Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
Report of key comparison CCQM – K92
"Electrolytic conductivity at 0.05 S·m-1 and 20 S·m-1“
Final report
L. Vyskočil, M. Máriássy (SMU),Adrian Reyes, Marcela Monroy (CENAM), Alena Vospělová (ČMI), Bertil Magnusson,Rauno Pyykkö (SP), Elena Kardash (INPL), Fabiano Barbieri Gonzaga, I.C.S. Fraga, J.C.Lopes, W.B. Silva Jr, P.P. Borges, W.F.C. Rocha (INMETRO), Francesca Durbiano, E. Orrù(INRiM), Kenneth W. Pratt (NIST), Pia Tønnes Jakobsen, Hans Dalsgaard Jensen, JørgenAvnskjold (DFM), L.A. Konopelko, Y.A. Kustikov, V.I. Suvorov (VNIIM), Song Xiaoping,Wang Hai (NIM), Steffen Seitz, Petra Spitzer (PTB), Vladimir Gavrilkin, Leonid Prokopenko,Oleksiy Stennik (Ukrmetrteststandart), Wladyslaw Kozlowski, Joanna Dumanska - Kulpa,Izabela Grzybowska (GUM), Yury A. Ovchinnikov (VNIIFTRI), Zsófia Nagyné Szilágyi,Judit Fükö (MKEH)
July 2013
Slovak Institute of MetrologyKarloveská 63, SK-84255 Bratislava 4, Slovakia
CCQM-K92 2
Abstract
The aim of the key comparison CCQM-K92 was to demonstrate the capabilities of the par-ticipating NMIs to measure electrolytic conductivity of an unknown sample.
Two samples with nominal electrolytic conductivity values of 0.05 S·m-1 and 20 S·m-1 havebeen prepared for comparison. For the first time conductivity value larger than those given inthe IUPAC document [1] was measured in CCQM comparison. Thus no calibration standardswith similar conductivity value were available. The comparison was an activity of the Elec-trochemical Working Group (EAWG) of the CCQM and was coordinated by SMU.
In the comparison NMIs from fifteen countries took part. The higher conductivity (20 S·m-1)was measured by ten participants. Good agreement of the results was observed for the major-ity of participants.
CCQM-K92 3
Contents
ABSTRACT .............................................................................................................................................................. 2
INTRODUCTION................................................................................................................................................ 4
METROLOGY AREA .................................................................................................................................................. 4BRANCH ................................................................................................................................................................ 4SUBJECT ................................................................................................................................................................ 4TIME SCHEDULE ...................................................................................................................................................... 4PARTICIPANTS......................................................................................................................................................... 4
SAMPLE DESCRIPTION...................................................................................................................................... 5
SAMPLE PREPARATION AND DISTRIBUTION.................................................................................................................... 5REPLACEMENT SAMPLE PREPARATION.......................................................................................................................... 5CHECK OF HOMOGENEITY ......................................................................................................................................... 6CHECK OF STABILITY................................................................................................................................................. 7STATISTICAL TESTING OF STABILITY .............................................................................................................................. 9
RESULTS ......................................................................................................................................................... 10
SAMPLE WITH NOMINAL VALUE 0.05 S·M-1
................................................................................................................ 10SAMPLE WITH NOMINAL VALUE 20 S·M
-1................................................................................................................... 12
DISCUSSION ................................................................................................................................................... 14
THE FORMULAS FOR CALCULATION OF ESTIMATORS ..................................................................................................... 14CALCULATION OF THE DEGREES OF EQUIVALENCE ........................................................................................................ 14COMMUNICATION WITH THE PARTICIPANTS ................................................................................................................ 15REFERENCE VALUE FOR 0.05 S·M
-1.......................................................................................................................... 15
Degrees of Equivalence - 0.05 S·m-1
............................................................................................................. 16
REFERENCE VALUE FOR 20 S·M-1
............................................................................................................................. 17Degrees of Equivalence - 20 S·m
-1................................................................................................................ 18
CONCLUSIONS ...................................................................................................................................................... 19ACKNOWLEDGMENT .............................................................................................................................................. 19
REFERENCES ................................................................................................................................................... 19
APPENDIX....................................................................................................................................................... 20
ADDRESSES OF PARTICIPANTS................................................................................................................................... 20
CCQM-K92 4
Introduction
Metrology AreaAmount of Substance
BranchElectrochemistry
SubjectDetermination of the electrolytic conductivity of two unknown samples with nominalvalue 0.05 S·m-1 a 20 S·m-1 (Water solution of KCl).
Time scheduleDispatch of the samples 9 February 2011Deadline for receipt of the report 25 April 2011Discussion of results EAWG meeting, April 2011 Draft A report October 2011 Draft B report September 2012 Draft B report corrected February 2013
Participants
Participants are listed in Table 1. VNIIM and VNIIFTRI measured one sample each, as theirresponsibilities are in different ranges in electrolytic conductivity.
Table 1 Table of Participants
No
Acronym Institute Country Contact Person
1 CENAM CENAM MEXAdrian Reyes,Marcela Monroy
2 CMI Český metrologický ústav CZE Alena Vospělová
3 DFM Danish Fundamental Metrology DNK Pia Tønnes Jakobsen
4 GUM Central Office of Measures POL Wladyslaw Kozlowski
5 INMETRONational Institute of Metrology, Quality andTechnology
BRA Fabiano Barbieri Gonzaga
6 INPL The National Physical Laboratory of Israel ISR Elena Kardash
7 INRiM Instituto Nazionale di Ricerca Metrologica ITA Francesca Durbiano
8 MKEH Hungarian Trade Licensing Office HUN Zsófia Nagyné Szilágyi
9 NIM National Institute of Metrology CHN Song Xiaoping
10 NIST National Institute of Standards and Technology USA Kenneth W. Pratt
11 PTB Physikalisch-Technische Bundesanstalt DEU Steffen Seitz
12 SMU Slovenský metrologický ústav SVK Leoš Vyskočil
13 SP SP Technical Research Institute of Sweden SWE Bertil Magnusson
CCQM-K92 5
14 UMTS Ukrmetrteststandart UKR Vladimir Gavrilkin
15 VNIIFTRINational Research Institute Physicotechnicaland Radio Engineering Measurements
RUS Yury A. Ovchinnikov
16 VNIIM D.I. Mendeleyev Institute for Metrology RUS Prof. L.A. Konopelko
Sample description
Sample preparation and distribution
Samples consisted of water solutions of potassium chloride. Reagent grade KCl and distilledwater were used for the solution with electrolytic conductivity 20 S·m-1. The 0.05 S·m-1 solu-tion was prepared by diluting the above solution with distilled water. Both solutions were pre-pared on February 2, 2001. The solutions were filled into 500 mL HDPE bottles (Nalgene),which were subsequently sealed into aluminium laminated plastic foil to prevent compositionchange of the solutions.The samples were distributed to the participants on February 9, 2011 by courier companiesFedEx and DHL (Russia, Mexico). In one case (NIM, China) the sample was received dam-aged. A replacement bottle was sent immediately and was received intact. The sample sent toMoscow stuck at the customs and was later returned to SMU. The second shipment arrived atits destination.
Replacement sample preparation
Some participants reported instability of 0.05 S·m-1 sample after opening, and the same effectwas confirmed by the coordinating laboratory. Therefore a new batch of this solution wasprepared from high-purity KCl and deionised water and the new samples were distributed tothe participants free of charge. The stability of new samples after opening was satisfactory.
Check of the bottle integrity
Participants were requested to weigh the received bottles to verify that they were unchangedduring the transport. The mass change was smaller than 0.05 g in all cases except VNIIM,where the difference amounted up to 0.5 g, and NIM that reported one leaking bottle with KClcrystallisation in the bag. NIM was sent a replacement bottle.
Figure 1 Relative differences between the weights of bottles - 0,05 S·m-1
CCQM-K92 6
Relative differences between the weights of bottles - 0,05 S·m-1
-0,010%
-0,008%
-0,006%
-0,004%
-0,002%
0,000%
0,002%
0,004%
0,006%
0,008%
0,010%
DNK MEX CZE POL BRA ISR ITA ITA HUN CHN DEU SVK SWE UKR RUS USA
Figure 2 Relative differences between the weights of bottles - 20 S·m-1
Relative differences between the weights of bottles - 20 S·m-1
-0,010%
-0,008%
-0,006%
-0,004%
-0,002%
0,000%
0,002%
0,004%
0,006%
0,008%
0,010%
DNK DNK MEX POL BRA ISR HUN CHN DEU UKR RUS
Check of Homogeneity
Homogeneity of the solution was checked after filling. To identify possible trends, solutionsfrom the first and the last bottle were measured. Both results were identical within uncertaintyof measurement. The data are depicted in figures 3 and 4.
CCQM-K92 7
Figure 3 Check of homogeneity for 20 S·m-1 solution
Check of Homogeneity for 20,0 S/m
20,20
20,22
20,24
20,26
20,28
20,30
20,32
20,34
Co
nd
uct
ivit
y
( S
/m)
First bottle Last bottle
Figure 4 Check of homogeneity for 0.05 S·m-1 solution
Check of Homogeneity for 0,05 S/m
0,04985
0,04990
0,04995
0,05000
0,05005
0,05010
0,05015
0,05020
Co
nd
uct
ivit
y
( S
/m)
First bottleLast bottle
Check of Stability
Several bottles were selected for stability measurements. Samples were measured in irregularintervals during 80 to 90 days. The measurement results for solution with nominal conductiv-ity 0.05 S·m-1 are given in figure 5 and table 2.
Figure 5 The stability measurement for sample with nominal conductivity value 0.05 S·m-1
CCQM-K92 8
Measurement of Stability for 0,05 S/m
0,04990
0,04995
0,05000
0,05005
0,05010
0,05015
0,05020
0 20 40 60 80 100Days
Co
nd
uct
ivit
y S
/m
Table 2 The stability Measurement for Sample with Nominal Value 0.05 S·m-1
Days Date Bottle Conductivity(S.m-1)
U (k=2)(S.m-1)
0 2011-03-22 B3 0,050040 0,0000310 2011-03-22 B3 0,050041 0,00003149 2011-05-10 B3 0,050058 0,00003149 2011-05-10 B3 0,050031 0,00003159 2011-05-20 B17 0,050034 0,00003159 2011-05-20 B17 0,050033 0,00003179 2011-06-09 B10 0,050054 0,00003179 2011-06-09 B10 0,050052 0,000031
The measurement results for solution with nominal conductivity 20 S·m-1 are given in figure 6and table 3.
Figure 6 The stability measurement for sample with nominal conductivity value 20 S·m-1
CCQM-K92 9
Measurement of Stability for 20 S/m
20,240
20,250
20,260
20,270
20,280
20,290
20,300
20,310
20,320
0 20 40 60 80 100Days
Co
nd
uct
ivit
y S
/m
Table 3 The stability measurement for sample with nominal conductivity value 20 S·m-1
Days Date Bottle Conductivity(S.m-1)
U (k=2)(S.m-1)
0 2011-03-09 B9 20,288 0,0120 2011-03-09 B9 20,287 0,0120 2011-03-09 B9 20,287 0,0120 2011-03-09 B9 20,287 0,0122 2011-03-11 B9 20,288 0,0122 2011-03-11 B1 20,288 0,0122 2011-03-11 B1 20,288 0,0122 2011-03-11 B1 20,287 0,01262 2011-05-10 B1 20,287 0,01262 2011-05-10 B18 20,287 0,01272 2011-05-20 B18 20,287 0,01272 2011-05-20 B18 20,287 0,01292 2011-06-09 B24 20,288 0,01292 2011-06-09 B24 20,288 0,012
Statistical testing of stability
The statistical testing of stability is based on the fact, that for a stable sample the is the trendstatistically not significant. Either a test of correlation coefficient can be used the slope ofa regression line can be tested. The procedure for the test of the slope is following:Using least-squares regression the slope b1 of the regression line and residual variance sR arecalculated. Test criterion t is calculated as follows:
CCQM-K92 10
( )R
i
s
xxbt
21 −
= (1)
In the statistical tables for critical values of Student distribution a critical value tα(n-2) for (n-2) degrees of freedom at significance level α=0,05 (95 % probability) is looked up. If thevalue of the test criterion does not exceed the critical value, the slope is statistically not sig-nificant.
Table 4 Results of Statistical Testing of Stability
Sample Value of Test.
Criterion t
Critical
Value
Degrees of
Freedom
Significance
Level
Verdict
0,05 S/m 0,779 2,447 6 0,05No trend was
observed
20,0 S/m 1,241 2,197 12 0,05No trend was
observed
As can be seen from the data in table 4, for both solutions the stability during the given timeperiod was confirmed.
Results
Sample with nominal value 0.05 S·m-1
The measurement conditions and methods used at different institutes are given in Table 5.The results of measurements of the new sample with nominal conductivity of 0.05 S·m-1 aregiven in Table 6 and displayed graphically in Figure 7. Four laboratories from 15 useda primary measurement procedure.
Table 5 Conditions of Measurement at Various Institutes - 0.05 S·m-1
Institute CountryDate of
reportTraceability Measurement
frequency
[Hz]
DFM DNK 2011-04-13 Primary CRM DFM Jones type cell 111 - 1000
CENAM MEX 2011-04-25 SMU CRM Jones type cell 1000 - 3000
CMI CZE 2011-06-01Primary
measurementRemovable central part 1000
GUM POL 2011-04-22 DFM CRM Jones type cell 12 - 1820
INMETRO BRA 2011-04-20Primary
measurementPiston type 20 - 5000
INPL ISR 2011-04-06 SMU CRM Four electrode DC cell DC method
CCQM-K92 11
INRIM ITA 2011-04-19Primary
measurementRemovable central part 20 - 2000 000
MKEH HUN 2011-04-19 OIML R56 Four electrode DC cell DC method
NIM CHN 2011-04-21 IUPAC Jones type cell 20 - 5000
PTB DEU 2011-04-06Primary
measurementPiston type 16 000 - 20 000
SMU SVK 2011-03-24 IUPAC Jones type cell 1000
SP SWE 2011-04-06 IUPAC WTW TetraCon 325 ?
UMTS UKR 2011-04-27 Primary CRM UMTS Jones type cell 1000
VNIIFTRI RUS 2011-04-25 VNIIFTRI CRM Jones type cell ?
NIST USA 2011-04-05 Primary NIST CRM Daggett type cell 10 - 10 000
Table 6 Results for sample with nominal value of electrolytic conductivity 0.05 S·m-1
0,05 S/m
Institute Country
EC u (k=1)
INRIM ITA 0,049855 0,000035
INMETRO BRA 0,049970 0,000048
CMI CZE 0,049980 0,000049
INPL ISR 0,049980 0,000038
MKEH HUN 0,049988 0,000013
GUM POL 0,050000 0,000030
SMU SVK 0,050018 0,000016
VNIIFTRI RUS 0,050021 0,000012
DFM DNK 0,050026 0,000019
NIST USA 0,050036 0,000024
NIM CHN 0,050044 0,000014
PTB DEU 0,050051 0,000012
CENAM MEX 0,050100 0,000080
SP SWE 0,050110 0,000075
UMTS UKR 0,050116 0,000016
Figure 7 The plot of results for sample with nominal conductivity value 0.05 S·m-1
(standard uncertainty given)
CCQM-K92 12
CCQM-K92 (Electrolytic Conductivity) - Nominal Value 0.05 S/m
ITA
BR
A
ISR
CZ
E
HU
N
PO
L
SV
K
RU
S (
VN
IIFT
RI)
DN
K
US
A
CH
N
DE
U
ME
X
SW
E
UK
R
0,0497
0,0498
0,0499
0,0500
0,0501
0,0502
0,0503
Ele
ctro
lyti
c C
on
du
ctiv
ity
/ S
·m-1
Sample with nominal value 20 S·m-1
The measurement conditions and methods used at different institutes are given in Table 7.The results of measurements of the sample with nominal conductivity of 20 S·m-1 are given inTable 8 and displayed graphically in Figure 8. Three laboratories from 10 used a primarymeasurement procedure.
Table 7 Conditions of Measurement at Various Institutes - 20 S·m-1
Institute CountryDate of regis-
tered mailTraceability Measurement frequency [Hz]
CENAM MEX 2011-04-25 SMU CRM Jones type cell 1000 - 10000
GUM POL 2011-04-22 DFM CRM Jones type cell 12 - 1820
INPL ISR 2011-04-06 SMU CRM Four electrode DC cell DC method
DFM DNK 2011-04-13 Primary CRM DFM Jones type cell 3000 - 9000
VNIIM RUS 2011-04-13 IUPAC Jones type cell 1000
NIM CHN 2011-04-21 IUPAC Jones type cell 20 - 5000
MKEH HUN 2011-04-19 OIML R56 Four electrode DC cell DC method
PTB DEU 2011-04-06Primary
measurementPiston type 4000 - 6000
UMTS UKR 2011-04-27 Primary CRM UMTS Jones type cell 1000
INMETRO BRA 2011-04-20Primary
measurementPiston type 20 - 5000
CCQM-K92 13
Table 8 Results for sample with nominal value of electrolytic conductivity 20 S·m-1
20 S/m
Institute Country
EC u (k=1)
CENAM MEX 20,123 0,025
GUM POL 20,279 0,011
INPL ISR 20,280 0,014
DFM DNK 20,283 0,007
VNIIM RUS 20,290 0,007
NIM CHN 20,300 0,006
MKEH HUN 20,306 0,005
PTB DEU 20,308 0,007
UMTS UKR 20,344 0,004
INMETRO BRA 20,412 0,423
Figure 8 The plot of results for sample with nominal conductivity value 20 S·m-1
(standard uncertainty given)
CCQM-K92 (Electrolytic Conductivity) - Nominal Value 20 S/m
BR
A
UK
R
DE
U
HU
N
CH
N
RU
S (
VN
IIM
)
DN
K
ISR
PO
L
ME
X
20,10
20,15
20,20
20,25
20,30
20,35
20,40
20,45
Ele
ctro
lyti
c C
on
du
ctiv
ity
/ S
·m-1
CCQM-K92 14
∑= iiWM xwκ
∑
= 2
2
1
1
i
ii
u
uw
Discussion
Nominal values of electrolytic conductivity of the samples were 0.05 S·m-1 and 20 S·m-1. 15laboratories took part in the measurement of the 0.05 S·m-1 sample. Sample with nominalvalue of electrolytic conductivity 20 S·m-1 was measured by 10 laboratories.
The Formulas for Calculation of Estimators
Arithmetic Mean (2)
Standard Deviation of Arithmetic Mean (3)
Weighted Mean (4)
Calculation of Weights for Weighted Mean (5)
Uncertainty of Weighted Mean (6)
Uncertainty of Median (7)
Calculation of the Degrees of Equivalence
The degrees of equivalence for each participant, Di, and its standard uncertainty, u(Di), aregiven by Eq 8 and Eq 9, respectively:
( )KCRV−= iiD κ (8)
( )( )1
2
−−
= ∑nn
u iAM
κκ
ni∑=
κκ
( )κκ ~1
858,1 −−
= imediann
u
( )( )( )∑∑
−−
=i
Rii
wn
xxwu
1
2
WM
CCQM-K92 15
22KCRVD uuu
ii+= κ (9)
The standardized deviations En are given by formula (10)
(10)
Communication with the participants
DFM and NIST highlighted the instability of the first (0.05 S·m-1) sampleINRIM and UMTS were requested to check their results; no numerical error was found, but
new results were sent in after recalibration of the cells. These new data are given indiscussion only, as the original data have to be used.
VNIIM was asked to correct the result for bottle weighing; corrected mass was sent.VNIIFTRI was requested to check its results; VNIIFTRI “has found a mistake by transfer of
value constant from primary to secondary cell“ and provided new results.CMI requested to postpone the deadline for internal reasons.
Reference Value for 0.05 S·m-1
Basic statistical data.
Arithmetic mean 0.050020 S·m-1
Standard uncertainty 0.000017 S·m-1
Median 0.050021 S·m-1
Standard uncertainty 0.000016 S·m-1
The consistency information for different datasets is given in table 9.
Table 9 Chi square values for nominal value - 0.05 S·m-1 (values in bold are criticalvalues)
22KCRV
in
UU
KCRVE
i+
−=
κ
κ
CCQM-K92 16
Participants
Degrees
of free-
dom
χχχχ2 - cal-
culated
χχχχ2222 − − − − tabu-
lated
95% prob-
ability
Weighted
mean
Stand. uncer-
tainty
(Birge treat-
ment)
Birge Ratio
All 14 78,437 23,685 0,0500284 0,0000115 2,37 1,30
ITA excluded 13 52,656 22,362 0,0500319 0,0000099 2,01 1,31
ITA, UKR excluded 12 22,171 21,026 0,0500231 0,0000070 1,36 1,32
ITA, UKR, HUN excluded 11 12,627 19,675 0,0500304 0,0000061 1,07 1,34
Numbers given in bold are tabulated data for 95 % probability and corresponding degrees offreedom. If ITA, UKR, HUN are not taken into account, the chi-squares value is smaller thanthe critical value. As a reference value KCRV = 0.0500304 S·m-1 (u = 0.0000061 S·m-1) wasagreed.
Degrees of Equivalence - 0.05 S·m-1
Table 10 Degrees of Equivalence - 0.05 S·m-1
Di UDi
Institute Country
S/m S/m
INRIM ITA -0,000175 0,000070
INMETRO BRA -0,000060 0,000096
CMI CZE -0,000050 0,000099
INPL ISR -0,000050 0,000077
MKEH HUN -0,000042 0,000028
GUM POL -0,000030 0,000061
SMU SVK -0,000012 0,000034
VNIIFTRI RUS -0,000009 0,000027
DFM DNK -0,000004 0,000039
NIST USA 0,000006 0,000049
NIM CHN 0,000014 0,000031
PTB DEU 0,000021 0,000027
CENAM MEX 0,000070 0,000160
SP SWE 0,000080 0,000150
UMTS UKR 0,000086 0,000034
Figure 9 Degrees of Equivalence for sample with nominal conductivity value 0.05 S·m-1
CCQM-K92 17
CCQM-K92 Degrees of Equivalence - 0.05 S/m
ITA
BR
A
ISR
CZ
E
HU
N
PO
L
SV
K
RU
S (
VN
IIFT
RI)
DN
K
US
A
CH
N
DE
U
ME
X
SW
E
UK
R
-0,0003
-0,0002
-0,0001
0,0000
0,0001
0,0002
0,0003
De
gre
es
of
Eq
uiv
ale
nce
Reference Value for 20 S·m-1
Basic statistical data.
Arithmetic mean 20.2924 S·m-1
Standard uncertainty 0.0227 S·m-1
Median 20.2950 S·m-1
Standard uncertainty 0.0087 S·m-1
The consistency information for different datasets is given in table 11.
Table 11 Chi square values for nominal value – 20 S·m-1 (values in bold are criticalvalues)
Participants
Degrees
of free-
dom
χχχχ2 - cal-
culated
χχχχ2222 − − − − tabulated
95% prob-
ability
Weighted
mean
(S.m-1
)
Stand. un-
certainty
(Birge
treatment)
Birge Ratio
All 9 192,287 16,919 20,3120 0,0096 4,62 1,37
UKR excluded 8 63,101 15,507 20,2945 0,0073 2,81 1,39
UKR, MEX excluded 7 15,528 14,067 20,2964 0,0039 1,49 1,42
CCQM-K92 18
Numbers given in bold are tabulated (critical) data for 95 % probability and correspondingdegrees of freedom. If MEX, UKR are not taken into account, the chi-squares value is stillslightly larger than the critical value. However, any further exclusion does not improve thechi-square value. As a reference value KCRV = 20.2964 S·m-1 (u = 0.0039 S·m-1) wasagreed.
Degrees of Equivalence - 20 S·m-1
Table 12 Degrees of Equivalence – 20 S·m-1
Di UDiInstitute Country
S/m S/m
CENAM MEX -0,173 0,051
GUM POL -0,017 0,023
INPL ISR -0,016 0,029
DFM DNK -0,013 0,015
VNIIM RUS -0,006 0,015
NIM CHN 0,004 0,014
MKEH HUN 0,009 0,013
PTB DEU 0,012 0,016
UMTS UKR 0,048 0,010
INMETRO BRA 0,115 0,845
CCQM-K92 Degrees of Equivalence - 20 S/m
ME
X
PO
L
ISR
DN
K
RU
S (
VN
IIM
)
CH
N
HU
N
DE
U
UK
R
BR
A
-0,20
-0,15
-0,10
-0,05
0,00
0,05
0,10
0,15
0,20
De
gre
es
of
Eq
uiv
ale
nce
Figure 8 Degrees of Equivalence for sample with nominal conductivity value 20S·m-1
CCQM-K92 19
Posterior work reported by DFM:„DFM has since submitting K92 results and Draft A, examined the detailed frequency beha-viour of its conductivity cells (cf. presentation EAWG/12-07 at CCQM-EAWG, Paris, April2012). On this basis, we have shifted the frequency range used for extrapolation towards hig-her frequencies (towards lower phase angles) for measurements of high conductivity in thesecondary cell, which provided traceability to the cell used at 20 S/m. The cell constant of thecell used in K92 at 20 S/m has thus been reevaluated and would today give a result with DoEof -0.004 ± 0.015.“
Conclusions
Sixteen laboratories took part in the comparison, 15 measured sample with nominal conduc-tivity of 0,05 S/m and 10 laboratories measured sample with nominal conductivity of 20 S/m.A good agreement of the results was observed for most laboratories. In some cases excessiveuncertainty was due to measurement of very small resistance (less than 0,1 Ω) due to low cellconstant of the conductivity cells used.In the case of measurements of sample with conductivity ~20 S/m in secondary cells therecould be some problems with calibration, as CRMs with such a high conductivity are notcommonly available. These measurements thus can be classified as “extrapolation measure-ments”.
How far the light shines statement:The results in this comparison on the 0.05 S/m solution can be considered to be representativefor measurement capabilities in the range from 0.016 S/m to 0.15 S/m. The results in thiscomparison on the 20 S/m solution can be considered to be representative for measurementcapabilities in the range from 6 S/m to 25 S/m. Due to the increased difficulty associated withperforming the measurement as the conductivity increases, for the range from 25 S/m to 60S/m the results from this comparison are to be complemented in the review process by a de-tailed technical evaluation of the measurement procedure.
AcknowledgmentThe coordinating laboratory gratefully acknowledges the contributions of all participants andof the members of the CCQM Working Group on Electrochemical Analysis for their valuablesuggestions concerning the measurement protocol and the evaluation process.
References
1. Pure Appl. Chem., Vol. 73, No. 11, pp. 1783–1793, 2001.2. Final Report for Key Comparison CCQM-K36, available at
http://www.bipm.org/utils/common/pdf/final_reports/QM/K36/CCQM-K36.pdf3. Final Report for Key Comparison CCQM-K36.1, available at
http://www.bipm.org/utils/common/pdf/final_reports/QM/K36/CCQM-K36.1.pdf
CCQM-K92 20
Appendix
Addresses of participants
Adrian Reyes,Marcela MonroyCENAMKm 4.5 Carretera a los Cues, Mpio. El Marques, Queretaro, Mexico.CP 76246MEXICO
Alena VospělováČeský metrologický ústav (ČMI)Okružní 31638 00 BrnoCZECH REPUBLIC
Bertil MagnussonSP Technical Research Institute of SwedenBrinellgatan 4501 15 BoråsSWEDEN
Elena KardashThe National Physical Laboratory of Israel (INPL)Danciger “A” bldg., Givat-Ram, Jerusalem, 91904,ISRAEL
Fabiano Barbieri GonzagaNational Institute of Metrology, Standardization and Industrial Quality - INMETROAv. Nossa Senhora das Graças, 50, XerémDuque de Caxias, RJ, Brazil25250-020BRAZIL
Francesca DurbianoInstituto Nazionale di Ricerca Metrologica (INRiM)Strada delle Cacce 91, CAP 10135, Torino,ITALY
Kenneth W. PrattNational Institute of Standards and TechnologyBuilding 227, Room B346100 Bureau Dr., Stop 8391Gaithersburg, MD 20899-8391U.S.A.
Leoš Vyskočil
CCQM-K92 21
Slovak Institute of MetrologyKarloveska 63, SK-842 55 BratislavaSLOVAKIA
Pia Tønnes JakobsenDanish Fundamental Metrology A/S (DFM)Matematiktorvet 307,DK-2800 Kgs. LyngbyDENMARK
Prof. L.A. KonopelkoD.I. Mendeleyev Institute for Metrology (VNIIM)19, Moskovsky pr., St. Petersburg, 190005RUSSIA
Song XiaopingNational Institute of Metrology (NIM)No. 18, Bei San Huan Dong Lu, Beijing 100013,P.R.CHINA
Steffen SeitzPhysikalisch-Technische Bundesanstalt (PTB)Fachbereich 3.1Bundesallee 10038116 BraunschweigGERMANY
Vladimir GavrilkinUkrmetrteststandartMetrologichna str.,4 Kiev, 03680UKRAINA
Wladyslaw KozlowskiCentral Office of Measures (GUM)Laboratory of ElectrochemistryElektoralna Str. 200-139 Warsaw,POLAND
Yury A. OvchinnikovVNIIFTRI (National Research Institute Physicotechnical and Radio Engineering Measurements)141570, Mendeleevo, Moscow region, RussiaVNIIFTRI, Lab 35RUSSIA