Chromatography - An introduction

 Introduction

·       Chromatography is a process for separating components of a mixture

·       Compound - any substance composed of identical molecules consisting of atoms of two or more chemical elements.

·       Solute – the sample components in partition chromatography.

·       Affinity – the strong link between two molecules

·       Adsorption - compounds stick to the surface of the molecule

·       Components of a mixture are separated based on their differential migration

·       Amino acids, fatty acids, carbohydrates

·       Tswett 1906 – separated the coloured substances from the leaf

·       Chroma- colour, graphing – to write

·       The mixture to be separate – solute

·       Two media- stationary phase, mobile phase

·       Stationary phase- liquid /gas/ solid. 

·       Solute to be separated is absorbed into the stationary phase.

·       Mobile phase- solvent system. Consist of a mixture of     Butanal, water, acetone.

Lesser affinity to the stationary phase, carry the solute components across the stationary phase.

Principle

    Mixture of components separated based on the molecules in a mixture applied onto the surface or into the solid, and fluid stationary phase (stable phase) is separating from each other while moving with the aid of a mobile phase.

·      Different rates of migration (mixture component) on the solvent system.

·  Different rates of adsorption in the stationary phase Adsorption- adherence of the components on the surface of the stationary phase.

·      Adsorption – stationary (solid) eg, silica, alumina, mobile (liquid /gas).

·      It utilizes a mobile liquid/gaseous phase i.e absorbed onto the surface of a stationary solid phase.

·      Partition – stationary (liquid), mobile (liquid /gas).

·      Separation is based on solute partitioning between two liquid phase.

·      Chromatography may be viewed as a series of equilibrations between the mobile and stationary phase.

Different types of  with phases 

Method/ Chromatography	Mobile/phase	Stationary phase
Gas-liquid chromatography	Gas	Liquid
Gas – solid	Gas	Solid
Reversed phase	Liquid	Liquid or solid
Ion – exchange	Liquid	Liquid or solid
Size exclusion	Liquid -solid	Solid
Affinity chromatography	Water	Binding sites