International Comparison Euramet.QM-K111 … · International Comparison Euramet.QM-K111 ... PSMs...

1

International Comparison Euramet.QM-K111 – Propane in

Nitrogen

J. Wouter van der Hout1, Adriaan M.H. van der Veen

1, Paul R. Ziel

1, Heinrich Kipphardt

2, Dirk Tuma

2, Michael

Maiwald2, Teresa E. Fernández

3, Concepción Gómez

3, Dariusz Cieciora

4, Grzegorz Ochman

4, Florbela Dias

5,

Victor Silvino5, Tatiana Macé

6, Christophe Sutour

6, Fabrice Marioni

6, Andreas Ackermann

7, Bernhard

Niederhauser7, Judit Fükő

8, Tamás Büki

8, Zsófia Nagyné Szilágyi

8, Tanıl Tarhan

9, Erinç Engin

9

1Van Swinden Laboratorium (VSL), Chemistry Group, Thijsseweg 11, 2629 JA Delft, The Netherlands

2 Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany

3Centro Español de Metrologia (CEM), Reference Material Laboratory, C / Alfar 2, 28760 Tres Cantos Madrid,

Spain

4Central Office of Measures (GUM), Elektoralna 2, 00-139 Warsaw, Poland

5Portuguese Institute of Quality (IPQ), Area Amount of Matter and Electrochemistry, Rua António Gião 2,2829

513 Caparica, Portugal 6Joint Laboratory of Metrology (LNE), 25 avenue Alber Bartolomé, 75015 Paris, France

7Federal Institute of Metrology (METAS), Sector Analytical Chemistry, Lindenweg 50, CH-3003 Bern Wabern,

Switzerland 8Magyar Kereskedelmi Engedéleyezési Hivatal (MKEH), Németvölgyi út 37-39, 1124 Budapest, Hungary

9National Metrology Institute TÜBİTAK (UME), Gas Metrology Laboratory, TÜBİTAK Gebze Yerleşkesi, Bariş

Mah. Dr. Zeki Acar Cad. No:1, 41470 Gebze Kocaeli, Turkey

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 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 ............................................................................................................................................. 6

4 Discussion and conclusions ............................................................................................................ 7

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

Coordinator ............................................................................................................................................. 8

Project reference ..................................................................................................................................... 8

Completion date ...................................................................................................................................... 8

Measurement report of BAM .............................................................................................................. 9 Measurement report of CEM ............................................................................................................ 12 Measurement report of GUM ............................................................................................................ 14

2

Measurement report of IPQ .............................................................................................................. 17 Measurement report of LNE ............................................................................................................. 19 Measurement report of METAS ....................................................................................................... 24 Measurement report of MKEH ......................................................................................................... 26 Measurement report of UME ............................................................................................................ 29 Measurement report of VSL ............................................................................................................. 32

1 Introduction

This key comparison belongs to a series of key comparisons in the field of gas analysis assessing core

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

prepare Primary Standard Gas Mixtures (PSMs), to 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 last but not least 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-1

[1]. The key comparison was organized in the same way

as previous comparisons on gravimetrically prepared mixtures [2].

2 Design and organisation of the key comparison

2.1 Participants

Table 1 lists the participants in this key comparison.

Table 1: List of participants

Acronym Country Institute

BAM DE Bundesanstalt für Materialforschung und -prüfung, Berlin,

Germany

CEM ES Centro Español de Metrología, Spanish Metrological Centre

Tres Cantos, Madrid, Spain

GUM PL Central Office of Measures, Warsaw, Poland

IPQ PT Instituto Português da Qualidade, Portuguese Institute of Quality

Monte de Caparica, Portugal

LNE FR Laboratoire national de métrologie et d'essais, Paris, France

METAS CH Federal Institute of Metrology, Bern Wabern, Switzerland

MKEH HU Magyar Kereskedelmi Engedélyezési Hivatal, Budapest,

Hungary

UME TR National Metrology Institute TÜBİTAK , Gebze Kocaeli, Turkey

VSL NL Van Swinden Laboratorium, Delft The Netherlands

2.2 Measurement standards

A set of mixtures was prepared gravimetrically by VSL. For the preparation propane was used from

Scott Specialty Gases grade 3.5 and nitrogen from Air Products, grade 6.0 respectively. The mixtures

to be distributed among the participants were verified against a set of VSL PSMs. The propane was

subjected to a purity analysis in accordance with ISO 19229 [3] prior to use for preparation of the gas

mixtures.

The filling pressure in the cylinders was approximately 100 bar. Aluminium cylinders of a 5 dm3

water volume from Luxfer UK with SpectaSeal treatment were used. The mixture composition and its

3

associated uncertainty were calculated in accordance with ISO 6142 [4]1. 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 an individual reference value.

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

The verification measurements were carried out in accordance with ISO 6143 [5]. For this purpose,

the measurement standards were compared against VSL PSMs. The suites of PSMs used for the

various verification measurements differed, because of the replacement of some PSMs due to

depletion. In this key comparison, an approach has been chosen which resembles that of CCQM-K3

[5] and takes advantage of the work done in the gravimetry study CCQM-P41 [6].

2.3 Measurement protocol

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

independent calibrations. The replicates, leading to the result reported here, were to be carried out

under repeatability conditions. The protocol informed the participants about the nominal

concentration ranges. The laboratories were also requested to submit a summary of their uncertainty

evaluation used for calculating 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

August 2014 Agreement on protocol

August 2014 Registration of participants

December 2014 Preparation of mixtures

January 2015 Verification of mixture compositions

January 2015 Dispatch of mixtures

April 2015 Reports and cylinder arrived at VSL

May 2015 Re-verification of the mixtures

July 2015 Draft A report available

November 2015 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 verification prior to shipping them to the

participants. After return of the cylinders, they were verified a second time to reconfirm the stability

of the mixtures.

In the preparation, the following four groups of uncertainty components were 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)

1 Once ISO 6142-1:2015 was published, VSL revisited its procedures which were based on the then valid

edition, ISO 6142:2001. This analysis showed that the procedures used in this key comparison are also

consistent with the requirements of ISO 6142-1:2015.

4

5. Previous experience has indicated that the mixture has proved stable and thus no correction is

needed for the partial recovery of a component. These terms and their associated standard

uncertainties can be set zero. The verification measurements (see Figure 1) confirm that beyond the

verification uncertainty, no extra uncertainty component due to instability had to be included.

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

,purity,grav,prep, iii xxx (1)

The equation for calculating the associated standard uncertainty reads as

.purity,

2

grav,

2

prep,

2

iii 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.

For a successful qualification, the reported result and the corresponding uncertainty should fulfil the

following condition [7]

.2 2

ver,

2

prep,ver,prep, iiii uuxx (3)

The factor 2 in equation 3 is a coverage factor (normal distribution, 95% level of confidence). The

assumption is made that both preparation and verification are unbiased. No such bias was observed

for the mixtures concerned in this key comparison.

The reference value of mixture i in this key comparison2 can thus be defined as

.ver,prep,ref, iii xxx (4)

where Δxi,ver denotes the correction due to verification. This correction is zero for the transfer

standards used in this key comparison, implying that the expected values from preparation and

verification should coincide. The expression for the standard uncertainty of a reference value is then

ver,

2

prep,

2

ref,

2

iii xuxuxu . (5)

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

2 This definition of a reference value is consistent with the definition of a key comparison reference

value, as stated in the mutual recognition arrangement (MRA) [9].

5

BA

M

CE

M

GU

M

IPQ

LN

E

ME

TA

S

MK

EH

UM

E

988

989

990

991

992

993

994

995

am

ount-

of-

substa

nce fra

ction p

ropane (

µm

ol/m

ol)

Laboratory

preparation

1st verificaton

2nd verificaton

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

The preparation and verification data (see figure 1) agree well.

2.6 Measurement methods

The measurement methods used by the participants are described in annex A of this report. A

summary of the calibration methods, dates of measurement and reporting, and the modality of

establishing metrological traceability is given in table 3.

Table 3: Summary of calibration methods and metrological traceability

Laboratory

Code

Measurements Calibration Traceability Matrix

standards

Measurement

technique

MKEH 28/29/30 April 2015 One point

calibration

Own standards Nitrogen GC-FID

METAS 12/16/18 March 2015 ISO 6143 Own standards Nitrogen GC-FID

VSL 22/27 May 2014 and

11/12 June 2014

ISO 6143 Own standards

(ISO 6142)

Nitrogen GC-FID

IPQ 8/14/16 April 2015 ISO 6143 Own standards

(ISO 6142)

Nitrogen ND-IR

LNE 12/13/16 March 2015 Bracketing Own standards

(ISO 6142)

Nitrogen GC-TCD

CEM 23/29 April and

5 May 2015


(ISO 6142)

Nitrogen GC-FID

BAM 18/18/19/20/23/23

March 2015

Bracketing Own standards

(ISO 6142)

Nitrogen GC-TCD

GUM 4/4/5/5/16/19 February

and 5 March 2015

One point

calibration (5*)

+ ISO 6143 (2*)

Own standards

(ISO 6142)

Nitrogen GC-FID

UME 24/25/25/27/27 March

2015


(ISO 6142)

Nitrogen GC-FID

2.7 Degrees of equivalence

A unilateral degree of equivalence in key comparisons is defined as

,KCRVi,ii xxd (6)

6

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

comparison reference value, and xi the result of laboratory i.3 With reference to the special conditions

in gas analysis, it can be expressed as

.refi,ii xxd (7)

The standard uncertainty of di can be expressed as

,ver,

2

prep,

222

iiii xuxuxudu (8)

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 the tables, the following data are

presented

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

uprep uncertainty of xprep (µmol/mol)

uver uncertainty from verification (µmol/mol)

uref uncertainty of reference value (µmol/mol)

xlab result of laboratory (µmol/mol)

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

klab stated coverage factor

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

k assigned coverage factor for degree of equivalence

U(di) expanded uncertainty of difference di, at 95 % level of confidence4 (µmol/mol)

Table 4: Results of Euramet.QM-K111

Laboratory Cylinder xprep uprep uver uref xlab Ulab klab di k U(di)

MKEH 153259 993.15 0.26 0.35 0.44 1000.8 6.8 2 7.6 2 6.9

METAS 153322 993.69 0.27 0.35 0.44 996.0 4.0 2 2.3 2 4.1

VSL 153513 993.40 0.27 0.35 0.44 993.4 0.7 2 0.0 2 1.1

IPQ 153743 991.72 0.26 0.35 0.44 999.4 7.4 1.98 7.7 2 7.5

LNE 153769 991.01 0.27 0.35 0.44 991.1 1.8 2 0.1 2 2.0

CEM 153885 993.04 0.27 0.35 0.44 992.0 3.0 2 -1.0 2 3.1

BAM 153929 989.47 0.26 0.35 0.44 987.4 4.6 2 -2.1 2 4.7

GUM 153933 991.07 0.26 0.35 0.44 993.0 4.0 2 1.9 2 4.1

UME 178727 991.53 0.26 0.35 0.44 991.06 1.75 2 -0.5 2 2.0

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 [9], 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.

3 Each laboratory has received one cylinder, so that the same index can be used for both a laboratory and

a cylinder. 4 As defined in the MRA [9], a degree of equivalence is given by x and U(x).

7

MKEH METAS VSL IPQ LNE CEM BAM GUM UME

-2

-1

0

1

2d

iffe

ren

ce

(%

)

Laboratory

Figure 2: Degrees of equivalence

4 Discussion and conclusions

The results in this Track A key comparison on 1000 µmol mol-1

are generally good. Two laboratories

report results that are slightly inconsistent with the KCRV, but all results are within ± 1 % 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 54

(2017), 08009

[2] Alink A., “The first key comparison of primary standard gas mixtures”, Metrologia 37 (2000),

pp. 35-49

[3] International Organization for Standardization, ISO 19229:2015 Gas analysis − Purity

analysis and the treatment of purity data, ISO Geneva, 2015

[4] International Organization for Standardization, ISO 6142:2001 Gas analysis − Preparation of

calibration gas mixtures - Gravimetric methods, ISO Geneva, 2001

[5] International Organization for Standardization, “ISO 6143:2001 Gas analysis − Comparison

methods for determining and checking the composition of calibration gas mixtures”, ISO

Geneva, 2001

[6] Van der Veen A.M.H, van Wijk J.I.T., van Otterloo R.P., Wessel R.M., 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., Maruyama M.,Takahashi C., Kim J.S., Kim Y.D., Kim B.M., Kustikov

Yu.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”, BIPM, 2000; van der Veen A.M.H., “CCQM key comparison CCQM-K3 of

measurements of CO, CO2, and C3H8 in N2”, Metrologia 39 (2002), pp. 121-122

[7] 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.,

8

Guenther F.R., “International comparison CCQM-P41 Greenhouse gases. 2. Direct

comparison of primary standard gas mixtures”, Metrologia 44 (2007), Techn. Suppl. 08003

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

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

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

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

Coordinator

VSL

Chemistry Group

J. Wouter van der Hout

Thijsseweg 11

2629 JA Delft

the Netherlands

Phone +31 15 269 1567

E-mail [email protected]

Project reference

Euramet.QM-K111

Completion date

October 2016

mailto:[email protected]

9

Measurement report of BAM

Laboratory name: Bundesanstalt für Materialforschung und -prüfung (BAM)

Cylinder number: 153929

1) Background

EURAMET.QM-K111 is a regional interlaboratory comparison organized by VSL succeeding and

linked to CCQM-K111. CCQM-K111 classified as a core comparison of GAWG was conducted in

2014 and due to capacity reasons has not been opened to all potentially interested participants.

2) Choice of method

For the determination of propane in nitrogen the method of choice is GC with TCD or FID detection.

Although FID could provide smaller uncertainties at that concentration level, it was decided at BAM

to use the Siemens Maxum II gas analyser, which is equipped with TCD detection only.

3) Sample: labeling, packing, pre-information

The sample was provided from VSL in a 5 L cylinder with the cylinder number NMI 153929 with a

DIN 477 thread No. 1 (hydrogen). The initial (and final) pressure was not measured.

4) Sample pretreatment No heating or rolling was applied.

5) Devices used and flushing

A DIN 477 No. 1 (hydrogen)-VRC ¼″ fitting was adapted to the sample cylinder. A reduction valve,

a needle valve for dosing, and a closing valve with an outlet to Swagelok 1/16″ capillaries were

attached. For the two simultaneously employed calibration gases a similar assembly was used. The

assembly for the sample cylinder was not changed during the entire measuring campaign, the

assembly of the individual calibration gases used had to be changed (i.e., disconnected/connected).

A freshly installed assembly was evacuated down to a pressure of approximately 10–3

mbar and then

filled with gas from the cylinder. The evacuating/flushing was repeated five times.

6) Measurement instruments and settings

A specially designed Siemens Maxum II process gas analyser was used applying “method 1” which

executes a sequence of 44 injections. The oven was set to 60 oC and operated in isothermal mode. The

dosing volume of each injection was 240 µL. Details on Maxum operation can be found in the BAM

SOP “GAS-StAA-027”.

7) Calibration Three starting mixtures prepared from high-purity propane (grade 3.5) and high-purity nitrogen (grade

5.0) were further diluted in two steps by a gravimetric method according to DIN EN ISO 6142:2006.

The resulting three calibration gases are:

Cylinder Amount-of-substance

fraction

propane / cmol/mol

Amount-of-substance

fraction

nitrogen / cmol/mol No.: 8081-150119

U

Urel

0.095046

0.000051

5.4E-04

balance

No.: 8086-150105

U

Urel

0.099997

0.000054

balance

10

5.4E-04

No.: 8003-150112

U

Urel

0.105070

0.000056

5.4E-04

balance

Expanded Uncertainties U with k=2

In a measurement campaign prior to the investigation of the sample, the three calibration gases were

found to be consistent [see file VAL-CCQM-K111].

The purity analysis of initial gases was based on the information provided by the supplier or on the

results of determination of impurities in pure gases using a measurement procedure developed at

BAM. It was proven that the purity of propane and nitrogen was not enlarging the uncertainty of the

final measurement results. For the sake of completeness, the impurities reported for the pure gases

used for preparation of calibration mixtures are given as a table (amount-of-substance fraction).

Sum of CxHy Nitrogen Others

Nitrogen 5.0 < 200 ppb - < 10 ppb

Propane 3.5 < 400 ppm < 30 ppm < 70 ppm

8) Measurement outline For a measurement sequence, the two calibration gases C1 & C2 and the sample S were connected to

the GC. Using a stream selector valve, each calibration gas was connected three times, the sample gas

five times to the GC in the following order: C1/S/C2/S/C1/S/C2/S/C1/S/C2. At each connection to the

GC, four injections were made, from which only the last three were used for data evaluation. One

sequence runs over a period of four hours.

Using the Maxum, two measurement campaigns with three sequences were conducted. In each

campaign, the sequences were portioned on two different days.

9) Considered sources of uncertainty

The results and uncertainties given here include the uncertainty of the composition of the calibration

gases, the uncertainty from the measurement statistics (i.e., consecutive portions of three injections),

the uncertainty propagation for the calibration approach, the bias within a measurement campaign

over the period of time, and finally from combining the different measurement campaigns. Main

source of uncertainty is the imprecision of the TCD used.

10) Raw data: 2015-03-18 – 2014-03-24; for more details see PAZ/Code-518

11) Results from individual measurement campaigns

Standard uncertainties: k=1

campaign 1 8081-K111-8003 2015-03-18 2015-03-18a 2015-03-19

x / cmol/mol 0,09880 0,09884 0,09876

u(x) / cmol/mol 0,00026 0,00021 0,00027

urel(x) 2,6E-03 2,1E-03 2,7E-03

campaign 2 8081-K111-8086 2015-03-20 2015-03-23 2015-03-23a

x / cmol/mol 0,09876 0,09864 0,09864

u(x) / cmol/mol 0,00025 0,00020 0,00017

urel(x) 2,5E-03 2,1E-03 1,8E-03

11

The consistency of the measurement campaigns is very good. The results from the two campaigns do

not differ significantly, all results were pooled.

Standard uncertainties: k=1

campaign 1 campaign 2 all campaigns

x / cmol/mol 0,09880 0,09868 0,09874

u(x) / cmol/mol 0,00024 0,00021 0,00023

urel(x) 2,5E-03 2,1E-03 2,3E-03

12) Consolidated results

From the two measurement campaigns, the amount-of-substance fraction of propane in the cylinder

NMI 153929 is:

x( C3H8, NMI 153929) = ( 0.098 74 ± 0.000 46 ) cmol/mol

Given is the expanded measurement uncertainty U =k uc with k = 2 according to the ISO/BIPM

Guide to the Expression of Uncertainty in Measurement. Values obtained from the individual

measurement campaigns are given in section 11.

13) Remarks The measurement result obtained seems to be compatible with the announced target value of 0.1

cmol/mol.

14) Responsibility

The calibration gases have been prepared by the filling team consisting of Claudia Boissière, Kerstin

Köster, Jeannette Pelchen, under supervision of Dr. Dirk Tuma. The measurements using the Maxum

II gas chromatograph have been performed by Jeannette Pelchen. Reporting and calculations have

been performed by Dr. Heinrich Kipphardt. Advice was given by Dr. Wolfram Bremser and Dr.

Michael Maiwald.

The overall technical responsibility for the measurement result is with Dr. Heinrich Kipphardt.

Berlin, 2015-04-30 Heinrich Kipphardt FB 1.4

15) Additional information

Customer: VSL, EURAMET.QM-K111

PAZ-No. -

Sample arrival: 2013-03-05

Internal No.: Code-518

Sample No.: NMI 153929

Task: Determination of propane amount-of-substance fraction

Period of measurement: 2015-03-18 – 2013-03-24

Location: Building 42 Room 049

Method: GC with TCD

12

Measurement report of CEM

Laboratory name: Centro Español de Metrología (CEM)


Measurement #1

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)

number of replicates

Propane 23/04/15 992.67 0.05 6

Measurement #2

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 29/04/15 991.52 0.06 6

Measurement #3

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 05/05/15 991.69 0.04 6

Results

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Expanded uncertainty

(µmol/mol)

Coverage factor

Propane 02/10/2015 992.0 3.0 2

Calibration standards

‒ Method of preparation: A set of primary standard gas mixtures (PSMs) were prepared

according the gravimetric method described in ISO 6142. All PSMs are binary mixtures in

nitrogen and the three calibration standards were prepared in a two stage dilution process.

PSM xC3H8 assigned value

(mol/mol)

uC3H8 (mol/mol)

MRP292346 901.1 1.8

MRP292345 1002.2 1.5

MRP292344 1102.2 1.7

‒ Weighing data: In the case of PSM MRP292345, the mixture was prepared weighing 21.44 g

from a 0.035 mol/mol pre-mixture and 711.46 g nitrogen. All weights were over 20 g.

‒ Purity tables (composition) of the parent gases:

PROPANE (3.5) - Air Liquide NITROGEN (BIP) - Air Products

COMPONENT xi (mol/mol) ui (mol/mol) xi (mol/mol) ui (mol/mol)

Carbon monoxide 0.25 0.14

Carbon dioxide 2.5 1.4 0.25 0.14

Hydrogen 20 12 0.50 0.29

Oxygen 5.0 2.9 0.005 0 0.002 9

13

Nitrogen 20 12 999 998.94 0.35

Water 2.5 1.4 0.010 0 0.005 6

Propene 100 58

Propane 999 750 83

Hydrocarbons 100 58 0.05 0.029

‒ Verification measures: The PSMs gravimetric values were verified against older CEM PSMs

and their analytical uncertainties are considered for the PSMs assigned values.

Instrumentation

A 6890 Agilent GC equipped with a FID is used. The sample is injected on a 6 ft Porapak Q column

at 90 ºC with a He carrier. The FID temperature is 250 ºC. After rolling the cylinders, the sample and

the PSMs are connected to pressure regulators and to a sample box and a 0.25 mL sample loop is

flushed for three minutes before performing the injections for each mixture at the atmospheric

pressure.

Calibration method and value assignment

Mixtures are analyzed in the increasing order of concentration for propane under repeatability

conditions for three days. The calibration method according ISO 6143 for a linear function is used

with goodness of fit lower than 2 in all cases. The assigned value for propane concentration is the

average of the three individual values obtained.

Uncertainty evaluation

The expression for combined standard uncertainty, as follows, includes the quadratic sum of

individual standard uncertainties as obtained according ISO 6143 and the standard deviation of the

mean of individual values for propane concentration:

22

3

2

2

2

1

33

1)

s()uuu(u

c

The expanded uncertainty is obtained by multiplying the combined uncertainty with a k = 2 factor for

a confidence level of 95 %.

14

Measurement report of GUM

Laboratory name: Central Office of Measures (GUM)


Measurement #1

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 04.02.2015 992,71 0,3 9

Measurement #2

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 04.02.2015 991,21 0,3 9

Measurement #3

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 05.02.2015 995,08 0,3 9

Measurement #4

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 05.02.2015 992,84 0,3 9

Measurement #5

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 16.02.2015 992,04 0,3 9

Measurement #6

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 19.02.2015 993,47 0,3 9

Measurement #7

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 05.03.2015 993,92 0,3 9

Results

Component Date

(dd/mm/yy)

Result

(µmol/mol)


(µmol/mol)

Coverage factor

Propane 31.03.2015 993,0 4,0 2

15


Composition of calibration standards:

Cylinder number Component Assigned value

· 10-6

mol/mol

Standard uncertainty

· 10-6

mol/mol

M60280_2 C3H8 255,6 0,4

D752048_2 C3H8 418,0 2,1

D752069_4 C3H8 504,9 0,7

D752081_2 C3H8 791,3 1,1

03/29554_3 C3H8 990,8 0,8

D518827_2 C3H8 1001,7 1,8

D518853_2 C3H8 1003,2 1,4

M60278_2 C3H8 1502,5 2,1

D402436_3 C3H8 1998,1 2,8

Standards were prepared (by Central Office of Measures) by gravimetric method according to ISO

6142 from separate premixtures. The premixtures were prepared by using propane 3.5 and nitrogen

6.0. The minimal weighed sample of propane is 40 g and the minimal weighed sample of nitrogen is

400 g. The cylinders were evacuated on turbo molecular pump, filled up an weighted on the

verification balance. The one standard (03/29554_3) was prepared in steel cylinder, the other

standards were prepared in aluminum (with coated layers) cylinders. The standards were (and still are)

under metrological control.

Instrumentation

The measurements were repeated 9 times for the sample and the standards by gas chromatograph

Varian Cx 3600 with FID detector and with capillary column.

The cylinders (standards and sample) were in the same room for the whole time also during the

measurements (temperature stabilization) and the mixtures were mixed up before the measurements.

Samples were transferred to the instrument via the reducing valve and the automatic input pressure

stabilization system.


The measurements 1÷5 were made by using standards: 03/29554_3, D518827_2, D518853_2 by one

point calibration according to equation:

w

w

xx C

Y

YC

where:

xC – component concentration in sample gas mixture in mol/mol

wC – component concentration in standard gas mixture in mol/mol

xY – chromatograph answer for sample gas mixture

wY – chromatograph answer for standard gas mixture

16

The measurements 6 and 7 were made by calibration method according to ISO 6143 by using standards:

M60280_2, D752048_2, D752069_4, D752081_2, D518827_2, M60278_2, D402436_3. The

calibration curve was calculated from ratios by the software B_leats.exe (linear case). Measurement sequence:

standards (for calculation of calibration curve) and sample.


The final uncertainty, consists of the following components:

- the uncertainty of standard preparation calculated according to ISO 6142

- the standard deviation of the measurement

Resolution of the chromatograph is negligible.

17

Measurement report of IPQ

Laboratory name: Instituto Português da Qualidade (IPQ) Cylinder number: 153743 NOMINAL COMPOSITION - Propane : 1000 ×10

-6 mol/mol

- Nitrogen : matrix

Measurement No. 1

Date

Result (10

-6 mol/mol)

stand. deviation (% relative)

number of sub- measurements

C3H8 08-04-2015 999,0 0,1 3

Measurement No. 2

Date

Result (10

-6 mol/mol)



C3H8 14-04-2015 999,7 0,1 3

Measurement No. 3

Date

Result (10

-6 mol/mol)



C3H8 16-04-2015 999,7 0,3 3

Results:

Gas mixture

Result (assigned value) (10

-6 mol/mol)

Coverage factor

Assigned expanded uncertainty (10

-6 mol/mol)

C3H8 999,4 1,98 7,4

Reference Method: Non Dispersive Infrared Spectroscopy (NDIR): Analyzer: URAS 4 Data Collection: Auto-sampler - Software Sira version 2.0 Calibration Standards: The preparation was done according to ISO 6142:2001- Gravimetric method The estimated uncertainty was done according ISO GUM: 2005 “Guide to the Expression of Uncertainty in Measurement”. Composition of calibrants:

Propane cylinder Assigned value(x) (x10-6

mol/mol) Standard uncertainty (u(x)) (x10

-6 mol/mol)

NMI2714 200,1 0,8

PSM108966 520,7 1,5

PSM308339 599,7 1,6

PSM202605 1010,7 2,2

Instrument Calibration: The calibration instrument was done according to ISO 6143. We have used the B_Least program to determine the best model for data handling. All components of mixture have a goodness of fit less than 2 using a linear or quadratic function. For all components were used a set of four PSM. At least three repeated analyses were performed in three independent days. Manual calibration (zero and span are calibrated separately by pressing the analyzer system display and control unit softkeys). Sample Handling:

18

The cylinder was storage at ambient temperature in a storage room. The cylinder was connected to a valve to reduce the pressure. The samples were transferred to the analyser through an auto-sampler. Uncertainty:

The uncertainty measurement was done according ISO GUM: 2005 “Guide to the Expression of

Uncertainty in Measurement”.

The uncertainty of measurement associated with the final result has been evaluated and includes three main uncertainty sources:

- Uncertainty in calibration; - Uncertainty of repeatability; - Uncertainty of reproducibility

These uncertainties were combined and the result was multiplied by a coverage factor with a

confidence interval of 95 %.

Uncertainty table: C3H8

Uncertainty source XI

Estimate xI

Assumed distribution

Standard uncertainty u(xi) (mol/mol)

Sensitivity coefficient cI

Contribution to standard uncertainty uI(y) (mol/mol)

Repeatability normal 9,600 ×10-7

1 9,600 ×10-7

Reproducibility normal 2,445 ×10-7

1 2,445 ×10-7

Calibration normal 3,617 ×10-6

1 3,617 ×10-6

Coverage factor: 1,98 Expanded uncertainty: 7,4 ×10

-6 mol/mol

19

Measurement report of LNE

Laboratory name: Laboratoire national de métrologie et d'essais (LNE)

Cylinder number: N°153769SG

Measurement #1

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 12/03/15 991.00 0.05 3

Measurement #2

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 13/03/15 991.17 0.11 3

Measurement #3

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 16/03/15 991.07 0.06 3

Results

Component Date

(dd/mm/yy)

Result

(µmol/mol)


(µmol/mol)

Coverage factor

Propane 991.1 1.8 2


The reference gas mixtures were prepared according to the gravimetric preparation method ISO 6142

from pure gases (propane and nitrogen).

A first high concentration gas mixture was prepared at about 2.6 10-2

mol/mol (C3H8/N2 0031) and

was diluted by the gravimetric method to prepare a gas mixture of propane in nitrogen at about

1000 µmol/mol (C3H8/N2 0032).

The mass of each component was determined by weighing the cylinder on a Mettler mass comparator

(32 kg with a resolution of 0.1 mg).

The purities of all used gases and the values of the masses introduced are shown in the following

tables.

20

Gravimetric composition of cylinder C3H8_N2_0032

Date: 09/03/2015

Time: 16:45:13

Operator: fm Mixture prepared by: lne

Lab book: le 09/03/15

OUTPUTS

=======

Component µmol/mol uncertainty % u/c

---------------------------------------------------------

N2 999004.5931 0.41030628 0.000

propane 995.0880162 0.38532651 0.039

propene 0.09953369 0.05746023 57.729

CnHm 0.09953369 0.05745997 57.729

H2 0.04488185 0.01799978 40.105

methane 0.02497512 0.01385279 55.466

CO2 0.01497590 0.00709266 47.361

CO 0.01248756 0.00694564 55.620

H2O 0.01247839 0.05562212 445.748

O2 0.00997171 0.00399818 40.095

N2O 0.00000599 0.00000144 24.073

INPUTS

======

File Mass (g) u/c (g)

--------------------------------------

melanges\C3H8_N2 60.05484 0.01700

Pur\N2_bip.txt 1468.434 0.02000

INPUT DATA FILES

================

°°°°°°°°°° melanges\C3H8_N2_0031.txt °°°°°°°°°°°

Component mol/mol uncertainty

------------------------------------------------

N2 0.9743086236 0.0000076518

propane 0.0256853796 0.0000073469

propene 0.0000025692 0.0000014832

CnHm 0.0000025692 0.0000014832

H2 0.0000005382 0.0000002970

O2 0.0000001333 0.0000000742

CO2 0.0000000764 0.0000000377

H2O 0.0000000740 0.0000000674

methane 0.0000000244 0.0000000140

CO 0.0000000122 0.0000000070

N2O 0.0000000000 0.0000000000

21

°°°°°°°°°°°°°°°° Pur\N2_bip.txt °°°°°°°°°°°°°°°°


------------------------------------------------

N2 0.9999999100 0.0000000520

O2 0.0000000050 0.0000000029

H2O 0.0000000100 0.0000000578

methane 0.0000000250 0.0000000144

CO2 0.0000000125 0.0000000072

CO 0.0000000125 0.0000000072

H2 0.0000000250 0.0000000144

N2O 0.0000000000 0.0000000000

Gravimetric composition of cylinder C3H8_N2_0031

Date: 11/02/2015

Time: 11:10:36

Operator: fm Mixture prepared by: lne

Lab book: le 28/01/2015

OUTPUTS

=======

Component µmol/mol uncertainty % u/c

---------------------------------------------------------

N2 974308.6236 7.65181592 0.001

propane 25685.37962 7.34689348 0.029

propene 2.56918026 1.48317849 57.730

CnHm 2.56918026 1.48317189 57.729

H2 0.53819376 0.29699459 55.184

O2 0.13333055 0.07422027 55.666

CO2 0.07640836 0.03774477 49.399

H2O 0.07397259 0.06742824 91.153

methane 0.02435770 0.01403004 57.600

CO 0.01217885 0.00703451 57.760

N2O 0.00000585 0.00000146 25.000

INPUTS

======

File Mass (g) u/c (g)

--------------------------------------

Pur\C3H8pur_0004 60.65832 0.01700

Pur\N2_bip.txt 1461.431 0.02000

22

INPUT DATA FILES

================

°°°°°°°°°°°°° Pur\C3H8pur_0004.txt °°°°°°°°°°°°°


------------------------------------------------

propane 0.9997500000 0.0000833417

CO2 0.0000025000 0.0000014434

propene 0.0001000000 0.0000577350

O2 0.0000050000 0.0000028868

N2 0.0000200000 0.0000115470

H2O 0.0000025000 0.0000014434

H2 0.0000200000 0.0000115470

CnHm 0.0001000000 0.0000577350

°°°°°°°°°°°°°°°° Pur\N2_bip.txt °°°°°°°°°°°°°°°°


------------------------------------------------

N2 0.9999999100 0.0000000520

O2 0.0000000050 0.0000000029

H2O 0.0000000100 0.0000000578

methane 0.0000000250 0.0000000144

CO2 0.0000000125 0.0000000072

CO 0.0000000125 0.0000000072

H2 0.0000000250 0.0000000144

N2O 0.0000000000 0.0000000000

The concentration of the prepared gas mixture was verified by the same chromatographic analytical

method than the method used for the comparison.

Instrumentation

The propane concentration was determined by chromatographic analysis on a µGC model 2003 from

Chrompack with a TCD detector and a 0.4 m Hayesep column.

The column was maintained at 120°C ; a flow of helium at a pressure of 150 kPa passed through the

column.

A sample loop was used for the injection of the gas during 200 ms, and a typical chromatogram was

performed in 40 seconds.


The gas chromatograph was calibrated at a single point close to the concentration of the sample gas

according to the sequence “reference gas mixture/sample gas/ reference gas mixture” with 30 runs for

each gas (only the last ten runs were used for the calculation).

The concentration of the sample gas was determined as follows:

21

2refref

refech

SS

CSC

With:

Sref1 : Average of the last 10 areas of the propane peak of the reference gas mixture

C3H8/N2 0032 at the beginning of the tests

23

Sech : Average of the last 10 areas of the propane peak of the sample gas N°153769 SG

Sref2 : Average of the last 10 areas of the propane peak of the reference gas mixture

C3H8/N2 0032 at the end of the tests

Cref : Concentration of the reference gas mixture C3H8/N2 0032

The procedure is repeated three times per day and on 3 different days.

The final concentration is the average of the three determinations obtained on the 3 different days.


The uncertainty budget is established by combining the uncertainty on the concentration of the

reference gas mixture and the repeatability and reproducibility standard deviations of the

measurements; they are sum up in the following table.

Uncertainty source Estimate

xI (µmol/mol)

Assumed

distribution

Standard

uncertainty

u(xi) (µmol/mol)

Mean concentration obtained by

comparison with the reference gas

mixture

- Mean standard deviation of the

values 2rS

0.78

Reproducibility of the three

measurements -

Standard deviation of the values

2RS

0.086

Concentration of the reference gas

mixture (C3H8/N2 0032) 995.09 - 0.39

The uncertainty on the concentration of the sample gas mixture is given by:

2222Rr0032 C3H8/N2SG SS) C(u)C(u

222 0860780390 ).().(.()C(u SG

mol/µmol .)C(u SG 880

mol/µmol . .C SG 811991

24

Measurement report of METAS

Laboratory name: Federal Institute of Metrology METAS

Cylinder number: VSL 153322

Measurement #1

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 12.03.2015 996.1 0.01 4

Measurement #2

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 16.03.2015 996.1 0.01 4

Measurement #3

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 18.03.2015 996.0 0.01 4

Results

Component Date

(dd/mm/yy)

Result

(µmol/mol)


(µmol/mol)

Coverage factor

Propane 01.04.2015 996.0 4.0 2


Reference 1: Cylinder No. Messer 80510 with METAS value (100.0 ± 0.8) mol/mol

Reference 2: Cylinder No. Carbagas 55101 with METAS value (100.1 ± 0.9) mol/mol

Reference 3: Cylinder No. Messer 76512 with METAS value (300.8 ± 2.5) mol/mol

Reference 4: Cylinder No. PanGas 221572 with METAS value (299.0 ± 2.4) mol/mol

Reference 5: Cylinder No. PanGas 225881 with METAS value (600.0 ± 4.8) mol/mol

Reference 6: Cylinder No. PanGas 2942 with METAS value (1002 ± 9) mol/mol

Reference 7: Cylinder No. Carbagas 7243 with METAS value (998 ± 8) mol/mol

Reference 8: Cylinder No. PanGas 221993 with METAS value (1997 ± 16) mol/mol

Purity: - Carbagas: C3H8: 3.5 N2 (Matrix): 5.7

- Messer: C3H8: 3.5 N2 (Matrix): 6.0

- PanGas: C3H8: 3.5 N2 (Matrix): 5.0

Instrumentation

A fully automatic pressure controlled Gas-Chromatograph with FID (Orthodyne S.A., Belgium) was

used with an autosampler (Swagelok IGC-III, all gas conduits are electropolished and pneumatically

controlled).

Sample Handling: The sample flow through the sample loop of the injector is controlled at 60 ml/min

@ 0 °C/1013 hPa, the pressure of the sample flow after the sample loop is also controlled at 1000 hPa

absolute.

25


The transfer standard has been compared against 8 standard mixtures. These mixtures were cylinders

out of the set of national reference gas mixtures for C3H8 in nitrogen in the range between

100 μmol/mol to 2000 μmol/mol C3H8.

The area results (responses) of known calculated mixtures and the unknown mixture have been

evaluated using the bracketing technique with a linear regression according to ISO standard 6143 by

using the programme B-Least.


Result:

Quantity Value Unit Expanded

Uncertainty

Coverage-

factor Coverage

Xmean 996.0 mol/mol 0.40 % (rel.) 2.00 95%

(t-table 95.45 %)

Budget:

Quantity Value Unit Standard

Uncertainty

Degrees of

Freedom

Distri-

bution

Sensitivity

Coefficient

Uncertainty

Contribution Index

x1 996.1 mol/mol 1.8 50 0.33 0.6 mol/mol 28.7 %

x2 996.1 mol/mol 1.8 50 0.33 0.6 mol/mol 28.4 %

x3 996.0 mol/mol 1.8 50 0.33 0.6 mol/mol 28.4 %

Fnc 1) 1.000 0.00075 50 normal 1000 0.8 mol/mol 14.6 %

1) factor for non-accounted correlations

26

Measurement report of MKEH

Laboratory name: Hungarian Trade Licensing Office (MKEH)


Measurement #1

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 28/04/2015 998.9 0.15 3

Measurement #2

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 29/04/2015 1003.8 0.17 3

Measurement #3

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 30/04/2015 999.8 0.25 3

Results

Component Date

(dd/mm/yy)

Result

(µmol/mol)


(µmol/mol)

Coverage factor

Propane 30/04/2015 1000.8 6.8 2


10 L aluminium cylinder (Luxfer) with stainless steel valve, high purity Propane (99,979%, unknown source of the origin, controlled by GC-FID-TCD for purity) and N2 (99.995%, Messer, Hungary, controlled by GC-FID-TCD and electrochemical sensor and mirror dew point meter for purity) gases were used for the preparation of the primary standard gas diluted by three steps: 8.8492 %(n/n), 1.0051 %(n/n) and 1003.17 ppm(n/n). The mass measurements of the gases were carried out by a balance (Mettler Toledo XP 26003 L) with repeatability of 0.0015 g and capacity of 15000 g. Purity table of Propane

Pure Propane Concentration %(mol/mol)

Uncertainty %(mol/mol)

Propane 99.9790 ± 0.0020

Nitrogen 0.0030 ± 0.0001

Methane 0.0060 ± 0.0001

Carbon-dioxide 0.0120 ± 0.0001

Purity table of Nitrogen

Pure Nitrogen Concentration %(mol/mol)

Uncertainty %(mol/mol)

Nitrogen 99.9988 ± 0.0020

Water 0.00050 ± 0.0001

Methane 0.00125 ± 0.0001

Oxygen 0.00050 ± 0.0001

Carbon-monoxide 0.00005 ± 0.0001

27

Instrument Calibration: MKEH primary standard No: OMH 31/2015.03.25. Propane: 1003.17 ppm ± 0.65 ppm(mol/mol) The measurement with a MKEH primary standard with 1000 ppm Propane nominal concentration. The standard gas and the sample gas were changed in every 20 minutes. The temperature and pressure correction were not done. Sample Handling: We used stainless steel valve for the cylinders and 50 mbar was set up on flow measurement, and the flow was stable.

Instrumentation

Gas chromatography (HP6890 GC-FID) was used to analyze Propane/N2 gas. The flow rate of the gases was controlled by EPC. Column: Porapack PS 4.4m, 0.75mm ID, Sulfinert; oven temp.: 70˚C; Carrier gas: 4.5 bar He to FID.


Reference Method: Gas chromatography (HP6890 GC-FID-TCD) was used to analyze Propane/N2 gas. The measurement method was direct comparison with a standard which has the same nominal concentration as the sample.


The potential sources of the uncertainty: Uncertainty of the primary reference material.

Uncertainty of calibration measurement series. Standard deviation of measurement series. Uncertainty table 1: Propane


Estimate xI


Standard uncertainty u(xi)


Contribution to standard uncertainty uI(y)

Standard reference material

1003.17 ppm(mol/mol)

ormal

0.325 ppm(mol/mol)

1

0.032

Standard deviation of the calibration measurement series

568.86 area

Normal

0.79 area

1

0.14

Standard deviation of the measurement series

566.47 area

Normal

0.31 area

1

0.06

Variancia

998.94 ppm(mol/mol)

1.52 ppm(mol/mol)

0.15

28

Uncertainty table 2: Propane


Estimate xI







Normal

0.325 ppm(mol/mol)

1

0.032


574.43 area

Normal

0.63 area

1

0.11


574.80 area

Normal

0.71 area

1

0.12

Variancia


1.69 ppm(mol/mol)

0.17

Uncertainty table 3: Propane


Estimate xI







Normal

0.325 ppm(mol/mol)

1

0.032


575.37 area

Normal

1.42 area

1

0.25


573,45 area

Normal

0.30 area

1

0.05

Variancia

999.82 ppm(mol/mol)

2.54 ppm(mol/mol)

0.25

Propane concentration: 1000.8 ppm (n/n) Coverage factor: 2 Expanded uncertainty: 6.8 ppm (mol/mol), Ui= 0.67

References

A van der Veen, Gergely Vargha, Éva Deák at all, CCQM key comparison CCQM-K3 of

measurements of CO, CO2, and C3H8 in N2, 2002 Metrologia 39 121. doi:10.1088/0026-1394/39/1/18,

29

Measurement report of UME

Laboratory name: National Metrology Institute TÜBİTAK (UME)

Cylinder number: VSL 178727

Measurement #1

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 24/03/2015 991.29 0.09 10

Measurement #2

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 25/03/2015 990.00 0.17 10

Measurement #3

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 25/03/2015 991.37 0.15 10

Measurement #4

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 27/03/2015 991.29 0.13 10

Measurement #5

Component Date

(dd/mm/yy)

Result

(µmol/mol)

Standard deviation

(% relative)


Propane 27/03/2015 991.37 0.13 10

Results

Component Date

(dd/mm/yy)

Result

(µmol/mol)


(µmol/mol)

Coverage factor

Propane 30/03/2015 991.06 1.75 2


Primary reference gas mixtures used in calibration are given in the Table 1. All the primary standards

are binary mixtures of propane in nitrogen. They were prepared individually according to ISO 6142

“Gas analysis - Preparation of calibration gases - Gravimetric Method” at TÜBİTAK UME. Three

different pre-mixtures were individually prepared from pure propane and nitrogen gases. Then, pre-

mixtures were diluted with the same pure nitrogen gas to prepare the standards. Pure propane (3.5

grade) and nitrogen (6.0 grade) were from Air Liquide Germany and Linde Gas Turkey, respectively.

The content of the impurities in the pure gases were determined based on the gas producers’

specifications. The uncertainties of the mixtures given in Table 1 were determined by combining the

standard uncertainties of weighing, purity and molar masses.

30

Table 1. List of primary reference gas mixtures

Item Prepared

By

Cylinder

Number

Mole Fraction

(µmol/mol) Uncertainty (k=1)

(µmol/mol)

1 UME 249096 947.43 0.47

2 UME 249207 1002.12 0.61

3 UME 249095 1039.90 0.62

Instrumentation

The propane in nitrogen was analyzed on an Agilent 6890N gas chromatography instrument equipped

with FID, split/splitless injector, gas injection valve, including Chemstation software (ver Rev. A.

10.02 [1757]) to collect and process data. The conditions for the analyses are given below:

Conditions:

Carrier gas : Helium

Inlet:

Mode : Split

Split ratio : 5:1

Injection temperature : 100 ºC

Sample loop : 1 ml

Column:

Type : HP-PLOT Q 30 m, 0.32 mm, 20 μm (19091P-Q04)

Flow rate : 8.0 ml/min (constant flow)

Oven:

Temperature : Isothermal @ 100 ºC

Duration : 5 min

Detector:

Type : FID

Temperature : 300 ºC

H2 flow rate : 40 ml/min

Air flow rate : 400 ml/min

Aux:

Valve box temperature : 100 ºC

Signal:

Data rate : 20 Hz

Sample injection:

Duration : between 0.1 and 0.6 min.


After the arrival of the cylinder from VSL, it was stored in the laboratory where the analyses were

carried out. Three primary standard gas mixtures were also stored in the same laboratory during all the

measurements. The cylinder and the calibration standards were equipped with pressure reducers and

connected to computer programmed multiposition valve gas sampling box. They were flushed before

the first measurement. The flow rates of sample and standard gases were controlled by a mass flow

controller at 40 ml/min.

The data was collected using Chemstation software. Each sample in the sequence was injected 12

times, and the first two injections in each case were discarded as they were considered as flushing of

sample loop. The responses were averaged. The software “B_Least” was utilized to determine the

31

fitting data for the calibrations. The value for goodness of fit in each measurement was found to be

less than 2 for linear function.

The assigned value was calculated by averaging the results of five independent measurements.


The measurement uncertainty of sample was determined according to ISO 6143 “Gas analysis -

Comparison methods for determining and checking the composition of calibration gas mixtures”

standard, using the B_Least software.

The combined standard uncertainty was determined by the following equation:

where

um, standard uncertainty from measurements

ug, standard uncertainty from gravimetric preparation

um = 0.064 % rel. (determined by selecting the largest uncertainty value among the obtained

uncertainties for each measurement)

ug = 0.061 % rel. (determined by selecting the largest uncertainty value among the uncertainties of

primary reference gas mixtures)

uc was determined as 0.088 % rel.

The expanded uncertainty was determined by multiplying the combined standard uncertainty by a

coverage factor of 2 with a confidence interval of 95%.

32

Measurement report of VSL

Laboratory name: Van Swinden Labratorium B.V. (VSL)


Measurement #1 (GC-6)

Component Date (yyyy-mm-dd)

Result

(mol/mol)

Standard deviation

(% relative) Number of replicates

C3H8 2014-05-22 993.90 × 10-6

0.02 6



Result

(mol/mol)

Standard deviation


C3H8 2014-05-27 993.80 × 10-6

0.03 6



Result

(mol/mol)

Standard deviation


C3H8 2014-06-11 992.77 × 10-6

0.02 6



Result

(mol/mol)

Standard deviation


C3H8 2014-06-12 993.30 × 10-6

0.02 6

Results

Component Result

(mol/mol)

Expanded Uncertainty

(mol/mol) Coverage factor5

C3H8 993.4 × 10-6

0.7 × 10-6

2

Reference Method and calibration:

Propane is analyzed on an Agilent 6890 GC equipped with a FID. Three times the sample is injected

on a 10 ft Porapak N column at 145 °C with a helium carrier (GC-6). One time the sample is injected

on a 10 ft Porapak T column at 150 °C with a hydrogen carrier (GC-3). Together with the CCQM-

K111 sample cylinder also 4 PSMs of C3H8 in N2 are connected to a computer programmed

multiposition valve gas sampling box. A sample loop, 1 mL in GC-6 and 0.25 mL in GC-3, is flushed

for 3 minutes before performing 6 injections for each mixture. A straight line is used as calibration

function in the regression analysis for propane. A correction cylinder is used for eliminating the

instrument drift. Each measurement is preformed in compliance with ISO 6143 [5].

Calibration Standards:

All Primary Standard gas Mixtures (PSMs) for the measurements of C3H8 are binary mixtures in

nitrogen. Preparation is performed according ISO 6142 [4]. The standard uncertainty is based on the

uncertainty of the gravimetric preparation process and the purity analysis of the parent gases.

5 The coverage factor shall be based on approximately 95% confidence.

33

Table 1: Purity table of propane.

Chemical symbol Amount fraction

x (mol/mol)


ux (mol/mol)

C2H6 0.0000001 0.00000001

C3H6 0.000114 0.000011

C3H8 0.9998556 0.000015

C4H8 0.00000006 0.00000003

n-C4H10 0.0000016 0.00000016

i-C4H10 0.00000023 0.00000003

1-C5H10 0.0000004 0.0000002

n-C5H10 0.00000004 0.00000002

Table 2: Purity table of nitrogen.

Chemical symbol Amount fraction

x (mol/mol)


ux (mol/mol)

H2 0.000005 0.000003

H2O 0.00000001 0.000000006

CH4 0.000000008 0.000000005

N2 0.999994927 0.000006

CO 0.000000015 0.000000009

O2 0.000000005 0.000000003

Ar 0.000005 0.000003

CO2 0.00000001 0.000000006

Table 3: Composition of PSMs and correction cylinder.

Component Cylinder number Assigned value

x (mol/mol)


u(x) (mol/mol)

C3H8 VSL303807 400.17 × 10-6

0.06 × 10-6

VSL204663 600.35 × 10-6

0.08 × 10-6

VSL328517 799.06 × 10-6

0.10 × 10-6

VSL238482 999.60 × 10-6

0.27 × 10-6

Correction

cylinder VSL423616 1000.90 × 10-6

0.27 × 10-6

Sample handling:

The CCQM-K111 cylinder 153513 and the PSMs used for calibration are equipped with a pressure

regulator. Sampling takes place with automated multiposition valve sample boxes as described in

VSL‘s work instructions for routine analyses.

Evaluation of measurement uncertainty:

The calibration curves where obtained in accordance with ISO 6143 [5]. As indicated, a straight line

was used. From the uncertainty associated with the amount-of-substance fractions propane of the

calibration mixtures and the repeatability standard deviation of the analyses of the calibration

mixtures and the sample mixture, the amount-of-substance fraction propane and its associated

standard uncertainty where calculated.

To arrive at the final result, the results of the four measurements were averaged. The standard error of

the mean was combined with the pooled uncertainty from evaluating the data from the calibration of

the GCs.

34

Table 4: Uncertainty evaluation

fit value

(mol/mol)

standard

uncertainty

u#x (mol/mol)

Expanded

Uncertainty

#1 9.9390 × 10-4

1.97 × 10-7

#2 9.9380 × 10-4

2.69 × 10-7

#3 9.9277 × 10-4

1.97 × 10-7

#4 9.9330 × 10-4

1.97 × 10-7

Standard

deviation 5.1951 × 10

-7 2.60 × 10

-7

mean 9.9344 × 10-4

6.77 × 10-7

The standard error of the mean is 2.17 × 10-7

and the pooled standard uncertainty is 2.60 × 10-7

. These

standard uncertainties were combined using the law of propagation of uncertainty. The expanded

uncertainty was obtained by multiplying the standard uncertainty with a coverage factor of k = 2.

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