Symmetric Potentiometric Cells for the Measurement of Unified pH Values

Heering, Agnes; Stoica, Daniela; Camões, Filomena; Anes, Bárbara; Dániel, Nagy; Szilágyi, Zsófia Nagyné; Quendera, Raquel; Ribeiro, Luis Filipe; Bastkowski, Frank; Born, Rasmus; Nerut, Jaak; Saame, Jaan; Lainela, Silvie; Liv, Lokman; Uysal, Emrah; Roziková, Matilda; Vičarová, Martina; Snedden, Alan; Deleebeeck, Lisa; Radtke, Valentin; Krossing, Ingo; Leito, Ivo

doi:10.3390/sym12071150

Cited by 15 publications

(36 citation statements)

References 25 publications

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“…For instance, a pH of 7 in water indicates neutrality, while acetonitrile having a pH of 7 is acidic. Unified pH (pH abs ) (Himmel et al, 2010) allows direct comparison of acidities in all media and is measured potentiometrically (Suu et al, 2015) by measuring directly the potential between two glass electrode half-cells.…”

Section: Introductionmentioning

confidence: 99%

“…The unified acidity scale uses an ideal proton gas as a theoretical, but universal reference point with its absolute chemical standard potential is set to zero. In solutions, the chemical potential of the proton is reduced by interaction with its environment which defines the pH scale of a specific solution (Himmel et al, 2010). However, the scales of different solutions can be related to each other through their common reference to the proton gas.…”

Section: Introductionmentioning

confidence: 99%

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Glass electrode half-cells for measuring unified pH in ethanol–water mixtures

Heering

Bastkowski

Seitz

2020

J. Sens. Sens. Syst.

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Abstract. The acidities of any given solvent or mixtures thereof can be compared by pH measurements on a unified scale, so-called pHabsH2O measurements. The method is quite new and has not been characterized with respect to metrological criteria to date. Metal solid-contact glass electrode half-cells, three commercial, conventional glass electrode half-cells with inner liquid filling and one pair of combined electrodes were used to investigate the stability of the measurement and the reproducibility of pHabsH2O results of ethanol mixtures with water. All electrodes are suitable for unified acidity measurements in standard aqueous buffers. In ethanol mixtures, the combined electrodes were found to be unsuitable. The half-cell electrodes can be reasonably used only in buffered solutions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Glass electrode half-cells for measuring unified pH in ethanol–water mixtures

Heering

Bastkowski

Seitz

2020

J. Sens. Sens. Syst.

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“…Solid-contact glass (half-cell) electrodes (SCGE) (Izmeritelnaya Tekhnika EST-0601 [ 24 ]) from the same production batch were purchased and distributed to all institutes. SCGEs have previously been proposed as the preferred electrodes for the differential potentiometry measurements enabling calculation of

values [ 19 , 25 ]. In addition to SCGEs, institutes purchased commercial combination and half-cell GEs, these are summarized in Table 1 .…”

Section: Methodsmentioning

confidence: 99%

“…Each institute made measurement on at least two aqueous pH buffers, and a number of organic solvents: methanol, acetonitrile, and ethanol, and their mixtures with water. Potential difference measurements were made between a pair of GEs immersed into two solutions separated by an ILSB, as described in Heering et al [ 25 ]. All measurements were made under thermostating conditions, at 25.0 °C.…”

Section: Methodsmentioning

confidence: 99%

“…These electrodes consist of a solid-contact between the glass membrane and the internal sensor [ 19 , 24 ], and are referred to as solid-contact glass electrodes (SCGE). The use of half-cells eliminates the possibility of interactions between the inner filling solution and solution under test [ 20 , 25 ]. However, the SCGE used here is not commercially available on a large scale.…”

Section: Introductionmentioning

confidence: 99%

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Unified pH Measurements of Ethanol, Methanol, and Acetonitrile, and Their Mixtures with Water

Deleebeeck

Snedden

Dániel

et al. 2021

Sensors

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Measurement of pH in aqueous-organic mixtures with different compositions is of high importance in science and technology, but it is, at the same time, challenging both from a conceptual and practical standpoint. A big part of the difficulty comes from the fundamental incomparability of conventional pH values between solvents (spH, solvent-specific scales). The recent introduction of the unified pH (pHabs) concept opens up the possibility of measuring pH, expressed as pHabsH2O, in a way that is comparable between solvent, and, thereby, removing the conceptual problem. However, practical issues remain. This work presents the experience of the authors with measuring pHabsH2O values in mixtures of methanol, ethanol, and acetonitrile, with water, but without the presence of buffers or other additives. The aim was to assigned pHabsH2O values to solvent–water mixtures using differential potentiometry and the ‘pHabs-ladder’ method. Measurements were made of the potential difference between glass electrodes immersed in different solutions, separated by an ionic liquid salt bridge. Data were acquired for a series of solutions of varying solvent content. This work includes experiences related to: a selection of commercial electrodes, purity of starting material, and comparability between laboratories. Ranges of pHabsH2O values for selected compositions of solvent–water mixtures are presented.

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Rigorous pH measurement in non-aqueous solution: measurement method and reference values in ethanol

Bastkowski,

Heering,

Uysal

et al. 2023

Anal Bioanal Chem

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The recently introduced unified pH ($${\mathrm{pH}}_{\mathrm{abs}}^{{\mathrm{H}}_{2}\mathrm{O}}$$ pH abs H 2 O ) 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 $${\mathrm{pH}}_{\mathrm{abs}}^{{\mathrm{H}}_{2}\mathrm{O}}$$ pH abs H 2 O 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 $${\mathrm{pH}}_{\mathrm{abs}}^{{\mathrm{H}}_{2}\mathrm{O}}$$ pH abs H 2 O 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 $${\mathrm{pH}}_{\mathrm{abs}}^{{\mathrm{H}}_{2}\mathrm{O}}$$ pH abs H 2 O measurement. This is an important step towards wider adoption of the $${\mathrm{pH}}_{\mathrm{abs}}^{{\mathrm{H}}_{2}\mathrm{O}}$$ pH abs H 2 O concept in practice, like liquid chromatography, biofuels analysis and electrocatalysis.

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Symmetric Potentiometric Cells for the Measurement of Unified pH Values

Cited by 15 publications

References 25 publications

Glass electrode half-cells for measuring unified pH in ethanol–water mixtures

Glass electrode half-cells for measuring unified pH in ethanol–water mixtures

Unified pH Measurements of Ethanol, Methanol, and Acetonitrile, and Their Mixtures with Water

Rigorous pH measurement in non-aqueous solution: measurement method and reference values in ethanol

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