ADSORPTION OF CARBOXYLIC-ACIDS, NUCLEOSIDES, AND NUCLEOTIDES ON SILICA ON NEUTRAL AQUEOUS-MEDIUM - ESTIMATION OF FREE-ENERGIES FROM DYNAMICAND STATIC MEASUREMENTS

Equilibrium constants (K) and free energies (-DELTAG) of adsorption on hydroxylated and gamma-aminopropylsilylated silicas from diluted neut ral aqueous solutions are calculated from retention values on silica-p acked chromatographic column (for mono- and dicarboxylic acids) and fr om initial rectilinear parts of adsorption isotherms measured by the b atch technique (for adenosine, inosine, adenosine- and uridine-5'-trip hosphates). For the first class of compounds adsorbed on hydroxylated silica, the equilibrium constant values range from 0.08 to 0.48, and - DELTAG values from -6100 to -1790 J/mol (fumartic and butyric acid, re spectively). For the nucleic acid compounds, much higher K and -DELTAG values were found, e.g. 1980 and 18200 J/mol for uridine-5'-triphosph ate adsorption on gamma-aminopropyl silica.