title: Electrodeless, accurate pH determination in highly basic media using a new set of (1)H NMR pH indicators.
abstract: A set of indicator molecules was selected and applied to elaborate an NMR-based pH determination method, free of glass electrode errors in highly basic media. Accurate measurement of pH values and protonation constants was achieved by a successive build-up of overlapping, increasingly high pH solutions, using a collection of 8 compounds of appropriately incremented basicities. In order to verify the method, acid-base properties were quantified for two compounds with very high basicities in conflicting reports: two pharmaceutically important biguanidine drugs, metformin and phenformin.
authors.affiliation: Department of Pharmaceutical Chemistry, Semmelweis University, Research Group of Drugs of Abuse and Doping Agents, Hungarian Academy of Sciences, Budapest H-1092, Hőgyes Endre u 9, Hungary.
authors.forename: Gábor
authors.initials: G
authors.lastname: Orgován
authors.forename: Béla
authors.initials: B
authors.lastname: Noszál
mesh_terms: D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008687:Metformin / Q000032:analysis / Q000737:chemistry; D015394:Molecular Structure; D009994:Osmolar Concentration; D004364:Pharmaceutical Preparations / Q000032:analysis* / Q000737:chemistry; D010629:Phenformin / Q000032:analysis / Q000737:chemistry; D011199:Potentiometry; D011522:Protons; D015203:Reproducibility of Results; D012996:Solutions; D013678:Technology, Pharmaceutical / Q000379:methods*
chemical_list: D004364:Pharmaceutical Preparations; D011522:Protons; D012996:Solutions; D008687:Metformin; D010629:Phenformin