Dublin City University. School of Chemical Sciences
Abstract
Silica based monolithic HPLC columns have received much attention in recent years, particularly those modified for reversed-phase separations. However, for ionexchange, silica based monolithic columns have received only limited attention. Therefore, the aim of this work was the development and characterisation of novel monolithic stationary phases for the rapid separation o f inorganic and organic ions.
A 10 cm bare silica monolith has been modified on-column with iminodiacetic acid (IDA) groups and characterised for its selectivity toward alkali, alkaline earth and selected transition metal cations. The applicability of this IDA silica monolithic column for the rapid determination of alkaline earth metals in complex matrices was demonstrated. A second 10 cm bare silica monolith was functionalised with lysine (2 ,6 -diaminohexanoic acid) groups, and both the cation- and anion-exchange properties of the lysine functionalised monolith were evaluated, with a separation of 6 UV absorbing anions achieved in less than 100 seconds. By dynamically modifying the surface of the lysine functionalised silica monolith with copper (II) ions, it was possible to separate L-amino acids via ligand-exchange chromatography, using flow rates up to 7 mL/min. Finally, the ion-exchange properties o f a bare silica monolith were evaluated. The separation of alkaline and transition metal ions on a 10 cm bare silica monolith was possible using acetonitrile or methanol based ammonium and sodium acetate buffered eluents. The effects o f eluent ionic strength, organic content and pH on cation retention were evaluated, and in addition, the effect of solvent polarity on cation selectivity was also investigated
