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Electrodeless, accurate pH determination in highly basic media using a new set of (1)H NMR pH indicators.

Journal of pharmaceutical and biomedical analysis (2010-12-21)
Gábor Orgován, Béla Noszál
RESUMEN

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.

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Sigma-Aldrich
tert-Butylamine, ≥99.5%