High-Performance Separation by Capillary Tube Isotachophoresis Utilizing Complex-Forming Equilibria

Developments in the migrating systems to improve the resolution and sensitivity of capillary tube isotachophoresis (ITP) are described. They are related to the use of complex-forming equilibria in the migrating column and nonaqueous solvents as the migrating medium. The considered sources of ligand for the complex-forming equilibria are (a) the counter ion in the leading electrolyte, (b) the neutral ligands added into the leading electrolyte and (c) the terminating ions. Actual separations performed by these systems are shown and their features and advantages are discussed. Migrating systems consisting of nonaqueous solvents such as dimethylformamide and acetonitrile enable the migration of analyte species which can not be realized in an aqueous medium to improve the selectively and sensitivity. Combining ITP with solvent extraction provides useful analytical techniques.