Pure 81 Appl. Chem., Vol. 67, No. 7, pp. 1069-1074,1995, Printed in Great Britain. 0 1995 IUPAC Solid phase extraction of ions using molecular recognition technology 1 1 2 2 2 R.M. Izatt, J.S. Bradshaw, R.L. Bruening, B. J. Tarbet, and M.L. Bruening 'Department of Chemistry, Brigham Young University, Provo, UT, 84602, U.S.A. IBC Advanced Technologies, Inc., Provo, UT, 84606, U.S.A. Abstract: Solid phase extraction (SPE) materials are described that are capable of highly selective separations of trace levels of cations and anions from aqueous solutions. The extraction kinetics are rapid, either small or large volumes of solution can be treated, and large volume reductions can be. achieved. By varying the SPE system, the separations are effective even in the presence of large concentrations of acid, base, or salt. A review is given of the application of SPE technology to a variety of industrial and analytical separations. INTRODUCTION A major interest in our research program at Brigham Young University during the past three decades has been the identification and investigation of factors affecting the cation selectivities shown by complexing agents. This investigationresulted in the early identificationof remarkable selectivities by certain macrocycles for uni and bivalent cations in single solvent systems (ref. 1-4). The high selectivities found by us and others (ref. 5-6) in macrocycle-cation systems led to an explosion of interest in the synthesis of new macrocycles with specific cation selectivities. Our early work in separating cations from one another involved the use of simple bulk liquid membrane systems (ref. 7). Subsequent separations systems used by us (ref. 8-10) included liquid membranes of the emulsion, supported, hollow fiber, and dual module hollow fiber types. These membrane systems provided much useful information concerning cation selectivities in separation systems. However, several features of the systems limited their use in practical separations. First, the preparation of water-insoluble macrocycles was expensive. Second, loss of these expensive reagents to the aqueous phase over time would be prohibitive. Third, large scale and continuous separationsapeared to be difficult to engineer with these devices with the possible exception of the hollow fiber systems. Fourth, the separation kinetics were slow. Separation rates were much more rapid for the emulsion and hollow fiber systems, but were still too slow for large scale commercial applications. Finally, all of these systems were subject to fouling which is a serious problem for membranes generally. The problems with membrane systems were overcome by attachment of macrocycles to silica gel by a chemical bond (ref. 1 1,12). This accomplishmentcoincided with the receipt by us of a research grant from the State of Utah Centers of Excellence Program. The purpose of this Grant was to accelerate the development of promising technologies on university campuses in Utah. The ultimate objective was to commercialize the particular technology through creation of a small business. The role of the university was to act as an incubator in this process. This goal was accomplished by the organization of IBC Advanced Technologies, Inc. (IBC) in 1988. The focus of IBC is to develop and commercializeseparationsof interest in the metallurgical processing; nuclear, mixed, and toxic waste; analytical; ultrapure fluids; electronics; and biopharmaceutical areas. Emphasis is on separationsusually of trace amounts of cations or anions, which are either difficult or impossible by conventional methods. These objectives are in line with the recommendations of a National Academy of Sciences (US.) report (ref. 13) which recommends the development of new separations systems capable of high selectivity and of use with very dilute solutions. 1069