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How does paper or plate chromatography separate substances in a sample?
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chemical analysis
Strip of pH paper resting on specimen, with a comparison chart.
In analytical chemistry, paper chromatography and thin-layer chromatography (a form of plate chromatography) separate substances by utilizing two distinct phases: a stationary phase and a mobile phase.1
The Separation Process
- Stationary Phase: In paper chromatography, the stationary phase is typically water bonded to the cellulose of the filter paper. In thin-layer chromatography, it consists of a thin layer of adsorbent material, such as silica gel or alumina, coated onto a glass or plastic plate.23
- Mobile Phase: A solvent acts as the mobile phase, moving across the stationary phase via capillary action.34
- Differential Migration: As the solvent carries the sample mixture across the stationary phase, the components move at different velocities based on their relative solubilities in the two phases and their degree of attachment to the stationary material. Components that are more strongly attracted to the stationary phase move more slowly, while those with a higher affinity for the mobile solvent move more rapidly.341
This process results in the components becoming spatially separated into individual spots on the paper or plate, allowing for their identification.41