Comparison Display

CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Degrees of equivalence D_i and expanded uncertainty U_i (k = 2)

Red diamonds: CCQM-K9 participants
Green triangle: SMU "subsequent" (CCQM-K9.1)
Orange circles: CCQM-K9.2 participants only
Blue squares: APMP.QM-K9 participants only

D_ITDI = -0.0377, and U_ITDI = 0.0502

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Degrees of equivalence D_i and expanded uncertainty U_i (k = 2)

Red diamonds: CCQM-K9 participants
Green triangle: SMU "subsequent" (CCQM-K9.1)
Orange circles: CCQM-K9.2 participants only
Blue squares: APMP.QM-K9 participants only

D_MSL= 0.0272, and U_MSL = 0.0040;
D_ITDI = -0.0642, and U_ITDI = 0.0530;
U_VMI-STAMEQ= 0.0840

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Degrees of equivalence D_i and expanded uncertainty U_i (k = 2)

Red diamonds: CCQM-K9 participants
Green triangle: SMU "subsequent" (CCQM-K9.1)
Orange circles: CCQM-K9.2 participants only
Blue squares: APMP.QM-K9 participants only

D_ITDI= -0.0794, U_ITDI = 0.0538

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MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 45 °C and 50 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Degrees of equivalence D_i and expanded uncertainty U_i (k = 2) for each temperature

Click on the graph for a closer view

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Degrees of equivalence D_i and expanded uncertainties U_i (k = 2)

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Degrees of equivalence D_i and expanded uncertainties U_i (k = 2)

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Degrees of equivalence D_i and expanded uncertainty U_i (k = 2)

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 45 °C and 50 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Degrees of equivalence D_i and expanded uncertainty U_i (k = 2) for each temperature

Click on the graph for a closer view

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C


Lab i	D_i	U_i
NRCCRM	-0.0025	0.0061
PTB	0.0017	0.0022
DPL	0.0008	0.0019
KRISS	-0.0034	0.0022
CENAM	0.0015	0.0061
GUM	0.0015	0.0022
VNIIFTRI	0.0005	0.0039
SMU	-0.0045	0.0022
NIST	-0.0002	0.0014

SMU(s)	0.0027	0.0031

DFM	-0.0001	0.0024
NMIJ	-0.0013	0.0032
INMETRO	-0.0097	0.0065
CMI	0.0264	0.0040

NIMT*	-0.0061	0.0094
GL*	0.0013	0.0114
MSL*	-	-
KIM-LIPI*	-	-
NML-SIRIM*	0.0041	0.0042
ITDI*	-0.0377	0.0502
VMI-STAMEQ*	-	-

'(s)' means 'subsequent bilateral comparison'.
Italics characters indicate that the erroneous result was used for computing the degrees of equivalence involving SMU.
Blue indicates participants in CCQM-K9.2 only.
* indicates participants in APMP.QM-K9 only.

Results are presented under A4 printable format in Summary Results (.PDF file).

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C


Lab i	D_i	U_i
NRCCRM	-0.0033	0.0042
PTB	0.0010	0.0025
DPL	0.0010	0.0020
KRISS	-0.0036	0.0023
CENAM	-0.0053	0.0121
GUM	0.0012	0.0021
VNIIFTRI	0.0007	0.0038
SMU	-0.0043	0.0023
NIST	-0.0003	0.0017

SMU(s)	0.0021	0.0033

DFM	0.0014	0.0024
NMIJ	-0.0009	0.0029
INMETRO	-0.0035	0.0062
CMI	0.0158	0.0040

NIMT*	-0.0041	0.0070
GL*	-0.0012	0.0118
MSL*	0.0272	0.0040
KIM-LIPI*	-0.0192	0.0134
NML-SIRIM*	-0.0045	0.0040
ITDI*	-0.0642	0.0530
VMI-STAMEQ*	-0.0042	0.0840

Results are presented under A4 printable format in Summary Results (.PDF file).

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C


Lab i	D_i	U_i
NRCCRM	-0.0024	0.0042
PTB	0.0012	0.0025
DPL	0.0013	0.0020
KRISS	-0.0034	0.0024
GUM	-0.0012	0.0022
VNIIFTRI	-0.0004	0.0040
SMU	-0.0044	0.0024
NIST	0.0012	0.0045

SMU(s)	0.0029	0.0036

DFM	0.0015	0.0026
NMIJ	-0.0008	0.0032
INMETRO	-0.0049	0.0062
CMI	0.0170	0.0048

NIMT*	-0.0019	0.0092
GL*	-0.0004	0.0116
MSL*	-	-
KIM-LIPI*	-	-
NML-SIRIM*	-0.0053	0.0042
ITDI*	-0.0794	0.0538
VMI-STAMEQ*	-	-

Results are presented under A4 printable format in Summary Results (.PDF file).

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MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 45 °C and 50 °C

NOMINAL VALUE : pH = 6.9 at 25 °C


Lab i	D_i	U_i
T = 5 °C
PTB	0.0017	0.0030
KRISS	-0.0031	0.0029
CENAM	-0.0077	0.0161
GUM	0.0035	0.0027
VNIIFTRI	0.0003	0.0041
NIST	-0.0007	0.0022
T = 10 °C
PTB	0.0016	0.0029
KRISS	-0.0030	0.0026
CENAM	-0.0083	0.0181
GUM	0.0021	0.0024
VNIIFTRI	0.0007	0.0041
NIST	-0.0005	0.0021
T = 20 °C
PTB	0.0018	0.0026
KRISS	-0.0030	0.0024
CENAM	0.0059	0.0101
GUM	0.0011	0.0023
VNIIFTRI	0.0009	0.0039
NIST	-0.0002	0.0018
T = 30 °C
PTB	0.0010	0.0026
KRISS	-0.0034	0.0024
CENAM	0.0028	0.0121
GUM	-0.0001	0.0023
VNIIFTRI	0.0008	0.0039
NIST	0.0008	0.0045
T = 40 °C
PTB	0.0013	0.0029
KRISS	-0.0034	0.0027
CENAM	0.0010	0.0082
GUM	-0.0016	0.0030
VNIIFTRI	-0.0020	0.0042
NIST	0.0022	0.0046
DPL	0.0022	0.0025
T = 45 °C
PTB	0.0011	0.0031
KRISS	-0.0031	0.0028
CENAM	0.0075	0.0083
GUM	-0.0028	0.0033
VNIIFTRI	-0.0015	0.0044
NIST	0.0022	0.0050
DPL	0.0021	0.0027
T = 50 °C
PTB	0.0032	0.0037
KRISS	-0.0018	0.0036
CENAM	0.0090	0.0104
GUM	-0.0038	0.0040
VNIIFTRI	-0.0010	0.0047
NIST	0.0067	0.0055

The full matrices of equivalence are available in Summary Results (summary of the results as a .PDF file).

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C


Lab i	D_i	U_i
NRCCRM	-0.0016	0.0044
PTB	0.0011	0.0028
DPL	0.0017	0.0023
KRISS	-0.0031	0.0023
NIMC	0.0104	0.0088
CENAM	0.0114	0.0111
GUM	-0.0015	0.0025
VNIIFTRI	0.0024	0.0042
SMU	-0.0056	0.0026
NIST	0.0047	0.0031

The full matrix of equivalence is available in Summary Results (summary of the results as a .PDF file).

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C


Lab i	D_i	U_i
NRCCRM	-0.0019	0.0042
PTB	0.0009	0.0026
DPL	0.0018	0.0021
KRISS	-0.0028	0.0021
NIMC	0.0028	0.0085
CENAM	0.0161	0.0131
GUM	-0.0002	0.0021
VNIIFTRI	0.0031	0.0039
SMU	-0.0059	0.0024
NIST	0.0036	0.0044

The full matrix of equivalence is available in Summary Results (summary of the results as a .PDF file).

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C


Lab i	D_i	U_i
NRCCRM	-0.0032	0.0043
PTB	0.0006	0.0027
DPL	0.0028	0.0022
KRISS	-0.0024	0.0022
NIMC	-0.0012	0.0076
CENAM	0.0078	0.0111
GUM	-0.0019	0.0027
VNIIFTRI	-0.0002	0.0041
SMU	-0.0062	0.0025
NIST	0.0040	0.0034

The full matrix of equivalence is available in Summary Results (summary of the results as a .PDF file).

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 45 °C and 50 °C

NOMINAL VALUE : pH = 6.9 at 25 °C


Lab _i	D_i	U_i
T = 5 °C
PTB	0.0014	0.0040
KRISS	-0.0023	0.0031
GUM	0.0020	0.0033
VNIIFTRI	0.0031	0.0046
T = 10 °C
PTB	0.0019	0.0037
KRISS	-0.0021	0.0027
GUM	0.0009	0.0027
VNIIFTRI	0.0038	0.0044
T = 20 °C
PTB	0.0022	0.0030
KRISS	-0.0018	0.0026
GUM	0.0001	0.0030
VNIIFTRI	0.0028	0.0041
T = 30 °C
PTB	0.0019	0.0027
KRISS	-0.0014	0.0023
GUM	0.0000	0.0023
VNIIFTRI	0.0026	0.0039
T = 40 °C
PTB	0.0017	0.0035
KRISS	-0.0003	0.0024
GUM	-0.0007	0.0028
VNIIFTRI	0.0005	0.0042
T = 45 °C
PTB	0.0013	0.0040
KRISS	-0.0014	0.0031
GUM	-0.0026	0.0032
VNIIFTRI	-0.0033	0.0048
DPL	0.0037	0.0031
T = 50 °C
PTB	0.0033	0.0040
KRISS	0.0007	0.0031
GUM	-0.0033	0.0034
VNIIFTRI	0.0006	0.0044

The full matrix of equivalence is available in Summary Results (summary of the results as a .PDF file).

Comparison

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CCQM-K9

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Information & contact
Participants

Metrology area, Sub-field	Chemistry and Biology, Electrochemistry
Description	pH measurement of phosphate buffer solutions
Time of measurements	1999 - 2000
Status	Approved for equivalence

Final Reports of the comparisons	CCQM-K9 Final Report, 2001, 39 pages
Measurand	pH 6.9 at 25 °C
Parameters	15 °C, 25 °C and 37 °C plus 7 other temperatures
Transfer device	Sample 1: 0.025 mol/kg of KH₂PO₄ and Na₂HPO₄ Sample 2: 0.02 mol/kg of KH₂PO₄ and Na₂HPO₄

Comparison type	Key Comparison
Consultative Committee	CCQM (Consultative Committee for Amount of Substance)
Conducted by	CCQM (Consultative Committee for Amount of Substance)
Comments	A subsequent bilateral comparison was carried out between SMU and PTB. Results published on 12 December 2001 Determination of the pH of two phosphate buffer solutions (sample 1 and sample 2) at different temperatures between 5 °C and 50 °C CCQM-K9.2 and APMP.QM-K9 results are linked to those of CCQM-K9 (sample 1)
Pilot institute	PTB Physikalisch-Technische Bundesanstalt Germany
Contact person	P. Spitzer +49 (0) 531 592 3130

Pilot laboratory
PTB	Physikalisch-Technische Bundesanstalt, Germany, EURAMET

CENAM

Centro Nacional de Metrologia, Mexico, SIM

GUM	Glowny Urzad Miar, Central Office of Measures, Poland, EURAMET

KRISS

Korea Research Institute of Standards and Science, Korea, Republic of, APMP

NIST	National Institute of Standards and Technology, United States, SIM

NMIJ AIST

National Metrology Institute of Japan, Japan, APMP

NRCCRM

National Research Centre for Certified Reference Materials, merged in NIM (National Institute of Metrology) starting 1st January 2006, China, APMP

Radiometer A/S

Radiometer Medical A/S, Denmark, EURAMET

SMU	Slovensky Metrologicky Ustav, Slovakia, EURAMET

VNIIFTRI

Institute of Physical Technical and Radiotechnical Measurements, Rosstandart, Russian Federation, COOMET

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

CCQM-K9 and CCQM-K9.1 (subsequent bilateral SMU - PTB)

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

The key comparison reference value, pH_R, is obtained as the variance-weighted mean of the results from the participants. The standard uncertainty, u_R, of pH_R is calculated according to the external consistency concept (see page 11 of the CCQM-K9 Final Report).

pH_R = 6.8975 and u_R = 0.0005

The degree of equivalence of each laboratory with respect to the reference value is given by a pair of terms: D_i= (pH_i - pH_R) and U_i, its expanded uncertainty (k = 2),
U_i = 2(u_i² + u_R²)^1/2. Note that this gives a conservative estimate of U_i.

The degree of equivalence between two laboratories is given by a pair of terms:
D_ij = D_i - D_j = pH_i - pH_j and U_ij, its expanded uncertainty (k = 2),
U_ij = 2(u_i² + u_j²)^1/2.

Within its uncertainty, the performance of PTB is assumed to be similar in the original full comparison and in the subsequent bilateral comparison between SMU and PTB. Following this bilateral comparison:

– the new degree of equivalence of SMU with respect to the key comparison reference value is D_SMU(s) = pH_SMU(s) - pH_PTB(s) + D_PTB and
U_SMU(s) = 2(u_SMU(s)² + u_PTB(s)² + u_R²)^1/2;

– the new degree of equivalence between SMU and any other laboratory j is
D_SMU(s) _j = D_SMU(s) - D_j and U_SMU(s) _j = 2(u_SMU(s)² + u_PTB(s)² + u_j²)^1/2_.

Linking CCQM-K9.2 results to CCQM-K9 results

The linkage process is detailed in Section 13 of the CCQM-K9.2 Final Report and is based on the performance of the common participants, PTB and VNIIFTRI, in both key comparisons. It leads to the computation of the degrees of equivalence of participants in CCQM-K9.2 only, relative to the CCQM-K9 key comparison reference values, and allows to extend the graph of equivalence obtained in CCQM-K9 at temperature 15 °C.

No pair-wise degrees of equivalence involving participants in CCQM-K9.2 only are computed.

Linking APMP.QM-K9 results to CCQM-K9 results

The linkage process is detailed in Section 8 of the APMP.QM-K9 Final Report and is ensured by the performance of SMU, NIM and NMIJ, which participated in APMP.QM-K9 and also in one of the key comparisons CCQM-K9, CCQM-K9 (subsequent) or CCQM-K9.2.
It leads to the computation of the degrees of equivalence of participants in APMP.QM-K9 only, relative to the CCQM-K9 key comparison reference values, and allows to extend the graph of equivalence obtained in CCQM-K9 at temperature 15 °C.

No pair-wise degrees of equivalence involving participants in APMP.QM-K9 only are computed.

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

CCQM-K9 and CCQM-K9.1 (subsequent bilateral SMU - PTB)

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_R = 6.8633 and u_R = 0.0006

Linking CCQM-K9.2 results to CCQM-K9 results

No pair-wise degrees of equivalence involving participants in CCQM-K9.2 only are computed.

Linking APMP.QM-K9 results to CCQM-K9 results

No pair-wise degrees of equivalence involving participants in APMP.QM-K9 only are computed.

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

CCQM-K9 and CCQM-K9.1 (subsequent bilateral SMU - PTB)

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_R = 6.8394 and u_R = 0.0006

Linking CCQM-K9.2 results to CCQM-K9 results

No pair-wise degrees of equivalence involving participants in CCQM-K9.2 only are computed.

Linking APMP.QM-K9 results to CCQM-K9 results

No pair-wise degrees of equivalence involving participants in APMP.QM-K9 only are computed.

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MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 45 °C and 50 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Temperature / °C	5	10	20	30
pH_R	6.9497	6.9213	6.8781	6.8512
u_R	0.0009	0.0008	0.0007	0.0007
Temperature / °C	40	45	50
pH_R	6.8360	6.8325	6.8290
u_R	0.0009	0.0011	0.0015

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_R = 6.9248 and u_R = 0.0009

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_R = 6.8905 and u_R = 0.0007

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_R = 6.8667 and u_R = 0.0008

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 45 °C and 50 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

Temperature / °C	5	10	20	30
pH_R	6.9756	6.9471	6.9046	6.8771
u_R	0.0013	0.0011	0.0010	0.0008
Temperature / °C	40	45	50
pH_R	6.8614	6.8592	6.8563
u_R	0.0009	0.0013	0.0013

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

CCQM-K9 and CCQM-K9.1 (subsequent bilateral SMU - PTB)

MEASURAND : pH value of phosphate buffer
Sample 1: [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

Lab i	Temperature		Date of measurement
Lab i	15 °C		Date of measurement
	pH_i	u_i
NRCCRM	6.8950	0.0030	99-12
PTB	6.8992	0.0010	99-11
DPL	6.8983	0.0008	99-10
KRISS	6.8941	0.0010	99-11
CENAM	6.8990	0.0030	99-11
GUM	6.8990	0.0010	99-12
VNIIFTRI	6.8980	0.0019	99-10
SMU*	6.8930	0.0010	00-02
NIST	6.8973	0.0005	00-01
SMU corrected	6.8970	0.0009	00-02

*SMU discovered a calculation error. The erroneous result is used for computing the degrees of equivalence involving SMU.
The erroneous result is corrected before it is used for evaluating the key comparison reference value.

A subsequent bilateral comparison was carried out between SMU and PTB in December 2000.
The composition of the measured sample was very similar to that of sample 1.
Measurements were also carried out at 25 °C and 37 °C.

PTB(s)	6.9004	0.0011	00-12
SMU(s)	6.9014	0.0010	00-12

'(s)' means 'subsequent bilateral comparison'.

CCQM-K9.2

MEASURAND : pH value of phosphate buffer
Sample 1: [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
U_{Lab i} : expanded uncertainty (k = 2) of pH_i

Lab i	Temperature		Date of measurement
Lab i	15 °C		Date of measurement
	pH_i	U_{Lab i}
CMI	6.9245	0.0036	Dec 2006
DFM	6.8980	0.0016	Nov 2006
INMETRO	6.8884	0.0062	Jan 2007
NMIJ	6.8968	0.0026	Dec 2006
PTB	6.8977	0.0020	Nov 2006
VNIIFTRI	6.9008	0.0022	Jan 2007

APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample : [0.0217 mol kg^-1 KH₂PO₄ + 0.0219 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.86 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

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CCQM-K9, CCQM-K9.1, CCQM-K9.2, and APMP.QM-K9

CCQM-K9 and CCQM-K9.1 (subsequent bilateral SMU - PTB)

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

Lab i	Temperature		Date of measurement
Lab i	25 °C		Date of measurement
	pH_i	u_i
NRCCRM	6.8600	0.0020	99-12
PTB	6.8643	0.0011	99-11
DPL	6.8643	0.0008	99-10
KRISS	6.8597	0.0010	99-11
CENAM	6.8580	0.0060	99-11
GUM	6.8645	0.0009	99-12
VNIIFTRI	6.8640	0.0018	99-10
SMU*	6.8590	0.0010	00-02
NIST	6.8630	0.0007	00-01
SMU corrected	6.8640	0.0009	00-02

PTB(s)	6.8657	0.0011	00-12
SMU(s)	6.8668	0.0011	00-12

'(s)' means 'subsequent bilateral comparison'.

CCQM-K9.2

MEASURAND : pH value of phosphate buffer
Sample 1: [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
U_{Lab i} : expanded uncertainty (k = 2) of pH_i

Lab i	Temperature		Date of measurement
Lab i	25 °C		Date of measurement
	pH_i	U_{Lab i}
CMI	6.8786	0.0036	Dec 2006
DFM	6.8642	0.0016	Nov 2006
INMETRO	6.8593	0.0059	Jan 2007
NMIJ	6.8619	0.0022	Dec 2006
PTB	6.8632	0.0020	Nov 2006
VNIIFTRI	6.8642	0.0021	Jan 2007

APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample : [0.0217 mol kg^-1 KH₂PO₄ + 0.0219 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.86 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

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CCQM-K9, CCQM-K9.1, CCQM-K9.2 and APMP.QM-K9

CCQM-K9 and CCQM-K9.1 (subsequent bilateral SMU - PTB)

MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

Lab i	Temperature		Date of measurement
Lab i	37 °C		Date of measurement
	pH_i	u_i
NRCCRM	6.8370	0.0020	99-12
PTB	6.8406	0.0011	99-11
DPL	6.8407	0.0008	99-10
KRISS	6.8360	0.0010	99-11
CENAM	-	-	-
GUM	6.8382	0.0009	99-12
VNIIFTRI	6.8390	0.0019	99-10
SMU*	6.8350	0.0010	00-02
NIST	6.8406	0.0022	00-01
SMU corrected	6.8397	0.0009	00-02

PTB(s)	6.8422	0.0011	00-12
SMU(s)	6.8439	0.0013	00-12

'(s)' means 'subsequent bilateral comparison'.

CCQM-K9.2

MEASURAND : pH value of phosphate buffer
Sample 1: [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
U_{Lab i} : expanded uncertainty (k = 2) of pH_i

Lab i	Temperature		Date of measurement
Lab i	37 °C		Date of measurement
	pH_i	U_{Lab i}
CMI	6.8564	0.0043	Dec 2006
DFM	6.8409	0.0016	Nov 2006
INMETRO	6.8345	0.0058	Jan 2007
NMIJ	6.8386	0.0024	Dec 2006
PTB	6.8403	0.0020	Nov 2006
VNIIFTRI	6.8393	0.0026	Jan 2007

APMP.QM-K9

MEASURAND : pH value of phosphate buffer
Sample : [0.0217 mol kg^-1 KH₂PO₄ + 0.0219 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.86 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

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MEASURAND : pH value of phosphate buffer
Sample 1 : [0.025 mol kg^-1 KH₂PO₄ + 0.025 mol kg^-1 Na₂HPO₄]
Measurements at 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 45 °C and 50 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

Lab i	Temperature		Date of measurement
Lab i	5 °C		Date of measurement
	pH_i	u_i
PTB	6.9514	0.0012	99-11
KRISS	6.9466	0.0011	99-11
CENAM	6.9420	0.0080	99-11
GUM	6.9532	0.0010	99-12
VNIIFTRI	6.9500	0.0018	99-10
NIST	6.9490	0.0006	00-01

Lab i	Temperature		Date of measurement
Lab i	10 °C		Date of measurement
	pH_i	u_i
PTB	6.9229	0.0012	99-11
KRISS	6.9183	0.0010	99-11
CENAM	6.9130	0.0090	99-11
GUM	6.9234	0.0009	99-12
VNIIFTRI	6.9220	0.0019	99-10
NIST	6.9208	0.0007	00-01

Lab i	Temperature		Date of measurement
Lab i	20 °C		Date of measurement
	pH_i	u_i
PTB	6.8799	0.0011	99-11
KRISS	6.8751	0.0010	99-11
CENAM	6.8840	0.0050	99-11
GUM	6.8792	0.0009	99-12
VNIIFTRI	6.8790	0.0018	99-10
NIST	6.8779	0.0006	00-01

Lab i	Temperature		Date of measurement
Lab i	30 °C		Date of measurement
	pH_i	u_i
PTB	6.8522	0.0011	99-11
KRISS	6.8478	0.0010	99-11
CENAM	6.8540	0.0060	99-11
GUM	6.8511	0.0009	99-12
VNIIFTRI	6.8520	0.0018	99-10
NIST	6.8520	0.0021	00-01

Lab i	Temperature		Date of measurement
Lab i	40 °C		Date of measurement
	pH_i	u_i
PTB	6.8373	0.0011	99-11
DPL	6.8382	0.0008	99-10
KRISS	6.8326	0.0010	99-11
CENAM	6.8370	0.0040	99-11
GUM	6.8344	0.0012	99-12
VNIIFTRI	6.8340	0.0019	99-10
NIST	6.8382	0.0021	00-01

Lab i	Temperature		Date of measurement
Lab i	45 °C		Date of measurement
	pH_i	u_i
PTB	6.8336	0.0011	99-11
DPL	6.8346	0.0008	99-10
KRISS	6.8294	0.0009	99-11
CENAM	6.8400	0.0040	99-11
GUM	6.8297	0.0012	99-12
VNIIFTRI	6.8310	0.0019	99-10
NIST	6.8347	0.0022	00-01

Lab i	Temperature		Date of measurement
Lab i	50 °C		Date of measurement
	pH_i	u_i
PTB	6.8322	0.0011	99-11
KRISS	6.8272	0.0010	99-11
CENAM	6.8380	0.0050	99-11
GUM	6.8252	0.0013	99-12
VNIIFTRI	6.8280	0.0018	99-10
NIST	6.8357	0.0023	00-01

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 15 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

Lab i	Temperature		Date of measurement
Lab i	15 °C		Date of measurement
	pH_i	u_i
NRCCRM	6.9232	0.0020	99-12
PTB	6.9259	0.0011	99-11
DPL	6.9265	0.0008	99-10
KRISS	6.9217	0.0008	99-11
NIMC	6.9352	0.0043	99-12
CENAM	6.9362	0.0055	99-11
GUM	6.9233	0.0009	99-12
VNIIFTRI	6.9272	0.0019	99-10
SMU*	6.9192	0.0010	00-02
NIST	6.9295	0.0013	99-11
SMU corrected	6.9242	0.0009	00-02

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 25 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

Lab i	Temperature		Date of measurement
Lab i	25 °C		Date of measurement
	pH_i	u_i
NRCCRM	6.8886	0.0020	99-12
PTB	6.8914	0.0011	99-11
DPL	6.8923	0.0008	99-10
KRISS	6.8877	0.0008	99-11
NIMC	6.8933	0.0042	99-12
CENAM	6.9066	0.0065	99-11
GUM	6.8903	0.0008	99-12
VNIIFTRI	6.8936	0.0018	99-10
SMU*	6.8846	0.0010	00-02
NIST	6.8941	0.0021	99-11
SMU corrected	6.8896	0.0009	00-02

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 37 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

Lab i	Temperature		Date of measurement
Lab i	37 °C		Date of measurement
	pH_i	u_i
NRCCRM	6.8635	0.0020	99-12
PTB	6.8673	0.0011	99-11
DPL	6.8695	0.0008	99-10
KRISS	6.8643	0.0008	99-11
NIMC	6.8655	0.0037	99-12
CENAM	6.8745	0.0055	99-11
GUM	6.8648	0.0011	99-12
VNIIFTRI	6.8665	0.0019	99-10
SMU*	6.8605	0.0010	00-02
NIST	6.8707	0.0015	99-11
SMU corrected	6.8657	0.0009	00-02

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MEASURAND : pH value of phosphate buffer
Sample 2 : [0.02 mol kg^-1 KH₂PO₄ + 0.02 mol kg^-1 Na₂HPO₄]
Measurements at 5 °C, 10 °C, 20 °C, 30 °C, 40 °C, 45 °C and 50 °C

NOMINAL VALUE : pH = 6.9 at 25 °C

pH_i : result of measurement carried out by laboratory i
u_i : combined standard uncertainty (k = 1) of pH_i

Lab i	Temperature		Date of measurement
Lab i	5 °C		Date of measurement
	pH_i	u_i
PTB	6.9770	0.0015	99-11
KRISS	6.9733	0.0008	99-11
GUM	6.9776	0.0010	99-12
VNIIFTRI	6.9787	0.0019	99-10

Lab i	Temperature		Date of measurement
Lab i	10 °C		Date of measurement
	pH_i	u_i
PTB	6.9490	0.0015	99-11
KRISS	6.9450	0.0008	99-11
GUM	6.9480	0.0008	99-12
VNIIFTRI	6.9509	0.0019	99-10

Lab i	Temperature		Date of measurement
Lab i	20 °C		Date of measurement
	pH_i	u_i
PTB	6.9068	0.0011	99-11
KRISS	6.9028	0.0008	99-11
GUM	6.9047	0.0011	99-12
VNIIFTRI	6.9074	0.0018	99-10

Lab i	Temperature		Date of measurement
Lab i	30 °C		Date of measurement
	pH_i	u_i
PTB	6.8790	0.0011	99-11
KRISS	6.8757	0.0008	99-11
GUM	6.8771	0.0008	99-12
VNIIFTRI	6.8797	0.0018	99-10

Lab i	Temperature		Date of measurement
Lab i	40 °C		Date of measurement
	pH_i	u_i
PTB	6.8631	0.0015	99-11
KRISS	6.8611	0.0008	99-11
GUM	6.8607	0.0011	99-12
VNIIFTRI	6.8619	0.0019	99-10

Lab i	Temperature		Date of measurement
Lab i	45 °C		Date of measurement
	pH_i	u_i
PTB	6.8605	0.0015	99-11
DPL	6.8629	0.0008	99-10
KRISS	6.8578	0.0008	99-11
GUM	6.8566	0.0009	99-12
VNIIFTRI	6.8559	0.0020	99-10

Lab i	Temperature		Date of measurement
Lab i	50 °C		Date of measurement
	pH_i	u_i
PTB	6.8596	0.0015	99-11
KRISS	6.8570	0.0008	99-11
GUM	6.8530	0.0011	99-12
VNIIFTRI	6.8569	0.0018	99-10

KCDB

CIPM MRA

CLASSIFICATION OF SERVICES

Key and supplementary comparisons - Print out