Chromatographic Techniques

Section 1: Basics of Chromatography

Chromatography: A technique used for the separation and identification of components within a mixture, based on the different speeds at which they move through a specific medium under the influence of a solvent.
Stationary Phase: This is the medium through which the components move; it can be a solid, a liquid supported on a solid or a gel.
Mobile Phase: The phase that moves over the stationary phase, carrying the components of the mixture with it.
Elution: It is the process of drawing out the components from the stationary phase using the mobile phase for analysis.

Section 2: Types of Chromatographic Techniques

Paper Chromatography: A method commonly used to separate pigments, it involves a piece of paper as the stationary phase and a liquid solvent as the mobile phase.
Thin Layer Chromatography (TLC): This technique involves a glass or plastic plate coated with a layer of solid (usually silica gel) as the stationary phase, and a suitable solvent as the mobile phase.
Gas Chromatography (GC): A technique used to separate volatile substances, it employs a very long tube (column) packed with a stationary phase, and an inert gas as the mobile phase.
High Performance Liquid Chromatography (HPLC): Involving a high pressure pump and a column packed with a stationary phase, it employs a liquid solvent as the mobile phase.

Section 3: Interpreting Chromatograms

Retention Factor (Rf value): The ratio of the distance travelled by the component to the distance travelled by the solvent, used to identify components in a chromatogram.
Baseline: It’s the line from which all distances are measured in a chromatogram. It is usually the line along which the solvent front advances.
Spot or Band: Represent components in a mixture on a chromatogram. Each one corresponds to a different substance.

Section 4: Importance of Chromatographic Techniques

Separation of Components: Chromatography is invaluable in separating complex mixtures into their individual components for further analysis.
Identification and Quantification: The components can be identified by comparing their Rf values with known standards and can be quantified based on their spot size or intensity.
Purity Check: It offers an efficient way to check the purity of a sample by checking for the presence of any additional spots on the chromatogram.