Lesson 18 - Thin Layer Chromatography

Thin Layer Chromatography (TLC)

A chromatography technique used to separate non-volatile mixtures based on interactions with a stationary phase and a mobile phase.

Stationary Phase

The stationary phase in TLC is typically a thin layer of silica gel or alumina, which does not move.

Mobile Phase

The mobile phase in TLC refers to the solvent that carries the components of the mixture as it rises up the plate.

Rf value

The retention factor (Rf) value is the ratio of the distance traveled by a compound to the distance traveled by the solvent front.

Measurement of Rf values

Rf values are calculated to help identify compounds based on the distance they travel relative to the solvent front.

Fluorescence in TLC

A technique used to visualize colorless compounds on a TLC plate by using a stationary phase that fluoresces under UV light.

Ninhydrin

A chemical used to visualize amino acids in TLC by producing colored compounds upon reaction.

Problems in TLC: Over-large Spots

Occurs when sample spots are too large, leading to overlap and difficulty in resolving components.

Problems in TLC: Uneven Advance of Solvent Front

Results in inaccurate Rf values due to a bowing or uneven solvent front, often caused by incorrect chamber setup.

Streaking in TLC

Refers to substances moving as streaks instead of discrete spots, typically caused by excessive sample application.

Applications of TLC

TLC is used to identify the number of components in a mixture and to analyze various substances in different fields.

Advantages of TLC

Some benefits of TLC include being cheap, easy to perform, fast, and sensitive to detecting different compounds.