(Midterm) pH and Buffers Flashcards
Ionization of Water and the pH phenomenon
● Hydronium Ion
● Ionization of water
Chemical Theories on Acids and Bases
● Bronsted-Lowry Acid-Base Theory
● Lewis Acids and Bases
Less than a full octet of electrons
Lewis Acids and Bases
Metal ions except those of the alkali
group
Lewis Acids and Bases
Compounds having double bonds
Lewis Acids and Bases
Mixture of compounds that, by their
presence in solution, resist changes in pH
upon the addition of an acid or alkali.
Buffers
It is a measure of the strength of an acid or
a base.
Dissociation Constant
What are the Uses of Buffers
● Preparation of such dosage of injections
and ophthalmic solutions.
● For product stability.
● Pharmaceutical tests and assays requiring
adjustment or maintenance of a specific pH.
It is the measure of the magnitude of the
buffer action of the buffer system.
Buffer Capacity
It is the amount in g/L of SA or SB required
to be added to a solution to change in pH by
1 unit
Buffer Capacity
Importance of Buffer Systems
In-vivo biological buffer systems
Blood buffer systems:
A. Primary Buffers
B. Secondary Buffers
Primary Buffers:
● Carbonic Acid/Bicarbonate
● Acid or Alkali Na salts of phosphoric acids
● Plasma CHONS
Secondary Buffers:
● Hemoglobin/Oxyhemoglobin
● Acid/Alkali potassium salts of phosphoric
acids
● Lacrimal Fluid
● Urine
- It can be as low as 4.5 or as high as 7.8.
- Physiological pH balance
Urine
Pharmaceutical buffers:
- Phosphate buffer System
- Borate Buffer Systems
Phosphate buffer System:
- Sorensen buffer
Sodium Chloride is added to make it
isotonic.
Sorensen buffer
It is a mixture of salts of Sodium
Phosphate for buffer solutions of
pH(6.8).
Sorensen buffer
Borate Buffer Systems:
- Gifford Buffer
- Feldman’s Buffer
- Atkins & Pantin Buffer
It contains Boric acid and Sodium
Carbonate.
Gifford Buffer
It is used as a buffer for solutions with pH of
5-9.
Gifford Buffer
● It contains boric acid and sodium borate.
● Sodium Chloride is added.
Feldman’s Buffer
It is used as a buffer for solutions with pH of
7-8.2.
Feldman’s Buffer
● It contains Boric acid & Sodium Carbonate.
● Sodium Chloride is added.
Atkins & Pantin Buffer
It is used as buffer for solutions with pH of
7.6-11.
Atkins & Pantin Buffer
The movement of solvent from a region of
low solute concentration to a region of a
high solute concentration through a
semi-permeable membrane.
Osmosis
And the pressure responsible is called ______________
Osmotic Pressure
If the solute is non-electrolyte, it will contain
_________________________________ will vary only with the concentration of solute.
only molecules and osmotic pressure
If the solute is electrolyte, it will contain _______________________ will vary with the
solute concentration but also with the
degree of dissociation of solute.
ions and the osmotic pressure
__________________will depend on the number of particles in solution.
Osmotic pressure
Solutions to be administered should be
_____________________________, for greater
comforter, efficacy and safety.
isosmotic with the body fluids
A solution with the same osmotic pressure
is said to be ______________________________.
isotonic with the body fluid
In most cases, preparations are isotonic, to
have ____________________________ but not most of the time.
homeostasis with the body’s intracellular fluids
Preparation ofIsotonic solutions
● Class 1
● Class 2
● Class 3
- Hemolytic Method
- Sodium chloride equivalent
Class 1
- Sprowl’s Method
- White Vincent Method
Class 2
- Liso value
- Cryoscopic Method
Class 3
_____________________maybe used for determining tonicity.
Colligative properties
Dissociation factors varies from the type of substance
● Non electrolytes = 1
● Substances that dissociates into 2 ions =
1.8
● Substances that dissociates into 3 ions =
2.6
● Substances that dissociates into 4 ions =
3.4
● Substances that dissociates into 5 ions =
4.2
Non electrolytes =
1
The freezing point of blood serum and
lacrimal fluid is _____________
– 0.52 deg C
2 ions =
1.8
3 ions =
2.6
4 ions =
3.4
5 ions =
4.2
∆Tf of blood and tears =
0.52 ̊C
Measurement of isotonicity
● Hemolytic Method
● Based on Osmotic pressure
● Based on Freezing point Depression
● ∆Tf of blood and tears = 0.52 ̊C
● Isotonic Solutions = 0.9% NaCl
Using Liso value
Isotonic Solutions=
0.9% NaCl
