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For screening of the correct eluent for Flash, you probably need to try the system with TLC.

I have this wild idea of how to minimize time an resources in such screening. But Im not som good in math, so I want some opinions...

Is it possible to run a TLC in pure hexane in one dimension
Rotate the TLC plate (and let it dry)
And run the TLC on pure EtoAc in the second dimension

Then by the distant the spots have traveled from origo (where you placed the sample)
calculate the right eluent to seperate two spots with the right retension times (Rf = 0.35 in flash)?

I guess there already is such a method in use somewhere. But where can I read about it?