pH of TBE/Glycerol

BC bruno.removethis.cenni at
Fri Feb 15 04:40:37 EST 2002

Hi all,

we ran into resolution troubles with our SSCP. One of the factors that we
then checked was the composition of the polymer and buffer. We routinely use
1xTBE/10Glycerol. The 5x and 1x TBE (=89mM Tris, 89 mM borate, 2 mM EDTA)
has the (expected) pH of about 8.3. However as soon as we add glycerol the
pH sinks to about 7.7. It's not the batch of glycerol or of the other
reagents...and 10% glycerol in 89 mM Tris pH 8.3 doesn't affect the pH. The
pH is measured with an electrode and with indicator paper.

So I thought to remember that borate makes complexes/chelates with OH groups
(a boron?, one of the reasons it's used for DNA-buffers), might this lead to
the acidification?

Until recently we simply assumed that the glycerol would not affect the pH,
but we never actually had controlled before. So has anyone ever measured the
pH of a TBE buffer before and after adding glycerol?


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