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 
its solutions.

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.

Dick

-- 
Richard W. Dapson, Ph.D.
Anatech Ltd.
Battle Creek, MI
800-ANATECH (800-262-8324)
email@anatechltdusa.com
Web address:  anatechltdusa.com