- lu - 



It represented an important modification of earlier coliimnar adsorption 

 procedures in which only the solution of the mixture was filtered 

 through the adsorption column. It made possible the extensive resolu- 

 I tion of complex mixtures and the recovery of the separated components5, 



Tswett recognized that his separation procedure depended upon 

 the selective adsorption of the pigments. As the separations revealed 

 the presence of colored substances, he called his method "chromatog- 

 raphische Adsorptionsanalyse" or chromatographic adsorption analysis, 

 now frequently condensed to chromatographic analysis or chromatography. 

 Tswett also recognized that colorless substances as well as pigments 

 were separated by the chromatographic adsorption procedure. 



With his mild adsorbents Tswett separated two chlorophylls, three 

 or four xanthophylls and the carotene mixture from leaf extracts. At 

 the time, it was not realized that the leaf carotene was frequently a 

 mixture of two or more isomeric pigments, alpha-carotene and beta-caro- 

 tene, and that two xanthophylls, lutein and zeaxanthin, usually form a 

 single zone when adsorbed under the mild conditions described by Tswett, 

 (See Figure 1,1.) 



For the separation of the leaf carotene, more active and more 

 selective adsorbents were needed. These were found in the form of 

 specially activated, finely powdered alumina, lime or magnesia-'--', 

 Mth columns of specially activated magnesiiim oxide (Micron Brand 

 Magnesium Oxide No. 26i4.l) and with petroleum ether as solvent, the 

 mixtures of carotenes in leaf extracts could be resolved without pre- 

 liminary separation from the other leaf pigments-'-^, as indicated in 

 Figure 1,2, 



Mixtures of lutein and zeaxanthin, which were not separable in 



