Page 75 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)

2. Phosphate buffer system:

Phosphate buffer system plays a major role in buffering renal tubular fluid and
intracellular fluids.

-
+
2-
H 2PO 4  H + HPO 4
3. . Protein buffer system:

All proteins can function as buffers.

Proteins are made up of amino acids, which contain positively charged amino groups

and negatively charged carboxyl groups.

The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus

function as buffers.

+
Amino acids Contains both acidic (COOH) and basic (-NH 2 ) groups, H can pass
between this two groups.

❖ Zwitterion form: it is an ion possessing both positive and negative electrical charges.

Addition or removal of H to or from zwitterion produces either cation or anion.
+

Acid-Base Indicators

• They are weak acids or weak bases
• Their colour in solutions depends on pH.
• They are used to detect the end point in acid-base titrations
• They may be used to determine the pH of solutions.
• Definition: They are highly colored organic compounds with weakly
acidic or basic characters that undergoes color change at a certain interval
of pH called “pH range of the indicator”.

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