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ELECTROCHR OMATOGRAPHY AND ANALOGOUS 

 DIFFERENTIAL MIGRATION METHODS OF ANALYSIS 



CHROMATOGRAPHY AND DIFFERENTIAL MIGRATION 



Mechanism for the Chromatographic Separations 



The studies of the chloroplast pigments provided numerous clues 

 to the mechanism of the chromatographic separations. They led to the 

 elaboration of these techniques, to the invention of analogous sepa- 

 ratory methods, and to the correlation of various analytical procedures 

 that depend upon the phenomenon of differential migrationo 



In the chromatographic columns, the pigments are transported by 

 the wash liquido The nonsorbed moleculeSj, those remaining in the liquid, 

 are carried along with the solvent until they become adsorbedo While 

 bound by the sorbent, they are fixed and are not conveyed by the wash 

 liquido In the dynamic system in the ool\jmn (see Figure IV, 1), the 

 migration of each pigment molecule is proportional to the time that 

 it remains in solution relative to the time that it is in the coliunn o 



The migration of each pigment zone depends upon the average dis- 

 tribution of the molecules between the solvent and the sorbento It is 

 proportional to the fraction in the solution and inversely proportional 

 to the fraction on the sorbento But with surface=active sorbents, the 

 nonsorbed fraction of the pigments decreases with decreasing concen- 

 tration,, As a consequence, the migration of the zones decreases with 

 decreasing, concentration! the leading boundaries of the zones remain 

 sharp? the trailing boundaries become diffuse o 



