Application of macrocyclic ligands to analytical chromatography

Abstract

As recognized from the time of their discovery, one of the most intriguing features of macrocyclic hosts is the selectivity with which they bind specific guest species. Cation, anion, and neutral guests have been selectively sequestered by macrocycles of widely varying design and size. This selectivity has prompted the incorporation of macrocyclic hosts into a variety of practical separations systems, including but not limited to, solvent extraction, liquid membranes, capillary electrophoresis, and chromatography. Such separations systems typically fall into three categories: batch processes designed to recover and concentrate desired species, e.g., the recovery of precious metals; purification processes designed to remove undesirable species, such as the purification of water; and analytical methods designed to analyze species of interest, such as the determination of metal ions in water. Related to this last category is the incorporation of macrocycles into other types of analytical techniques which do not rely on separations, such as luminescent sensors and ion selective electrodes. Several reviews detail the broad range of applications of macrocyclic ligands to analytical applications in general, many of which are referenced below. This review chapter focuses on research in one important separations-based analytical technique, chromatography. Specifically, we summarize recent advances in the application of macrocyclic ligands to analytical chromatography for the determination of ions and neutral species. We have organized the review by macrocycle type, beginning with synthetic macrocycles, and followed by a series of naturallyoccurring macrocycles and their analogs, including porphyrins, cyclodextrins, and macrocyclic antibiotics. Most of the review describes the direct incorporation of macrocycles into the stationary or mobile phases of high performance chromatographic systems. However, brief mention is also made of analyte concentration methods which exploit macrocyclic ligand selectivity and which are based on chromatographic principles. © 2005 Springer. Printed in the Netherlands.