Chromatography is one of the most widely used separation techniques in chemistry. It appears in IB Chemistry Topic 11 (Analytical Techniques) and Paper 3 practical questions. Whether you're working with pigments, amino acids, organic mixtures, or environmental samples, chromatography provides a reliable way to separate components based on their interactions with different phases. This article clearly explains the fundamental principle behind chromatography and how it achieves separation.
What Is Chromatography?
Chromatography is a separation technique based on the different affinities of substances for a stationary phase and a mobile phase.
The key idea is that each component in a mixture interacts differently with these phases.
Because of these differences, components move at different speeds and eventually separate.
Chromatography works for:
- Solids
- Liquids
- Gases
- Complex mixtures
It is widely used in laboratories, industry, and forensic science.
The Two Phases in Chromatography
Every chromatography technique involves two phases:
1. Stationary Phase
This phase does not move.
It could be:
- Paper
- Silica gel
- Resin beads
- A metal column coating
The stationary phase attracts some components more strongly than others.
2. Mobile Phase
This phase moves through or across the stationary phase.
It could be:
- A solvent (liquid chromatography)
- A gas (gas chromatography)
- A buffer solution (ion-exchange chromatography)
