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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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2
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Radtke V, Priester D, Heering A, Müller C, Koslowski T, Leito I, Krossing I. The Unified Redox Scale for All Solvents: Consistency and Gibbs Transfer Energies of Electrolytes from their Constituent Single Ions. Chemistry 2023; 29:e202300609. [PMID: 37191477 DOI: 10.1002/chem.202300609] [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: 02/23/2023] [Revised: 04/28/2023] [Accepted: 05/11/2023] [Indexed: 05/17/2023]
Abstract
We have devised the unified redox scale Eabs H2O , which is valid for all solvents. The necessary single ion Gibbs transfer energy between two different solvents, which only can be determined with extra-thermodynamic assumptions so far, must clearly satisfy two essential conditions: First, the sum of the independent cation and anion values must give the Gibbs transfer energy of the salt they form. The latter is an observable and measurable without extra-thermodynamic assumptions. Second, the values must be consistent for different solvent combinations. With this work, potentiometric measurements on silver ions and on chloride ions show that both conditions are fulfilled using a salt bridge filled with the ionic liquid [N2225 ][NTf2 ]: if compared to the values resulting from known pKL values, the silver and chloride single ion magnitudes combine within a uncertainty of 1.5 kJ mol-1 to the directly measurable transfer magnitudes of the salt AgCl from water to the solvents acetonitrile, propylene carbonate, dimethylformamide, ethanol, and methanol. The resulting values are used to further develop the consistent unified redox potential scale Eabs H2O that now allows to assess and compare redox potentials in and over six different solvents. We elaborate on its implications.
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Affiliation(s)
- Valentin Radtke
- Institut für Anorganische und, Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Denis Priester
- Institut für Anorganische und, Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Agnes Heering
- Institute of Chemistry, University of Tartu, Ravila 14a Str, 50411, Tartu, Estonia
| | - Carina Müller
- Institut für Anorganische und, Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Thorsten Koslowski
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Ivo Leito
- Institute of Chemistry, University of Tartu, Ravila 14a Str, 50411, Tartu, Estonia
| | - Ingo Krossing
- Institut für Anorganische und, Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
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3
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Radtke V, Gebel N, Priester D, Ermantraut A, Bäuerle M, Himmel D, Stroh R, Koslowski T, Leito I, Krossing I. Measurements and Utilization of Consistent Gibbs Energies of Transfer of Single Ions: Towards a Unified Redox Potential Scale for All Solvents. Chemistry 2022; 28:e202200509. [PMID: 35446995 PMCID: PMC9401597 DOI: 10.1002/chem.202200509] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Indexed: 11/08/2022]
Abstract
Utilizing the "ideal" ionic liquid salt bridge to measure Gibbs energies of transfer of silver ions between the solvents water, acetonitrile, propylene carbonate and dimethylformamide results in a consistent data set with a precision of 0.6 kJ mol-1 over 87 measurements in 10 half-cells. This forms the basis for a coherent experimental thermodynamic framework of ion solvation chemistry. In addition, we define the solvent independent pe abs H 2 O - and the E abs H 2 O values that account for the electronating potential of any redox system similar to the pH abs H 2 O value of a medium that accounts for its protonating potential. This E abs H 2 O scale is thermodynamically well-defined enabling a straightforward comparison of the redox potentials (reducities) of all media with respect to the aqueous redox potential scale, hence unifying all conventional solvents' redox potential scales. Thus, using the Gibbs energy of transfer of the silver ion published herein, one can convert and unify all hitherto published redox potentials measured, for example, against ferrocene, to the E abs H 2 O scale.
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Affiliation(s)
- Valentin Radtke
- Institut für Anorganische und Analytische ChemieFreiburger Materialforschungszentrum (FMF) andFreiburg Center for Interactive Materials and Bioinspired Technologies (FIT)Albert-Ludwigs-Universität FreiburgAlbertstr. 2179104FreiburgGermany
| | - Niklas Gebel
- Institut für Anorganische und Analytische ChemieFreiburger Materialforschungszentrum (FMF) andFreiburg Center for Interactive Materials and Bioinspired Technologies (FIT)Albert-Ludwigs-Universität FreiburgAlbertstr. 2179104FreiburgGermany
| | - Denis Priester
- Institut für Anorganische und Analytische ChemieFreiburger Materialforschungszentrum (FMF) andFreiburg Center for Interactive Materials and Bioinspired Technologies (FIT)Albert-Ludwigs-Universität FreiburgAlbertstr. 2179104FreiburgGermany
| | - Andreas Ermantraut
- Institut für Anorganische und Analytische ChemieFreiburger Materialforschungszentrum (FMF) andFreiburg Center for Interactive Materials and Bioinspired Technologies (FIT)Albert-Ludwigs-Universität FreiburgAlbertstr. 2179104FreiburgGermany
| | - Monika Bäuerle
- Institut für Anorganische und Analytische ChemieFreiburger Materialforschungszentrum (FMF) andFreiburg Center for Interactive Materials and Bioinspired Technologies (FIT)Albert-Ludwigs-Universität FreiburgAlbertstr. 2179104FreiburgGermany
| | - Daniel Himmel
- Institut für Anorganische und Analytische ChemieFreiburger Materialforschungszentrum (FMF) andFreiburg Center for Interactive Materials and Bioinspired Technologies (FIT)Albert-Ludwigs-Universität FreiburgAlbertstr. 2179104FreiburgGermany
| | - Regina Stroh
- Institut für Anorganische und Analytische ChemieFreiburger Materialforschungszentrum (FMF) andFreiburg Center for Interactive Materials and Bioinspired Technologies (FIT)Albert-Ludwigs-Universität FreiburgAlbertstr. 2179104FreiburgGermany
| | - Thorsten Koslowski
- Institut für Physikalische ChemieAlbert-Ludwigs-Universität FreiburgAlbertstr. 23a79104FreiburgGermany
| | - Ivo Leito
- Institute of ChemistryUniversity of TartuRavila 14a Str50411TartuEstonia
| | - Ingo Krossing
- Institut für Anorganische und Analytische ChemieFreiburger Materialforschungszentrum (FMF) andFreiburg Center for Interactive Materials and Bioinspired Technologies (FIT)Albert-Ludwigs-Universität FreiburgAlbertstr. 2179104FreiburgGermany
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4
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Deleebeeck L, Snedden A, Stoica D. Reconciling the pHe measurements of bioethanol: pHabs measurements of buffered 50-50 wt% water-ethanol mixtures. Anal Chim Acta X 2022; 10:100085. [PMID: 35923414 PMCID: PMC9240372 DOI: 10.1016/j.acax.2022.100085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 10/29/2021] [Accepted: 06/19/2022] [Indexed: 11/25/2022] Open
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5
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da Silva RJNB, Saame J, Anes B, Heering A, Leito I, Näykki T, Stoica D, Deleebeeck L, Bastkowski F, Snedden A, Camões MF. Evaluation and validation of detailed and simplified models of the uncertainty of unified [Formula: see text] measurements in aqueous solutions. Anal Chim Acta 2021; 1182:338923. [PMID: 34602195 DOI: 10.1016/j.aca.2021.338923] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Revised: 08/04/2021] [Accepted: 08/05/2021] [Indexed: 11/24/2022]
Abstract
The use of the unified pH concept, [Formula: see text] , applicable to aqueous and non-aqueous solutions, which allows interpreting and comparison of the acidity of different types of solutions, requires reliable and objective determination. The [Formula: see text] can be determined by a single differential potentiometry measurement referenced to an aqueous reference buffer or by a ladder of differential potentiometric measurements that allows minimisation of inconsistencies of various determinations. This work describes and assesses bottom-up evaluations of the uncertainty of these measurements, where uncertainty components are combined by the Monte Carlo Method (MCM) or Taylor Series Approximation (TSM). The MCM allows a detailed simulation of the measurements, including an iterative process involving in minimising ladder deviations. On the other hand, the TSM requires the approximate determination of minimisation uncertainty. The uncertainty evaluation was successfully applied to measuring aqueous buffers with pH of 2.00, 4.00, 7.00, and 10.00, with a standard uncertainty of 0.01. The reference and estimated values from both approaches are metrologically compatible for a 95% confidence level even when a negligible contribution of liquid junction potential uncertainty is assumed. The MCM estimated pH values with an expanded uncertainty, for the 95% confidence level, between 0.26 and 0.51, depending on the pH value and ladder inconsistencies. The minimisation uncertainty is negligible or responsible for up to 87% of the measurement uncertainty. The TSM quantified measurement uncertainties on average only 0.05 units larger than the MCM estimated ones. Additional experimental tests should be performed to test these uncertainty models for analysis performed in other laboratories and on non-aqueous solutions.
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Affiliation(s)
| | - Jaan Saame
- University of Tartu, Institute of Chemistry, Ravila 14a, 50411, Tartu, Estonia
| | - Bárbara Anes
- Centro de Química Estutural, Faculdade de Ciências da Universidade de Lisboa, Ed. C8, Campo Grande, 1649-016, Lisboa, Portugal
| | - Agnes Heering
- University of Tartu, Institute of Chemistry, Ravila 14a, 50411, Tartu, Estonia
| | - Ivo Leito
- University of Tartu, Institute of Chemistry, Ravila 14a, 50411, Tartu, Estonia
| | - Teemu Näykki
- Finnish Environment Institute SYKE, Laboratory Centre, Mustialankatu 3, 00790, Helsinki, Finland
| | - Daniela Stoica
- Laboratoire National de Metrologie et D'Essais, 1 Rue Gaston Boissier, 75015, Paris, France
| | | | - Frank Bastkowski
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116, Braunschweig, Germany
| | | | - M Filomena Camões
- Centro de Química Estutural, Faculdade de Ciências da Universidade de Lisboa, Ed. C8, Campo Grande, 1649-016, Lisboa, Portugal
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Abstract
Fluctuations of pH in coastal systems are generally surveyed through potentiometric pH measurements. A new concept of a unified pH scale was introduced with the great advantage of enabling comparability of absolute values, pHabs, pertaining to any medium. Using water as an anchor solvent, yielding pHabsH2O, enables referencing the pHabs values to the conventional aqueous pH scale. The current work aims at contributing to implement pHabsH2O to saline solutions. To this purpose, differential potentiometric measurements, with a salt bridge of ionic liquid [N2225][NTf2], were carried out aiming at overcoming problems related to residual liquid junction potentials that affect the quality of such measurements. The ability to measure pHabsH2O with acceptable uncertainty was evaluated using Tris-Tris·HCl standard buffer solutions prepared in a background matrix close to the characteristics of estuarine systems (salinity of 20) as well as with NaCl solutions with ionic strength between 0.005 and 0.8 mol kg−1. The present study shows that for high ionic strength solutions, such as seawater, challenges remain when addressing the assessment and quantification of ocean acidification in relation to climate change. Improvements are envisaged from the eventual selection of a more adequate ionic liquid.
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Radtke V, Stoica D, Leito I, Camões F, Krossing I, Anes B, Roziková M, Deleebeeck L, Veltzé S, Näykki T, Bastkowski F, Heering A, Dániel N, Quendera R, Liv L, Uysal E, Lawrence N. A unified pH scale for all solvents: part I – intention and reasoning (IUPAC Technical Report). PURE APPL CHEM 2021. [DOI: 10.1515/pac-2019-0504] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The definition of pH, its measurement and standard buffers, is well developed in aqueous solutions. Its definition in solvents other than water has been elaborated for a couple of solvents and their mixtures with water. However, the definition of a universal pH scale spanning all solvents and phases, not to mention standard procedures of measurement, is still a largely uncharted territory. UnipHied is a European collaboration and has the goal of putting the theoretical concept of an earlier introduced (2010) unified pHabs scale on a metrologically well-founded basis into practice. The pHabs scale enables the comparability of acidity between different phases. This article draws the connection of the concepts of unified acidity and secondary pH measurement.
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Affiliation(s)
- Valentin Radtke
- Universität Freiburg, IAAC , Albertstr. 21, 79104 Freiburg , Germany
| | - Daniela Stoica
- Laboratoire de Métrologie et d’Essais , 1 Rue Gaston Boissier, 75015 , Paris , France
| | - Ivo Leito
- University of Tartu , 14a Ravila Street, 50411 Tartu , Estonia
| | - Filomena Camões
- FCiências.ID, Centro de Química Estrutural, Faculdade de Ciências da Universidade de Lisboa , Campo Grande, 1749-016 Lisboa , Portugal
| | - Ingo Krossing
- Universität Freiburg, IAAC , Albertstr. 21, 79104 Freiburg , Germany
| | - Bárbara Anes
- FCiências.ID , Centro de Química Estrutural , Faculdade de Ciências da Universidadede Lisboa, Campo Grande , 1749-016 Lisboa , Portugal
| | - Matilda Roziková
- Czech Metrology Institute , Okružní 31/772, 638 00 , Brno , Czech Republic
| | - Lisa Deleebeeck
- Danish Fundamental Metrology , Kogle Allé 5 2970 Hørsholm , Denmark
| | - Sune Veltzé
- Danish National Metrology Institute , Hørsholm , Denmark
| | - Teemu Näykki
- Suomen ympäristökeskus (SYKE) , Latokartanonkaari 11, 00790 Helsinki , Finland
| | - Frank Bastkowski
- Physikalisch-Technische Bundesanstalt , Bundesallee 100, 38116 Braunschweig , Germany
| | - Agnes Heering
- Physikalisch-Technische Bundesanstalt , Bundesallee 100, 38116 Braunschweig , Germany
| | - Nagy Dániel
- Metrological and Technical Supervisory Department of the Government Office of the Capital City Budapest (BFKH) , Németvölgyi út 37-39, 1124 Budapest , Hungary
| | - Raquel Quendera
- Instituto Português da Qualidade , Rua António Gião, 2, 2829-513 Caparica , Portugal
| | - Lokman Liv
- Electrochemistry Laboratory, Chemistry Group, The Scientific and Technological Research Council of Turkey - National Metrology Institute (TUBITAK UME) , Gebze , Kocaeli , 41470 , Turkey
| | - Emrah Uysal
- Electrochemistry Laboratory, Chemistry Group, The Scientific and Technological Research Council of Turkey - National Metrology Institute (TUBITAK UME) , Gebze , Kocaeli , 41470 , Turkey
| | - Nathan Lawrence
- ANBSensors , Unit 4, Penn Farm Studios, Haslingfield , Cambridge , CB23 1JZ , UK
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8
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Deleebeeck L, Snedden A, Nagy D, Szilágyi Nagyné Z, Roziková M, Vičarová M, Heering A, Bastkowski F, Leito I, Quendera R, Cabral V, Stoica D. Unified pH Measurements of Ethanol, Methanol, and Acetonitrile, and Their Mixtures with Water. SENSORS 2021; 21:s21113935. [PMID: 34200436 PMCID: PMC8201227 DOI: 10.3390/s21113935] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/27/2021] [Accepted: 06/02/2021] [Indexed: 11/16/2022]
Abstract
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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Affiliation(s)
- Lisa Deleebeeck
- DFM A/S, Kogle Allé 5, 2970 Hørsholm, Denmark;
- Correspondence:
| | | | - Dániel Nagy
- Government Office of the Capital City Budapest (BFKH), Németvölgyi út 37-39, 1124 Budapest, Hungary; (D.N.); (Z.S.N.)
| | - Zsófia Szilágyi Nagyné
- Government Office of the Capital City Budapest (BFKH), Németvölgyi út 37-39, 1124 Budapest, Hungary; (D.N.); (Z.S.N.)
| | - Matilda Roziková
- Czech Metrology Institute (CMI), Okružní 31, 63800 Brno, Czech Republic; (M.R.); (M.V.)
| | - Martina Vičarová
- Czech Metrology Institute (CMI), Okružní 31, 63800 Brno, Czech Republic; (M.R.); (M.V.)
- Faculty of Mechanical Engineering, Slovak University of Technology, Namestie Slobody 17, SK-81231 Bratislava 1, Slovakia
| | - Agnes Heering
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany; (A.H.); (F.B.)
- Institute of Chemistry, University of Tartu (UT), Ravila Street 14a, 50411 Tartu, Estonia;
| | - Frank Bastkowski
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany; (A.H.); (F.B.)
| | - Ivo Leito
- Institute of Chemistry, University of Tartu (UT), Ravila Street 14a, 50411 Tartu, Estonia;
| | - Raquel Quendera
- Instituto Português da Qualidade (IPQ), R. António Gião, 2, 2828-513 Caparica, Portugal; (R.Q.); (V.C.)
| | - Vítor Cabral
- Instituto Português da Qualidade (IPQ), R. António Gião, 2, 2828-513 Caparica, Portugal; (R.Q.); (V.C.)
| | - Daniela Stoica
- Laboratoire National de Metrologie et d’Essais (LNE), 1 rue Gaston Boissier, 75015 Paris, France;
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9
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The use of the reference electrode equipped with an ionic liquid salt bridge in electrochemistry of ionic liquids: A convenient way to align the formal potentials of redox reactions in ionic liquids based on the standard hydrogen electrode scale. Electrochem commun 2021. [DOI: 10.1016/j.elecom.2021.107021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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10
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Radtke V, Pütz K, Himmel D, Krossing I. The Inverted Philosopher’s Stone: how to turn silver to a base metal. J Solid State Electrochem 2020. [DOI: 10.1007/s10008-020-04633-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AbstractMetals often are classified as “noble” or “base”—characterizing their reduction potential as one of the most important chemical properties. We show that metals are only as noble as allowed by their environment, i.e. this is a relative term, and the “frame of reference” simply is the solvent in which the redox system is present. We prove that silver is a prime example for a noble metal that forfeits its noble character in the simple ionic liquid HMIM Br (1-hexyl-3-methylimidazolium bromide) as an example for such a solvent.
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11
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Single-ion activity: a nonthermodynamically measurable quantity. J Solid State Electrochem 2020. [DOI: 10.1007/s10008-020-04758-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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12
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Abstract
A unified pH scale of absolute values (pHabs scale) enables the comparison of acidities in different solvents. To date, very few different experimental setups have been used for the measurement of values on this scale. The article describes the design and performance of the different symmetric cells used for unified pH measurement by several institutions. Well-established and reliable standard aqueous buffer solutions are the first step of method validation necessary to achieve a robust metrological level for more complex media. The pH of aqueous standard buffers was measured by differential potentiometry, where the potential between two glass electrodes is measured directly. All the tested electrochemical cells prove to be suitable for unified pH measurements. This validation highlights that the method is, to a large extent, independent of the used equipment, including the cell geometry. The inherent symmetry of the cell design helps to reduce the experimental workload and improve the accuracy of obtained results.
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13
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Himmel D, Radtke V, Butschke B, Krossing I. Grundlegende Bemerkungen zur Azidität. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201709057] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Daniel Himmel
- Institut für Anorganische und Analytische Chemie, und Freiburger Materialforschungszentrum (FMF); Universität Freiburg; Albertstraße 21 79104 Freiburg Deutschland
| | - Valentin Radtke
- Institut für Anorganische und Analytische Chemie, und Freiburger Materialforschungszentrum (FMF); Universität Freiburg; Albertstraße 21 79104 Freiburg Deutschland
| | - Burkhard Butschke
- Institut für Anorganische und Analytische Chemie, und Freiburger Materialforschungszentrum (FMF); Universität Freiburg; Albertstraße 21 79104 Freiburg Deutschland
| | - Ingo Krossing
- Institut für Anorganische und Analytische Chemie, und Freiburger Materialforschungszentrum (FMF); Universität Freiburg; Albertstraße 21 79104 Freiburg Deutschland
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14
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Himmel D, Radtke V, Butschke B, Krossing I. Basic Remarks on Acidity. Angew Chem Int Ed Engl 2018; 57:4386-4411. [PMID: 29171707 DOI: 10.1002/anie.201709057] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/16/2017] [Indexed: 12/21/2022]
Abstract
This Review provides a unified view on Brønsted acidity. For this purpose, a brief overview of the concepts acidity, acid strengths, and pH value is given, including problems, proposed solutions, and the use of the pHabs /pHabsH2O scale as a unifying concept. Thereafter, some examples of the accessibility and application of unified pHabs values are given. The Review is rounded off with the analogy of acid-base chemistry to redox chemistry with the introduction of the unified redox scale peabs . The combination of pHabs and peabs values in the protoelectric potential map (PPM), as elaborated in ongoing studies on the thermochemistry of single ions, provides a means to classify and to compare all possible acid-base/redox reactions in a medium-independent and, thus, unified fashion.
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Affiliation(s)
- Daniel Himmel
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
| | - Valentin Radtke
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
| | - Burkhard Butschke
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
| | - Ingo Krossing
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
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