Buffering Phenol

Manuel Simon ma at ABC.univie.ac.at
Wed Jun 8 16:36:28 EST 1994

In article <199406071653.JAA27400 at net.bio.net> MUNGO at UVVM.UVIC.CA writes:
>Subject: Buffering Phenol
>Date: 7 Jun 1994 09:53:41 -0700

> We have on occaison found that it can be very difficult to buffer phenol to
>pH 8.  For reasons nobody here can explain certain lots of high quality phenol
>are impossible to get to pH 8 even after overnight extraction with Tris base
>0.5 M unbuffered.  The phenol remains at pH 6.8.  However someone in the lab
>added a few drops of 10 M NaOH and the two phases then mixed and wouldn't
>seperate.  Upon addition of 50 mM Tris pH 8 the pahses seperated and the phenol
>was at pH 8 (sort of...).  Repeated extraction with 50 mM then 10 mM Tris pH 8
>does not change the pH of the phenol.  While I don't wish to address this
>rather novel approach to buffering phenol can anyone tell me what is going on?
>Why does adding NaOH cause the phases to mix ?  Is it the salt ?  Why do we
>have trouble buffering the phenol in the first place if it easily buffers once
>the phases mix ?  If the salt is causing the phases to mix why does the phenol
>remain buffered after repeated extractions with low salt buffer ?  And
>is this "solution" usable ?

High Mungo
I am not sure whether this is your solution: phenol is an acid; raising the pH 
will deprotonate the phenol and the ionic form will have altered solubility in 
water. If you dilute the aqueous phase I would expect that you get phase 
separation. I usually mix the adjusted phenol with CHCl3 (e.g. 1:5) - and 
normally can separation th phases


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