How is column chromatography and planar chromatography methods are performed?
Column chromatography and planar chromatography are two methods commonly used in separation and purification processes.
Column Chromatography:
1. Sample Preparation: The mixture to be separated is dissolved in a suitable solvent.
2. Column Packing: A glass column is packed with a stationary phase, typically a solid material such as silica gel or alumina, which acts as an adsorbent.
3. Loading the Sample: The dissolved mixture is loaded onto the top of the column.
4. Elution: A mobile phase (solvent or mixture of solvents) is repeatedly added to the top of the column and allowed to flow down through the stationary phase. As the mobile phase passes through, different components of the mixture interact differently with the stationary phase, causing them to move at different rates. This leads to separation of the components.
5. Collection: Fraction collectors are used to collect the eluted fractions as they come out of the column. Each fraction contains a mixture enriched in one of the separated components.
Planar Chromatography:
1. Sample Application: The mixture to be separated is spotted as a small concentrated spot or line on a solid stationary phase, such as a thin layer of silica gel or cellulose, coated on a plate.
2. Developing Solvent: The plate is then placed vertically in a dish containing a small amount of developing solvent. The solvent rises up the plate via capillary action.
3. Separation: As the solvent ascends the plate, it carries the sample components along. Different components interact differently with the stationary phase and the solvent, causing them to move at different rates. This leads to the separation of the components.
4. Visualization: Once the solvent front reaches the desired height, the plate is removed from the dish. The separated components remain as individual spots on the plate.
5. Detection and Analysis: The separated spots on the plate can be detected and analyzed using various techniques, such as UV light, iodine vapor, or specific chemical reagents.
In both column chromatography and planar chromatography, the separation is based on the differential interactions between the components of a mixture and the stationary and mobile phases. The separation is driven by the equilibrium between the components' affinities for the two phases. The choice of stationary and mobile phases, sample preparation, and detection methods can vary depending on the nature of the mixture being separated.