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Frequently Asked Question
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Explain the uses of silica and alumina as adsorbents in column chromatography
Accepted Answer
Silica and alumina are widely used as adsorbents in column chromatography due to their unique properties and advantages:
Silica (SiO2)
- High surface area, providing a large number of active sites for adsorption.
- Polar surface, suitable for adsorbing polar compounds through hydrogen bonding or dipole-dipole interactions.
- Chemically inert, allowing for compatibility with a wide range of solvents and analytes.
- High mechanical strength, making it suitable for packing chromatography columns.
Alumina (Al2O3)
- Also possesses a high surface area and can adsorb both polar and nonpolar compounds.
- Exhibits both acidic and basic surface properties, allowing for selective adsorption based on the analyte's charge.
- Can be activated by heating to remove moisture and increase its adsorption capacity.
In column chromatography, silica and alumina are packed into a glass or plastic column, and the sample is applied to the top of the column. The mobile phase (solvent) is then passed through the column, carrying the sample components down the column. The different components of the sample will interact with the adsorbent to varying degrees, causing them to separate into bands. The separated bands can then be eluted from the column and collected for further analysis.
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