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129
For a polyacids such as alginic acid or protonated forms of hyaluronan or
CMC (carboxymethyl cellulose) the titration of carboxyl groups with strong
alkali leads to progressively higher density of negative charges:
This is reflected in the titration curves (pH versus
α
), as shown below for
hyaluronic acid. In this case the hyaluronan was first transferred to the acidic
form by using a cation exchanger (exchange Na
+
with H
+
), and then titrated
with NaOH at 4 different ionic strengths (0, 0.01,0.1 and 0.45 M)
⊝ ⊝ ⊝ ⊝ ⊝
⊝ ⊝⊝ ⊝ ⊝⊝⊝ ⊝
⊝ ⊝⊝ ⊝ ⊝⊝⊝ ⊝
⊝ ⊝⊝⊝ ⊝ ⊝⊝ ⊝
α
=0 (H
n
A)
α
=1 (A
n-
)
Titration with OH
-