Wednesday, April 09, 2008
The Invisible Phase Boundary
All organic chemists have experienced it. Your reaction is done and your transfer it to a separatory funnel with an aqueous and an organic phase. You do your shaky, shaky bit and the phases separate but it is impossible to tell where the phase boundary is. The problem is most commonly encountered when very dark phases are obtained but it can also occur with perfectly clear phases (see picture). The solution to this problem is very simple. Simply tip a clean NMR tube cap into the separatory funnel and observe as it settles on top of the bottom phase. Problem solved. D!