-96 = 



of mixtures of vmknown substances, yarious combinations of sorbents and 

 sol-vents should be tested. The sequences observed under these different 

 conditions provide a basis for the description of the components of the 

 mixture So 



CHROMATOGRAPHIC SYSTEMS 



Com plex of Mixture, Solvent, and Sorbent 



As shown first with chloroplast pigments, chromatographic sepa- 

 rations are based upon a very selective and reversible interaction among 

 the mixture, the solvent, and the sorbent. On the sorbent there is 

 sorption of the solvent and of the pigments or solutes. In the solvent 

 there are molecules of the solutes and their reaction or solvation pro- 

 ducts. 



At any point in the column there is a dynamic interaction among 

 solutes, solvent and sorbent. Each component reacts reversibly with the 

 others as indicated by the following diagraW+. 



Solvent 



/ \ 



Mixture ^ ^ Sorbent 



For definition of this kind of chromatographic system, the princi- 

 pal components must be specified. The mixture of the sorbed substances 

 is usually defined with respect to the chemical nature of the constitu- 

 ents or with respect to the physical condition of the mixture as a gas, 

 a vapor, or a solution. The solvent is described with respect to its 

 chemical composition or with respect to its physical state, usually a 

 liquid or a gas as now employed in the new field of gas chromatography. 



