Sol-Gel Glass-Encapsulated Crown Ethers for the Separation and Preconcentration of Strontium from Acidic Media

Abstract

Extraction chromatography employing an inert polymeric support impregnated with a crown ether (typically, 4,4’,(5’)-di-(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6)), either neat (i.e., undiluted) or as a solution in 1-octanol, has previously been shown to provide an effective means for the isolation of radiostrontium from a variety of sample types for subsequent determination. In this study, sol-gel chemistry has been employed to prepare sorbents in which DtBuCH18C6 is encapsulated in a silica matrix. The resultant materials have been evaluated for their ability to retain strontium ion and compared to a commercially available extraction chromatographic (EXC) resin. Certain of the new materials are shown to provide uptake efficiencies comparable to those obtained with the commercial resins, although unless a porogen is employed, the kinetics of strontium uptake are significantly slower. In contrast to conventional EXC materials, however, strontium uptake by DtBuCH18C6-loaded glasses does not increase in proportion to the amount of extractant present, indicating that not all of the crown ether present is available for interaction with the metal ion.

Keywords:

• extraction chromatography
• strontium
• crown ethers
• sol-gel encapsulation

Additional information

Funding

The authors gratefully acknowledge the financial support of this work by the Office of Basic Energy Sciences of the United States Department of Energy under the Single Investigator Small Group Research (SISGR) Program through sub-contract with Brookhaven National Laboratory (TGA/SEM/BET studies) and the Centers for Disease Control and Prevention, National Center for Environmental Health, Division of Laboratory Sciences (initial metal ion uptake studies).