Petra Spitzer et al 2008 Metrologia 45 08006 doi:10.1088/0026-1394/45/1A/08006
Petra Spitzer1,7, Janine Giera1, Isabel C Fraga2, Pia Tønnes Jakobsen3, Hans D Jensen3, Peter Hyllested3, Oleg Karpov4, Viatcheslav Kutovoy4, Susumu Nakamura5, Alena Vospelova6 and Valentina Zvezdina4
Show affiliationsCCQM-K9.2 was performed supplementary to the key comparison CCQM-K9 on the pH determination of a phosphate buffer with nominal pH ~ 6.9 (at 25 °C). The sample composition was very similar in both comparisons. Only the source of the starting material used for sample preparation was different. The comparison was restricted to the use of the primary method for pH (Harned cell measurement) as defined in the IUPAC Recommendations [2]. The measurement temperatures were 15 °C, 25 °C, 37 °C.
CCQM-K9.2, CCQM-K.9 and the first supplementary comparison CCQM-K9.1 [5] are activities of the Electrochemical Working Group (EAWG) of the CCQM. All three comparisons were coordinated by the PTB, Germany.
The Danish Primary Laboratory (DPL) successfully took part in the CCQM-K9. Meanwhile the primary set-up for pH in Denmark moved from DPL affiliated to Radiometer Medical to DFM, Denmark. The subsequent comparison allows assessing the degree of equivalence for the measurement of pH at DFM after the move. Due to the interest of other laboratories in demonstrating their progress in pH measurements on the primary level the CCQM-K9.2 supplementary comparison was extended to other participants than DFM, namely NMIJ, VNIIFTRI, INMETRO and CMI.
The reported quantity for CCQM-K9.2 was not the pH of the sample but the acidity function at zero chloride molality (see chapter 12). To calculate the pH value from the acidity function it is necessary to know the ionic strength of the sample buffer solution, which was undisclosed by the coordinator.
With the exception of the Czech Metrology Institute, CMI, good agreement in the determined acidity function is found between the participants.
The results reported by DFM and by PTB agree within their measurement uncertainty at all measurement temperatures.
Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.
The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
Issue 1A ( 1 January 2008)
Petra Spitzer et al 2008 Metrologia 45 08006
C S J Wolff Briche 2003 Metrologia 40 08010
A V Lyashenko et al 2007 JINST 2 P08004
Ruth Hearn et al 2008 Metrologia 45 08001
P J Allisy-Roberts et al 2009 Metrologia 46 06007
C Kessler et al 2009 Metrologia 46 06009
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Maurizio Porfiri 2009 Smart Mater. Struct. 18 015016
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