Ion Chromatography and Membrane Separations Using Macrocyclic Ligands

Abstract

AbstractThe selectivity of macrocyclic ligand hosts in binding ionic and neutral guests was recognized early and has been applied to separations science in a number of ways. Prominent among these applications are ion chromatography (IC) and liquid membranes. This chapter summarizes the various ways by which macrocyclic ligands have been incorporated into these two separations techniques. It begins with a description of the intrinsic selectivities of the macrocyclic hosts used in these applications to date. The next section describes the basic elements of IC and the chemical features of standard ion chromatographic separations. It then proceeds to describe how macrocycles such as crown ethers, cryptands, resorcinarenes, and others have been incorporated into both the mobile and stationary phases of ion chromatographic systems to effect novel separations of both cations and anions. The development of capacity gradient chromatography of anions, unique to macrocycle‐based IC, is described. The application to both analytical separations and preconcentration/matrix elimination is also included. The next section introduces the various types of liquid membranes, including bulk liquid membranes, solid supported liquid membranes, emulsion liquid membranes, and polymer inclusion membranes. This section then proceeds to describe the various studies conducted to characterize the use of macrocyclic ligands as selective carriers of cations, anions, and neutral species across these membranes for separations purposes.