Practical High-Performance Liquid Chromatography (Meyer/Practical High-Performance Liquid Chromatography) || Ion-Exchange Chromatography

✍ Scribed by Meyer, Veronika R.

• Publisher: John Wiley & Sons, Ltd
• Year: 2010
• Tongue: English
• Weight: 554 KB
• Edition: 5
• Category: Article
• ISBN: 0470682183
• DOI: 10.1002/9780470688427.ch12

✦ Synopsis

Ion-exchange chromatography has been used to separate amino acids since 1956. 1 These early separations are comparable to classical column chromatography on silica or alumina as regards both expenditure and output. The resins or gels used were relatively coarse, pressures were low and the chromatography of complex biological mixtures could take several days. Hence, the biochemistry sector felt an urgent need for instrumental analysis accompanied by automation and optimization techniques, the eventual outcome being modern HPLC.

A large number of stationary phases are now pressure-resistant and capable of high performance in ion-exchange chromatography also, so the scope of HPLC can be extended into this field: complex mixtures can be separated over a short period of time.

12.2 PRINCIPLE

The principle of ion-exchange chromatography is not unlike that of adsorption chromatography. In the latter case, the adsorbent bears 'active sites' which interact with molecules in their vicinity to a more or less specifically defined extent. Sample and solvent molecules compete with each other for adsorption.

A stationary phase capable of ion exchange, on the other hand, has electric charges on its surface. Ionic groups such as SO 3 2À , COO À , NH 3 þ or NR 3 þ are incorporated in the resin or gel. Charges are neutralized by mobile counter ions. The mobile phase contains ions, and ionic sample molecules compete with these for a place on the surface of the stationary phase.