Chromatography today is a top ranking technique for separation and quantification of components of organic liquid or gas phase mixtures. Several innovations of the technique have contributed to speed of analysis and lowering of detection limits but it is remarkably surprising that all the variants ranging from simplest paper chromatography, column chromatography, thin- layer chromatography to most advanced techniques such as LC – MS – MS are widely accepted and are in common use in college/university. industrial and sophisticated research and development laboratories across the world. Even to this day no claim can be made that any one technique has made the popularity of another chromatographic technique outdated or obsolete.
The purpose of writing this article is to briefly review the evolution of the earliest liquid chromatography technique – Paper chromatography which has provided an initial approach to determine the components of liquid mixtures and has paved the future for more sophisticated instrumental techniques.
Chromatography, true to its literal Greek translation, means colour writing. It was successfully applied by Dr Michael Tswett in 1906 for separation of plant pigments by allowing vegetable extracts to percolate through a column packed with calcium carbonate powder. The extract comprising of different coloured substances appeared as distinct coloured bands in the packed column. The coloured bands were extracted sequentially by washing down the column with the liquid carrier phase.
Paper chromatography is a variant of liquid chromatography where the components of the mixture are separated by the unidirectional flow of the liquid mobile solvent over the filter paper to which the spot of the mixture is applied.
Earliest work on paper chromatography dates back to 1855 when Runge separated inorganic mixtures using impregnated filter paper.In 1865, Schoenbein made the observation of upward movement of aqueous salt solution through capillary action when a paper strip was dipped into the solution.
Martin and Synge in 1941 made significant contribution to liquid – liquid partition chromatography through analysis of amino acids in protein hydrolysates using partition chromatography which cut down the separation times drastically. In 1952 Martin and Synge were honoured with the Noble prize for their path breaking discovery.
Today paper chromatography is commonly employed for separation of mixtures of amino acids, plant pigments, sugars, inorganic ionic species and phenolic constituents of wood, etc.
A subsequent article will deal with the types of papers used in paper chromatographic separations.