Characteristics of Solid-phase Extraction for Inorganic Anions and Organic Acids on Titania and Alumina

In this study, the solid-phase extraction (SPE) characteristics of metal oxides for inorganic anions and organic acids were investigated, considering the application to ion analysis by an inline pretreatment Porous titania and alumina were packed into empty SPE cartridges, respectively, and applied to the SPE of inorganic anions and organic acids. The SPE characteristics were evaluated by determining the ion concentrations in solutions that passed through SPE cartridges at the sample loading and the eluate with the alkaline eluent by ion chromatography. Other inorganic anions, except phosphate ions, were scarcely adsorbed on the metal oxides due to the ion exclusion effect of the metal oxides. On the other hand, phosphate ion was strongly retained by the Lewis acid-base reaction. For organic acids, monocarboxylic acids were also not retained on these metal oxides, but dicarboxylic acids were clearly retained by coordination. To recover the phosphate ion and dicarboxylic acids strongly retained on these metal oxides, the alkaline solutions were used as eluents, but they could not be completely recovered. Although further studies are required, it is expected to be applied to the determination of trace inorganic anions by combining the column switching method using these metal oxides and the concentration column method.