International Comparison CCQM-K101：Oxygen in Nitrogen10National Metrology Institute of South...

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)


(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

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Table 5 Assay of the pure nitrogen


(mol/mol)


(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


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

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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

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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


Sevomex Xenra 4100C O2

traces analyzer

5 measurements, each with 6

sub-measurements

CERI One primary standard prepared


GC-MS (Quadruplet) 8 measurements, each with 8

sub-measurements

NMIJ Four primary standards prepared


GC-TCD 3 measurements, each with 4

sub-measurements

NIM Three primary standards prepared


Delta F 310ɛ analyzer 3 measurements, each with 3

sub-measurements

KRISS Four primary standards prepared



sub-measurements

VSL One primary standard prepared


GC-PDHID 5 measurements, each with 7

sub-measurements

VNIIM Three primary standard prepared


Delta F 310 6 measurements, each with

2-4 sub-measurements

SMU Three primary standards prepared



sub-measurements

NMISA Five primary standards prepared


GC-PDHID 3 measurements, each with

10 sub-measurements

NPL NPL PRGMs standard prepared


GC-HDID/CRDS 5 measurements, each with

2-4 sub-measurements

NIST Five primary standard prepared


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#


Result

(mol/mol)



O2 03/01/2012 9.984 0.16 3

Measurement 3#


Result

(mol/mol)



O2 04/01/2012 9.974 0.12 3

Measurement 4#


Result

(mol/mol)



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


C=448.75 µmol/mol

U (k=2)=0.48 µmol/mol


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)


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)


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



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


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

Materialforschung

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

[email protected]

Task

Dr. habil. Michael Maiwald

Tel.: +49 30 8104-1140

[email protected]

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

\\scl1\service03\FG14SERV\FGJ.4_Prozessanalytik\Analysenberichte\2013\BAM-l 4-2013-0002_CCQM-K101.docx

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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Analysis report BAM-I 4-2013-0002_CCQM-K101

Datum 2013-02-21

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SBAMBundesanstalt für

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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


Laboratory name: BAM Federal Institute for Materials Research and Testing


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


6


6


6


6


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


(u.mol/mol)

0.15

Coverage factor

k = 2



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.


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


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)


O2 29/1/2013 9.877 0.850 8

Measurement 2#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 30/1/2013 9.863 0.544 8

Measurement 3#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 31/1/2013 9.964 1.758 8

Measurement 4#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 1/2/2013 9.966 0.776 8

Measurement 5#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 5/2/2013 9.713 0.521 8

Measurement 6#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 6/2/2013 9.724 0.838 8

Measurement 7#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 7/2/2013 9.796 1.085 8

Measurement 8#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


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



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)


Mathematical model:

One-point calibration was used.


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)


(10-6 mol/mol) Coverage factor

O2 9.977 0.079 k = 2

Cylinder number of the sample : FB03058



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.


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


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.



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)



Oxygen

10/16/2013

10.022

0.024

3

Measurement No. 3

Date

Result (µmol/mol)



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.


(mol/mol)


(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)


(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)


Reporter: Jinsang Jung ([email protected])

Measurement 1#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 30/04/2013 10.029 0.35 3

Measurement 2#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 02/05/2013 10.024 0.43 3

Measurement 3#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 08/05/2013 10.009 0.28 3

Measurement 4#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 09/05/2013 10.023 0.09 3

Results

Component Result

(mol/mol)


(mol/mol)

Coverage factor

O2 10.021 0.063 k=2


Please complete the following data regarding the description of methods and the uncertainty

evaluation.


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)


(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)


(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.


Please include a list of the uncertainty contributions, the estimate of the standard uncertainty,

probability distribution, sensitivity coefficients, etc.


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


Laboratory name: VSL


Measurement 1#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 2013-06-27 10.13 0.11 7

Measurement 2#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 2013-06-28 9.98 0.25 7

Measurement 3#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 2013-07-04 10.06 0.06 6

Measurement 4#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 2013-07-17 10.06 0.06 7

Measurement 5#

Component Date

(dd/mm/yy)

Result

(mol/mol)

Standard deviation

(% relative)


O2 2013-07-18 9.98 0.06 7

Results

Component Result

(mol/mol)


(µmol/mol)

Coverage factor

O2 10.04 0.07 2


Please complete the following data regarding the description of methods and the uncertainty

evaluation.


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)


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).


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


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


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


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


10-6

mol/mol


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


10-6

mol/mol


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.


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.


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


(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


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.


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.


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)


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)


(mol/mol)

Coverage factor

O2 9,86 0,19 k =2


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.


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.


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


standard deviation

(µmol/mol)

No. of

replicates

O2 13/09/2013 9.953 0.021 4

Measurement#3 : GC-HDID

Component Date


standard deviation

(µmol/mol)

No. of

replicates

O2 17/09/2013 9.954 0.016 4

Measurement#4 : CRDS

Component Date


standard deviation

(µmol/mol)

No. of

replicates

O2 19/09/2013 9.950 0.034 2

Measurement#5: CRDS

Component Date


standard deviation

(µmol/mol)

No. of

replicates

O2 19/09/2013 9.980 0.057 2

Final Result:

Component Date


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





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)



Oxygen

2/7/2013

9.919

0.025

3

Measurement No. 2

Date

Result (µmol/mol)



Oxygen

2/8/2013

9.916

0.015

3

Measurement No. 3

Date

Result (µmol/mol)



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.

3

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 (%)

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