I have a foreign student intern who can benefit from improving her flash chromatography techniques. Rather explaining things verbally, I feel that it is faster to let her learn by doing. For you educators out there, what will be a good mixture, perhaps colored, organic compounds with good, somewhat close, and tight delta Rf using chemicals that are available in common organic synthesis lab ?
Any suggestions are welcomed, please refrain from suggesting something that you have never taught or tried yourself, thanks a lot.
We have found by ourselves that 100 mg of mixture composed from equal masses of fluorene and fluorenone can be successfully separated with Hex/EtOAc at 10 g SNAP column employing Biotage Isolera.
I like to use CAMAG part # 032.8001 for this purpose. You can use it to show the relationship between TLC plate Rf and elution time (in column volumes (Elution time in CV = 1/Rf). It is Dimethyl yellow, Oracet blue 2R, and Oracet red G dissolved in toluene.
In addition, teach the intern about sample loading techniques. I've seen purifications which should work easily go bad due to loading in a very strong solvent, for example.
Flash using the dyes: (see the last page after the conclusion): http://www.isco.com/WebProductFiles/Applications/101/Poster_and_Paper_Reprints/Spherical_Silica_Increases_Loading_Capacity.pdf
Loading technique comparison, Silica flash: http://www.isco.com/WebProductFiles/Applications/101/Application_Notes/AN29_Overview_of_Silica_Column_Sample_Loading_Techniques.pdf
Loading technique comparison, C18 flash: http://www.isco.com/WebProductFiles/Applications/101/Application_Notes/AN88_C18_Flash_Column_Loading.pdf
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