Phenol pH?

Dr. Hiranya S. Roychowdhury hroychow at
Tue Oct 31 23:52:09 EST 2000

I suspect that the yield of DNA following the acidic phenol extraction
would be lower than with phenol at 7.5 and higher. That is what my
experience has been. The acidity needed for complete partitioning of DNA
with phenol is around pH4.0. Phenol itself does not have that low pH, AFAIK.
Chrloroform has no effect on the pH.

At 10:12 PM 10/31/00 -0000, Alan Smith wrote:
>I have a question about the pH of Phenol and its effect on DNA.  According
>to Maniatis phenol must equibilated to pH 7.8 or above to prevent the
>movement of DNA into the organic phase (I have  done this my whole life). I
>also have preformed many RNA extraction in which case acidic phenol is used
>to remove DNA.  However, digging through the refrigerator in my lab I
>realized to my horror that every one in the lab was using water saturated
>phenol about pH 6.6 from Fisher, but nobody is having problems with loss of
>DNA to the organic phase in either plasmid or genomic DNA preps.  The techs
>didnt even know why little bottles of Tris came with the phenol and just
>left them sit in the fridge (found about 6 of them)  Does the addition of
>chloroform somehow prevent DNA from moving into the organic phase?  As far
>as I know straight phenol is not used in any of the labs DNA preps, just
>P/C/I.  Could someone please describe to me how the chloroform can protect
>the DNA from being removed by the acidic phenol.
>Thank You
>Alan Smith
Dr. Hiranya Sankar Roychowdhury
College Asst. Prof.
Molecular Biology,
Dept. of Chemistry & Biochemistry	
Box 30001 - 3MLS
New Mexico State University
Las Cruces, NM 88003

Lab: (505) 646 4722
Office: (505) 646 8256
hroychow at


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