apmp.qm-k111 propane in nitrogen - kcdb.bipm.org · newly prepared psms against existing ones, and...

1

APMP.QM-K111 – Propane in nitrogen

Shinji Uehara1, Tomoe Nishino1, Dai Akima1, Tsai-Yin Lin2, Hsin-Wang Liu2, Chiung-Kun Huang2, Namgoo

Kang3, Hyun Kil Bae3, Jin Chun Woo3, Zhe Bi4, Zeyi Zhou4, Ratirat Sinweeruthai5, Arnuttachai Wongjuk5, Hou

Li6, Teo Beng Keat6, Liu Hui6, Thomas Wu6, Chua Hock Ann6, Damian Smeulders7, John Briton McCallum7,

Raymond Tendai Satumba7, Takuya Shimosaka8, Nobuhiro Matsumoto8, Haslina Abdul Kadir9, Mohamad Fauzi

Ahmad9, Noor Hidaya Abdul Nasir9

1 Chemicals Evaluation and Research Institute, Japan (CERI), 1600, Shimo-Takano, Sugito-machi,

Kitakatsushika-gun, Saitama 345-0043, Japan 2 Center For Measurement Standards/Industrial Technology Research Institute (CMS/ITRI), CMS/ITRI,

Rm.216, Bldg. 17, 2F, No.321, Sec.2, Kuang Fu Rd., Hsinchu, 30011, Taiwan, R.O.C 3 Korea Research Institute of Standards and Science (KRISS), Division of Metrology for Quality Life, P.O.Box

102, Yusong, Taejon, Republic of Korea

4National Institute of Metrology (NIM), Beijing Beisanhuan East road Nop.18, Beijing 100029, China 5National Institute of Metrology (Thailand) (NIMT), 3/4-5 Moo 3, Klong 5, Klong Luang, Pathumthani 12120,

Thailand 6National Metrology Centre, Agency for Science, Technology and Research (NMC, A*STAR) , Singapore#02-

27, TUV SUD PSB building, 1 Science Park Drive, Singapore 118221 7 National Measurement Institute, Australia (NMIA), 36 Bradfield road, Lindfield NSW 2070 Australia 8 National Metrology Institute of Japan (NMIJ), 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8563, Japan 9 National Metrology Laboratory SIRIM Berhad (NML-SIRIM), LOT PT4803, Bandar Baru Salak

Tinggi,43900, Sepang, Selangor, Malaysia.

Field

Amount of substance

Subject

Comparison of propane in nitrogen (track A – core competences)

Table of contents

Field ........................................................................................................................................................ 1

Subject .................................................................................................................................................... 1

Table of contents ..................................................................................................................................... 1

1 Introduction ................................................................................................................................ 2

2 Design and organisation of the APMP key comparison ............................................................ 2

2.1 Participants ................................................................................................................................. 2 2.2 Measurement standards .............................................................................................................. 2 2.3 Measurement protocol ................................................................................................................ 3 2.4 Schedule ..................................................................................................................................... 3 2.5 Measurement equation ............................................................................................................... 3 2.6 Measurement methods ............................................................................................................... 5 2.7 Degrees of equivalence .............................................................................................................. 5

3 Results ........................................................................................................................................ 5

4 Supported CMC claims .............................................................................................................. 7

5 Discussion and conclusions ........................................................................................................ 7

References ............................................................................................................................................... 7

Coordinator ............................................................................................................................................. 7

Project reference ..................................................................................................................................... 7

Completion date ...................................................................................................................................... 7

Annex A : Measurement reports ............................................................................................................. 8

2

Measurement report CERI .................................................................................................................. 8 Measurement report CMS/ITRI ........................................................................................................ 12 Measurement report KRISS .............................................................................................................. 15 Measurement report NIM ................................................................................................................. 19 Measurement report NIMT ............................................................................................................... 24

Measurement report NMC A*STAR ................................................................................................ 27 Measurement report NMIA ............................................................................................................... 30 Measurement report NMIJ ................................................................................................................ 36 Measurement report NML SIRIM .................................................................................................... 40

1 Introduction

This APMP key comparison is one of a series of key comparisons in the gas analysis area assessing

core competences (track A key comparisons). Such competences include, among others, the

capabilities to prepare Primary Standard gas Mixtures (PSMs) [5], perform the necessary purity

analysis on the materials used in the gas mixture preparation, the verification of the composition of

newly prepared PSMs against existing ones, and the capability of calibrating a gas mixture.

For this key comparison, a binary mixture of propane in nitrogen has been chosen at an amount-of-

substance fraction level of 1000 µmol/mol [2]. The key comparison design follows that of the key

comparisons for gas mixture that are prepared gravimetrically [3].

KRISS and CERI participated in the key comparison, CCQM- K111 (1000 µmol/mol propane in

nitrogen). Therefore, the results of APMP.QM-K111 are related with CCQM-K111 through the

results of KRISS and CERI. CERI used the same calibration standards in CCQM-K111 and

APMP.QM-K111.

2 Design and organisation of the APMP key comparison

2.1 Participants

Table 1 lists the participants in this key comparison.

Table 1: List of participants

Acronym Country Institute

CMS/ITRI TW Center For Measurement Standards/Industrial Technology

Research Institute

KRISS KR Korea Research Institute of Standards and Science,

Deajeon, Republic of Korea

NIM CN National Institute of Metrology

NIMT TH National Institute of Metrology (Thailand)

NMC, A*STAR SG National Metrology Centre, Agency for Science, Technology

and Research, Singapore

NMIA AU National Measurement Institute, Australia

NMIJ JP National Metrology Institute of Japan

NML-SIRIM MY National Metrology Laboratory SIRIM Berhad

CERI JP Chemical Evaluation and Research Institute,

Saitama, Japan

2.2 Measurement standards

A set of mixtures were prepared gravimetrically by CERI. For the preparation, NMIJ-CRM was used

for high purity propane and special grade nitrogen was used from Takachiho Chemical industrial co.,

3

Ltd. The mixtures were verified against a set of CERI PSMs. The PSMs were used for the evaluation

of CCQM-K111 sample for CERI.

The filling pressure in the cylinders was approximately 10 MPa. Aluminium alloy cylinders from

Luxfer Australia of which volume were 9.6 dm3, were used. The mixture composition and its

associated uncertainty was calculated in accordance with ISO 6142 [4]. The amount-of-substance

fractions as obtained from gravimetry and purity verification of the parent gases were used as key

comparison reference values (KCRVs). Each cylinder had its own reference value.

The nominal amount-of-substance fraction of propane was 1000 µmol/mol.

2.3 Measurement protocol

The measurement protocol requested each laboratory to perform at least 3 measurements, with

independent calibrations. The replicates, leading to a measurement, were to be carried out under

repeatability conditions. The protocol informed the participants about the nominal amount-of-

substance fraction ranges. The laboratories were also requested to submit a summary of their

uncertainty evaluation used for estimating the uncertainty of their result.

2.4 Schedule

The schedule of this key comparison was as follows (Table 2).

Table 2: Key comparison schedule

Date Stage

September 2013 Review of protocol by GAWG

October 2014 Approval of protocol & Registration to Appendix B

October 2014 Registration

November 2014 Preparation of mixtures

December 2014 Verification of mixture compositions

March 2015 Distribution of mixtures

December 2015 Reports arrived at CERI

February 2016 Cylinder arrived at CERI

March 2016 Re-verification of the mixtures

March 2016 Draft A report available

October 2016 Draft B report available

2.5 Measurement equation

The key comparison reference values are based on the weighing data from gravimetry, and the purity

verification of the parent gases. All mixtures underwent first verification before shipping them to the

participants. After returning of the cylinders, they went through second verification to reconfirm the

stability of the mixtures.

In the preparation, the following four groups of uncertainty components have been considered:

1. gravimetric preparation (weighing process) (xi,grav)

2. purity of the parent gases (xi,purity)

3. stability of the gas mixture (xi,stab)

4. correction due to partial recovery of a component (xi,nr)

Previous experience has indicated that there are no stability issues and no correction is needed for the

partial recovery of a component. These terms are zero, and so are their associated standard

uncertainties.

4

The amount-of-substance fraction, xi,prep, of a particular component in mixture i, as it appears during

use of the cylinder, can now be expressed as

,,,, purityigraviprepi xxx (1)

The equation for calculating the associated standard uncertainty reads as

.,

2

,

2

,

2

purityigraviprepi xuxuxu (2)

The validity of the mixtures has been demonstrated by verifying the composition as calculated from

the preparation data with that obtained from (analytical chemical) measurement. In order to have a

positive demonstration of the preparation data (including uncertainty, the following condition should

be met [3]

.2 2

,

2

,,, veriprepiveriprepi uuxx (3)

The factor 2 is a coverage factor (normal distribution, 95% level of confidence). The assumption must

be made that both preparation and verification are unbiased. Such bias has never been observed. The

uncertainty associated with the verification highly depends on the experimental design followed. In

this particular key comparison, an approach has been chosen which is consistent with CCQM-K3 [4]

and takes advantage of the work done in the gravimetry study CCQM-P41 [5].

The expression for the standard uncertainty of the key comparison reference value is

veriprepirefi xuxuxu ,

2

,

2

,

2 . (4)

The preparation and verification data for the gas mixtures used in this key comparison (see figure 1)

agree. The values for ui,ver are given in table 4 containing the results of this key comparison.

Figure 1: Preparation and verification data of the transfer standards used in this key comparison

992

993

994

995

996

997

998

999

1000

1001

1002

NIM

NM

C A

*S

TA

R

NIM

T

KR

ISS

NM

IA

NM

IJ

CM

S/I

TR

I

NM

L S

IRIM

CE

RI

amo

un

t-of-

sub

stan

ce f

ract

ion

of

pro

pan

e

(mm

ol/

mol)

Laboratory

■ preparation

● 1st verification

▲ 2nd verification

5

2.6 Measurement methods

The measurement methods used by the participants are described in each participant report. A

summary of the calibration methods, dates of measurement and reporting, and the way in which

metrological traceability is established is given in table 3.

Table 3: Summary of calibration methods and metrological traceability

Laboratory

code

Measurements Calibration Traceability Matrix

standards

Measurement

technique

NIM 23/25/26 June 2015 One-point

calibration

Own standards

(ISO 6142) Nitrogen GC-FID

NMC A*STAR 05/06/18 May 2015 One-point

calibration

Own standards


NIMT 02/03/04 Dec. 2015 ISO 6143 Own standards


KRISS 19/20/21/22/26/30 May 2015 One-point

calibration

Own standards


NMIA 18/19/20/21 June 2015 Multipoint

calibration

Own standards

(ISO 6142) Nitrogen

NGA(GC-FID)

GC-TCD

GC-FID

NMIJ 30/Apr. and 01/02 May 2015 Multipoint

calibration

Own standards

(ISO 6142) Nitrogen GC-TCD

CMS/ITRI 27/28/30/Apr. 2015 One-point

calibration

Own standards


NML SIRIM 27 May and 03/10 June 2015 ISO 6143 KRISS CRM Nitrogen GC-FID

CERI 02/23/28/29 July 2015 Multipoint

calibration

Own standards

(ISO 6142) Nitrogen FID

2.7 Degrees of equivalence

A unilateral degree of equivalence in key comparisons is defined as

,KCRVi,iii xxDx (5)

and the uncertainty of the difference di at 95% level of confidence. Here xi,ref denotes the key

comparison reference value, and xi denotes the result of laboratory i.1 Appreciating the special

conditions in gas analysis, it can be expressed as

.i,refiii xxDx (6)

The standard uncertainty of ⊿xi can be expressed as

,,

2

,

22

,

222

veriprepiirefiii xuxuxuxuxuxu (7)

assuming that the aggregated error terms are uncorrelated. As discussed, the combined standard

uncertainty of the reference value comprises that from preparation and that from verification for the

mixture involved.

3 Results

In this section, the results of the key comparison are summarised. In table 4, the following data is

presented

xprep amount of substance fraction, from preparation (µmol/mol)

uprep uncertainty of xprep (µmol/mol) (k=1)

1 Each laboratory receives one cylinder, so that the same index can be used for both a laboratory and a

cylinder.

6

uver uncertainty from verification (µmol/mol) (k=1)

uref uncertainty of reference value (µmol/mol) (k=1)

xlab result of laboratory (µmol/mol)

Ulab stated uncertainty of laboratory, at 95 % level of confidence (µmol/mol)

klab stated coverage factor

x difference between laboratory result and reference value (µmol/mol)

k assigned coverage factor for degree of equivalence

U(x) Expanded uncertainty of difference x, at 95 % level of confidence2 (µmol/mol)

Table 4: Results of APMP.QM-K111

Laboratory Cylinder xprep

/μmol/mol

uprep

/μmol/mol

uver

/μmol/mol

uref

/μmol/mol

xlab

/μmol/mol

Ulab

/μmol/mol klab Δx k

U(Δx)

/μmol/mol

NIM CPB20810 995.10 0.28 0.26 0.38 993.81 0.99 2 -1.3 2 1.3

NMC A*STAR CPB21192 998.52 0.28 0.26 0.38 1000.6 4.5 2 2.1 2 4.6

NIMT CPB25989 999.09 0.28 0.26 0.38 1001.0 3.5 2 1.9 2 3.6

KRISS CPB25963 1000.38 0.28 0.26 0.38 1001.1 1.0 2 0.7 2 1.3

NMIA CPB25966 999.41 0.28 0.26 0.38 1000.0 1.5 2 0.6 2 1.7

NMIJ CPB25981 996.77 0.28 0.26 0.38 996.5 1.1 2 -0.3 2 1.3

CMS/ITRI CPB25984 994.27 0.28 0.26 0.38 994.9 2.0 2 0.6 2 2.1

NML SIRIM CPB25987 998.59 0.28 0.26 0.38 960.41 1.5 2 -38.2 2 1.7

CERI CPB25989 999.09 0.28 0.26 0.38 999.84 0.76 2 0.8 2 1.1

In figure 2, the degrees of equivalence for all participating laboratories are given relative to the

gravimetric value. The uncertainties are, as required by the MRA [6], given as 95% confidence

intervals. For the evaluation of uncertainty of the degrees of equivalence, the normal distribution has

been assumed, and a coverage factor k = 2 was used. For obtaining the standard uncertainty of the

laboratory results, the expanded uncertainty (stated at a confidence level of 95%) from the laboratory

was divided by the reported coverage factor.

Figure 2: Degrees of equivalence

2 As defined in the MRA [6], a degree of equivalence is given by x and U(x).

-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

NIM

NM

C A

*S

TA

R

NIM

T

KR

ISS

NM

IA

NM

IJ

CM

S/I

TR

I

NM

L S

IRIM

CE

RI

dif

fere

nce（

μm

ol/

mol）

Laboratory

7

4 Supported CMC claims

The results of this key comparison can be used to support CMC claims as described in the final report

of CCQM-K111 [1].

5 Discussion and conclusions

The results in this Track A key comparison on 1000 µmol/mol propane in nitrogen are generally good.

All but one result are within ± 0.25 % of the KCRV.

References

[1] Van der Veen A.M.H., Van der Hout J.W., Ziel P.R., Oudwater R.J., Fioravante A.L.,

Augusto C.R., Brum M.C., Uehara S., Akima D., Bae H.K., Kang N., Woo J.C., Liaskos C.E.,

Roderick G.C., Brewer P.H., Brown A.S., Bartlett S., Downey M.L., Konopelko L.A.,

Kolobova A.V., Pankov A.A., Orshanskaya A.A., Efremova O.V., “International Comparison

CCQM-K111 – Propane in nitrogen”, Final Report, Metrologia Technical Supplement, to be

published

[2] Alink A., “The first key comparison on Primary Standard gas Mixtures”, Metrologia 37

(2000), pp. 35-49

[3] International Organization for Standardization, ISO 6142:2001 Gas analysis - Preparation of

calibration gas mixtures - Gravimetric methods, 2nd edition

[4] Alink A., Van der Veen A.M.H., “Uncertainty calculations for the preparation of primary gas

mixtures. 1. Gravimetry”, Metrologia 37 (2000), pp 641-650

[5] Van der Veen A.M.H, De Leer E.W.B., Perrochet J.-F., Wang Lin Zhen, Heine H.-J., Knopf

D., Richter W., Barbe J., Marschal A., Vargha G., Deák E., Takahashi C., Kim J.S., Kim

Y.D., Kim B.M., Kustikov Y.A., Khatskevitch E.A., Pankratov V.V., Popova T.A.,

Konopelko L., Musil S., Holland P., Milton M.J.T., Miller W.R., Guenther F.R., International

Comparison CCQM-K3, Final Report, 2000

[6] Van der Veen A.M.H., Brinkmann F.N.C., Arnautovic M., Besley L., Heine H.-J., Lopez

Esteban T., Sega M., Kato K., Kim J.S., Perez Castorena A., Rakowska A., Milton M.J.T.,

Guenther F.R., Francy R., Dlugokencky E., “International comparison CCQM-P41

Greenhouse gases. 2. Direct comparison of primary standard gas mixtures”, Metrologia 44

(2007), Techn. Suppl. 08003

[7] CIPM, “Mutual recognition of national measurement standards and of calibration and

measurement certificates issued by national metrology institutes”, Sèvres (F), October 1999

Coordinator

CERI

Gas Standards area, Chemical Standards Department

Shinji UEHARA

1600 Shimotakano, Sugito-machi, Kitakatsushika-gun, Saitama 345-0043, Japan

Phone +81-480-37-2601

E-mail [email protected]

Project reference

APMP.QM-K111

Completion date

April 2017

8

Annex A : Measurement reports

Measurement report CERI

Laboratory name: Chemicals Evaluation and Research Institute, Japan (CERI)

Cylinder number: CPB25989

Measurement #1

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)

number of replicates

Propane 02/07/2015 1000.15 0.0291 4

Measurement #2

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 23/07/2015 999.78 0.0197 4

Measurement #3

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 28/07/2015 999.76 0.0074 4

Measurement #4

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 29/07/2015 999.67 0.0096 4

Results

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Expanded Uncertainty

(μmol/mol)

Coverage factor

Propane 999.84 0.76 2

9

Calibration standards

‒ Method of preparation: ISO 6142

These calibration standards were used in CCQM-K111.

‒ Weighing data (1 000 μmol/mol C3H8 in N2)

1) Evacuated cylinder – Tare cylinder : 2.548 g

2) Cylinder filled with parent gas – Tare cylinder : 22.641 g

3) Cylinder filled with nitrogen – Tare cylinder : 976.242 g

‒ Purity tables (composition) of the parent gases

NMIJ CRM was used for pure Propane. Purity analysis of propane was performed by NMIJ

and provided as a certified reference material to CERI.

Impurities of nitrogen were analysed by CERI.

Table 5: Purity table of propane

Component Purity (certified value)

mol/mol

Expanded uncertainty (k=2)

mol/mol

C3H8 0.9999 0.0001

Table 6: Impurity table of propane

Component Mole fraction

cmol/mol

Standard uncertainty (k=1)

cmol/mol

N2 0.00023 0.00013

O2 0.00018 0.00010

Ar 0.00028 0.00016

CO2 0.00028 0.00016

C2H6 0.00038 0.00022

C3H6 0.00306 0.00002

cyclo- C3H6 0.00025 0.00014

C4H10 0.00019 0.00011

iso- C4H10 0.00019 0.00011

H2O 0.00662 0.00180

NMIJ CRM

(Pure propane)

0.05 mol/mol

C3H8 in N2

1 200 μmol/mol

C3H8 in N2

1 000 μmol/mol

C3H8 in N2

800 μmol/mol

C3H8 in N2

600 μmol/mol

C3H8 in N2

10

Table 7: Purity table of nitrogen

Component Analytical

value

μmol/mol

Distribution Mole

fraction

μmol/mol

Uncertainty

μmol/mol

(k=1)

Verification

measures

O2 ≤ 0.1 Rectangular 0.05 0.02887 GC-MS

Ar ≤ 1 Rectangular 0.5 0.2887 GC-MS

CO ≤ 0.01 Rectangular 0.005 0.002887 GC-FID with

methanizer

CO2 ≤ 0.01 Rectangular 0.005 0.002887 GC-FID with

methanizer

Total hydro

carbon

(THC)

≤ 0.01 Rectangular 0.005 0.002887 GC-FID

SO2 ≤ 0.005 Rectangular 0.0025 0.001443 Chemiluminescent

gas analyzer

NOx ≤ 0.005 Rectangular 0.0025 0.001443 Pulsed fluorescence gas analyzer

N2 - - 999 999.43 0.2902 -

Each mole fraction of impurity in nitrogen is adequately low. Therefore, the average molar

mass of dilution gas wasn’t affected from the impurities.

Instrumentation

Flame ionization detector, Rosemount Analytical Inc. Model 400A

Calibration method and value assignment

The instrument was calibrated using four gravimetrically prepared PRMs ranging in concentration

from 1 200 μmol/mol to 600 μmol/mol. Analytical scheme was, Std. A – Std. B – CCQM Sample –

Std. C – Std. D. This scheme was repeated 4-times in a day. These measurements were carried out for

4-days.

Each calibration curve was linear given by :

y = a1xs + b1

where,

y: CCQM sample concentration

n: Gas standards number

xS: Indicated value of sample

xi: Indicated value of standard material i

yi: Concentration of standard material i

)xx(S

xySa 1

n

xayb ii

1

1

n

xxxxS i

i

22

n

yxyxxyS ii

ii

11

Uncertainty evaluation

Table 8: Budget Sheet for 1 000 μmol/mol C3H8 in N2

Uncertainty

source

Value

xi

Estimate

+/-

Method of

evaluation

(type A or typeB)

Assumed

probability

distribution Divisor

Standards

uncertainty

u(xi)

Sensitivity

coefficient

|ci|

Contribution

u(yi)

Parent

gas

76 156.8 μg/g

9.553

μg/g A normal 1

9.553

μg/g 0.01312

0.1251

∙10-6

Weighing

data 1) 2.548 g

3.597

∙10-3g A normal 1

3.597

∙10-3 g

0.04872

∙10-3 g-1

0.1752

∙10-6

Weighing

data 2)

22.641

g

3.597

∙10-3g A normal 1

3.597

∙10-3 g

0.05069

∙10-3 g-1

0.1823

∙10-6

Weighing

data 3)

976.242

g

30.71

∙10-3g A normal 1

30.71

∙10-3 g

1.027

∙10-6 g-1

0.03154

∙10-6

Molar

mass of

C3H8

44.0596

g/mol

0.00140

g/mol B normal 2

0.00070

g/mol

22.63

∙10-6

mol/g

0.01584

∙10-6

Molar

mass of

N2

28.0134

g/mol

0.00028

g/mol B normal 2

0.00014

g/mol

35.62

∙10-6

mol/g

0.004892

∙10-6

Combined uncertainty: 0.2843 μmol/mol

Uncertainty of NMIJ CRM (high purity C3H8) is included in uncertainty of parent gas.

Table 9: Budget Sheet for APMP.QM-K111

Uncertainty source

Value xi

Estimate +/-

Method

of

evaluation

(type A or typeB)

Assumed

probability distribution Divisor

Standards

uncertainty

u(xi)

Sensitivity

coefficient

|ci|

Contribution u(yi)

Std. 1000 998.96 μmol/mol

0.2843 μmol/mol

A normal 1 0.2843

μmol/mol 1

0.2843

μmol/mol

Measurement 999.84 μmol/mol

0.1042 μmol/mol

A normal 1 0.1042

μmol/mol 1

0.2496 μmol/mol

THC(as methane)

in N2 0.005 μmol/mol

0.005 μmol/mol

A rectangular √3 0.00289

μmol/mol 1/3

0.00096 μmol/mol

Round off - 0.005

μmol/mol B rectangular √3

0.002877 μmol/mol

1 0.002877 μmol/mol

Combined uncertainty: 0.3783 μmol/mol

Expanded uncertainty (k=2): 0.76 μmol/mol

12

Measurement report CMS/ITRI

Laboratory name: CMS/ITRI


Measurement #1

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard

deviation

(% relative)

Number of

replicates

Propane 27/04/2015 994.56 0.14 5

Measurement #2

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard

deviation

(% relative)

Number of

replicates

Propane 28/04/2015 994.96 0.22 5

Measurement #3

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard

deviation

(% relative)

Number of

replicates

Propane 30/04/2015 995.26 0.14 5

Results

Component Result

(μmol/mol)

Expanded

Uncertainty

(μmol/mol)

Coverage factor

Propane 994.93 1.96 2

Calibration standards The primary reference materials (PRMs) of C3H8 in N2 were gravimetrically prepared according to

ISO 6142: 2001 by CMS/ITRI. The high purity propane from NMIJ (National Metrology Institute of

Japan) and BIP Nitrogen from Air Products were used to prepare the PRMs. The 99.99% purity of

propane was certified by NMIJ. The impurities in nitrogen were determined with various gas analyzers

and were described in Table 10. The uncertainty associated with the C3H8 determination was taken into

account during the gravimetric calculations and uncertainty evaluation. The prepared PRMs were

verified by analytical comparisons against existing gravimetrically prepared standards, and the

characteristics of calibration standards are described in Table 11.

13

Table 10 : Purity table for nitrogen


(μmol/mol)

Standard uncertainty

(μmol/mol)

Method

O2 0.005 0.0029 Trace oxygen analyzer

CO 0.005 0.0029 GC-FID

CO2 0.025 0.015 GC-FID

CH4 0.0025 0.0015 GC-FID

C3H8 0.025 0.015 GC-FID

SO2 0.025 0.015 GC-MS

NO 0.005 0.0029 NOx analyzer

N2 999999.9075 0.026 -

Table 11 : Propane concentration of primary reference materials (PRMs)

Instrumentation A GC specifically set up for C3H8 in N2 analysis was described in Table 12.

Table 12 : Analytical conditions

Body Agilent GC-7890A

Software for data collection Agilent ChemStation

Column HP-PLOT/Q column (30 m × 0.53 mm, 40.0 mm)

Oven temp. 160°C isothermal

Detector FID (Flame gases flows: air = 400 ml/min, H2 = 40

ml/min)

Detector temp. 250°C

Carrier gas He: 2 ml/min

Analytical time for one injection 6.5 min


GC-FID was used to determine C3H8 concentration in the sample cylinder. Five standards were used

to construct a calibration curve for the preliminary evaluation of C3H8 concentration in sample cylinder

CPB25984. After that, standard with concentration close to that of the sample cylinder was chosen for

single-point calibration to determine the concentration of C3H8 in sample cylinder. The sample cylinder

was analyzed with a reference cylinder in the following order.

Reference – Sample – Reference – Sample – Reference – Sample – Reference – Sample – Reference –

Sample – Reference

The mathematical model shown below was used to calculate the concentration of C3H8 in sample

cylinder:

1,,

5

1

3

1 2;

5;;

3

isis

ii

i

i

isiii

i

RR

Rr

r

rCrC

C

C

C =the reported concentration, CPB25984

Ci = the ith measured concentration of sample, CPB25984

Cs = concentration of standard, CAL013019

Cylinder number Assigned value

(μmol/mol)

Expanded uncertainty

(μmol/mol) (k=2)

5603591 500.15 0.58

D247796 699.88 0.49

CAL013019 999.76 0.78

CAL013006 1500.56 0.71

FF19460 1999.80 0.90

14

ir = the average ratio of GC-FID response of sample to standard

ri = the ith calculated ratio of response of sample to standard

Ri = the ith response of GC-FID for sample, CPB25984

Rs,i = the ith response of GC-FID for reference standard, CAL013019


The final uncertainty was estimated by combining two uncertainty components (i.e., PRM and

analysis).

- total standard uncertainty of C3H8 mole fraction in PRMs (including uncertainty of weighing of

parent gases and pre-mixture, uncertainty in the purity of the parent gas and balance gas);

- standard uncertainty of the measurement result of C3H8 mole fraction in cylinder number

CPB25984 (including uncertainties of repeatability and reproducibility)

The equations described below were used to evaluate the uncertainty for C3H8 measurement.

1,,

5

1

3

1 2;

5;;

3

isis

ii

i

i

isiii

i

RR

Rr

r

rCrC

C

C

issii ruCCurCu 2222

2

3

3

1

2

i

i

p

ss

)5

(

222

22 p

ssi

SCCurCu

ir = the average of calculated mean ratios, ir , for the five sets of measurements

sp = pooled standard deviation of the five sets of measurements

si = standard deviation of each set of measurements The uncertainty budget for C3H8 measurement in the cylinder number CPB25984 is shown in Table

13.

Table 13 : Uncertainty budget for C3H8 measurement

Uncertainty source

Xi

Estimate

xi

Evaluation

type

Distribution Standard

uncertainty

u(xi)

Sensitivity

coefficient

ci

Contribution

to standard

uncertainty

ui(y)

Repeatability and

reproducibility of ratio of

signal, r

ir ;0.9952 A Normal 8.96×10-4 999.76×10-6 8.95×10-7

Uncertainty of calibration

standard

Cs ;

999.76×10-6 A Normal 0.39×10-6 0.9952 3.88×10-7

Combined Uncertainty, (μmol/mol) 0.98

Expanded Uncertainty, (k=2) , (μmol/mol) 1.96

Expanded Uncertainty, (k=2) , (% relative) 0.19

15

Measurement report KRISS

Laboratory name: KRISS


Measurement #1

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)

Number of

replicates

Propane 19/05/15 1001.1 0.06 5

Measurement #2

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)

Number of

replicates

Propane 20/05/15 1001.0 0.04 11

Measurement #3

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)

Number of

replicates

Propane 21/05/15 1001.1 0.04 4

Measurement #4

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)

Number of

replicates

Propane 22/05/15 1001.0 0.08 5

Measurement #5

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)

Number of

replicates

Propane 26/05/15 1001.2 0.02 4

Measurement #6

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)

Number of

replicates

Propane 30/06/15 1001.1 0.05 12

Results

Component Result

(μmol/mol)


(μmol/mol) Coverage factor

Propane 1001.1 1.0 2

1. Calibration standards

‒ Method of preparation

16

Several cylinders of primary standard mixtures (PSM) for propane in nitrogen were

prepared by KRISS using a gravimetric technique based on the KRISS Standard

Procedure (R-112-001-2012).

‒ Weighing data

A 2-step dilution process was adopted. For example, the weighing data of a KRISS PSM

(D233583) was summarized as follows: Parent gases of nitrogen (616.446 g) and propane

(29.847 g) were mixed into the 1st diluted gas mixture (KRISS PSM L1268). The 1st

diluted gas mixture (38.125 g) and additional nitrogen (1078.0 g) were mixed into the 2nd diluted gas mixture (KRISS PSM D233583).


Table 14 : Purity table of high-purity nitrogen gas

Serial No. Impurity Component Mole Fraction (μmol/mol)

1

2

3

4

5

6

H2

O2+Ar

CO

CO2

CH4

H2O

<0.07

9.18

0.01

0.16

<0.05

1.2

Purity N2 999 989

Table 15 : Purity table of high-purity propane gas

Serial No. Impurity Component Mole Fraction (μmol/mol)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

CH4

C2H6

C2H4

C2H2

C3H6

i-C4H10

n-C4H10

C4H8

C5H12

N2

CO2

CO

H2

Ar and O2

H2O

< 0.1

< 0.1

< 0.1

< 0.1

< 0.1

9.7

4.4

< 0.1

< 0.1

1.5

0.7

0.03

0.05

0.7

0.3

Purity Propane 999 982

‒ Verification measures

1) Verification of internal consistency between the KRISS PSMs

Gravimetric results of the primary gas mixtures were compared by GC analysis and

differences were tested by the KRISS Standard Procedures (R-112-001-2012 and R112-

004-2012).The uncertainty of gravimetric preparation was included in the final result.

17

2) Verification of instability of the KRISS PSMs

Gas adsorption or any unstable effect was not observed in the gas cylinders of KRISS

PSMs used. Previous experimental results were summarized at the KRISS standard

procedures. Since the uncertainty due to instability was so negligible, it was not included

to the final uncertainty value.

2. Instrumentation

Determination of mole fraction of propane in nitrogen was conducted using a GC-FID

(Agilent 6890N). The chromatographic column was alumina (80/100 mesh) with 12-feet

length. The oven temperature was 150oC. A mass flow controller (MFC) was used to

maintain gas flow constant (100 mL/min). The nominal volume of the gas sample loop was

0.5 cm3. No changes were made and no additional devices were used for the GC-FID. The

retention time of propane was 2.08 min.

3. Calibration method and value assignment

The overall procedures for calibration and value assignment are based on the KRISS

Standard Procedure (R-112-004-2012). We used a one-point calibration method for the

determination of the mole fraction (x) of propane in the test cylinder (CPB25963) of the

coordinating laboratory (CERI). A bracketing method (KRISS Calibration Cylinder-

CERI Test Cylinder-KRISS Calibration Cylinder) was adopted for both value assignment

and verification. We adopted the KRISS PSM D233583 (1 002.73 μmol/mol) as a

calibration cylinder for the one-point calibration method. Results were obtained by direct

comparison of GC-FID responses for propane between the KRISS Calibration cylinder

(D233583) and the test cylinder (CPB25963) by taking drift compensation into account.

The results of KRISS were verified against the other three KRISS PSMs (D233650,

D233665, and D233615). These KRISS PSMs used for value assignment and verification

for AMPM.QM-K111 was also used for the verification of the KRISS results submitted

to the international comparison CCQM-K111 Propane in nitrogen in the current status of

Draft A Report.

4. Uncertainty evaluation

1) Model equation

A model equation of the measurand (xKRISS) was used for the one-point calibration

method:

XKRISS = (Atest/Acal)･Xcal ･fconsistency

where

xKRISS : the measurand of this comparison, i.e., mole fraction of propane in nitrogen from the

test cylinder (CPB25963) determined by KRISS

(Atest /Acal) : the ratio of response areas from GC-FID between the test cylinder (CERI

CPB25963) and the calibration cylinder (KRISS PSM D233583)

xcal : the mole fraction of the calibration cylinder (KRISS PSM D233583)

fconsistency: the factor of bias from internal consistency of the KRISS PSMs for verification

where the factor is assumed 1.

18

Uncertainties due to impurities of all parent gases used for gravimetric preparation were

combined into the preparation uncertainty of the KRISS PSMs.

2) Combined standard uncertainty

(𝑢(𝑋𝐾𝑅𝐼𝑆𝑆)

𝑋𝐾𝑅𝐼𝑆𝑆)

2

= (𝑢(𝐴𝑡𝑒𝑠𝑡 𝐴𝑐𝑎𝑙⁄ )

𝐴𝑡𝑒𝑠𝑡 𝐴𝑐𝑎𝑙⁄)

2

+ (𝑢(𝑋𝑐𝑎𝑙)

𝑋𝑐𝑎𝑙)

2

+ (𝑢(𝑓𝑐𝑜𝑛𝑠𝑖𝑠𝑡𝑒𝑛𝑐𝑦)

𝑓𝑐𝑜𝑛𝑠𝑖𝑠𝑡𝑒𝑛𝑐𝑦)

2

3) Uncertainty budget

We used the GUM Workbench Pro (Version 2.3.6.141, Metrodata Gmbh) for

uncertainty analysis.

Table 16 : Uncertainty budget

No.

Estimate Uncertainty Analysis

Variable Value Uncertainty

Source

Type

Assumed Distribution

Standard Uncertainty

u(xi)

Contribution to total

variance(%)

1 Atest /Acal 0.9984 Repeatability A t 0.00003 1

2 Xcal 1002.73

μmol/mol Gravimetric

preparation B Normal 0.2 4

3 fconsistency 1 Internal

consistency B Rectangle 0.00049 95

4 XKRISS 1001. 1

μmol/mol Combined - Normal 0.50 100

4) Measurand and expanded uncertainty

xKRISS ± UKRISS = (1001.1 ± 1.0) μmol/mol (Confidence level of about 95%, coverage

factor of 2)

19

Measurement report NIM

Laboratory name: National Institute of Metrology, China (NIM)


Measurement #1

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)

Number of replicates

Propane 23/06/2015 993.74 0.061% 6

Measurement #2

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 25/06/2015 993.54 0.061% 6

Measurement #3

Results

Component Result

(μmol/mol)


(μmol/mol)

Coverage factor

Propane 993.81 0.99 2


Please provide a brief description of the calibration standards used, including

‒ Method of preparation

‒ Weighing data


‒ Verification measures

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 26/06/2015 994.15 0.061% 6

20

-Method of preparation

The standard gas mixtures were prepared gravimetrically through a two step dilution according to

ISO6142. The parent gas mixtures of 0.0147734 (cylinder # 813455) mol/mol and 0.0149844

(Cylinder # 813472) mol/mol (propane in nitrogen) were prepared in the first step of dilution,

and four reference gas mixtures were prepared at the second step of dilution which were used

as the calibration gas mixtures. Table 17 listed the results of the calibration gas mixtures

preparation by gravimetric method.

Table 17 : Preparation of the calibration gas mixtures

Cylinder Number

Assigned value

(μmol/mol)


(μmol/mol)

L51010161 1000.11 0.19

L33913032 1008.78 0.19

813865 1000.77 0.19

813941 1003.40 0.19

After verification of the calibration gas mixtures each other, one cylinder (L51010161) was

selected as calibration standard to measure the comparison cylinder.

-Weighing data

Cylinders (L51010161) preparation results listed in table 18:

Table 18 : weigh of components for the gravimetric method

Components Weigh (g) Standard uncertainty(g)

Parent gas mixtures1 24.6760 0.0023

Dilution gas (N2) 336.9773 0.0053

1The parent gas mixture (cylinder # 813455):14773.4 µmol/mol

21

-Purity tables:

Table 19 : Nitrogen source gas: 99.99506% mol/mol

Component Amount fraction

(10-6mol/mol)


(10-6mol/mol) Assumed distribution

Hydrogen 0.10 0.02 Normal

Oxygen 0.70 0.07 Normal

Carbon monoxide 0.015 0.001 Rectangular

Carbon dioxide 0.025 0.001 Rectangular

Methane 0.009 0.002 Rectangular

Argon 48.3 0.5 Normal

Water 0.25 0.05 Normal

Nitrous oxide 0.001 0.001 Rectangular

Nitrogen 999950.6 0.3 Normal

Table 20 : Propane source gas: 99.99746% mol/mol

Component Amount fraction

(10-6mol/mol)


(10-6mol/mol)

Assumed

distribution

Propene 10.556 1.277 Normal

n-Butane 0.186 0.043 Normal

Nitrogen 14.63 0.15 Normal

Hydrogen 0.05 0.03 Rectangular

Carbon monoxide 0.002 0.004 Rectangular

Carbon dioxide 0.02 0.01 Rectangular

Methane 0.005 0.003 Rectangular

Argon 0.05 0.03 Rectangular

Oxygen 0.002 0.001 Rectangular

Propane 999974.6 1.7 Normal

22

Instrumentation

Please provide a brief description of the particulars of the instrument used in this key comparison

(principle, make, type, configuration, data collection, and etc.).

Table 21 : Analytical Instrument: HP7890A GC analyzer equipped with a FID detector and auto

sampling valve

Agilent 7890A Condition

Detector Flame Ionization Detector (FID)

Detector Temperature 300°C

Column HP-Plot Al2O3/KCl, 50m×0.32μm×8μm

Oven Temperature 100°C for 10min

Sample Flow rate 100 mL/min

Specification of a balance:

Model No.: Mettler-Toledo

Resolution: 1 mg, Capacity: 26 kg

Weighing method: A-B-A, substitution method.


Please provide a brief description how the equipment was calibrated and how the assigned value was

calculated (including the necessary formulae).

(mathematical model or calibration curve, number and concentration of standards, measurements

sequence, etc.)

Cylinder L51010161 calibration gas mixture was used for the measurement.

Single point calibration was used to calculate the mole fraction of the target compound in a comparison

cylinder CPB20810 provided by CERI.

When analyzing the sample gas mixture, “A-B-A” type calibration procedure was used. It means that

the sample and calibration gases were measured in the order of Calibration-Sample-Calibration. This

procedure was carried out 3 times on different days.

The calibration and sample gas mixtures were directly introduced to the GC through a three-way valve

and a mass flow controller.


Please provide a brief description of the evaluation of measurement uncertainty, including the

expressions used.

The uncertainty of calibration standard (L51010161) was evaluated according to ISO6142.

23

“A-B-A” type calibration procedure was used. The calibration uncertainty was evaluated based on the

equation (1):

( / ) res s r r proC C fA A

(1)

Cs - the mole fraction of sample gas mixture;

As - the peak area of sample cylinder in GC-FID;

Cr- the mole fraction of calibration gas mixtures;

Ar - the peak area of calibration gas mixtures in GC-FID.

frepro - the reproducibility of the measurement for different days

The uncertainty budget for this measurement is given in Table 22:

Table 22 : Uncertainty budget for the sample cylinder measurement

Component distribution Sensitivity

coefficient

Relative standard

uncertainty, ui

As Normal 1 0.025%

Ar Normal 1 0.025%

Cr Normal 1 0.019%

frepro Normal 1 0.030%

2 2 2 2

s A r r reprosC A c fu u u u u (2)

sCu - the combined relative standard uncertainty of the measurement;

2 2 2 20.025% 0.025% 0.019% 0.030% 0.050%sCu

The expanded relative uncertainty with 95% confidence and a coverage factor k=2 is:

0.10%s sC cU k u

For the sample cylinder, the measurement result with an absolute uncertainty is:

993.81±0.99 μmol/mol

24

Measurement report NIMT

Laboratory name: National Institute of Metrology (Thailand)


Measurement #1

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 02/12/2015 1001.2 0.045 3

Measurement #2

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 03/12/2015 1001.1 0.026 3

Measurement #3

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 04/12/2015 1000.7 0.010 3

Results

Component Result

(μmol/mol)

Expanded

Uncertainty

(μmol/mol)

Coverage factor

Propane 1001.0 3.5 2

25


The standard gas mixtures used are traceable to the National Institute of Metrology (Thailand) and

are prepared and verified according to ISO 6142 and ISO 6143. The purity of Nitrogen is more than

99.9995% and the purity of propane is more than 99.99% from the specification of manufacturer. These

standard gas mixtures used were prepared by 2-step of dilution. Uncertainty values of standard gas

mixtures are evaluated from the gravimetry, verification, stability and measurement bias. The

characteristics of the standard gas mixtures are listed in Table 23.

Table 23 : Concentration of standard gas mixtures.

Cylinder number Assigned value Expanded uncertainty

(Relative value, k = 2)

PRM 129830 799.95 0.3%

PRM 129832 999.13 0.3%

PRM 129807 1201.84 0.3%

Table 24 : Purity table of propane gas

Impurity Mole fraction

(µmol/mol)


(µmol/mol)

CH4 < 40 12

C2H6 < 40 12

C3H6 < 10 3.0

H2O < 3 1.0

N2 < 10 2.9

CO2 < 10 3.0

O2 < 2 6.0

H2 < 0.5 0.2

Table 25 : Purity table of nitrogen gas

Impurity Mole fraction

(µmol/mol)


(µmol/mol)

CH4 < 0.1 0.03

CO < 0.1 0.03

H2O < 0.5 0.15

CO2 < 0.1 0.03

O2 < 0.5 0.15

H2 < 0.5 0.15

)(22

6143

2

6142

2

Biasstabilitysik xuxuxuxuxu

26

Instrumentation

The measurements were performed using a 6890 Gas Chromatograph with flame ionization detector

(FID). The GC column used was Porapak Q, 6 ft and mesh 80/100, and with nitrogen as carrier gas.

The measured condition was sample loop 0.5 ml, temperature of oven 80oC, temperature of detector

250oC, hydrogen flow 30 ml/min and air flow 400 ml/min. The flow rate of propane gas mixtures was

controlled by using a mass flow controller at 20 ml/min. The GC-FID was calibrated with three

standard gas mixtures in range 800 to 1200 µmol/mol.


The measurement procedure is shown as follow; “Calibration 1 – Sample – Calibration 2 – Sample

–Calibration 3 – Sample” The linear function was used for determining the sample content including

the quality control gas (QC) is used for correction of a drift of analysis instruments. It acts as the

blank when doing the analysis of sample. A QC gas was injected into GC-FID before and after the

measurement reference gases and sample gas. The standard, sample and QC gases were injected into

the ten-port gas sampling valves of GC-FID. The average response was calculated by using the last

three of six times for each cylinder.


The procedure for the estimation of measurement uncertainty is following a 3-point calibration and

according to ISO 6143 using B_least software for selecting the analytical function and JCGM

100:2008 “Evaluation of Measurement Data-Guide to The Expression of Uncertainty in

Measurement". The standard uncertainty u(xs) of the sample gas mixture is calculated from the following equations;

BsAksA XuxuXuxu 2

6143,

22

,

2 .)(

where

u(Xk) is the standard uncertainty of standard gas mixtures,

u(xA,s)6143 is the standard uncertainty of the sample content from analytical equation,

u(XB) is the standard uncertainty due to the measurement bias.

Table 26 : Uncertainty Budget for of C3H8 measurement

Quantity

(Uncertainty source),

Xi

Estimate

xi

(µmol/mol)

Evaluation

type

(A or B)

Distribution

Standard

uncertainty

u(xi)

Sensitivity

coefficient

ci

Contribution

u(yi)

(µmol/mol)

The standard gas

mixture 999.13 B Rectangular 1.5 1.0 1.5

Analytical content of

sample gas mixture, 1001.0 A Normal 0.9 1.0 0.9

Measurement Bias, 0.01 B Rectangular 0.01 1.0 0.01

Combined Uncertainty, (µmol/mol) 1.75

Expanded Uncertainty, (k=2) , (µmol/mol) 3.5

Expanded Uncertainty, (k=2) , (%relative) 0.35

27

Measurement report NMC A*STAR

Laboratory name: National Metrology Centre, A*STAR, Singapore


Measurement #1

Component Date

(dd/mm/yy) Result

(µmol/mol)

Standard deviation

(% relative)


Propane 05/05/15 999.7 0.104 3

Propane 05/05/15 999.4 0.044 3

Propane 05/05/15 1002.2 0.041 3

Measurement #2

Component Date

(dd/mm/yy) Measured Result

(µmol/mol)

Standard Deviation

(% relative)

Number of Replicates

Propane 06/05/15 998.6 0.115 3

Propane 06/05/15 1002.2 0.118 3

Propane 06/05/15 1002.1 0.103 3

Measurement #3

Component Date

(dd/mm/yy) Measured Result

(µmol/mol)

Standard Deviation

(% relative)

Number of Replicates

Propane 18/05/15 998.5 0.076 3

Propane 18/05/15 1000.6 0.062 3

Propane 18/05/15 1001.8 0.115 3

Results:

Component Result

(µmol/mol) Expanded uncertainty

(µmol/mol) Coverage Factor

Propane 1000.6 4.5 2

28

Calibration standards Calibration Standards used for the comparison were maintained in 2 separate cylinders with the following details: Table 27 : Calibration standards

Calibration Standard

Cylinder No. Mole Fraction Expanded

Uncertainty (mol/mol)

A PSM118654 0.0010003 0.000001

B PSM118655 0.0010049 0.000001

Calibration Standard A, which was used for measurements 1 and calibration standard B, which was used for measurements 2 and 3, were prepared at NMC, A*STAR using gravimetric method following ISO6142 Standard. The purity of balance gas, nitrogen, was analysed using gas chromatograph with PDHID detector. The regulator used was SS Verifo single stage (with no gauges), which was purged 5 times based on operation procedure. Cylinders for Calibration Standards A & B were 5-litre aluminum cylinder with Aculife-3 treatment supplied by Scott Specialty Gases. The Calibration Standards had been verified against with reference material D-233603 (1000.6 umol/mol) from KRISS (Certificate No.: 1407-00827-001). Instrumentation The sample cylinder and reference cylinder were stored at a room temperature (20 ± 2) °C for 3 days before an analysis. The gas mixture in cylinder CERI05 (Travelling Standard) was analysed over 3 days against Calibration Standards A and B maintained at NMC using gas chromatography (Agilent model 7890A) with FID detector and a sampling system consisting of valves, pressure regulator and flow meter. Modified Teflon was used in the sampling line. The measurements were carried out under ambient temperature of (20 ± 2) °C. Calibration method and value assignment Reference standards which are close to transfer standard’s concentration were chosen to as the one-point calibration standard. The number of injections from each cylinder was 5, and only the last 3 injections were used for the calculation of the mole fraction of the Travelling Standard. The Calibration Standards and Travelling Standard were injected directly into the gas chromatography through the multi-valves sampling system. Average results obtained in each individual analysis were combined and averaged to produce a single measurement result.

29

Uncertainty evaluation Table 28 : Uncertainty evaluation

Uncertainty

source, Xi

Evaluation type

(A or B)

Standard uncertainty,

u(xi) (mol/mol)

Sensitivity coefficient,

ci Distribution

Contribution, ui(y)

(µmol/mol)

Gas standard

uncertainty

-Purity analysis

-Gravimetric

method

-Molar mass

-Consistency

Type B 0.0000005 1 Normal 0.6

Linearity Type B 0.0000003 1 Rectangular 0.3

Analytical

uncertainty

-Repeatability

Type A 0.0000012 1 Normal 1.9

Combined

uncertainty, uc

Normal 2.04

Expanded

uncertainty

(k = 2), U

Normal 4.5

30

Measurement report NMIA

Laboratory name: National Measurement Institute, Australia (NMIA)


Measurement #1

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 18/06/15 999.597 0.08% 5 (repeated 3 times)

Measurement #2

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 19/06/15 1000.464 0.07% 5 (repeated 3 times)

Measurement #3

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 20/06/15 999.893 0.06 5 (repeated 3 times)

Measurement #4

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 21/06/15 999.977 0.07 5 (repeated 3 times)

Results

Component Result

(μmol/mol)


(μmol/mol)

Coverage factor

Propane 1000.0 1.5 2


Four calibration standards were used for this comparison. The concentrations of the calibration

standards closely bracketed the nominal 1000 ppm propane concentration – with 2 cylinders higher and

2 cylinders lower than the target value. The 4 calibration standards were prepared independently from

2 cylinders of propane (2 standards from each propane).

The standards were prepared gravimetrically at the NMI using a Sartorius CC10000S mass comparator.

Environmental conditions were monitored during the use of the mass comparator to allow for the

correction of buoyancy. The purity of the source gases was also included in the calculation of mixture

composition and for the assignment of the concentration of each gas component.

The gravimetric uncertainty of the gas mixtures was calculated using the principles described in ISO 6142,

2001. The gravimetric uncertainty budget included contributions from:

31

Balance uncertainty

Buoyancy of cylinders

Expansion of cylinders

Tare mass uncertainty

Tare mass buoyancy

Purity of gases

Molar mass

Reference standards were manufactured in the following sequence:

2.51 bar

Evacuated cylinder

100 mmol/mol Propane

Balance Nitrogen

25.0 g

2.51 bar

Propane

PV 8.83 bar

25.9 bar

142.94 g

23.39 bar

Nitrogen

T > Tc

Designed at 22°C

in 5.3 litre cylinder

3.9 bar

Evacuated cylinder

10 mmol/mol Propane

Balance Nitrogen

25.0 g

3.9 bar

100 mmol/mol Propane in Nitrogen

38.5 bar

212.78 g

34.6 bar

Nitrogen

T > Tc

32

Standard 1 FF51752

Propane: 987.659 µmol/mol

Preparation uncertainty: 0.441 µmol/mol (k = 1)

Standard 2 FF51753



Standard 3 FF51754



Standard 4 FF51755



4.1 bar

Evacuated cylinder

0.9 mmol/mol Propane

Balance Nitrogen

25.0 g

4.1 bar


45 bar 251.33 g Nitrogen

T > Tc

4.1 bar

Evacuated cylinder


Balance Nitrogen

25.0 g

4.1 bar



T > Tc

4.1 bar

Evacuated cylinder


Balance Nitrogen

25.0 g

4.1 bar


40.3 bar 216.5 g Nitrogen

T > Tc

4.1 bar

Evacuated cylinder


Balance Nitrogen

30.0 g

4.1 bar



T > Tc

33

Prior to the gravimetric preparation of the standards, the purity of the propane cylinders and nitrogen

were determined. Several GCs were used to determine the impurity concentrations in each gas (GC

detectors included PDHID, FID and TCD).

Purity tables:

Table 29 : Propane 1 (C3H8-01A)

Table 30 : Propane 2 (C3H8-14A)

Table 31 : Nitrogen

Verification: Mixtures were verified through comparison with 5 other gas standards containing

propane in nitrogen. 4 mixtures were manufactured covering the range 900 – 1100 µmol/mol range,

plus a historical cylinder (MD8874) from 2011 containing 994.7 µmol/mol propane in nitrogen was

also used. These cylinders were in good agreement with the standards used in this comparison.

Instrumentation

Two GCs were used for the analysis of the propane. GCs were run simultaneously with the same

sequence. The results from the 2 GCs agreed to within 0.1 ppm.

Bruker 456GC Natural gas analyser (configuration C). Column: 60m x 0.25 mm CP-Sil 5 CB, df =

1µm to FID. Data collection was handled by Compass CDS software.

Varian 3800 gas chromatograph with a 6’ x 1/8” Hayesep R column with TCD and FID in series. Data

collection was handled by Star WS software.

Results from both GCs were processed off-line using MS Excel to calculate propane concentration

and measurement uncertainty.


The sample cylinder was run with the four calibration standards (detailed previously). A sequence of

runs ABCADEA (repeated three times in each analysis) was used to determine the concentration of

components in the sample cylinder:

- A was the APMP sample cylinder.

- B was the first reference standard.

Nitrogen N2 24 3 μmol/mol Normal NMI analysis GC8 cryo 2/02/15, Log book 32 page 10

Oxygen O2 1.5 0.6 μmol/mol Normal NMI analysis GC8 cryo 2/02/15, Log book 32 page 10

Ethane C2H6 17 2 μmol/mol Normal NMI analysis GC7 methanizer 25-26/02/15, Log book 31 page 91

Propane C3H8 0.9999575 3.66E-06 mol/mol Normal Nominally pure component

Notes (lab book details, certificate details, etc)C3H8_01A Concentration U(Concentration)Composition

RangeUncertainty Type Justification of Value

Nitrogen N2 90 30 μmol/mol Normal NMI analysis GC8 cryo, 03/02/15 Lab book 32 page10

Oxygen O2 50 20 μmol/mol Normal NMI analysis GC8 cryo, 03/02/15 Lab book 32 page10

Ethane C2H6 52 4 μmol/mol Normal NMI analysis GC7 methanizer, 25-26/02/15 Lab book31 page91

Propane C3H8 0.999808 3.63E-05 mol/mol Normal Nominally pure component

Notes (lab book details, certificate details, etc)C3H8_14A Concentration U(Concentration)Composition


Argon Ar 222.7 1.7 μmol/mol Normal NMI analysis 2/06/16 Log Book 32 p19

Nitrogen N2 0.999775852 1.70098E-06 mol/mol Normal Nominally pure component

Oxygen O2 1.373 0.029 μmol/mol Normal NMI analysis 2/06/16 Log Book 32 p19

Carbon Monoxide CO 0.025 0.025 μmol/mol Rectangular Below NMI detection limit 13/05/16 Log Book 31 p102

Carbon Dioxide CO2 0.025 0.025 μmol/mol Rectangular Below NMI detection limit 13/05/16 Log Book 31 p102

Methane CH4 0.025 0.025 μmol/mol Rectangular Below NMI detection limit 13/05/16 Log Book 31 p102

Notes (lab book details, certificate details, etc)Concentration U(Concentration)Composition


34

- C was the second reference standard.

- D was the third reference standard.

- E was the fourth reference standard.

Each stage of the measurement sequence represents 5 repeat analyses of a cylinder. Each run took 10

minutes under isothermal conditions. Stream selection was controlled with an electric actuated 10-

position VICI valve. Sequences were left to run unattended overnight.

Concentrations were calculated using the mathematical model for 2-point bracketed standards.

Cx = (C2-C1)*(Rx-R1)/(R2-R1)+C1

Where:

- Cx = concentration of sample

- C1 = concentration of first standard

- C2 = concentration of second standard

- Rx = average response of GC for sample

- R1 = average response of GC for first standard

- R2 = average response of GC for second standard

The 4 reference standards were used in the model by grouping the 2 standards closest in concentration

to the sample cylinder (FF51753 and 55) and grouping the 2 standards furthest away from the sample

concentration of the sample cylinder (FF51752 and 54).

The measurement results for each sequence were combined and averaged to produce a single

measurement result for each gas cylinder with the purpose of averaging out any instrumental drift.

The 2 GCs produced results that agreed to within 0.1 ppm for each analysis.

The entire sequence of runs was repeated four times from the 18th to 21st of June 2015. Four tables of

measurement results are included in this report containing average values from the 2 GCs for the

concentrations calculated from the 4 reference standards.

Sample flow was controlled with a MFC and the gas flowed continuously while being analysed. The

analysis results were not corrected for variations in laboratory air pressure or temperature.


The uncertainty budget had 2 main components:

- Gravimetric uncertainty, and

- Analytical uncertainty

The Gravimetric uncertainty contributions included:

- Balance uncertainty

- Buoyancy of cylinders

- Expansion of cylinders

- Tare mass uncertainty

- Tare mass buoyancy

- Impurity of gases

The analytical uncertainty contributions included:

- Uncertainty of sample measurement

- Uncertainty of measurement of reference gases

35

The analytical uncertainty was calculated by using the mathematical model for 2-point bracketed

calibrations. The standard uncertainty of the analytical response for each standard was calculated;

along with the standard uncertainty for the analytical response of the test cylinder. The uncertainty

obtained from the analytical measurement was combined with the gravimetric uncertainty of the

reference standards to give the total combined uncertainty.

Table 32 : Calculated uncertainties for each measurement:

Measurement 1

Measurement 2

Measurement 3

Measurement 4

Combined uncertainty (µmol/mol) 0.73 0.67 0.67 0.7

Expanded Uncertainty (µmol/mol) 1.5 1.3 1.3 1.4

36

Measurement report NMIJ

Laboratory name: National Metrology Institute of Japan (NMIJ)


Measurement #1

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 30/04/15 996.31 0.10 5

Measurement #2

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 01/05/15 997.13 0.093 5

Measurement #3

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 02/05/15 995.91 0.14 5

Results

Component Result

(μmol/mol)


(μmol/mol)

Coverage factor

Propane 996.5 1.1 2


Preparation method

Three calibration standards were used for the determination of propane in nitrogen. The standards

were prepared from pure propane and pure nitrogen in accordance with ISO6142:2001.

Pure propane and pure nitrogen were purchased from Takachiho and Japan Fine Products,

respectively. The purity tables based on the analytical results by NMIJ are shown in Table 33-34.

Two-step dilution was used to make the calibration standards, whose propane mole fraction is

between 800 μmol/mol and 1200 μmol/mol. An electronic mass-comparator (“Mettler Toledo model

XP26003L, capacity 26 kg , readability 1 mg”, or “Mettler Toledo model KA10-3/P, capacity 15 kg ,

readability 1 mg” ) with automatic loading system of cylinders was used for preparation of all

calibration gas standards. Table 35 shows characteristics of the calibration standards.

37

Table 33 : Purity table for propane gas used as parent gas.


(μmol/mol)


(μmol/mol)

C3H8 999900 50

N2 0.78 0.02

O2 0.55 0.04

C2H6 2.2 0.4

C3H6 27.68 0.28

H2O 47.3 13.0

Ar 0.06 0.03

n-C4H10 0.50 0.29

i-C4H10 0.50 0.29

C3H6 30.0 1.2

Table 34 : Purity table for nitrogen gas used as parent gas.


(μmol/mol)


(μmol/mol)

N2 999999.996 0.0022

C3H8 0.0039 0.0022

Table 35 : Gravimetric mole fractions of propane in calibration gas standards. The balance gas of all

calibration standards is nitrogen.

Calibration standard, r Gravimetric mole fraction, Xr

μmol/mol

Expanded uncertainty [k=2], U(Xr)

μmol/mol

1 787.89 0.23

2 1205.88 0.35

3 997.64 0.31

38

Instrumentation

The analysis of propane in the transfer standard was done by a gas chromatograph with TCD whose

analytical conditions are summarized in Table 36.

Table 36 : Analytical conditions.

Gas chromatograph Shimadzu GC-14B

Software for data collection GC solution (Shimadzu)

Column Porapak Q 2 m

Oven temp. 100 °C

Detector TCD with pre-amplifier (Shimadzu model AMP-7B)

Current of detector 100 mA

Temp. of detector 110 °C

Carrier gas He

Volume of sample loop 5 mL

Flow rate of sample gas controlled

with electronic mass flow controller 30 mL/min

Analytical time for one measurement 6.5 min

Number of measurements

per one cylinder

10 (However, only last five measurements were

adopted for the determination)


A Quality Control (QC) cylinder gas, transfer standard of this comparison, and the calibration

standards were measured as follows.

“QC(i=1) −calibration standard 1− QC(i=2) – transfer standard of this comparison− QC(i=3)

−calibration standard 2− QC(i=4) − calibration standard 3−QC(i=5)”

Measurements of peak area were repeated 10 times a sample. The last 5 measurements in each sample

were used for the average of peak areas.

This series of measurements (“QC(i=1)−···−QC(i=5)”) was repeated three times.

The QC cylinder was used to evaluate correlation between peak area and retention time of propane

peak in chromatogram. The peak areas were corrected based on the results of the correlation.

39

We defined

Xr : the gravimetric mole fraction of calibration standard r,

Yr, j : corrected peak area for calibration standard r at j th series is Yr, j ,

u(Z) : standard uncertainty of Z.

From the data set of (X1, X2, X3, Yr, j), parameters and their uncertainty of the analytical function, X =

b0 + b1 ·Y, were calculated by the Deming’s least squared method. The analytical content Xs,j and its

standard uncertainty u(Xs,j) of the transfer standard were calculated from the peak area, Ys,j , and its

uncertainty, u(Ys,j) by the analytical function.

The measurements of Xs,j were repeated three times. Final mole fraction of the sample gas in the table

of “Results” in page 1, Xs, was derived from

𝑋𝑠 = ∑ 𝑋𝑠,𝑗

3

𝑗=1

3⁄ . (1)

The standard uncertainty of Xs was given as

𝑢2(𝑋𝑠) = ∑ (𝑋𝑠,𝑗 − 𝑋𝑠)2

3(3 − 1) + ∑ 𝑢2(𝑋𝑠,𝑗) 32⁄ (2)

3

𝑗=1

⁄

3

𝑗=1


Please see the above section.

40

Measurement report NML SIRIM

Laboratory name: National Metrology Laboratory, SIRIM Berhad, MALAYSIA.

Cylinder number: CPB- 25987

Measurement #1

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 27/05/15 960.36 0.33 7

Measurement #2

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 03/06/15 960.45 0.51 7

Measurement #3

Component Date

(dd/mm/yy)

Result

(μmol/mol)

Standard deviation

(% relative)


Propane 10/06/15 960.43 0.10 7

Results

Component Result

(μmol/mol)


(μmol/mol)

Coverage factor

Propane 960.41 1.5 2

41

CALIBRATION STANDARD:

Three calibration standards gases from KRISS were used to calibration the gas chromatography. The

CRM in table 37 were used for calibration of the instruments.

Table 37 : List of calibration standards

CRM No Concentration

µmol/mol

Matrix

112-01-064 1004 Nitrogen

112-03-002 1995.7 Nitrogen

112-01-065 3005 Nitrogen

Instrumentation

A standards and sample gases were injected into 6 port valves of Agilent Technology Model 7890A

GC equipped with a Flame Ionization Detector (FID).

GC conditions:-

Carrier gas: Helium

Column type: HP-AL/S 30m, 0.25 mm, 5 µm

Oven:

Temperature: Isothermal @ 100ºC

Duration: 3 min

Detector:

Temperature: 250 ºC

H2 Flow: 50mL/min

Air Flow: 400mL/min

Make up flow (N2): 25mL/min

The data was collected using Chemstation software. Each sample was manually injected for 8 times

and the first injection in each case was discarded which were considered as flushing of sample loop.

The responses were averaged.

42


Calibration Method

The calibration of the instruments has carried out according ISO 6143. The standards used were listed

in table 37. The standards were injected before the sample. Sample flow of each cylinder was

constantly at 40ml/min by a mass flow controller.

Sample Handling

During the measurement, the cylinders of standards and sample were stabilized at room temperature.


The uncertainty of the unknown sample was calculated according to ISO 6143. The combined

uncertainty was multiplied by a coverage factor of 2 with a confidence interval of 95%. Two sources of

uncertainty were considered:

Table 38 : Source of uncertainty

Source of uncertainty

Symbol Type Distribution Std

Uncertainty (%)

Precision up A Normal 0.31

Calibration standard

ustd B Normal 0.25

Combined uncertainty, uc 0.56

Expanded uncertainty,U 1.12

apmp.qm-k111 propane in nitrogen - kcdb.bipm.org · newly prepared psms against existing ones, and...

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