Chromatography Techniques

Chromatography is termed as the technique through which a complex mixture of chemical components are separated, identified and determined. The compounds obtained have high grade purity and components of a mixture are separated based on the rates through which they move the stationary phase (column) by a gaseous or liquid mobile phase.

Column Chromatography

A type of adsorption chromatography and separate the compounds on the basis of polarity or hydrophobicity. In a classical column chromatography, a stationary phase consist on a glass column packed with silica accompanied by packing of sludge (the mixture of sample to be separated adsorbed in silica). In a carbon column chromatography (CCC), an adsorbent other than silica, activated carbon, porous graphitic-carbon, and activated carbon combined with poly-urethane foam, glass fiber, silica gel, celite, and Chromosorb W-HP can be used. 

Importance:

An eluent of mobile phase is poured into column, and eluate is collected at the bottom. The components of sludge have lower affinity or adsorption move faster and are removed first. The slower moving ones are eluted last.
Thus, this technique has great importance in separating the single chemical compound from the mixture of molecules on the basis of varying affinities for a mobile and stationary phase.

Thin Layer Chromatography

A technique in which stationary phase of fine solid layer affixed on glass or aluminium and a mobile phase includes either a single solvent or solvent mixtures ascend through the stationary phase by capillary action.

Importance:

It is invaluable in assessing the number of components in a sample during purification.
It is instrumental in setting up the initial parameters for column chromatography.

Preparative Thin Layer Chromatography

It is a modified and updated form of thin-layer chromatography. In this technique, silica gel is used as absorbent on a pre-coated or custom plates.

Benefits:

This technique can separate components ranging from mg to g (relatively higher amount than TLC). 

Limitations:

It is limited to deal with small sample size volume.
Recovery of separated components from the plate can be a daunting task.
Manual application of samples can be haphazard.

Types of Membrane Chromatography

 1. Membrane Chromatography

2. Ion-Exchange membrane chromatography

3. Affinity membrane chromatography

4. Hydrophobic membrane chromatography

Types of Multi-modal Membrane Chromatography

1. Natural polymer material

2. Polymer membrane

3. Commercial membrane matrix

4. Electro-spinning membrane matrix


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