Natural auxins 



workers in different laboratories arrived at various recipes for solvent 

 mixtures that would separate certain auxins, especially the acid ones. In 

 general, a mixture of an alcohol, ammonia, and water has been adopted. 

 Stowe and Thimann (1954) substantiated this through systematic studies 



IV- 



^C(^T 



h 



fi 



Figure 5. (a) The chromatoamm is first 

 equilibrated over the solvent overnight. A paper 

 wick (W) keeps the upper part of the tube 

 saturated with the vapour of the solvent. A 

 ring of rubber tubing (R) supports the inner 

 glass rod. (b) After equilibration, the inner 

 glass rod is pushed down so that the lower 5 mm 

 oj the paper strip will penetrate into the solvent. 

 {c) When the solvent has travelled up a height 

 (H) of 20 cm. the paper is air-dried, and 

 sprayed with a suitable reagent. Both the 

 position (h) and length (I) of the coloured 

 spots are noted. The technique illustrated 

 under (a) and (b) is essentially that of Stowe 

 and Thimann, 1954. {After Nitsch and 

 Nitsch, 1955.) 



and recommended a mixture of zVopropanol (80) +28 per cent ammonia 

 ( 1 0) + water ( 1 0) (v/v) which we have used on many occasions with good results. 

 We have tried to go further in this investigation by asking this question: 

 'What is the simplest mixture which can separate auxins on paper?' The 

 results of Table 2 speak for themselves : first of all, the presence or the absence 

 of ammonia does not appreciably affect the separation of the three auxins 



Table 2 

 Search for the simplest chromatographic solvent 

 All paper strips were equilibrated overnight over the solvent. 



Solvent 



RA 



IB AX 



lAE 



woPropanol (80%) + water (10%) 

 f.roPropanol (80%) + water (10%) 

 woPropanol (100%) 

 Water (100%) 



28% ammonia (10%) 



0-83 

 0-83 

 0-83 

 0-47 



t The symbol Rf ('ratio front') designates the ratio of the movement of a given conipouml to the movement 

 of the front of the solvent. Rf — hjH {see Figure 5). 

 } IBA = indole-3-butyric acid. 



10 



