Natural auxins 



the ?Vobiitanol solvent proposed here separates a greater number of different 

 compounds in bean extracts than does the zi-opropanol-ammonia-water 

 solvent. 



In attempting to separate the neutral auxins such as IAN and lAE, it was 

 observed that they generally have high R/a in the alcohol-water or 

 acetonitrile-water mixtures. We looked, therefore, for solvents in which 

 these substances would be very slightly soluJDle. Thus hexane and heptane 

 were tried, together with carbon tetrachloride, jjenzene, carbon disulphide, 

 toluene, etc. It was soon found that success or failure in these attempts 

 depended on the presence of a very small amount of water, even though these 

 solvents were water-insoluble. In the case of carbon tetrachloride and carbon 

 disulphide, which are heavier than water, the paper strip was lowered in a 

 beaker containing the organic solvent with water surrounding the beaker. 

 When water was present, IAN and lAE were usually separated, except in the 

 case of CCI4, CS2, and benzene, which are slightly soluble in water. The 

 best results were obtained with hexane {Table 5) and the 'practical' grade 



Table 5 



The use of water-insoluble compounds in the chromatographv of auxins 



(Eastman P 1 135) was better than w-hexane. Although water is insoluble in 

 hexane, it was noted that the amount of water in the tube modifies the 

 position of the IAN spot on the chromatogram (Nitsch and Nitsch, 1955). 

 This peculiarity seems to depend on how well the paper wick plunges into the 

 water phase to provide enough water vapour above the solvent; indeed, 

 when the paper wick does not touch the water, the chromatograms may 

 behave as if they were run in anhydrous hexane. 



The fact that two types of chromatographic solvents are now available, one 

 for the acid auxins, the other for some neutral ones, does not, unfortunately, 

 solve everybody's problems. Rather, it seems that each worker may have to 

 devise his own solvent to fit his particular needs, though it is hoped, at least, 

 that the principles studied above may be useful in this task. 



14 



