Separation of Inorganic Anions by a Diol-modified Silica Stationary Phase with Acidic Eluent

This study describes inorganic anions using a column packed with a diol-modified silica gel stationary phase (diol-silica; TSKgel OH-120). In an acid eluent, such as tartaric acid or malic acid, the elution order of the analyte anions in ion chromatography using a diol-silica column was comparable to that using conventional anion-exchange columns, except for the fluoride ion. Fluoride ion would be strongly retained onto the silica gel, which is a support to fix diol functional groups. The retentions for anions was found to be enhanced by H+ in the eluent. This might electrostatically interact anions by protons retained onto diol functional groups in the column. Furthermore, the retention time of sulfate ion, which is a divalent strong acid anion, was largely reduced with increases of the column temperature up to 80 degrees C, while nitrite ion was slightly increased. The increase of the retention time of the nitrite ion was considered because of oxidization with elution of acidic eluent at a higher column temperature than 70 degrees C. The anion separation the by diol-silica stationary phase under acidic elution conditions was expected to be an ion-dipole interaction with the eluent ion and/or an electrostatic interaction with the stationary phase.