The key difference between ascending and descending paper chromatography is that ascending paper chromatography involves the movement of the solvent in an upward direction whereas descending paper chromatography involves the movement of the solvent in a downward direction.
Paper chromatography is a type of chromatographic technique in which the components in the analyte mixture are distributed and partitioned between liquid phases. Generally, paper chromatography uses water as one liquid phase; water that is held in the pore of the filter paper used for the analysis is the stationary phase while a mobile phase moves through this stationary phase.
CONTENTS
1. Overview and Key Difference
2. What is Chromatography
3. What is Ascending Paper Chromatography
4. What is Descending Paper Chromatography
5. Side by Side Comparison – Ascending vs Descending Paper Chromatography in Tabular Form
6. Summary
What is Chromatography?
Chromatography is a type of analytical technique used to separate and determine the components in a mixture. During this analysis, we need to dissolve the analyte mixture in a fluid. This fluid is called the mobile phase because it acts as the medium that carries the analyte components through another material called the stationary phase. Various components in the mixture then travel through the stationary phase at different speeds, causing the separation of the components. Chromatography can be used for the analysis of both organic and inorganic component mixtures.
What is Ascending Paper Chromatography?
Ascending paper chromatography is an analytical technique in which the mobile phase moves upward through the stationary phase. We can call this situation “chromatogram ascends”. In order to observe the movement of the solvent in an upward direction, the solvent reservoir should lie at the bottom of the container we use for the analysis.
In this technique, the chromatographic paper with the tip having sample spots is dipped into the solvent at the bottom, so the spots remain well above the solvent. After some time, we can observe the solvent, along with the contents of the analyte mixture, is travelling upward the chromatographic paper. After the solvent front has reached the end of the paper, we can take out the paper from the solvent to determine the relative rates of each constituent in the analyte mixture that has travelled through the paper over a particular time period.
What is Descending Paper Chromatography?
Descending paper chromatography is an analytical technique in which the mobile phase moves downward through the stationary phase. In other words, in this method, the development of the paper occurs due to the movement of the solvent downwards on the paper. Therefore, the solvent reservoir should be at the top of the paper. In this process, the movement of the solvent is governed by gravity as well as capillary action.
What is the Difference Between Ascending and Descending Paper Chromatography?
Ascending and descending paper chromatography are two types of chromatographic techniques. The key difference between ascending and descending paper chromatography is that ascending paper chromatography involves the movement of the solvent in the upward direction whereas descending paper chromatography involves the movement of the solvent in the downward direction.
Moreover, in ascending paper chromatography, movement occurs due to capillary action while in descending paper chromatography, movement occurs due to capillary action and gravity.
Below infographic tabulates the differences between ascending and descending paper chromatography.
Summary – Ascending vs Descending Paper Chromatography
Ascending and descending paper chromatography are two types of chromatographic techniques. The key difference between ascending and descending paper chromatography is that ascending paper chromatography involves the movement of the solvent in the upward direction whereas descending paper chromatography involves the movement of the solvent in the downward direction.
Reference:
1. “What Is Paper Chromatography: Principle, Types, & Uses.”Owlcation. 28 Mar. 2011, Available here.
Image Courtesy:
1. “Chromatography tank” By Theresa Knott – (CC BY-SA 3.0) via Commons Wikimedia