Gradient Elution Chromatography
Published Online: 15 JUN 2012
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Dolan, J. and Snyder, L. 2012. Gradient Elution Chromatography. Encyclopedia of Analytical Chemistry.
- Published Online: 15 JUN 2012
Elution chromatography can be carried out in either isocratic or gradient modes. In isocratic elution, the mobile-phase composition is held constant during separation of the sample, e.g. 60% v acetonitrile–water. In gradient elution, the mobile-phase composition will be varied during sample separation, e.g. changing from 0 to 100% v acetonitrile–water. Gradient elution requires special chromatographic equipment, as well as somewhat greater care on the part of the operator, but it has important advantages for many separations. Thus, in isocratic elution, sample peaks tend to ‘bunch up’ at the beginning of the chromatogram (often with decreased resolution) and to broaden at the end of the chromatogram (with reduced detection sensitivity). Gradient elution, on the other hand, provides a more even spacing of peaks, similar widths throughout the chromatogram, and often a shorter run time. For these and other reasons, gradient elution is preferred for the separation of many samples.