Chapter 2 - Separations in High-Performance Liquid Chromatography

Abstract

A variety of chromatographic modes have been developed on the basis of the mechanisms of retention and operation. The key chromatographic modes are normal-phase, reversed-phase, ion exchange, size-exclusion, and affinity chromatography. This chapter introduces the chromatographic modes and explains how they work. In addition to the major modes, there are a number of techniques that could be viewed as submodes. Examples of compounds separated by each mode, and the advantages and disadvantages, are provided to help chromatographers choose the most appropriate mode for a given group of analytes. There are a number of applications of high-performance liquid chromatography (HPLC). Normal-phase chromatography is used for the separation of neutral species on the basis of polarity, reversed-phase chromatography is used for the separation of neutral species on the basis of hydrophobicity, ion-exchange chromatography is used for the separation of ionic solutes on the basis of charge, size-exclusion chromatography is used for the separation of molecules on the basis of differences in molecular size, and affinity chromatography is used for the separation of biomolecules on the basis of the lock-and-key mechanism prevalent in biological systems.