Alcian blue at pH 0.4
Marlene Nardi inquired about Lee Luna's Alcian blue at pH 0.4. There
are several reasons why her pH readings are not the same as Luna's.
First, taking a reading below 2.0 is prone to machine error, and this
just gets worse below 1.0. Be sure to standardize the meter with pH
2.0 buffer if that is possible (some meters do not allow this, and
taking a reading below 1.0 is nearly meaningless if you are looking
at the tenth's decimal place.
Assuming the meter reading is correct (highly doubtful, and that goes
for Luns's measurement as well - no reflection on Lee), does the
monobasic sodium phosphate contain the same waters of hydration?
Finally, the problem may reside with the dye. Various batches of
Alcian blue 8GX made before 2001 varied widely in the amount of boric
acid used as a filler and stabilizer. This would affect the pH of
Since early 2001, Alcian blue has been made via a different process
and the composition is quite uniform from batch to batch. This may
not really solve your problem, however, as you don't know how well
fortified with boric acid Luna's dye was.
Now the good news: it won't make a real difference in the results.
Staining at any pH around 1.0 or below is restricted to highly
sulfonated compounds. Specificity for mast cells will not be
altered, as you have already seen.
Richard W. Dapson, Ph.D.
Battle Creek, MI
Web address: anatechltdusa.com
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