Buffers in chemical analysis, types of buffers

Buffers in chemical analysis. its uses and function
types of buffers

1. BUFFERS IN
CHEMICAL
ANALYSIS
ChiragPatel

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

3. What exactly is a buffer?
A buffer solutionis a solution which resists changes in pH when a
small amount of acidor baseis added.
The resistive action is the result of equilibrium between the weak acid
(HA) and its conjugate base (A
-
).
HA
(aq) + H
2O
(l) → H
3O
+
(aq) + A
-
(aq)

4. •A buffer works best in the middle of its range, where the amount of
undissociatedacid 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
H
3O
+
ion into its acid (conjugate base removes excess H
3O
+
)
H
3O
+
(aq) + A
-
(aq) → HA
(aq) + H
2O
(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) + H
2O
(l)

7. Buffer with equal
concentrations of conjugate
base and acid
OH
-
H
3O
+
Buffer after addition of H
3O
+
H
2O + CH
3COOH H
3O
+
+ CH
3COO
-
Buffer after addition of OH
-
CH
3COOH + OH
-
H
2O + CH
3COO
-

8. In actual fact, the pH changes but very slightly
Large amounts of added H
3O
+
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 Acidand the Salt of Its Conjugate
Base (useful in the acidic range)
•eg. 1.0 M CH
3COOH & 1.0 M CH
3COONa
II. BASIC BUFFER:A Weak Baseand the Salt of Its Conjugate Acid
(useful in the basic range)
•eg. 1.0 M NH
3& 1.0 M NH
4Cl

12. -A measure of how well a solution resists changes in pH
-Increases with increasing concentration of buffer
-Maximum when pH = pK
a
-The greater the buffer capacity the less the pH changes upon addition
of H
+
or OH
-
-Choose a buffer whose pK
ais closest to the desired pH
-pH should be within pK
a±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 pK
aof 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 Neutraliseris an easy to use saturated solution
•usable at room temperature without precipitating out.
•Creates a boric acid/potassium borate buffer solution
Borax Decahydrate( Powder )
[Na
2B
4O
7: 10H
2O]
•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 HydroxyAcids(AHA)
•Triethanolamine, Diethanolamineand Ethanolamine are clear,
colourless, viscous liquids with ammonia-like odours.
•Triethanolamineis 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, H
2CO
3, acts as the weak acid
•Hydrogen carbonate, HCO
3
-
, acts as the conjugate base
•Increase in H
+
(aq) ions is removed by HCO
3
-
(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 H
2CO
3
•The small concentration of H
+
(aq) ions reacts with the OH
-
(aq) ions
•H
2CO
3dissociates, shifting the equilibrium to the right, restoring
most of the H
+
(aq) ions

22. •Most materials released into blood are acidic
•The HCO
3
-
ions removes these by being converted into H
2CO
3
•This acid is converted into CO
2(aq) through the action of an enzyme.
•CO
2(aq) is converted into CO
2(g) in the lungs, which is then exhaled
•The amount of CO
2(aq) in the blood can be regulated by changing
breathing rate
•Heavy breathing removes more CO
2(g)
•Breathing less quickly removes less CO
2(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)
2resulted in steady hydrolysis due to its
buffering property.