16 



the sugar column (Figure 1,1), were readily resolved by use of magnesia 

 columns provided chlorinated solvents or petroleum ether plus acetone 

 were employed to accelerate the migration of the pigments through the 

 strongly sorptive magnesia^ With columns of magnesia the mixture of 

 xanthophylls in leaf extracts could be resolved without preliminary 

 separation from the other leaf pigments''-^* as shown in Figure I^Jo 

 Under these conditions^ the neoxanthin and the zeaxanthin were frequently 

 sorbed in different sequences as indicated in the figure. This varia= 

 tion in the sequence of the two zones is due, apparently, to various 

 colorless sorbed substances in the plant extractSo 



The filtration rate of magnesia columns and therefore the rate 

 of separation of the pigments was increased by mixing the finely powdered 

 adsorbent with a nonsorptive filter aid such as Celite, a heat-treated 

 diatomaceous earth -^^^ •'■5. These mixtures served for separation of the 

 carotenes and leaf xanthophylls, but the reactive magnesia destroyed 

 the chlorophylls., The activated magnesia also slowly destroyed certain 

 labile xanthophylls obtained from algae-'- o 



Thus far, no single adsorbent has been found that will separate 

 all the chloroplast pigments from one another by a single application 

 of the chromatographic procedure. With columns of powdered sugar and 

 with petroleum ether containing about Oo5 per cent n-propanol as wash 

 liquid, it has been possible to separate the chlorophylls and many of 

 the oarotenoids obtained from various kinds of photosynthetic plantSo 

 And with columns of magnesia it has been possible to make a more exten- 

 sive resolution of these carotenoid pigments and to compare their chro- 

 matographic behavior (by mixed adsorption) with oarotenoids obtained 

 from the yellow organs of nonphotosynthetic plant parts^* o 



