Retention of ionizable compounds in high-performance liquid chromatography. 14. Acid-base pK values in acetonitrile-water mobile phases.
Linear relationships between sspKa values in acetonitrile-water mixtures and wwpKa values in pure water have been established for five families of compounds: aliphatic carboxylic acids, aromatic carboxylic acids, phenols, amines, and pyridines. The parameters (slope and intercept) of the linear correlations have been related with acetonitrile-water composition. The proposed equations allow accurate estimation of the pKa values of any member of the studied families at any acetonitrile-water composition up to 60% of acetonitrile in volume (100% for pyridines). Conversely, the same equations can be used to estimate aqueous pKa values from chromatographic pKa values obtained from any acetonitrile-water mobile phase between the composition range studied. Estimation of pKa values have been tested with chromatographic literature data.
Departament de Química Analítica, Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Spain.
Sonia
S
Espinosa
Elisabeth
E
Bosch
Martí
M
Rosés
D000097:Acetonitriles / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D014867:Water / Q000737:chemistry*
D000097:Acetonitriles; D007477:Ions; D014867:Water; C032159:acetonitrile