Tuesday, June 2, 2020

What is the difference between ascending and descending paper chromatography?

Paper chromatography is a separation technique in analytical chemistry that is used to separate the sample mixtures into their individual components. By capillary action, the sample mixture is moved to the stationary phase using the mobile phase. They move at different speeds, since, their different affinity with the stationary phase, and thus, get separated. Generally, the cellulose filter paper is used as solid support. Five types of paper chromatography are used, depending on how the chromatogram is developed such as ascending chromatography, descending chromatography, ascending- descending mode, radial mode, and two-dimensional chromatography, etc.
Both ascending chromatography and descending chromatography are types of paper chromatography used to separate molecules. The major difference between ascending and descending paper chromatography is that, In ascending chromatography, the analytes are in the mobile phase and travels from bottom to top (by capillary action). Similarly, in descending chromatography, the solvent travels from top to bottom. This method gives rapid separation as the mobile phase moves with gravity. However, the principle of separation in both types remains the same; ascending chromatography is technically easy to execute.

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