Rigorous pH measurement in non-aqueous solution: measurement method and reference values in ethanol
Creators
- 1. Phys Tech Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany
- 2. Univ Tartu, 14a Ravila St, EE-50411 Tartu, Estonia
- 3. Natl Metrol Inst, Sci & Technol Res Council Turkey, Electrochem Lab, Chem Grp,TUBITAK UME, TR-41470 Gebze, Kocaeli, Turkiye
- 4. Inst Portugues Qualidade, R Antonio Giao 2, P-2829513 Caparica, Portugal
- 5. DFM AS, Kogle Alle 5, DK-2970 Horsholm, Denmark
- 6. Govt Off Capital City Budapest BFKH, Nemetvolgyi Ut 37-39, H-1124 Budapest, Hungary
- 7. Univ Lisbon, Ctr Quim Estrutural, FCiencias ID, Fac Ciencias, P-1749016 Lisbon, Portugal
- 8. Czech Metrol Inst, Okruzni 31, Brno 63801, Czech Republic
- 9. Lab Natl Metrol & Essais LNE, 1 Rue Gaston Boissier, F-75015 Paris, France
Description
The recently introduced unified pH (pH(abs)(H2O)) concept enables rigorous pH measurements in non-aqueous and mixed media while at the same time maintaining comparability to the conventional aqueous pH scale. However, its practical application is hindered by a shortage of reference pH(abs)(H2O) values. In order to improve this situation, the European Metrology Research Project (EMPIR) UnipHied ("Realisation of a UnipHied pH scale") launched an interlaboratory comparison among highly experienced electrochemistry expert laboratories to assign the first such reference pH(abs)(H2O) values by adopting an extensive statistical treatment of the reported measurement data: to phosphate buffer in water-ethanol mixture (50 wt% of ethanol) and ammonium formate buffer in pure ethanol. Two different measurement setups - one capable of being easily adopted in industrial applications - have been used to demonstrate the robustness of pH(abs)(H2O) measurement. This is an important step towards wider adoption of the pH(abs)(H2O) concept in practice, like liquid chromatography, biofuels analysis and electrocatalysis.
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