Chromatography is a laboratory technique used in chemistry for separating mixtures into their individual components. It's widely used in research, pharmaceuticals, forensic science, and environmental testing.

Basic Principle

Chromatography separates substances based on how they move through two different phases:

• Stationary Phase: A solid or a liquid supported on a solid.

• Mobile Phase: A liquid or gas that moves through the stationary phase.

Different components of the mixture move at different speeds due to differences in:

• Solubility

• Molecular size

• Affinity to the stationary phase

Types of Chromatography

1. Paper Chromatography:

   • Used mainly for separating pigments or inks.

   • Stationary phase: paper; mobile phase: solvent.

2. Thin Layer Chromatography (TLC):

   • A thin layer of silica gel on glass or plastic acts as the stationary phase.

   • Used for purity checks and identifying compounds.

3. Column Chromatography:

   • A column filled with adsorbent (like silica gel) separates compounds as a solvent passes through.

   • Used in organic chemistry labs.

4. Gas Chromatography (GC):

   • Separates volatile compounds.

   • Mobile phase: gas; stationary phase: liquid on a solid support inside a column.

5. High-Performance Liquid Chromatography (HPLC):

   • A powerful technique for precise and quick separation.

   • Uses high pressure to push solvents through a column.

Applications

• Identifying unknown substances

• Testing drug purity

• Detecting pollutants

• Food analysis