Aim: To prepare 100 ml of a pharmaceutical buffer solution of pH 5.0 (acetate buffer) and verify the same by measuring pH using a pH meter.
Principle of Buffer Solution
Buffers are compounds or mixtures of compounds; when present in solution, resist change of pH upon the addition of a small quantity of acid or alkali. Such solutions are called buffer solutions and are usually solutions of weak acids (or bases) and their corresponding salts (acetic acid and sodium acetate; ammonia and ammonium chloride).
The buffer equation is utilized to find out the quantity of weak acid and salt; or weak base and salt; required to get a buffer solution of desired pH. The buffer equation (also known as Henderson – Hasselbalch equation):
For weak acid and its salt:
![Preparation of Buffer](https://pharmacyscope.com/wp-content/uploads/2023/02/Screenshot-2023-02-07-091753.png)
, and for acetate buffer of pH 5.0, the equation is:
![Preparation of Buffer Solution](https://pharmacyscope.com/wp-content/uploads/2023/02/Screenshot-2023-02-07-091933-1024x153.png)
![mole fraction of salt](https://pharmacyscope.com/wp-content/uploads/2023/02/Screenshot-2023-02-07-092104-1024x117.png)
The mole fraction of salt in the solution =
The concentration of salt in the buffer solution (mole fraction) = 63.5%
The concentration of acid in the buffer solution (mole fraction) = 36.5%
![acetic acid](https://pharmacyscope.com/wp-content/uploads/2023/02/Screenshot-2023-02-07-092257-1024x94.png)
(the molecular weight of acetic acid is 60.05)
Then the weight of acetic acid is converted to volume using weight per ml data.
![sodium acetate](https://pharmacyscope.com/wp-content/uploads/2023/02/Screenshot-2023-02-07-092409-1024x114.png)
(The molecular weight of sodium acetate is 82.08)
Apparatus and materials required: Standard buffers, Acetic acid, Sodium acetate, and pH meter.
Preparation of Buffer Solution
Process:
- The quantity of acetic acid and sodium acetate are dissolved in around 90 ml of distilled water and the volume is adjusted to 100 ml.
- The pH meter is calibrated using a standard buffer.
- The pH of the buffer solution is recorded.
Observation and Calculation:
Room temperature: ________0C
The pH of the prepared buffer solution is _______
Report: The prepared buffer solution has pH ____________
Make sure you also check our other amazing Article on: Determination of Critical Micelle Concentration