- A buffer solution resists changes in pH when small amounts of acid or base are added due to the equilibrium between a weak acid and its conjugate base. Commonly used buffers include a weak acid and the salt of its conjugate base or a weak base and the salt of its conjugate acid. - Buffers work best when the concentrations of the weak acid and its conjugate base are equal and the pH is within 1 unit of the pKa. Their buffering capacity depends on their concentration and is highest when the pH equals the pKa. - Common applications of buffers include controlling pH in chemical reactions, biological systems, pools, and more. The carbonic acid-bicarbonate buffer system is particularly important for maintaining

1. BUFFERS IN
CHEMICAL
ANALYSIS
Chirag Patel

2. an unbuffered solution
or a buffered solution
acid added base added
acid added base added

3. What exactly is a buffer?
A buffer solution is a solution which resists changes in pH when a
small amount of acid or base is added.
The resistive action is the result of equilibrium between the weak acid
(HA) and its conjugate base (A-).
HA(aq) + H2O(l) → H3O+
(aq) + A-
(aq)

4. • A buffer works best in the middle of its range, where the amount of
undissociated acid is about equal to the amount of the conjugate
base.
• Commonly used in biological systems.
• Enzyme-catalyzed reactions depend on pH.

6. When an acid is added, the conjugate base converts the excess
H3O+ ion into its acid (conjugate base removes excess H3O+)
H3O+
(aq) + A-
(aq) → HA(aq) + H2O(l)
When a base is added, the acid converts the excess OH- ion into
its conjugate base and water (acid removes excess OH- ion)
HA(aq) + OH-
(aq) → A-
(aq) + H2O(l)

7. Buffer with equal
concentrations of conjugate
base and acid
OH-H3O+
Buffer after addition of H3O+
H2O + CH3COOH H3O+ + CH3COO-
Buffer after addition of OH-
CH3COOH + OH - H2O + CH3COO-

8. In actual fact, the pH changes but very slightly
Large amounts of added H3O+ or OH- may overcome the buffer action
and change pH of solutions
Buffers are most effective when the ratio of acid to conjugate base is
1:1
Buffers are less efficient in handling acids if the acid is more than the
conjugate base
Buffers are less efficient in handling bases if the acid is less than the
conjugate base

9. There are two kinds of Buffer Solutions:
I. ACIDIC BUFFER: A Weak Acid and the Salt of Its Conjugate
Base (useful in the acidic range)
• eg. 1.0 M CH3COOH & 1.0 M CH3COONa
II. BASIC BUFFER: A Weak Base and the Salt of Its Conjugate Acid
(useful in the basic range)
• eg. 1.0 M NH3 & 1.0 M NH4Cl

12. - A measure of how well a solution resists changes in pH
- Increases with increasing concentration of buffer
- Maximum when pH = pKa
- The greater the buffer capacity the less the pH changes upon addition
of H+ or OH-
-Choose a buffer whose pKa is closest to the desired pH
- pH should be within pKa ± 1

14. The buffer range is the pH range over which the buffer is effective.
Buffer range is related to the ratio of buffer component concentrations.
[HA]
[A-]
The closer is to 1, the more effective the buffer.
If one component is more than 10 times the other, buffering action is
poor. Since log10 = 1, buffers have a usable range within ± 1 pH
unit of the pKa of the acid component.

15. • Calibration of pH meters
• Control of pH in industrial reactions
• Used in maintaining water quality
• Pools and hot tub
• Wine making
• pH balanced shampoos and deodorants
• Soil pH
• Minimizing effects of acid rain

16. Borax Neutraliser
• Boric Acid Neutraliser is an easy to use saturated solution
• usable at room temperature without precipitating out.
• Creates a boric acid/potassium borate buffer solution
Borax Decahydrate ( Powder )
[Na2B4O7 : 10H2O]
• Borax dissolves to form a boric acid/sodium borate buffer solution
• will not allow pH to be reduced too much, avoiding clouding.
• when using Borax to neutralise, although minimum pH achieved is
not quite as low as with other neutralisers.

17. • Cleopatra used raw milk which has the lactic acid in it.
• This is because it is unpasteurised and thus poses a potential health
risk.
• AHAs most commonly used in cosmetic products are glycolic acid
and lactic acid.
• AHAs function as pH adjusters, these are materials added to
products to make sure they are not too acidic or basic and are
therefore mild and non-irritating.

18. Alpha Hydroxy Acids(AHA)
• Triethanolamine, Diethanolamine and Ethanolamine are clear,
colourless, viscous liquids with ammonia-like odours.
• Triethanolamine is used in makeup products such as eyeliners,
mascara, eye shadows, blushers, etc. as well as in fragrances, hair
dyes, wave sets, sunscreens, skin care and skin cleansing products.

19. The carbonic acid-hydrogen carbonate buffer system.
Human blood plasma needs to have a pH between 7.35 and 7.45.
Acidosis and alkalosis.
The pH of blood is controlled by a mixture of buffers.

20. • The carbonic acid-hydrogen carbonate ion buffer is the most
important buffer system.
• Carbonic acid, H2CO3, acts as the weak acid
• Hydrogen carbonate, HCO3
-, acts as the conjugate base
• Increase in H+(aq) ions is removed by HCO3
-(aq)
• The equilibrium shifts to the left and most of the H+(aq) ions are
removed

21. • Any increase in OH-(aq) ions is removed by H2CO3
• The small concentration of H+(aq) ions reacts with the OH-(aq) ions
• H2CO3 dissociates, shifting the equilibrium to the right, restoring
most of the H+(aq) ions

22. • Most materials released into blood are acidic
• The HCO3
- ions removes these by being converted into H2CO3
• This acid is converted into CO2(aq) through the action of an enzyme.
• CO2(aq) is converted into CO2(g) in the lungs, which is then exhaled
• The amount of CO2(aq) in the blood can be regulated by changing
breathing rate
• Heavy breathing removes more CO2(g)
• Breathing less quickly removes less CO2(g)

23. • The Chemistry of Natural Rainwater
• The Chemistry of Acid Rain
• The Buffering Capacity of Limestone Chemistry of Acid Rain

24. • During electrophoresis, the electric field electrolyses the water
molecules into H+ and OH- ions that migrate to the respective
migrate to the respective electrodes.

25. Glycine as buffer
• Unlike most other buffering compounds, which are capable of
stabilizing pH in only one pH range, glycine has two pH buffering or
stabilizing regions.
• The accompanying graph illustrates the change in pH after addition
of acid (HCl) or base (NaOH) to glycine. As you can see, glycine
exhibits excellent buffering action between pH 1.5 to 3.0 and
between pH 9.0 to 13.0.

26. Soft drinks, Lozenges and tablets
Syrups
Mouthwashes
Livestock feed
Antacids
Analgesics
Cosmetics
Antiperspirants
Toiletries
Pharmaceuticals
Agricultural chemicals

28. • Always buffer the aqueous component of the mobile phase
separately7. pH of the mobile phase and pKa of Analyte will change
in the presence of organic solvents
• High buffering power at prescribed pH.
• Does not damage column or equipment.

29. • It seems that using Ca(OH)2 resulted in steady hydrolysis due to its
buffering property.