Our body maintains the acid-alkali balance, slight disturbance in the buffer system may lead to health issues.

1. BUFFER
Presented by-
Rubina Roy
Assam University, Silchar

2. INTRODUCTION
 A buffer is a compound or mixture of compounds which when present in a solution resists changes
in pH upon the addition of small quantities of acid and bases.
 Buffer systems follow Le-Chatelier’s Principle.
 Buffers are significant in maintaining pH of living system.
Image source: Chemed.chem.purdue.edu

3. TYPES OF BUFFER
Buffer
Acidic Buffer Basic Buffer
(combination of weak acid &
its salt with strong base) (combination of weak base & its salt
with strong acid)
CH3COOH/CH3COONa NH4OH/ NH4Cl
H3PO4/ NaH2PO4 NH3/NH4Cl

4. Buffer Action
Mechanism of action in acidic buffer
• Let us consider a buffer system of CH3COOH & CH3COONa.
• CH3COOH CH3COO- + H+
• CH3COONa CH3COO- + Na+
Adding small amount of acid Adding small amount of Base
(HCl) (NaOH)
HCl H+ + Cl- NaOH Na+ + OH-
H+ + H2O H3O+
H3O+ + CH3COO- CH3COOH + H2O OH- + H3O+ 2 H20
Image source: Chemguide

5. Mechanism action of basic buffer
• Let us consider a buffer system of NH4OH & NH4Cl.
• NH4OH NH4
+ + OH-
• NH4Cl NH4
+ + Cl-
Adding small amount of base Adding small amount of acid
(NaOH) (HCl)
NaOH Na+ + OH- HCl H+ + Cl-
OH- + NH4
+ NH4OH H+ + H2O H3O+
H3O+ + OH- 2H2O
Image source: Chemguide

6. Hendersen-Hasselbalch Equation
Buffer Equation
Acid Buffer Basic Buffer
(CH3COOH) (NH4OH)
CH3COOH CH3COO- + H+ NH4OH NH4 + OH-
Weak acid salt weak base salt
Ka = Kb =
[H+] = Ka [OH-]= Kb
-log [H+] = -log Ka –log -log [OH-]= -log Kb - log
pH = pKa – log pOH = pKb – log
pH = pKa + log pOH = pKb + log
So, pH = pKa + log pOH = pKb + log

7. Buffer Capacity
• Buffer capacity is the efficiency of a buffer solution to resist pH change on addition of small amount
of acid or base.
• Buffers can resist pH change upto ±1 unit of its buffering zone.
• Buffering capacity =
Fig. Titration Curves of Different Buffers
Image source: www.bioinfo.org

8. Applications of Buffer
In Pharmaceutical Preparation
– To adjust the pH of drug and medicine , in order to minimize drug degradation & to improve patient’s
comfort
– The drugs applied through injections are maintained at an ideal pH of 7.4 (as that of blood)
– Buffers used in injections are acetate, phosphate, citrate, etc.
– Buffers like borate, carbonate, phosphate are used in ophthalmic preparations to maintain the pH of the
medicine within the pH range of lacrimal fluid (7-8).
In Laboratory
To callibrate pH meter for determination of pH of water, soil, food and other samples
To carry out various biological research such as DNA & RNA isolation, protein crystallisation.
In Industrial Preparation
To ensure stability of ointments and creams on applied areas like skin
To set up appropriate conditions for dyeing fabrics
To set up appropriate conditions for fermentation process in food production

9. List of Commercial Buffers
Name Composition pH Range Use
Phosphate Buffer Sodium Phosphate
Dibasic + Sodium
Phosphate Monobasic +
Distilled water + HCl
/NaoH
6.36-7.36 Ophthalmic preparations,
biological research
Citrate Buffer Citric acid + Sodium
Citrate + distilled water
+ HCl/NaoH
3-6.2 Pharmaceutical preparations,
biological research, RNA isolation
Acetate Buffer Sodium acetate + Acetic
acid + distilled water +
HCl/NaoH
4.26-5.26 Purification & precipitation of
nucleic acids, Protein
crystallization
Carbonate-Bicarbonate
Buffer
Sodium Carbonate +
Sodium Bicarbonate +
Distilled water + HCl
9.2-10.6 Used in protein-coating in Enzyme
Immunoassay (EIA) technique,
Dairy product preservation
Tris-acetae-EDTA
Buffer (TAE)
Trisaminomethane +
EDTA + Glacial Acetic
acid + water + HCl
8-8.5 DNA & RNA extraction by gel
electrophoresis
Tris-borate-EDTA buffer
(TBE)
Trisaminomethane +
Boric Acid+ EDTA +
Distilled Water + HCl
8-8.3 Gel electrophoresis

10. In Biological System
Criteria of Good Biological Buffer
A) Solubility
More water soluble
B) Permeability
Freely permeable to cell membranes
C) Ionic strength & Inertness
Should not hinder enzyme activity
D) UV absorption
Light absorption should be within 230 nm
Should not interfere with the spectrophotometric studies in biological research.

11. Image source: onlinebiologynotes.com

12. Phosphate buffer
Image source: Chemistry@Elmhurst

13. Protein Buffer
Haemoglobin Buffer
Image source: Biology Discussion

14. Amino Acid Buffer
Image source: BiologyDiscussion

15. Plasma Protein Buffer
• All proteins with positively charged & negatively charged groups can act as buffer.
• Proteins having histidine residues are adept in buffering.
• Albumin is the predominant plasma protein functioning as buffer.
• Albumin consists of 610 amino acids.
Amino acids in Albumin
Acidic amino acid Basic amino acid Neutral amino acid
Aspartic acid Histidine, lysine, arginine Phenylalanine, valine,
threonine, leucine

16. Carbonic acid-Bicarbonate buffer

17. Acid-Base Balance Disorders

18. ACIDOSIS
Image source: www.bioinfo.org

19. Diabetic Ketoacidosis

20. ALKALOSIS
Image source: www.bioinfo.org

21. SUMMARY
• Acid-base balance is necessary to be maintained for the functioning of all biological activities.
• Various types of buffers work in a coordinated manner in the living body.
• In plants bicarbonate and phosphate buffers are found in the chloroplast, protoplasm, and vacuoles.
• Drastic deviation from normal pH of body leads to chronic situations resulting death.

22. REFERENCES
• Kosikowsky, F. V., & Dahlberg, A. C. (1949). Application of a Sodium Carbonate-
Bicarbonate Buffer in the Phosphatase Test for Cheese1. Journal of Dairy
Science, 32(9), 760-763.
• Lebovitz, H. E. (1995). Diabetic ketoacidosis. The Lancet, 345(8952), 767-772.
• Nelson, D. L., Lehninger, A. L., & Cox, M. M. (2008). Lehninger principles of
biochemistry. Macmillan.

23. THANK YOU