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Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)
pH range of buffer = pK ± 1
a
at pH = pK
a
the buffer has maximum capacity
Examples:
pK of acetic acid = 4.74 so acetate buffer is effective in the pH range from 3.74
a
to 5.74.
pK of ammonium hydroxide = 9.24 (= 14 - pK ) so ammonia buffer is effective
a b
in the pH range from 8.24 to 10.24.
Buffers in Biological Systems
❖ Buffers are very important to chemical and biological systems.
❖ The pH in the human body varies from one fluid to another,
for example: the pH of blood is about 7.4, whereas the gastric juice has a pH
about 1.5.
❖ These pH values, which are critical for enzyme function, are maintained by
biological buffers.
Biological buffers help in maintaining the body at the correct pH so that
biochemical processes continue to run optimally.
1. Carbonic acid bicarbonate buffer system
2. Phosphate buffer system
3. Protein buffer system
1. Carbonic acid bicarbonate buffer system:
The blood plasma is buffered in part by the carbonic acid bicarbonate buffer system
which consists of carbonic acid, a weak acid, and the bicarbonate anion, its conjugate base.
+
-
H 2CO 3 + H 2O H + HCO 3
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