Thin Layer Chromatography (TLC) Tutorial
- Thin Layer chromatography (TLC) is an analytical technique used to separate a mixture into its components.
- The process of thin layer chromatography is similar to paper chromatography but thin layer chromatography:
(a) is usually faster
(b) achieves better separations
(due to greater choice in stationary and mobile phases)
- The stationary phase is a usually a thin layer of silica gel or alumina.
- The stationary phase is coated onto a piece of glass, metal or plastic to make it rigid.
- The combination of the glass (metal or plastic) and the stationary phase is referred to as the thin layer chromatography plate (TLC plate).
- The mobile phase refers to the solvent that moves up the TLC plate by capillary action.
- Components in a mixture are separated based on their different abilities to bind or adsorb to the stationary phase, and on their different abilities to desorb or dissolve in the mobile solvent phase.
- The retardation factor, Rf, is a comparison of the distance travelled by a component to the distance travelled by the mobile solvent.
Rf = distance component travelled
distance solvent travelled
- Rf values depend on temperature, composition of the TLC plate used and the composition of the solvent used.
For these reasons, it is usual to run samples of known substances at the same time as you run the sample of the unknown mixture.