Improved pH measurement of mobile phases in reversed-phase liquid chromatography.

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.

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

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.

The Unified Redox Scale for All Solvents: Consistency and Gibbs Transfer Energies of Electrolytes from their Constituent Single Ions.

We have devised the unified redox scale E , 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.

Retention mechanisms of acidic and basic analytes on the Pentafluorophenyl stationary phase using fluorinated eluent additives.

This work explores the effects of three selected fluoroalcohols - 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), 1,1,1,3,3,3-hexafluorotert‑butyl alcohol (HFTB) and hexafluoro-2,3-(trifluoromethyl)-2,3-butanediol (PP) as novel eluent additives and their effect on the retention of basic and acidic analytes, using a reversed phase (RP) column with a fluorophenyl (PFP) stationary phase. In order to observe the changes in the model analytes' retention, chromatograms were obtained at multiple (5.0; 6.

Evaluation and validation of detailed and simplified models of the uncertainty of unified [Formula: see text] measurements in aqueous solutions.

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).

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

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 (pH, solvent-specific scales). The recent introduction of the unified pH (pH) 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.

Kinetic insights into the role of the reductant in HO-driven degradation of chitin by a bacterial lytic polysaccharide monooxygenase.

Lytic polysaccharide monooxygenases (LPMOs) are monocopper enzymes that catalyze oxidative cleavage of glycosidic bonds in polysaccharides in the presence of an external electron donor (reductant). In the classical O-driven monooxygenase reaction, the reductant is needed in stoichiometric amounts. In a recently discovered, more efficient HO-driven reaction, the reductant would be needed only for the initial reduction (priming) of the LPMO to its catalytically active Cu(I) form.