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Armbruster C, Sellin M, Seiler M, Würz T, Oesten F, Schmucker M, Sterbak T, Fischer J, Radtke V, Hunger J, Krossing I. Pushing redox potentials to highly positive values using inert fluorobenzenes and weakly coordinating anions. Nat Commun 2024; 15:6721. [PMID: 39112470 DOI: 10.1038/s41467-024-50669-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2024] [Accepted: 07/16/2024] [Indexed: 08/10/2024] Open
Abstract
While the development of weakly coordinating anions (WCAs) received much attention, the progress on weakly coordinating and inert solvents almost stagnated. Here we study the effect of strategic F-substitution on the solvent properties of fluorobenzenes C6FxH6-x (xFB, x = 1-5). Asymmetric fluorination leads to dielectric constants as high as 22.1 for 3FB that exceeds acetone (20.7). Combined with the WCAs [Al(ORF)4]- or [(FRO)3Al-F-Al(ORF)3]- (RF = C(CF3)3), the xFB solvents push the potentials of Ag+ and NO+ ions to +1.50/+1.52 V vs. Fc+/Fc. The xFB/WCA-system has electrochemical xFB stability windows that exceed 5 V for all xFBs with positive upper limits between +1.82 V (1FB) and +2.67 V (5FB) vs. Fc+/Fc. High-level ab initio calculations with inclusion of solvation energies show that these high potentials result from weak interactions of the ions with solvent and counterion. To access the available positive xFB potential range with stable reagents, the innocent deelectronator salts [anthraceneF]+∙[WCA]- and [phenanthreneF]+∙[WCA]- with potentials of +1.47 and +1.89 V vs. Fc+/Fc are introduced.
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Affiliation(s)
- Christian Armbruster
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Malte Sellin
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Matthis Seiler
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Tanja Würz
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Friederike Oesten
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Maximilian Schmucker
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Tabea Sterbak
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Julia Fischer
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Valentin Radtke
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Johannes Hunger
- Molecular Spectroscopy Department, Max-Planck-Institut for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
| | - Ingo Krossing
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany.
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Heering A, Lahe M, Vilbaste M, Saame J, Samin JP, Leito I. Improved pH measurement of mobile phases in reversed-phase liquid chromatography. Analyst 2024; 149:1481-1488. [PMID: 38314857 DOI: 10.1039/d3an02029k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Mobile phase pH is a critically important parameter in reversed-phase liquid chromatographic (RPLC) separations involving analytes that display acidic or basic properties in the pH range used for the mobile phase. The main problem in measuring mobile phase pH lies in the fact that RPLC mobile phases are typically aqueous-organic mixtures. In addition to experimental difficulties, the pH values refer to different aqueous-organic compositions that cannot be correctly compared. Given this situation, the unified pH (wabspH, also termed as ) based on the absolute chemical potential of the solvated proton has been proposed as a rigorous way of characterising mobile phase acidity that is fully inter-comparable between mobile phases of any composition. Here we report the wabspH values of 78 reversed-phase liquid chromatography-mass spectrometry mobile phases that were carefully measured by potential differences in a symmetric cell with two glass electrode half-cells and almost ideal ionic liquid triethylamylammonium bis((trifluoromethyl)sulfonyl)imide [N2225][NTf2] salt bridge with multiple overlapping measurements. The system of altogether 300 ΔwabspH values was anchored to the pH value of standard pH 7.00 aqueous buffer solution. The consistency standard deviation of the whole set of measurements was 0.09 pH units. In addition to the differential potentiometric reference method, simpler measurement methods that use double junction reference or double junction combined electrodes were tested and were found suitable for routine laboratories if high accuracy is not required.
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Affiliation(s)
- Agnes Heering
- Institute of Chemistry, University of Tartu (UT), Ravila Street 14a, 50411 Tartu, Estonia.
| | - Markus Lahe
- Institute of Chemistry, University of Tartu (UT), Ravila Street 14a, 50411 Tartu, Estonia.
| | - Martin Vilbaste
- Institute of Chemistry, University of Tartu (UT), Ravila Street 14a, 50411 Tartu, Estonia.
| | - Jaan Saame
- Institute of Chemistry, University of Tartu (UT), Ravila Street 14a, 50411 Tartu, Estonia.
| | - John Paulo Samin
- Institute of Chemistry, University of Tartu (UT), Ravila Street 14a, 50411 Tartu, Estonia.
| | - Ivo Leito
- Institute of Chemistry, University of Tartu (UT), Ravila Street 14a, 50411 Tartu, Estonia.
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Bastkowski F, Heering A, Uysal E, Liv L, Leito I, Quendera R, Ribeiro L, Deleebeeck L, Snedden A, Nagy D, Szilágyi ZN, Camões F, Anes B, Roziková M, Stoica D. Rigorous pH measurement in non-aqueous solution: measurement method and reference values in ethanol. Anal Bioanal Chem 2024; 416:461-465. [PMID: 38001374 PMCID: PMC10761385 DOI: 10.1007/s00216-023-05043-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 10/26/2023] [Accepted: 10/30/2023] [Indexed: 11/26/2023]
Abstract
The recently introduced unified pH ([Formula: see text]) 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 [Formula: see text] 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 [Formula: see text] 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 [Formula: see text] measurement. This is an important step towards wider adoption of the [Formula: see text] concept in practice, like liquid chromatography, biofuels analysis and electrocatalysis.
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Affiliation(s)
- Frank Bastkowski
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116, Brunswick, Germany.
| | - Agnes Heering
- University of Tartu, 14a Ravila Street, 50411, Tartu, Estonia
| | - Emrah Uysal
- Electrochemistry Laboratory, Chemistry Group, The Scientific and Technological Research Council of Turkey, National Metrology Institute, (TUBITAK UME), 41470, Gebze, Kocaeli, Turkey
| | - Lokman Liv
- Electrochemistry Laboratory, Chemistry Group, The Scientific and Technological Research Council of Turkey, National Metrology Institute, (TUBITAK UME), 41470, Gebze, Kocaeli, Turkey
| | - Ivo Leito
- University of Tartu, 14a Ravila Street, 50411, Tartu, Estonia
| | - Raquel Quendera
- Instituto Português da Qualidade, R. António Gião, 2829-513, Caparica, Portugal
| | - Luís Ribeiro
- Instituto Português da Qualidade, R. António Gião, 2829-513, Caparica, Portugal
| | | | | | - Dániel Nagy
- Government Office of the Capital City Budapest (BFKH), Németvölgyi Út 37-39, 1124, Budapest, Hungary
| | - Zsófia Nagyné Szilágyi
- Government Office of the Capital City Budapest (BFKH), Németvölgyi Út 37-39, 1124, Budapest, Hungary
| | - Filomena Camões
- FCiências.ID, Centro de Química Estrutural, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal
| | - Bárbara Anes
- FCiências.ID, Centro de Química Estrutural, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal
| | - Matilda Roziková
- Czech Metrology Institute, Okružní 31, 63801, Brno, Czech Republic
| | - Daniela Stoica
- Laboratoire National de Métrologie Et d'Essais (LNE), 1 Rue Gaston Boissier, 75015, Paris, France
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