Extraction chromatographic (EXC) resins comprising an appropriate crown ether in an oxygenated organic solvent (e.g., 1-octanol) are well established as sorbents for the analytical-scale separation and preconcentration of radiostrontium from a variety of sample types. Recent solvent extraction studies employing crown ethers (CE) in various 1-alkyl-3-methylimidazolium-based (Cnmim+) room-temperature ionic liquids (RTILs) indicate that under certain conditions, distribution ratios (DSr) for strontium far greater than those obtained with conventional organic solvents are observed. To determine if this increase in liquid-liquid extraction efficiency will lead to improved strontium sorbents, a series of EXC resins and sol-gel glasses incorporating di-tert-butyl-cyclohexano-18-crown-6 (DtBuCH18C6) in any of several Cnmim+ or related hydroxyalkyl-functionalized ILs were prepared and characterized. Unexpectedly the performance of the new IL-based sorbents was not uniformly better than that of a conventional EXC resin, an apparent result of the greater viscosity of the ionic liquids and the lower solubility of the crown ethers in ILs versus conventional organic solvents. For the silica-based sorbents, the presence of either an alcohol or an ionic liquid is shown to have no beneficial impact on strontium retention. Therefore, several silica-based sorbents have been prepared in which neat DtBuCH18C6 is encapsulated in a silica matrix. The resultant materials have been evaluated for their ability to retain strontium ion and compared to conventional EXC resins. Certain of these materials are shown to provide uptake efficiencies comparable to those obtained with commercial resins and satisfactory uptake kinetics at low CE loadings. The sol-gel encapsulation process thus provides a simple and convenient approach to the preparation of novel metal ion sorbents.

Improved extraction chromatographic materials for the separation and 
preconcentration of metal ions

249th National Meeting (2015)

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Improved extraction chromatographic materials for the separation and<br /> preconcentration of metal ions