Chapter 5 Ion-exchange chromatography

Abstract

This chapter focuses on high-resolution, high-performance liquid chromatography (HPLC) that uses ion exchange or ion-exchanging materials. “High performance” requires high resolution, high speed, and continuous detection. High speed and high resolution are achieved by the use of surface-functional exchangers and continuous detection of ionic species is accomplished through electrical conductivity. All ions conduct an electric current, and measurement of electrical conductivity is the obvious way to detect and measure ionic species as they emerge from the column. There are two ways to use electrical conductivity to detect ionic species in chromatography: (1) one is to measure the conductivity of the effluent and look for changes, keeping the background conductivity as low as possible by using dilute eluents, and choosing the eluents to give maximum conductivity changes. This method is called “nonsuppressed or single-column ion chromatography.” (2) The other way is to remove selectively the excess eluent from the solution as it leaves the column, and then measure the conductivity. This method is called “suppressed ion chromatography.” The first method is simpler and requires less equipment whereas the second promises greater sensitivity.