18 " 



Separations by Paper- Chromat ography 



Another remarkably effecti-ve, extremely sensitive, and widely 

 applicable separatory procedure, now called paper chromatographyj was 

 first demonstrated by separation of the chloroplast pigments » It had 

 been known for many years that mixtures of -various substances were 

 partially resolved when their solutions were drawn into filter paper 

 by capillary action,, This procedure, which provided partial resolu- 

 tion of the mixture at the leading boundaries of the migrating solutes 

 had been called capillary adsorption analysis and had been extensively 

 investigated by Goppelsroeder-'o 



In 1959, Brown modified the capillary analysis procedure by in- 

 troducing the development or washing step of columnar chromtography-'-' o 

 In his demonstration. Brown adsorbed a little of a petroleum ether ex= 

 tract of dried leaves in the center of a sheet of filter papero Then 

 he added fresh solvent to the center of the spot so that as this wash 

 liquid flowed outward it carried the pigments along at different rates 

 and separated them from one another <> In this separation by paper 

 chromatography, the two green chlorophylls, two or three xanthophylls 

 and the carotene mixture formed a series of concentric zoneSo 



Since Brown's experiment, the paper chromatography of leaf pig= 

 ments has been modified in many ways and reapplied to separation of 

 the chloroplast pigments^ » In one modification, the paper was moistened 

 slightly with aqueous glycerine j, so that the separation of the pigments 

 depended upon their sorption at the petroleum ether=aqueous glycerine 

 interface, a liquid- liquid interface rather than the liquid-solid inter- 

 face in dried paper and in powdered sugar^°o 



