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Effect of temperature on the chromatographic retention of ionizable compounds. III. Modeling retention of pharmaceuticals as a function of eluent pH and column temperature in RPLC
Author(s) -
Gagliardi Leonardo G.,
Castells Cecilia B.,
Ràfols Clara,
Rosés Martí,
Bosch Elisabeth
Publication year - 2008
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200700491
Subject(s) - chemistry , analyte , chromatography , acid–base reaction , dissociation (chemistry) , solvent , column chromatography , dissociation constant , base (topology) , buffer (optical fiber) , analytical chemistry (journal) , organic chemistry , mathematical analysis , telecommunications , biochemistry , receptor , mathematics , computer science
We propose a general simple equation for accurately predicting the retention factors of ionizable compounds upon simultaneous changes in mobile phase pH and column temperature at a given hydroorganic solvent composition. Only four independent experiments provide the input data: retention factors measured in two pH buffered mobile phases at extreme acidic and basic pH values ( e. g. , at least ± 2 pH units far from the analyte p K a ) and at two column temperatures. The equations, derived from the basic thermodynamics of the acid–base equilibria, additionally require the knowledge of the solute p K a and enthalpies of acid–base dissociation of both the solute and the buffer components in the hydroorganic solvent mixture. The performance of the predictive model is corroborated with the comparison between theoretical and experimental retention factors of several weak acids and bases of important pharmacological activity, in mobile phases containing different buffer solutions prepared in 25% w/w ACN in water and at several temperatures.