertainty source Estimate
xI (µmol/mol) Assumed
distribution
Standard
uncertainty u(xi) (µmol/mol)
Mean concentration obtained by comparison with the gravimetric gas
mixture 9.973
Mean standard deviation of the
values 2rS
0.016
Reproducibility of the four measurements
- Standard deviation
of the values 2RS
0.004
Gravimetric gas mixture concentration (O2/N2 0021)
10.105 - 0.0145
The concentration of the unknown gas mixture n°FB03488 is the mean concentration of the 4 mean
concentrations obtained by comparison with the gravimetric gas mixture O2/N2 0021.
The uncertainty on the unknown gas mixture concentration is given by:
22203488
2RrFB SS)C(u)C(u 0021 O2/N2
mol/祄ol....)C(u FB 0004800040016001450 222030488
2
And mol/祄ol.)C(U FB 044003488
Division 1.4 Process Analysis
Richard-Willstätter-Str. 11
12489 Berlin
GERMANY
XBAMBundesanstalt für
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und -prüfung
Internal Analysis Report
BAM-I 4-2013-0002 CCQM-K101
Date
Customer
Date of order
Operator
2013-02-21
Internal for CCQM GAWG
2012-11-08
Dr. Heinrich Kipphardt
Tel.: +49 30 8104-1116
Task
Dr. habil. Michael Maiwald
Tel.: +49 30 8104-1140
CCQM-K101: Measurement of the amount fraction of 10 umol/mol
oxygen in pure nitrogen in the presence of 40 umol/mol argon:
x(O2, FB03490)
Summary From the five measurement campaigns, the amount of substance
fraction of oxygen in the cylinder no. FB03490 is:
x(O2, FB03490) = (9.96 ± 0.15) umol/mol
Given is the expanded measurement uncertainty U = uc-k with k = 2
according to the ISO/BIPM Guide.
Date/Signature
Operator Head of Division L/[/
Analysis report BAM-I 4-2013-0002_CCQM-K101 jj^ |Datum 2013-02-21 Bundesanstalt für
Materialforschung
Page 2 VOn 7 und-Prüfung
CCQM-K101:
Measurement of
the amount fraction of
about 10 [jmol/mol oxygen
in pure nitrogen
in the presence of 40 |jmol/mol argon
compiled by
Heinrich Kipphardt
BAM Bundesanstalt für Materialforschung und -prüfung
Unter den Eichen 87
12205 Berlin
GERMANY
Hinweis: Note: This technical report is for BAM-internal use. It can be quoted only after approval by
the authors and referred to as a 'private communication'.
Version of 2013-02-21
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Analysis report BAM-I 4-2013-0002_CCQM-K101 ^ jDatum 2013-02-21 Bundesanstalt für
Materialforschung
Page 3 VOn 7 und -prüfung
CCQM-K101: Measurement of the amount fraction of 10 umol/mol oxygen in pure nitrogen in
the presence of 40 umol/mol argon: x(O2, FB03490)
1) Background
Background
CCQM-K101 is a core component-interlaboratory comparison conducted in the frame of the GAWG of
CCQM. Technical Details can be found in the Technical Protocol for CCQM-K101 issued 2012-03-20
by Dr. ZHOU (NIM China).
2) Choice of method
There are basically two strategies for O2 determination, one being classical GC with PDID as
sensitive detector. The other one would be a specific method for oxygen only, such as paramagnetic
properties or ZrO2 sensors.
A difficulty in the oxygen determination in the case of CCQM-K101 is the presence of argon in the
sample, as Ar and O2 are not separated at room temperature on molecular sieve columns. Separation
would require cooling down the column to about -20 °C. At BAM two instruments equipped with PDID
are available. However, the first instrument (Unicam-Pro-GC) is designed for specific Separation
Problems. Due to design-related problems, cooling of the column is technically not possible. As tested
earlier, the Condensed moisture will create a short circuit in the electronics. The second instrument
equipped with PDID is used for the national Standard of ethanol and therefore not available for
change of column and modification of the instrument.
Paramagnetic measurements are not sensitive enough for determination of oxygen traces. With ZrO2
sensors determination of oxygen down to Iower umol/mol level is possible. Due to the working
principle, based on a solid conductor for oxygen ions, the measurement is not affected by the
presence of argon. Thus, a ZrO2 sensor was employed for the comparison.
3) Sample: labeling, packing, pre-information
The sample was provided from NIM China in a 5 L cylinder with the cylinder number FB03490 with a
CGA80 thread. The initial (and final) pressure was not measured. The initial pressure was supposed
to be 80 bar.
4) Sample pretreatment
No heating or rolling.
5) Devices used and flushing
A CGA80-VRC %" fitting was installed to the sample cylinder.
The same assembly of VCR %" reduction valve, needle valve and closing valve and transfer line was
used for connection of all cylinders.
For the calibration gases, also only one fitting from the testing gas thread (M19 X 15 Li) to VCR 1/4"
was used and attached freshly each time.
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The freshly installed assembly was evacuated down to 10 3 mbar and then filled with gas from the
cylinder. The evacuating/flushing was repeated six times (which is a major cause of gas
consumption).
The gas was passed through 1/16" capillaries via a set of two 3-port valves, a mass flow meter of
type Analyt-MCT model 35810, and a particle filter 2 um from HAM-LET into the instrument. One port
of the two 3-port valves was intended to permanently connect a cylinder with calibration gas, but this
was not used. The last port of the valves was attached to a nitrogen cylinder (Air Products, BIP, spec.
< 10 ppb O2). It turned out that flushing was very useful to bring the (vented) instrument quickly back
to a steady State.
The flow was set to (76 ± 1) mL/min at a typical System pressure of 1.7 bar. Previous measurements
revealed that changing the flow to 50 mL/ min or 100 mL/min had an effect of much less than 1 %
(see 2012-11-13). This flow rate is very much below the recommendation of the instrument
manufacturer, i.e., 200 to 450 mL/min. However, previous experience has shown that also a smaller
flow rate works well. As an improvement, a long exhaust tube should be installed to avoid back-
diffusion.
6) Sample consumption
A measurement took typically 1 h at a flow rate of 75 mL/min. As the same assembly of reduction
valve, needle valve, and closing valve was used for connection of all cylinders, flushing the assembly
six times before each measurement caused the major gas consumption.
7) Measurement instrument
Servomex Xenra 4100C, equipped with measurement cell "Zr 704 O2 traces" (and the unused sensor
of type "4100995 O2 purity").
8) Instrument settings
The instrument is used as a comparator, thus absolute calibration is not really relevant here.
(According to the manufacturer, the ZrO2 cell was calibrated using two points, i.e., laboratory
atmosphere and a Standard at 0.5 % (5000 umol/mol) of O2 in nitrogen. Apparently, a Special zero
gas was not used.)
9) Calibration
The following three calibration gases prepared at BAM by a gravimetric method according to DIN EN
ISO 6142:2006 were used (U with k = 2):
cylinder
5055-120625
7087-120814
Amount fraction
Oxygen/%
0.000 901 4
0.000 000 2
(2.3E-4)
0.000 699 8
0.000 000 2
(2.3E-4)
Amount fraction
Nitrogen / %
99.999 099
(9E-5)
99. 999 300
(9E-5)
Amount fraction
Argon / %
-
-
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6042-120705 0.001 108 4
0.000 000 3
(2.9E-4)
99.994 904
(1E-5)
0.003 987
(1E-4)
10) Blanks
The instrument reading for the blank after one hour for a preconditioned instrument was 0.3 umol/mol
with nitrogen (spec. < 10 nmol/mol O2). After one day, it dropped to 0.2 umol/mol. The reading for the
blank sample and all investigated gases was very stable, i.e., < 0.05 umol/mol.
11) Measurement outline
After a few preliminary runs, five measurement campaigns with different order of the cylinders were
performed. After adjusting the flow, the instrument was flushed for 15 minutes with the gas and the
first data point recorded. Five further data points were recorded manually every 5 minutes. A
measurement for one gas took 1:05 h, including assembling and flushing 1:30 h. One complete
measurement campaign took 7:30 h. The sequence of cylinders was changed each day.
12) Raw data: 2012-11-26 - 2012-12-03; for more details see 2012-CCQM-K101_1_von3.xls
Recorded values, Standard deviation, and relative Standard deviation in brackets; each value consists
of six readings:
x(02)
5055-
120625
7087-
120814
6042-
120705
2012-11-26
Reading
0.000 943
0.000 005
(5.5E-3)
0.000 720
0.000 000
(0)
0.001 132
0.000 004
(3.6E-3)
2012-11-27
Reading
0.000 933
0.000 005
(5.5E-3)
0.000 720
0.000 000
(0)
0.001 130
0.000 000
(0)
2012-11-28
Reading
0.000 933
0.000 005
(5.5E-3)
0.000 725
0.000 005
(7.6E-3)
0.001 142
0.000 004
(3.6E-3)
2012-11-29
Reading
0.000 963
0.000 005
(5 4E 31
0.000 940
0.000 000
(0)
0.000 723
0.000 005
(7.1E-3)
0.001 122
0.000 004
(3.6E-3)
0.001 130
0.000 000
2012-12-03
Reading
0.000 933
0.000 005
(5.5E-3)
0.000 720
0.000 000
(0)
0.001 125
0.000 005
(4.9E-3)
Certified
value (k = 2)
0.000 901 4
0.000 000 2
(2.3E-4)
0.000 699 8
0.000 000 2
(2.3E-4)
0.001 108 4
0.000 000 3
(2.9E-4)
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FB034
90
0.001 022
0.000 004
(4.0E-3)
0.001 018
0.000 004
(4.1E-3)
0.001 040
0.000 000
(0)
(0)
0.001 020
0.000 000
(0)
0.001 012
0.000 004
(4.0E-3)
The repeatability of the measurements was good, typically smaller than the readability of the
instrument (i.e., 0.05 umol/mol, as only one digit after the decimal point is given by the instrument).
13) Calculation of results
The result is calculated using GLS according to ISO 6143 using the five measurement campaigns.
Two parameter with two settings (evaluating each campaign individually vs. directly pooling all data;
considering blank Signal (0.2 ±0.1) umol/mol with k = 2) vs. not taking blank Signal into account) were
considered, resulting in four different assessment scenarios. Using B_Least all scenarios
convergence at 1e-09. Although results from all assessment scenarios are mutually compatible,
separate calibrations by campaign and taking the blank Signal into account are considered more
trustworthy.
For details of the calculation, see the EXCEL-files. (The file 2012-CCQM-K101_2_von_3.xls contains
a version that does not take the limited resolution of the instrument into account.) The file 2012-
CCQM-K101_3_von_3.xls takes the limited resolution of the instrument fully into account and was
therefore used. (Anyhow, the differences between the two versions were small.)
14) Individual results
The five measurement campaigns evaluated by campaign and accounting forthe blank led to the
following results with Standard uncertainties uc:
Campaign
no.
all
result for the
sample in the
series /
umol/mol
9.9426
0.0752
9.9454
0.0731
10.0820
0.0658
9.9126
0.0627
9.8973
0.0767
9.9560
0.0726
SSD/GoF
still acceptable
okay
excellent
border line
okay
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15) Uncertainty estimation
Estimation of uncertainty is based on the gravimetric values of the Standard used, the stability of the
Signals obtained for calibration samples and sample, and the limited resolution of the measurement
device, blank, and the GLS fit. As indicated in the section above, a relative Standard uncertainty of
0.73 % is obtained.
16) Final result
From the five measurement campaigns, the amount-of-substance fraction of oxygen in the cylinder
no. FB03490 is:
x(O2, FB03490) = (9.96 ± 0.15) pmol/mol
Given is the expanded measurement uncertainty U = uckwith k = 2 according to the ISO/BIPM
Guide. Values obtained from the individual measurement campaigns are given in section 14.
17) Remarks
The measurement result obtained seems to be compatible with the announced target value of 10
umol/mol.
18) Responsibility
The calibration gases have been prepared by the filling team consisting of Claudia Boissiere, Kerstin
Köster, Stephanie Näther, Jeannette Pelchen, Gert Schulz under guidance of Dr. Dirk Tuma. The
measurements and reporting have been performed by Dr. Heinrich Kipphardt. The calculations using
BJeast have been performed by Dr. Wolfram Bremser.
The overall technical responsibility for the measurement result is with Dr. Heinrich Kipphardt.
Heinrich KipprflrdTBerlin, 2013-02-21 1.4
19) Additional Information
Customer:
PAZ-No.:
Sample arrival:
Internal No.:
Sample:
Task:
Time of measurement:
Place:
Method:
CCQM, core component
-
2012-11-07
CCQM-K101
Cylinder FB03490
Determination of Oxygen
2012-11-26-2012-12-03
UE HS40 R423
ZrO2 Sensor
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Appendix A
Report Form oxygen in nitrogen
Laboratory name: BAM Federal Institute for Materials Research and Testing
Cylinder number: FB03490
Measurement
Component
o2
Measurement
Component
o2
Measurement
Component
o2
Measurement
Component
O2
Measurement
Component
O2
[campaign)
Date
(dd/mm/yy)
26/11/12
[campaign)
Date
(dd/mm/yy)
27/11/12
[campaign)
Date
(dd/mm/yy)
28/11/12
[campaign)
Date
(dd/mm/yy)
29/11/12
[campaign)
Date
(dd/mm/yy)
03/12/12
No. 1
Result
(pmol/mol)
9.9426
No. 2
Result
(fimol/mol)
9.9454
No. 3
Result
(u.mol/mol)
10.082
No. 4
Result
()j.mol/mol)
9.9126
No. 5
Result
(u.mol/mol)
9.8973
Standard
deviation11
(% relative)
0.04
Standard
deviation1'
(% relative)
0.04
Standard
deviation11
(% relative)
0
Standard
deviation11
(% relative)
0
Standard
deviation11
(% relative)
0.04
Number of replicates
6
Number of replicates
6
Number of replicates
6
Number of replicates
6
Number of replicates
6
11 The Standard deviation caiculated from the replicate results may underestimate the uncertainty
of the mean given the limited readability of the instrument (one digit after the decimal point).
For data processing, the uncertainty of any measured value has duly been expanded, taking into
account also the instrument resolution.
Results
Component
o2
Result
(|.imol/mol)
9.96
Expanded uncertainty
(u.mol/mol)
0.15
Coverage factor
k = 2
Method description forms
Details of the measurement method used:
Reference Method:
For details see internal measurement report sections 2, 7, 8, and 11: A ZrO2 sensor was used,
Servomex Xenra 4100C, equipped with measurement cell "Zr 704 O2 traces".
Calibration Standard:
For details see internal measurement report section 9: Three gravimetrically prepared gas
mixtures with nominal values of 9, 7, and 11 ppm were used. Only in the latter 40 ppm Ar were
present.
Instrument calibration:
For details see internal measurement report sections 13, 9, and 11: The instrument was used in a
comparator mode. GLS regression technique according to ISO 6143:2001 was used to establish
the calibration function separately for each measurement campaign.
Samplingand handling:
For details see internal measurement report sections 4 and 5: The sample cylinder remained in
the laboratory for 19 days. Neither heating nor rolling was applied.
Uncertainty:
For details see internal measurement report sections 13,14, and 15.
Uncertainties related to balances and weights are covered by the Standard uncertainties of the
calibration gases used. Uncertainties of balances and weights in the preparation step of the
sample gas and those related to the cylinder of the sample gas have to be duly considered by the
organiser of the KC.
Uncertainty contributions considered in the measurement campaigns are the uncertainties of the
calibration gases used (specific for each gas), the stability of the Signals obtained for the
calibration gases and the sample (expressed as a Standard deviation of the mean of replicate
measurements), the resolution of the measurement device, and the contribution of the blank
(blank signal vs purity of the blank gas). Contributions are detailed in the table below.
The above-mentioned uncertainties have correspondingly been assigned to the mean values
obtained in the 5 measurement campaigns. GLS regression according to ISO 6143:2001 has been
applied to determine the analysis function(s) and value and uncertainty of the unknown. lh)s
technique strictly propagates all uncertainty contributions to the uncertainty of the unknown,
using the corresponding sensitivity coefficient for the uncertainty of each value.
Data have been submitted to GLS analysis both separately for each measurement campaign and
pooled for all five campaigns, as well as with and without including the blank. Although all four
assessment scenarios provide combined results fully compatible within the stated uncertainty,
pooling of all calibrations violates the limits of the quality parameters given in ISO 6143:2001
(SSD and GoF), meaning that calibrations are subject to a daily drift.
Calibrations treated separately fully comply with the QA requirements of ISO 6143:2001. Thus,
determinations obtained for the unknown in this approach were combined into the final result.
Notably, there was a fully negligible difference (with respect to the uncertainty stated) for
calibrations either including or not including the blank. The System is linear within the ränge
considered, and the estimates for the blank (blank signal vs purity of the blank gas) reasonable.
The uncertainty is dominated by the resolution of the measurement device and the blank. As the
individual uncertainty contributions are combined via GLS regression, the values given here will
not exactly amount to the combined uncertainty given.
Detailed uncertainty budget:
Typical evaluation of the measurement uncertainty ofO2
Quantity
(Uncertainty
source), X,
Gravimetric
values for
calibration gases
Signal stability
for calibration
gases and
sample
Resolution of
the
measurement
device
Blank
contribution
GLS
assessment
Estimate
~ 10.000
u.mol/m
ol
~ 10.000
Umol/m
ol
~ 10.00
u.mol/m
ol
0.2
u.mol/m
ol
-
Evaluatio
n type
(A or B)
A and B
combined
A
B
B
A
and B
Distrib
ution
normal
normal
rectan
gular
rectan
gular
as
listed
above
Standard
uncertainty
u(x-,)
0.015
u,mol/mol
0.02
umol/mol
0.05
u.mol/mol
0.1
umol/mol
-
Sensitivity
coefficient
1
1
1
1
MU
propagation
according to
ISO
6143:2001
Contribution
0.01
u.mol/mol
0.02
u.mol/m
ol
0.05
umol/rn
ol
0.1
u.mol/mol
at the
calibration
point of
Iowest
concentration
Report Form oxygen in nitrogen
Laboratory name: Chemicals Evaluation and Research Institute, Japan (CERI)
Cylinder number: FB-03506
Measurement 1#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 29/1/2013 9.877 0.850 8
Measurement 2#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 30/1/2013 9.863 0.544 8
Measurement 3#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 31/1/2013 9.964 1.758 8
Measurement 4#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 1/2/2013 9.966 0.776 8
Measurement 5#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 5/2/2013 9.713 0.521 8
Measurement 6#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 6/2/2013 9.724 0.838 8
Measurement 7#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 7/2/2013 9.796 1.085 8
Measurement 8#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 8/2/2013 9.826 0.757 8
Results
Component Result
(mol/mol)
Expanded uncertainty Coverage factor
O2 9.84 0.27 k=2
Details of the measurement method used:
Calibration standard:
Preparation method: Gravimetric method
Purity analyses
O2: NMIJ-CRM
N2: The purity is calculated as below.
Impurities in N2 are determined by analyses.
N
i
ipure xx1
1
where,
xi=mole fraction of impurity i
N=number of impurities
xpure=mole fraction purity of pure gas (N2)
The concentration of O2 in N2 was evaluated with instrument shown in Reference Method
Gas standard
Cylinder number Gravimetric concentration Expanded uncertainty(k=2)
CPB-21257 9.916 [mol/mol] 0.172 [mol/mol]
Reference Method:
Principle: GC-MS (Quadrupole)
Make: CANON ANELVA CORPORATION
Type: L-400G-GC
Data collection: L-400G-GC TRACEGAS ANALYZER AutoSampling Software
Measuring conditions
Carrier gas: Helium (20 mL/min)
Column: Molecular sieve 5A (60-80 mesh), 2 m×2.2 mm I.D.
Column temperature: 80 C
Sample loop: 1 mL
Sample handling:
A regulator with two gauges was attached to the cylinder. The output pressure of the regulator was
controlled at 0.1 MPa. The flow rate of sample gas was controlled at approximately 50 mL/min.
Measurement sequence:
R1→K1→R2→K2→R3→K3→R4→K4→R5…
Where
Ri: Measurement of gas standard (i=1-8)
Ki: Measurement of the K101 gas mixture (i=1-7)
Instrument calibration:
Mathematical model:
One-point calibration was used.
Detailed uncertainty budget:
Quantity
(Uncertainty
source), Xi
Estimate
xi
Evaluatio
n type
(A or B)
Distributi
on
Standard
uncertainty
u(xi)
Sensitivity
coefficient
ci
Contributio
n
u(yi)
Parent gas 0.15204
μmol/mol
B normal
0.07602
μmol/mol 1
0.07602
μmol/mol
Conc. of oxygen
in Nitrogen
0.02521
μmol/mol
A
- 0.02521
μmol/mol 1
0.02521
μmol/mol
Gravimetric
preparation of
gas standard
0.00078
μmol/mol
B
rectangle 0.00045
μmol/mol 1
0.00045
μmol/mol
Repeatability of
preparation
0.03077
μmol/mol
A -
0.03077
μmol/mol 1
0.03077
μmol/mol
Repeatability of
measurement
0.10108
μmol/mol
A -
0.10108
μmol/mol 1
0.10108
μmol/mol
Other Impurities
in nitrogen
negligible A - - -
Combined uncertainty: 0.1326 μmol/mol
Coverage factor: 2
Expanded uncertainty: 0.27 μmol/mol
Authors:
Dai Akima
Yukari Kawase
Shinji Uehara
Measurement report NMIJ
Measurement 1#
Component Date
(dd/mm/yy)
Result
(10-6 mol/mol)
Standard deviation
(% relative)
Number of
replicates
O2 02/04/2013 10.000 0.37% 4
Measurement 2#
Component Date
(dd/mm/yy)
Result
(10-6 mol/mol)
Standard deviation
(% relative)
Number of
replicates
O2 03/04/2013 9.918 0.44% 4
Measurement 3#
Component Date
(dd/mm/yy)
Result
(10-6 mol/mol)
Standard deviation
(% relative)
Number of
replicates
O2 04/04/2013 10.012 0.38% 4
Results
Component Result
(10-6 mol/mol)
Expanded uncertainty
(10-6 mol/mol) Coverage factor
O2 9.977 0.079 k = 2
Cylinder number of the sample : FB03058
Method description forms
Details of the measurement method used:
Reference Method:
Amount of substance of oxygen in the sample was determined by GC-TCD which has two ovens;
one is of Shimadzu GC-2014 and the other is an extra oven for low temperature. Volume of a
sample loop is 5 mL, and pressure in the loop was monitored by an absolute pressure transducer.
Temperature of the sample loop is thought to be constant because the loop is in the GC-2014
oven. A MS 5A column (2m; 60/80 mesh) in the GC 2014 oven (30 °C) separated Ar and O2 from
N2 which were not injected into MS 5A columns (2m X 3; 60/80 mesh) in cold oven (-15 °C) by
valve switching technique. The MS 5A columns (-15 °C) separate O2 from Ar, and they were
detected by the TCD. Current and temperature of the TCD were set to be 190 mA and 55 °C,
respectively. Pure He (Air Liquid Japan, alpha 2) was used as a carrier gas. Flow rate
(approximately 30 ml/min) of the carrier gas was controlled by automatic pressure controller.
The obtained peak areas were compensated by the pressure in the sample loop when the sample
was injected.
Calibration standard:
Four primary standard gas mixtures for calibration were prepared by mixing pure nitrogen and
oxygen by four steps of the gravimetric dilution method according to ISO 6142. The uncertainty
for the primary standard gas mixtures consists of uncertainties of weighing, amount of
substances of components in parent gases, and molar mass. Assigned values for the calibration
gases and their uncertainties are listed below.
Cylinde Number Component Assigned Value
(10-6 mol/mol)
Relative Standard
Uncertainty (%)
CPC00220 O2 8.0258 0.021
CPB32036 O2 9.0036 0.019
CPB32031 O2 9.9549 0.018
CPC00218 O2 10.9095 0.017
Results of impurity analysis of the pure oxygen and nitrogen gases are summarized below.
Oxygen in pure nitrogen was determined by APIMS.
Oxygen
Component Amount of substance
(10-6 mol/mol)
Standard Uncertainty
(10-6 mol/mol)
CH4 0.002 0.001
CO 0.007 0.004
CO2 0.052 0.001
Ar 0.09 0.05
N2 0.08 0.05
H2O 0.44 0.25
O2 999999.33 0.45
Nitrogen
Component Amount of substance
(10-6 mol/mol)
Standard Uncertainty
(10-6 mol/mol)
CH4 0.15 0.09
CO 0.44 0.26
CO2 0.16 0.09
Ar 0.50 0.29
O2 0.0025 0.0014
H2O 0.05 0.03
N2 999998.70 0.41
Instrument calibration:
The primary standard gas mixtures were used for the calibration of GC-TCD. Calibration curves
were obtained by Deming’s least squares method with a model “y = a + bx”. Variances of peak
areas to the primary standard mixtures and sample were thought to be the same.
The primary standard mixtures and the sample were measured four times. The order of the
measurement sequence was as follows: two or three of the primary standard mixtures sample
the rest of the primary standard mixtures. The obtained peak areas were corrected by the
pressure in the sample loop. There was no temperature correction because the sample loop
was in the GC oven in which the temperature was considered to be constant.
Sampling handing:
The sample cylinder was in a storage room (about 20 °C) after arrival. The cylinder was
stabilized to the room temperature (21 °C) before measurement. Flushing of a pressure
regulator was carried out with the sample or the primary standard gas mixtures at least 5 times.
The sample and the primary standard gas mixtures were transferred to the sample loop of GC by
mass flow controller (MFC), whose flow rate was set to be 75 sccm. The absolute pressure in
the sample loop was about 700 kPa.
Uncertainty:
a. Uncertainty related to the balance and weights; pooled uncertainty was used.
b. Uncertainty related to the gas cylinder; it was neglected.
c. Uncertainty related to the components gases; it was neglected.
d. Uncertainty related to the analysis; The uncertainty was estimated from the repeatability of
the peak areas for the calibration gases. The uncertainty related to the analysis was
reflected into the calibration curves.
Detailed uncertainty budget:
Typical evaluation of the measurement uncertainty of O2:
Quantity
(Uncertainty
source), Xi
Estimate
xi
Evaluation
type
(A or B)
Distributi
on
Standard
uncertainty
u(xi)
Sensitivity
coefficient
ci
Contribution
u(yi)
Standard gas
mixtures /
10-6 mol/mol
8 – 11 A Normal 0.02% 1 0.02%
Determination
by GC-TCD /
10-6 mol/mol
10 A Normal 0.4% 1 0.4%
1
CCQM-K101 Comparison Measurement report: Oxygen in Nitrogen Laboratory: National Institute of Metrology Cylinder number: FB03496
Measurement No. 1
Date
Result (µmol/mol)
Stand. deviation (µmol/mol)
number of sub- measurements
Oxygen
10/15/2013
10.026
0.027
3
Measurement No. 2
Date
Result (µmol/mol)
Stand. deviation (µmol/mol)
number of sub- measurements
Oxygen
10/16/2013
10.022
0.024
3
Measurement No. 3
Date
Result (µmol/mol)
Stand. deviation (µmol/mol)
number of sub- measurements
Oxygen
10/17/2013
10.028
0.022
3
Summary Results:
Gas mixture
Result
(assigned value) (µmol/mol)
Coverage
factor K
Assigned expanded
Uncertainty (µmol/mol)
Oxygen
10.025 ± 0.048
2
± 0.048
Reference Method: The oxygen was analyzed using a Delta-F 310ɛ analyzer. This analyzer utilizes an electrochemical cell and is capable of making oxygen measurements at the 10 nmol/mol level. Its upper range is 0-100 µmol/mol and does not over-range, and in order to display at nmol/mol resolution for the responding, a digital signal transfer was used to connect the Delta-F 310ɛ analyzer. A gas sampling
system was used to indicate a manual switchover from the NIM standard or CCQM cylinder to the Control cylinder (FB03513). The CCQM cylinder and the PRMs listed below were measured against the Control cylinder nine times during three different analytical periods. Calibration Standards: Three NIM’s gravimetrically prepared primary reference materials ranging in concentration from 9.5 µmol/mol to 10.0 µmol/mol oxygen/nitrogen were used in this analysis. The PRMs and their expanded uncertainties are listed below:
2
Cylinder Number Concentration (µmol/mol) Gravimetric Uncertainty (µmol/mol) FB03502 10.0253 0.0076 FB03487 9.9923 0.0081 CAL017807 9.5644 0.0085 These standards were prepared from different parent mixtures but all with the same source of balance gas (nitrogen) and component gas (oxygen). The table below gives an assay of the pure nitrogen and pure oxygen used to prepare these standards.
Component Purity of N2
(mol/mol)
Standard uncertainty
(mol/mol)
H2O 1.9E-08 1.0E-08
O2 1.40E-08 5.0E-10
H2 1.0E-07 1.0E-07
CO 2.0E-08 2.0E-08
CO2 1.0E-07 1.0E-07
CH4 1.0E-07 1.0E-07
Ar 4.9E-05 1.0E-06
N2 0.999951 1.02E-06
Component Purity of O2
(mol/mol)
Standard uncertainty
(mol/mol)
H2O 4.9E-09 5.0E-09
N2 3.0E-06 1.5E-06
H2 3.0E-07 1.5E-07
CO 2.0E-08 2.0E-08
CO2 5.0E-07 3.0E-07
CH4 1.0E-07 1.0E-07
Ar 2.0E-06 1.0E-06
O2 0.999994 1.84E-06 Instrument Calibration:
The Delta-F 310ɛ analyzer was calibrated using three gravimetrically prepared PRMs. The CCQM
sample (FB03496) was included in the analysis with the PRMs. They were all compared to the Control cylinder a minimum of two times during each of the three analytical days. The analytical scheme used for each primary standard and the CCQM cylinder on each analytical day was: Control cylinder PRM Standard (1st measurement) CCQM cylinder Control cylinder Control cylinder (2nd measurement) PRM Standard CCQM cylinder
3
Control cylinder Control cylinder (3rd measurement) PRM Standard CCQM cylinder Control cylinder Sample Handling: This analysis is to quantify the O2 in a single CCQM-K101 cylinder (FB03496). The sample was fitted with a low dead-volume, stainless steel regulator (no pressure gauges) with a CGA-590 fitting. Sample selection was achieved manually using a stainless steel six way valve and 1/8” stainless steel lines. The procedure called for each cylinder to have a 8.0 minutes period of equilibration and 3-minute data collection period. Uncertainty: PRM Validator is an ISO 6143-based spreadsheet that calculates the value-assignment and combined uncertainty using a suite of primary reference materials (PRMs), As uncertainty of CCQM sample, it incorporates the uncertainties in the gravimetric values of each PRM along with the standard deviation of the instrument measurement responses in different day’s measurements.
uv = ugrv2 + (
Sd′
n)2 + (
Sd′′
n)2
uv ---verification uncertainty ugrv---gravimetric uncertainty S
’d ---responses standard deviation in one day measurement
S’’d ---responses standard deviation in three days measurement
The coverage factor for the expanded uncertainty is 2.
a) Uncertainty Components for Analysis of Oxygen in CCQMK-101 Cylinder FB03496:
Uncertainty source
Xi
Assumed
distribution
Standard deviation/ u(xi)
mol/mol
Contribution to standard uncertainty
u(yi)
mol/mol
Repeatability Normal 0.027 0.016
Reproducibility Normal 0.027 0.016
Gravimetric uncertainty
Rectangular 0,005 0,005
b) CCQM cylinder assignment value:10.025 µmol/mol
Expanded uncertainty: ± 0.048 µmol/mol Coverage factor: k=2
CCQM-K101 Comparison
Measurement Report: Oxygen in Nitrogen
Report Date: 30 July 2013
Laboratory name: Korea Research Institute of Standards and Science (KRISS)
Cylinder number: FB03510
Reporter: Jinsang Jung ([email protected])
Measurement 1#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 30/04/2013 10.029 0.35 3
Measurement 2#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 02/05/2013 10.024 0.43 3
Measurement 3#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 08/05/2013 10.009 0.28 3
Measurement 4#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 09/05/2013 10.023 0.09 3
Results
Component Result
(mol/mol)
Expanded uncertainty
(mol/mol)
Coverage factor
O2 10.021 0.063 k=2
Method description forms
Please complete the following data regarding the description of methods and the uncertainty
evaluation.
Details of the measurement method used:
1) Reference Method:
Describe your instruments (principle, maker, type, configuration, data collection, and etc.)
-Analytical Instrument: HP7890A GC analyzer equipped with a TCD detector and sampling valve line
without an injection port
-Analytical Condition
Condition
Detector Thermal Conductivity Detector (TCD)
Detector Temperature 250°C
Carrier Flow rate 70 psi
Reference Flow rate 45 mL/min
Column ResteckMolesieve 5A, 4m, 1/8”, SS
Oven Temperature -25°C for 11min, 30°C/min till 200°C,
200°C for 5min, -25 for 4min(post run)
Oven Equilibrium Time 1 min
Valve Box Temperature Not control
Sample Flow rate 100 mL/min
Sample Loop Volume 10 mL
2) Calibration standard
Describe your calibration standards for the measurements. (preparation method, purity analysis,
estimated uncertainty, and etc.)
Four reference gas mixtures were prepared by gravimetric method according to ISO 6142.
Cylinder Number Assigned value (μmol/mol) Standard uncertainty
(μmol/mol)
D929255 9.5379 0.0018
D015142 9.5208 0.0018
D014941 9.6434 0.0018
D014989 10.2138 0.0018
After verification of the reference gas mixtures, one reference cylinder (D929255) was
chosen for a sample analysis.
-Gravimetric preparation data
Primary standard gas mixtures were prepared gravimetrically through a three step dilution according
to ISO6142.
Specification of a balance
Model No.:Mettler-Toledo
Resolution: 1 mg, Capacity: 10 kg
Uncertainty (k=2): 3.2 mg
Weighing method (A-B-A, substitution method)
Substitution method, tare cylinder (A-B-A)
-Purity Analysis
Nitrogen source gas: 99.99932%mol/mol
Component Amount fraction
(10-6
mol/mol)
Standard uncertainty
(10-6
mol/mol)
Assumed
distribution
Hydrogen 0.05 0.0289 Rectangular
Oxygen 0.0007 0.00007 Normal
Carbon monoxide 0.007 0.0014 Normal
Carbon dioxide 0.0025 0.0014 Rectangular
Methane 0.009 0.0018 Normal
Argon 2.4 0.24 Normal
Water 0.25 0.075 Normal
Nitrous oxide 0.0001 0.00006 Rectangular
Hydrocarbons (CxHy) 0.025 0.01443 Rectangular
Neon 4.1 0.82 Normal
Nitrogen 999993.2 0.253 Normal
Oxygen source gas: 99.99978%mol/mol
Component Amount fraction
(10-6
mol/mol)
Standard uncertainty
(10-6
mol/mol)
Assumed
distribution
Hydrogen 0.05 0.0289 Rectangular
Nitrogen 0.73 0.146 Normal
Carbon monoxide 0.02 0.004 Normal
Carbon dioxide 0.2 0.02 Normal
Methane 0.005 0.0029 Rectangular
Argon 0.05 0.0289 Rectangular
Water 1.1 0.33 Normal
Oxygen 999997.8 0.364 Normal
-Estimated Uncertainty of the reference gas mixture(D929255), 9.5379µmol/mol
Weight of the parent gas mixture: 51.0406g
Weight of N2 dilution gas: 1291.006g
Amount fraction of oxygen in the parent gas mixture: 250.774 µmol/mol
Coverage factor: 2
Expanded Uncertainty: 0.0037 µmol/mol (0.039% relative)
Quantity
(Uncertainty source), Xi
Estimate
xi
Distribut
ion
Standard
uncertainty
u(xi)
Sensitivity
coefficient
ci
Contribution
u(yi)
Mass of parent gas (g) 51.0406 Normal 0.00378
Mass of N2 diluent gas (g) 1291.006 Normal 0.00353
Concentration of O2 in
parent gas (%mol/mol)
0.0250774 Normal 0.00000396
Purity of pure N2 gas
(mol/mol)
0.9999932 Normal 0.000000126 -0.0028 -0.0000035
µmol/mol
Concentration of O2 in pure
N2 gas (µmol/mol)
0.0007 Normal 0.00007 1 0.00007
µmol/mol
Concentration of Ne in pure
N2 gas (µmol/mol)
4.10 Normal 0.820 -0.00000000095 -0.0000078
Concentration of Ar in pure
N2 gas (µmol/mol)
2.40 Normal 0.240 -0.00000000095 -0.0000023
Impurity of pure N2 gas
except O2 (µmol/mol)
0.3636 Rectang
ular
0.0866 -0.00000000095 -0.00000083
Molecular weight of O2
(g/mol)
15.9994 Normal 0.00015 -0.00006 -0.000089
Molecular weight of N2
(g/mol)
14.006740 Normal 0.000035 0.000068 0.000024
Uncertainty of balance (mg) 0.0 Normal 1.51 0.00000000011 0.0000016
3) Instrument calibration:
Describing your calibration procedure. (mathematical model/calibration curve, number and
concentration of standards measurements sequence, temperature/pressure correction (if necessary),
etc.)
Single point calibration was used to calculate the concentration of a target compound in a sample
cylinder (FB03510) provided by NIM.
D929255 reference gas mixture was used for the calibration.
When analyzing the sample gas, “A-B-A” type calibration procedure was used. It means that the
sample and reference gases were measured in the order of Reference-Sample-Reference. This
procedure was carried out 3 times on 4 different days.
4) Sampling handing:
How are the cylinders treated after arrival (e.g. stabilized) and how are samples transferred to the
instrument? (Automatic, high pressure, mass flow controller, dilution, and etc.)
The sample cylinder from NIM was unpacked and stored at a room temperature for 3 days before an
analysis. The reference cylinder was also stored at the same condition. The room temperature of our
laboratory was maintained at ~22±2°C for all the period.
A SS regulator was connected to the reference and sample cylinders. The reference and sample gases
were directly introduced to the GC through a multi-positioning valve and a mass flow controller.
The injection of two different gases was switched automatically using a multi-positioning valve.
5) Uncertainty:
There are potential sources that influence the uncertainty of the final measurement results. Depending
on the equipment, the applied analytical method, and the target uncertainty of the final results, they
have to be taken into account or can be neglected.
Describe in detail how estimates of the uncertainty components are obtained and how they are
combined to calculate the total uncertainty.
a. Uncertainty related to the balance and weights;
b. Uncertainty related to the gas cylinder;
c. Uncertainty related to the components gases;
d. Uncertainty related to the analysis.
Detailed uncertainty budget:
Please include a list of the uncertainty contributions, the estimate of the standard uncertainty,
probability distribution, sensitivity coefficients, etc.
Typical evaluation of the measurement uncertainty of O2:
Uncertainty
[µmol/mol]
Uncertainty
[%]
Gravimetric uncertainty 0.0037 0.039
Verification uncertainty 0.0087 0.087
Uncertainty driven by the interference of
high Argoncontent in a GC analysis
0.0300 0.3
Combined uncertainty 0.0315 0.315
Expanded uncertainty (k=2) 0.0630 0.629
Report Form oxygen in nitrogen
Laboratory name: VSL
Cylinder number: FB03484
Measurement 1#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 2013-06-27 10.13 0.11 7
Measurement 2#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 2013-06-28 9.98 0.25 7
Measurement 3#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 2013-07-04 10.06 0.06 6
Measurement 4#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 2013-07-17 10.06 0.06 7
Measurement 5#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard deviation
(% relative)
Number of replicates
O2 2013-07-18 9.98 0.06 7
Results
Component Result
(mol/mol)
Expanded uncertainty
(µmol/mol)
Coverage factor
O2 10.04 0.07 2
Method description forms
Please complete the following data regarding the description of methods and the uncertainty
evaluation.
Details of the measurement method used:
Reference Method:
The measurements are performed using an Agilent 6890 GC equipped with a 1 mL sample loop, a
50 meter (0,53 µm) Molsieve 5A column and a Pulsed discharge Helium ionisation detector
(PDHID). The column is kept at 30 °C for ten minutes and then heated to 150 °C (60 °C /min)
and kept as this temperature for 5 minutes, resulting in a total cycle time of 17 minutes with
Argon eluting at 7.80 minutes and Oxygen at 8.03 minutes. The data handling is performed with
Chemsation software (Rev. B.02.01)
Calibration standard:
The calibration standard was specially prepared for this comparison, the standards normally used
for this measurement contain only low concentrations of argon, so that baseline separation of
argon and oxygen is achieved. Since the mixture from NIM contains a large amounts of argon,
separation was not so good and the oxygen peak was ”tangent skimmed” from the argon, thus
making a direct comparison with the regular standards impossible.
The standard used was a gravimetrical prepared mixture containing (nominal) 10 mol/mol
oxygen and 60 mol/mol argon in nitrogen. The nitrogen used was analyzed for impurities of
argon and oxygen. The impurities (and their uncertainties) were incorporated in the calculation of
the final composition of the calibration standard. The gravimetrical uncertainty and the
uncertainty from purity analyses combined results in an overall uncertainty of the standard used
to be 0.2 %-relative (k = 1).
Instrument calibration:
Since our regular standards could not be used, a one on one comparison was used to determine
the amount—of—substance fraction oxygen in the gas mixture. Hence, the measurement model
reads as
yx
yx
std
std (1)
The standard uncertainty associated with xstd is 0.2% relative (k = 1). The repeatability standard
deviations are much smaller than the reproducibility between the measurements. For the
uncertainty evaluation, the reproducibility standard deviation of the values obtained using
equation (1) is used as basis for the uncertainty evaluation of the responses y and ystd. This
standard deviation is 0.63% relative. Applying the law of propagation of uncertainty to equation
(1) yields
2
std
std
2
2
std
std
2
2
std
std
222
y
yu
y
yu
x
xuxxu (2)
The value of the last two terms in equation (2) is taken to be equal to (0.63%)2/5. Combining this
with the standard uncertainty associated with xstd yields
035.00028.0002.004.105
0063.0 222
2
std
std
2
x
xuxxu µmol mol-1`
The expanded uncertainty is 0.07 µmol mol-1. This uncertainty is atypical for measurements of
the amount—of—substance fraction oxygen in nitrogen. The large amount of argon present in
the mixture is atypical for good grade calibration gas mixtures. In fact, in its services, VSL
maintains different regimes for measuring the amount—of—substance fraction oxygen in
nitrogen in the presence of argon and in the absence of it. Calibration and measurement
capabilities of these two services differ appreciably.
Sampling handing:
No special treatment was applied when the gas mixture arrived. The sample and the reference
standard are connected to a high pressure multiposition valve of which the outlet is connected to
a (single) reducer and mass flow controller. After flushing the system, both cylinders are analyzed
7 times.
D.I.MENDELEYEV INSTITUTE FOR METROLOGY (VNIIM)
RESEARCH DEPARTMENT FOR THE STATE MEASUREMENT STANDARDS IN THE
FIELD OF PHYSICO-CHEMICAL MEASUREMENTS
Key Comparison CCQM-K101
Oxygen in Nitrogen at 10 μmol/mol level
REPORT
Date: 28.05.13
L.A. Konopelko, Y.A. Kustikov, A.A. Kolobova, V.V. Pankratov, I.I. Vasserman,
B.V. Ivahnenko, O.V. Efremova, A.A. Orshanskaya
Cylinder number: FB03498
Measurement #1
Component Date
(dd/mm/yy)
Result
(10-6
mol/mol)
Standard deviation
(% relative)
number of
replicates
O2 10/04/13 10,041 0,23 2
Measurement #2
Component Date
(dd/mm/yy)
Result
(10-6
mol/mol)
Standard deviation
(% relative)
number of
replicates
O2 17/04/13 10,006 0,27 4
Measurement #3
Component Date
(dd/mm/yy)
Result
(10-6
mol/mol)
Standard deviation
(% relative)
number of
replicates
O2 18/04/13 9,994 0,52 4
Measurement #4
Component Date
(dd/mm/yy)
Result
(10-6
mol/mol)
Standard deviation
(% relative)
number of
replicates
O2 19/04/13 10,015 0,35 4
Measurement #5
Component Date
(dd/mm/yy)
Result
(10-6
mol/mol)
Standard deviation
(% relative)
number of
replicates
O2 23/04/13 9,982 0,26 4
Мeasurement #6
Component Date
(dd/mm/yy)
Result
(10-6
mol/mol)
Standard deviation
(% relative)
number of
replicates
O2 24/04/13 10,015 0,25 4
2
Result
Component
Result
(10-6
mol/mol)
Expanded
Uncertainty
(10-6
mol/mol)
Relative
Expanded
Uncertainty (%)
Coverage
factor
O2 10,01 0,07 0,7 2
Details of the measurement method used:
Reference method: coulometric
Instrument: gas analyser Delta-F 310E, serial number PT-17896 (“Delta F Corporation”, USA)
included in the set of State Primary Measurement Standard GET 154-11.
Calibration standards:
The calibration standards were prepared from pure gases (by 3 stage dilution series) in accordance
with ISO 6142: 2001 (Gas analysis – Preparation of calibration gas mixtures – Gravimetric method).
After preparation the composition was verified. The verification process was used to confirm the
gravimetric composition by checking internal consistency between prepared gas mixtures, in
accordance with requirements of ISO 6143:2001 (Gas analysis – Comparison methods for
determining and checking the composition of calibration gas mixtures).
Characteristics of pure substances used for preparation of the calibration standards are shown in the
tables 1, 2, 3.
Table 1– Description of pure component O2 № D778643
Component Mole fraction
10-6
mol/mol
Standard uncertainty
10-6
mol/mol
O2 999998,415 0,14976
N2 1,051 0,037
H2O 0,25 0,15
CO2 0,1297 0,0027
Ar 0,0663 0,0014
H2 0,0480 0,0012
CO 0,0217 0,0010
CH4 0,0176 0,0004
Table 2– Description of pure component Ar № 205863
Component Mole fraction
10-6
mol/mol
Standard uncertainty
10-6
mol/mol
Ar 999999,496 0,0326
O2 0,174 0,004
N2 0,170 0,023
CH4 0,0950 0,0014
CO2 0,030 0,017
H2 0,025 0,014
CO 0,010 0,006
Table 3– Description of pure component N2 № 136255
3
Component Mole fraction
10-6
mol/mol
Standard uncertainty
10-6
mol/mol
N2 999999,156 0,017349
H2O 0,50 0,02
Ar 0,295 0,004
CO2 0,0277 0,0010
O2 0,0141 0,0009
CH4 0,0025 0,0014
H2 0,0025 0,0014
CO 0,0010 0,0006
All the calibration standards were prepared in aluminium cylinders,
(Luxfer, V = 10 L ). Preparation of the calibration standards was carried out in 3 stages.
1 stage:
Preparation of the first gas pre-mixtures O2/N2 with O2 mole fraction 210-2
mol/mol.
3 standard gas mixtures were prepared.
Verification of mole fraction was carried out by “Agilent 6890” carrier gas Ar, TCD detector,
serial number US10713044 (Agilent Technologies, USA). Relative standard deviation for each
measurement series was not more than 0,03 %.
1a stage
Preparation of gas pre-mixture Ar/N2 with Ar mole fraction 0,610-2
mol/mol %.
1 pre-mixture was prepared.
This gas mixture was investigated by gas analyser Delta-F 310E, serial number PT-17896
(“Delta F Corporation”, USA) on impurities of oxygen.
2 stage:
Preparation of the second gas pre-mixtures O2/N2 with O2 mole fraction 200 10-6
mol/mol.
3 standard gas mixtures were prepared.
Verification of mole fraction was carried out by “Agilent 6890” carrier gas Ar, TCD detector,
serial number US10713044 (Agilent Technologies, USA). Relative standard deviation for each
measurement series was not more than 0,17 %.
3 stage:
Preparation of the calibration gas mixtures O2/N2(+Ar) with O2 mole fraction on the level of
10 10-6
mol/mol.
3 standard gas mixtures were prepared.
Verification of mole fraction was carried out by gas analyser Delta-F 310E. Standard
deviation for each measurement series was on the level of 0,2 %.
Weighing was performed on the balances RAYMOR HCE-25G (“RAYMOR Tool Co. Inc.”,
USA). Experimental standard deviation for 10 L cylinders: 2 mg.
Instrument calibration
4
The characteristics of the calibration standards are shown in table 5.
Table 5 – Characteristics of calibration standards
Standard gas
mixture N Component Assigned value,
10-6
mol/mol
Standard uncertainty
(gravimetry),
10-6
mol/mol
D910304 O2 10,056 0,003
Ar 49,818 0,020
N2 balance -
D910242 O2 9,9124 0,0022
Ar 50,973 0,016
N2 balance -
D910252 O2 9,962 0,003
Ar 50,48 0,02
N2 balance -
One point calibration was used for instrument calibration with each of 3 standard gas
mixtures.
There were made 6 independent measurements under repeatability conditions with 6
independent calibrations. One single measurement consisted of 2 sub-measurements.
Measurement sequence was in the order: standard1- sample - standard1- standard2 – sample -
standard2 (etc.). Temperature and pressure were not corrected during the calibration procedure.
Sample handling
Prior to measurements the cylinders were stabilized to room temperature. Prior to
measurements the transfer system (stainless steel fine metering valve Concoa 426 series, stainless
steel lines) and the measuring instrument were purged with high purity He (6.0 grade) during 12
hours. During the measurement series the transfer system and the measuring instrument were
thoroughly purged (during 40-50 min) with the gas mixture to be analysed before each single
measurement. The sample was fed into the instrument at a flow rate 460 cm3/min. The flow rate
was controlled by rotameter. Setting time for single measurement was 10 min.
Evaluation of uncertainty of measurements
Combined standard uncertainty of oxygen mole fraction was calculated on the base of the
following constituents:
- uncertainty related to the balance and weights (includes uncertainty of weights used,
standard deviation of weighings, uncertainty due to balance drift, uncertainty due to buyoncy effect,
uncertainty due to residual mass of pure nitrogen after evacuation);
- uncertainty related to the gas components (includes uncertainties due to impurities in all the
parent gases);
- uncertainty related to the analysis (includes uncertainties due to between days and within day
measurements).
Table 6– Uncertainty budget for oxygen mole fraction in gas mixture in cylinder № FB03498
5
Quantity
(Uncertainty source), Xi
Estimate
xi
Evaluation
type
(A or B)
Distributio
n
Standard
uncertainty
u(xi)
Sensitivity
coefficient
ci
Contribution
u(yi)
(10-6
mol/mol)
Preparation
of calibration
standards
balance and
weights
10,056 B Rectangular 0,00314 0,995 0,00314
purity of
gases 10,056 A,B Rectangular 0,00056 0,995 0,00056
Analysis (Between days
and within day measure-
ments)
10,008 A Normal 0,033 1 0,033
Combined standard uncertainty 0,0332 ppm
Expanded uncertainty (k=2) 0,07 ppm
Report Form oxygen in nitrogen (CCQM K-101)
Laboratory name: Slovak Institute of Metrology
Cylinder number: FB_03507
Measurement 1#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard
deviation
(% relative)
Number of
replicates
O2 5/9/2013 9.852 0.87 6
Measurement 2#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard
deviation
(% relative)
Number of
replicates
O2 6/9/2013 9.754 0.92 6
Measurement 3#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard
deviation
(% relative)
Number of
replicates
O2 4/11/2013 9.778 0.85 6
Result
Component Result
(mol/mol)
Expanded uncertainty Coverage factor
O2 9.80 0.15 K=2
Method description forms
O2 was analysed using gas chromatography method. Instrument in use was GC Varian
equipped with Porapack and Molsieve packed columns, 2x 1mL sample loops, TCD detector.
Oven temperature was 40 °C, method time 9 min, carrier gas Helium. All measurements
were done in automatic way using selector gas valve. Before entering sample loops all gas
mixtures went through a mass flow controller and pressure controller for regulation.
Details of the measurement method used:
Measurement method with several automated runs was used. All runs in first, third, fifth
measurement sequence had rising molar fraction, second, fourth, sixth were processed in
reverse order. At least 3 calibration standards and sample were used at each automated run.
From each run was made one calibration curve with sample signals. Data were subjected to
the b_least program (weighted least square regression). The result of the measurement
sequence was the average of molar fractions.
All calibration standards were made gravimetrically according ISO 6142 and ISO 6143 in
SMU. Impurities in parent gases quality BIP plus- oxygen and nitrogen were analysed on GC
and FTIR. Content of oxygen impurity in nitrogen was measured using Trace oxygen analyzer
Teledyne 3000 TA –XL with the detection limit 0.01x10-6
mol/mol.
All cylinders were at SMU kept at 17 – 22 °C before measurement. Measuring cylinders were
equipped with pressure reducers. Sample was transferred to the instrument GC throw mass-
flow controller and pressure controller automatically in sequences.
Detailed uncertainty budget:
Uncertainty of instrument response consisted from figure characterized roughly immediate
repeatability and from signal drift estimated. From each run was made one calibration curve
with sample signals. These figures together with molar fraction data were subjected to b_least
program (weighted least square regression). Each run produced sample molar fraction with its
standard uncertainty. From all runs results = average of molar fractions in one sequence were
standard deviation found (uncertainty of type A) and from runs results uncertainties the mean
(through squares) was found (uncertainty of type B).
For each i-th
day the average xi was calculated (1). Standard uncertainty assigned to each i-th
day result (4) is from standard deviation of the average (2) and average from all b_least
uncertainties that day (3).
)1(1
n
x
x
n
j
j
i
)4()()()(
)3(
)(
)(
)2()1(*
)(
)(
2
2
2
1
2
1
2
2
1
2
1
iii
n
j
j
i
n
j
ij
i
xuxuxu
n
xu
xu
nn
xx
xu
To estimate uncertainty from 3 days results we have kept “Standard Practice for Conducting
an Interlaboratory Study to Determine the Precision of a Test Method” (Annual Book of ASTM
Standards E 691-87) with some approximations.
)8(
)7(3
max
)6(
)(
)5(1
21
1
2
2
xxx
xs
p
xu
s
n
nsss
x
p
i
i
r
rxR
p – number of days (3)
n – number of measurements in 1 day
index i represents particular day
index j represents particular result (evaluated) from one calibration curve
Final result is average from 3 day results
)9(1
p
x
x
p
i
i
)10();max( Rr ssxu
Second part of final combined uncertainty is the standard uncertainty due to the calibration
standards derived from gravimetric preparation, impurity analysis and validation.
u(kal) is the uncertainty of PSM closest to the unknown sample
Estimation of the mole fraction component standard uncertainty measured sample is shown
in table number 1
Tab.1
Influence
parameter
Estimate Standard
uncertainty
Statistical
distribution
Sensitivity
coefficient
Contribution to
st.uncertainty
x 0.00000980
mol/mol
0.00000011
mol/mol
normal 1.0 0.00000011
xPSM 0.00000951
mol/mol
0.000000104
mol/mol
normal 1.0 0.000000104
together 0.00000015
Laboratory of gases optochemistry and CRM
Ing. Miroslava Valkova (SMU)
Measurement Report
CCQM-K101
Oxygen in Nitrogen at 10 mol/mol level
Laboratory name:National Metrology Institute of South Africa (NMISA)
Cylinder number: FB03494
Measurement 1#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard
deviation
(% relative)
Number of
replicates
O2 21/01/2013 9,96 0,9 10
Measurement 2#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard
deviation
(% relative)
Number of
replicates
O2 23/01/2013 9,79 1,3 10
Measurement 3#
Component Date
(dd/mm/yy)
Result
(mol/mol)
Standard
deviation
(% relative)
Number of
replicates
O2 06/02/2013 9,84 0,5 10
Result
Component Result
(mol/mol)
Expanded uncertainty
(mol/mol)
Coverage factor
O2 9,86 0,19 k =2
Details of the measurement method used:
Reference Method:
Gas Chromatographywith a Pulsed Discharged Helium Ionisation Detector (GC-PDHID)
Instruments:
The oxygen was analysed using a gas chromatograph equipped with a pulsed discharged helium ionisation
detector (GC-PDHID). The oxygen was separated from argon and nitrogen using a 30 m x 0,53 mm ID
capillary column (RT-MoleSieve 5Å), which was operated isothermally at 25 C with a carrier gas pressure of
450kPa helium. A 250 µℓ sample loop was used to inject the sample and the standard at the head of the
column. The PDHID-detector was operated at 100 C.
Calibration standards:
The primary standard gas mixtures (PSGMs) used for the calibration were prepared from pre-mixtures in
accordance with ISO 6142:2001 (Gas analysis - Preparation of calibration gas mixtures – Gravimetric method).
After preparation, the composition was verified using the method described in ISO 6143:2001. BIP Nitrogen
(6.0 quality), Oxygen (5.0 ultra-high pure) and Argon (5.0 quality) from Air Products, South Africa, were used to
prepare the PSGMs. The nitrogen impurities were below detection limits of the method.
Instrument calibration:
A set of five (5) PSMs of O2/Ar in nitrogen ranging from 8,0μmol/mol to 12,5 μmol/mol of oxygen and 81,0
μmol/mol to 20,4μmol/mol of argon were used to calibrate the Varian CP3800 GC-PDHID with a 250 µℓ
stainless steel sample loop, and a MoleSieve 5Å capillary column (30 m length, 0,53 mm internal diameter).
Certificate/Cylinder
number
O2
Gravimetric
concentration
(mol/mol)
O2
Standard
uncertainty
(mol/mol)
Ar
Gravimetric
concentration
(mol/mol)
Ar
Standard
uncertainty
(mol/mol)
NMISA20008335 8,0424 0,0056 20,4289 0,1122
NMISA20004937 9,0034 0,0062 30,5046 0,1161
NMISA20004909 10,0053 0,0069 40,7836 0,0618
NMISA3000543883 11,0049 0,0074 50,8556 0,1209
NMISA30008345 12,5020 0,0278 80,9690 6,4133
Sample handling:
After arrival, the cylinder was kept in the laboratory to stabilisein the laboratory environment. Each cylinder
(sample and standards) was equipped with a Tescom stainless steel pressure regulator that was adequately
purged. The sample flow rate was set at approx. 100 mℓ/min.
Uncertainty:
All measured certification data and calculations for the component concentrations of FB03494 have been
reviewed for sources of systematic and random errors. The review identified three sources of uncertainty whose
importance required quantification as estimated % relative uncertainties. These uncertainties are:
a) Gravimetric uncertainties of the PSGMs in the order of 0,07%.
b) Repeatability uncertainty (run-to-run) which ranged from 0,8 to 1,0% relative standard deviation.
c) Reproducibility uncertainty (day-to-day) which gives the % relative standard deviation represented in
the measurement report.
Detailed uncertainty budget:
The results for each day yielded an average concentration and a standard deviation. The average concentration
and ESDM were obtained by the method of bracketing.
The predicted concentrations for the sample for the three days were averaged, and a standard deviation
calculated for the three values. The uncertainties for the three different days and the verification uncertainty
(ESDM) were combined as shown in Equation 1:
2
2
3
2
2
2
12 )(3
ESDM
DayDayDayu
uuuu
c
………………..Equation 1
This combined standard uncertainty was converted to an expanded uncertainty by multiplying by a coverage
factor k = 2 as in Equation 2.
cukU , where k = 2. ...................................... Equation 2
Report Form: K101 - Oxygen in nitrogen
Laboratory: National Physical Laboratory
Cylinder Number: F803480
Measurement #1: GC-HDID
Component Date
(dd/mm/yy) Result (µmol/mol)
standard deviation
(µmol/mol)
No. of
replicates
O2 12/09/2013 9.946 0.007 4
Measurement#2 : GC-HDID
Component Date
(dd/mm/yy) Result (µmol/mol)
standard deviation
(µmol/mol)
No. of
replicates
O2 13/09/2013 9.953 0.021 4
Measurement#3 : GC-HDID
Component Date
(dd/mm/yy) Result (µmol/mol)
standard deviation
(µmol/mol)
No. of
replicates
O2 17/09/2013 9.954 0.016 4
Measurement#4 : CRDS
Component Date
(dd/mm/yy) Result (µmol/mol)
standard deviation
(µmol/mol)
No. of
replicates
O2 19/09/2013 9.950 0.034 2
Measurement#5: CRDS
Component Date
(dd/mm/yy) Result (µmol/mol)
standard deviation
(µmol/mol)
No. of
replicates
O2 19/09/2013 9.980 0.057 2
Final Result:
Component Date
(dd/mm/yy) Result (µmol/mol)
expanded uncertainty
(µmol/mol)
Coverage
Factor
O2 19/09/2013 9.96 0.08* 2
*The reported uncertainty is based on a standard uncertainty multiplied by a coverage factor k = 2, providing a
coverage probability of 95 %. Due to the presence of argon, the uncertainty is larger than would normally be
achieved for certifying a 10 µmol/mol O2/N2 mixture. Hence K101 should be considered as an analytical challenge
as opposed to a core comparison.
Details of the measurement method used
Reference method
The amount fraction of oxygen in the NIM mixture was measured using two methods. The first
involved a Cavity Ring Down Spectrometer (CRDS) and the second an Agilent-Technologies-7890A
Gas Chromatograph with a Helium Discharge Ionisation Detector (GC-HDID). The GC-HDID was set up
with a 50m-5A molecular sieve column.
Calibration standards
Two NPL Primary Standard Mixtures of nominally 10 µmol/mol oxygen in nitrogen were prepared in
accordance with ISO 6142. The purity of both source gases were analysed and each found to be
>99.9999 %. The mixtures were prepared in BOC 10 litre cylinders with Spectraseal passivation. The
schematic below shows the steps of oxygen dilution with nitrogen used in the gravimetric
preparation with nominal O2 amount fractions. Both were used in determining the amount fraction
of the NIM mixture.
Pure N6 O2
↓
1000 µmol/mol
↓
10 µmol/mol
Instrument calibration, data analysis and quantification
Reference mixtures were prepared with oxygen amount fractions that differed by less than 1% from
the nominal composition of the NIM mixture. This ensured that the uncertainty contribution from
any deviation from the linearity of the analyser response was negligible.
For GC-HDID analysis (measurements 1-3), the NPL reference standards and NIM mixture were
connected to a GC-HDID using purpose-built minimised dead volume connectors and 1/16 inch
Silcosteel tubing. Specialised NPL-designed flow restrictors were used to allow a stable sample flow
of 20 ml/min to be maintained throughout the analysis. The lines were thoroughly purged and flow
rates were allowed to stabilise before commencing. The oven was maintained at -60 °C by using
cryogenic cooling. The method was set up to alternate between the reference and NIM mixtures
using an automated switching valve. This method was repeated multiple times in order to obtain a
comprehensive data set. The detector responses were recorded as peak areas, and it was via the
comparison of the NPL and NIM mixture peak areas that the quantification of oxygen amount
fraction was achieved. A ratio of consecutive peak areas were taken to minimise the uncertainty
associated with detector drift.
For CRDS analysis (measurements 4-5), the CRDS analyser response to the matrix gas was recorded.
A comparison of the reference mixtures to the NIM mixture was achieved by measuring the analyser
response to the reference mixture for a twenty minute period followed by the NIM mixture for the
same time. At the end of the experiment the analyser response to the matrix gas was recorded a
second time. To minimise the effects from zero drift, a mean of the analyser response to the matrix
gas before and after the experiment was used. The amount fraction of oxygen in the NIM mixture
was determined using the amount fraction of the reference mixture and the ratio of the analyser
response to the reference and unknown mixtures. Samples were introduced into the CRDS at
approximately 4 bar using a low volume gas regulator.
Uncertainty
The amount fraction of oxygen in the NIM mixture, xc, was determined using the following
expression:
Where xr is the amount fraction of oxygen in the reference standard, yc, yr and yz are the analytical
responses obtained during measurements of the NIM mixture, the reference standard and zero
respectively. Both yc and yr are dominated by instrument repeatability. In the case of the GC analysis,
yz = 0. For the purposes of the uncertainty calculation, the equation above represents a situation
where repeatability of the measurement takes into account any drift over the measurement period.
The uncertainty in the amount fraction of oxygen in the NIM mixture was determined by adding the
four components in quadrature. The table which follows details the uncertainty analysis for an
example measurement using CRDS.
quantity unit example
value
standard
uncertainty
sensitivity coefficient
uncertainty
contribution
uncertainty type
distribution
xr µmol/mol 10.003 0.010 0.997 0.010 A normal
yz µmol/mol 0.014 0.020 -0.003 -5.7 x 10-5
A normal
yr µmol/mol 10.019 0.067 -0.997 -0.066 A normal
yc µmol/mol 9.991 0.052 1.000 0.052 A normal
xc µmol/mol 9.974
u(xc) µmol/mol 0.085
U(xc) µmol/mol 0.170
To obtain the final result for the comparison, an average was taken for the five measurements. The
following table shows the calculation of the final results and its uncertainty.
quantity unit example
value
standard
uncertainty
sensitivity coefficient
uncertainty
contribution
uncertainty type
distribution
x1 µmol/mol 9.946 0.075 0.200 0.015 A normal
x2 µmol/mol 9.954 0.076 0.200 0.015 A normal
x3 µmol/mol 9.953 0.080 0.200 0.016 A normal
x4 µmol/mol 9.950 0.085 0.200 0.017 A normal
x5 µmol/mol 9.980 0.087 0.200 0.017 A normal
r µmol/mol - 0.013 1.000 0.013 A normal
xf µmol/mol 9.96
u(xf) µmol/mol 0.04
U(xf) µmol/mol 0.08
Where x1-x5, r is a component from the reproducibility of the five separate measurements and xf is
the final value of the amount fraction of oxygen in the NIM mixture.
)(
)(
zr
zcr
cyy
yyxx
−
−
=
1
CCQM-K101 Comparison Measurement report: Oxygen in Nitrogen Laboratory: National Institute of Standards and Technology Cylinder number: FB03481
Measurement No. 1
Date
Result (µmol/mol)
Stand. deviation (µmol/mol)
number of sub- measurements
Oxygen
2/7/2013
9.919
0.025
3
Measurement No. 2
Date
Result (µmol/mol)
Stand. deviation (µmol/mol)
number of sub- measurements
Oxygen
2/8/2013
9.916
0.015
3
Measurement No. 3
Date
Result (µmol/mol)
Stand. deviation (µmol/mol)
number of sub- measurements
Oxygen
2/14/2013
9.901
0.017
3
Summary Results:
Gas mixture
result (assigned value) (µmol/mol)
Coverage factor
Assigned expanded Uncertainty (%)
Oxygen
9.912 ± 0.048
2
± 0.48
Reference Method: The oxygen was analyzed using a Delta-F Nanotrace II™ analyzer (NIST# 592249). This analyzer utilizes an electrochemical cell and is capable of making oxygen measurements at the nmol/mol level. Its upper range is 0-10 µmol/mol and does not over-range. A computer-operated gas sampling system (COGAS #15) was used to audibly indicate a manual switchover from the NIST standard or CCQM cylinder to the Control cylinder (CC336387). The CCQM cylinder and the PSMs listed below were measured against the Control cylinder nine times during three different analytical periods. Calibration Standards: Five NIST gravimetrically prepared primary reference materials ranging in concentration from 3.7 µmol/mol to 9.8 µmol/mol oxygen/nitrogen were used in this analysis. The PSMs and their expanded uncertainties are listed below:
2
Cylinder Number Concentration (µmol/mol) Uncertainty (µmol/mol) FF17720 3.6665 0.0019 FF17691 5.4678 0.0021 FF17703 7.3199 0.0023 FF17699 9.0634 0.0019 FF17692 9.8402 0.0020 These standards were prepared from different parent mixtures but all with the same source of balance gas (nitrogen). The table below gives an assay of the nitrogen used to prepare these standards. Mole fraction Uncertainty Component µmol/mol µmol/mol Oxygen 0.003 0.001 Argon 97 5 Moisture 0.06 0.02 Nitrogen (Difference) 999902.9 5.0 Instrument Calibration: The Delta-F Nanotrace II™ analyzer was calibrated using these five gravimetrically prepared PSMs. The CCQM sample (FB03481) was included in the analysis with the PSMs. They were all compared to the Control cylinder a minimum of three times during each of the three analytical days. The analytical scheme used for each primary standard (or the CCQM cylinder) on each analytical day was: Control cylinder PSM Standard (1st measurement) Control cylinder PSM Standard (2nd measurement) Control cylinder PSM Standard (3rd measurement) Control cylinder Sample Handling: This analysis is to quantify the O2 in a single CCQM-K101 cylinder (FB03481). The sample was fitted with a low dead-volume, stainless steel regulator (no pressure gauges) with a CGA-590 fitting. Sample selection was achieved manually using a stainless steel three way valve and 1/8” stainless steel lines. The computer operated gas analysis system (COGAS #15) was used as an audible cue to manually switch the three way valve from Control cylinder position to the respective NIST standard or CCQM cylinder. Prior to starting each set of analyses the regulator was flushed five times. The output pressure of each regulator was set to 25psig (using an exterior Heise gauge) and the needle valve was adjusted to provide 1.0L sample flow to the instrument and 0.2L bypass flow. The procedure called for each cylinder to have a 4.0 minutes period of equilibration and two-minute data collection period. Due to the time required to completely purge the sample lines, each analytical measurement was repeated and the instrument response for this second measurement was used to calculate the CCQM cylinder’s concentration. Uncertainty: PSM Validator is an ISO 6143-based spreadsheet that calculates the value-assignment and combined uncertainty using a suite of primary standard materials (PSMs), a Control cylinder and the CCQM sample. It incorporates the uncertainties in the gravimetric values of each PSM along with the imprecision of the instrument measurement responses.
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The coverage factor for the expanded uncertainty is 2.
a) Uncertainty Components for Analysis of Oxygen in CCQMK-101 Cylinder FB03481:
Uncertainty source XI
Assumed distribution
Standard
Uncertainty (%) Relative),
u(xi)
Gravimetric Standard or Analytical Component
GenLine Curve Fit Gaussian ± 0.24 Gravimetric and
Analytical (combined)
Expanded uncertainty: ± 0.48 (%)