[mir]

I tried doing a flash chromatography yesterday. But I ran imidiatly into trouble.
I packed to column correctly. And the flow rate was correct.
But the solvent system I used was probably incorrect. Even it worked pretty well on TLC. The Rf was wrong (0.6). It should have been around 0.35 I have recently learned. But anyway, I didnt get the fraction of product I wanted, I checked with TLC, but the product wasnt around anywere in the fraction before I ran out of solvent (the volume is instructed in a standardized table). This doesnt make sense. Could my fractioon be to dilute, to see in TLC? I even tried UV and a chemical that react with a color (hydrizine?) with an amine (my product), but no sign of product.

Can I compare the solvent systems in TLC with the solvent systems in Flash chromatography to find the correct Rf value?
Any tips around choosing solvents?

And I also wished to have five arms and two heads while doing the separation, it went to quickly (the instructions tell 2.5 cm/30 seconds). My column was emptied in only ten minutes. I suppose when I am out of solvent the separation is finish?

[chiralic]

Hi mir:

I recommend you visit this page...on this page you can find some tips on flash chromatography:

http://www.labhut.com/education/flash/index.php

Regards,

Chiralic