INTRODUCTION " 



tive chromatography, (3, 4, 5). Countercurrent distribution methods are also widely used 

 although they require more complex apparatus than most chromatographic procedures. 

 Reviews of this technique may be found in articles by Hecker (6) and Thompson et al. , (7). 



Cheronis (8) has proposed a general fractionation procedure applicable to any aque- 

 ous plant tissue extract. The broad outlines of this procedure are indicated by the fol- 

 lowing diagram. Further separation of the different fractions can be achieved by appro- 

 priate methods of column chromatography. 



PLANT EXTRACT 



(steam distil) 



volatile 



acids 

 alcohols 

 carbonyls 

 (anion exchanger - HCO3 



non-volatile 

 (cation exchanger) 



absorbed 

 acids 

 phenols 



absorbed 



effluent 



(anion exchanger - HSO3 ) 



absorbed 

 amino compounds 

 alkaloids 



carbonyl compounds 



effluent 

 alcohols 

 esters 



absorbed 



acids 

 phenols 



effluent 

 (anion 

 exchanger -HCO3 



effluent 

 sugar 



Obviously many types of compounds present in plants are not shown in this scheme, but 

 everything must fall (even though incompletely) into one fraction or another, so that as a 

 preliminary separation the method has much to offer. Further fractionation must take 

 into account the properties of the desired compounds. As with any fractionation scheme, 

 it can be applied most intelligently if some qualitative information is available regarding 

 the constituents of the original mixture. The following discussion of "Characterization" 

 is intended to suggest means for obtaining such information. 



CHA RA CTERIZA TION 



Under characterization are included methods for identifying a pure compound and 

 also methods for determining what types of compounds are present in a crude mixture. 

 Many times characterization procedures necessarily include the separation of somewhat 

 purified compounds from mixtures, so that characterization cannot be strictly distinguished 

 from the isolation methods described in the previous section. Complete characterization 

 of a mixture requires quantitative analysis of the constituents in addition to knowledge of 

 what they are. However, becaue of the space that would be required, all quantitative de- 

 terminations have been excluded from this book. In most cases qualitative determina- 

 tions performed with care permit some rough quantitative conclusions to be drawn, so 

 that major and minor components of a mixture can be distinguised from one another. The 



