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A buffer is an aqueous solution consisting of a mixture of a weak acid & its salt or a weak base & its salt that resist a change in pH on the addition of either acid or base.
Note:- A lot of biological & chemical reactions need a constant pH for the reaction to proceed. Buffers are extremely useful in these systems to maintain the pH at a constant value. This does not mean that the pH of buffers doesn’t change. It only means that the change in pH is not as much as it would be with a solution that is not a buffer.
TYPES OF BUFFER SOLUTIONS
Buffers are broadly divided into two types:
1. Acidic buffer solution: These are solutions that have a pH below 7 and contain a weak acid and one of its salts. For example, a mixture of acetic acid and sodium acetate acts as a buffer solution with a pH of about 4.75.
2. Alkaline (Basic) buffer solution: These are solutions that have a pH above 7 and contain a weak base and one of its salts. For example, a mixture of ammonium chloride and ammonium hydroxide acts as a buffer solution with a pH of about 9.25.
Physiological Buffers are chemicals used by the body to prevent sudden, rapid changes in the pH of a fluid. As buffers are most able to resist changes in pH when the pH of the solution is close to the unique pH of the buffer. Consequently, physiological buffers must be chemicals whose pH are near the normal blood pH which ranges from 7.37 – 7.42. The primary buffers of the ECF appear to be inorganic phosphate (pH 6.8) and bicarbonate (pH 6.1).
The most important examples of physiological buffers system are as follows:-
i) Bicarbonate buffer
ii) Phosphate buffer
iii) Oxyhaemoglobin buffer
IMPORTANCE OF BUFFER IN BIOLOGICAL RESEARCHES
1. Buffers are used to maintain some drug or medicine in ionized form as ionized forms are more soluble in aqueous solutions.
2. Buffers are used to maintain the pH of most of the drugs near-neutral otherwise it causes irritation in body tissue.
3. It is used to check the performance of electrodes used in pH determination.
4. It is used to control the pH of the chemical reaction catalyzed by enzymes.