Paper chromatography makes use of paper which acts as a stationary phase. Paper essentially consists of cellulose fibers which are polymers having – OH functional groups sticking out of the polymer chains. These groups lead to retention and separation of surface absorbed molecules. In practice the separating molecules equilibrate between the layer of adsorbed water and the mobile phase solvent.
Different types of paper have been tried but Whatman No1 and 3 filter papers are found more suitable for analytical work. Chromatography paper is commonly available as 18”X22” rectangular sheets. Apart from Whatman other popular manufacturers of chromatographic paper are Schleicher and Schull, Macherey Nagel, and Eaton-Dikeman but Whatman appears to be a popular choice.
Choice of Paper
Coarseness of the fibers and packing density of papers decides between speed and resolution. Fast papers are useful for major applications and when high resolutions are necessary slow papers are preferred
Examples of Whatman filter paper
|No 4||No 7||No 2|
|No 17||No 3 and 3 MM|
In addition to pure cellulose several modified versions are also available to meet the specific separation requirements which include acetylated papers, silicone oil impregnated papers, silica and alumina impregnated papers and papers impregnated with ion exchange materials. Some typical applications of modified papers are
|Type of paper||Typical applications|
|Ion exchange papers||Charged molecule or ionic separations|
|Silica or Alumina impregnated papers||low polarity molecules such as amines steroids, fatty acids, vitamins and pesticides|
|Acetylated papers||insecticides, pigments and metal
|Carboxylated papers||cationic separations of proteinated
amines and amino acids