injections - tonicity, depression of the freezing point

Question 1

What is tonicity?

Answer 1

measurement of the concentration of ions present in solution

Question 2

What are the different types of tonicity?

Answer 2

isotonic

• minimises damage to erythrocytes
• same inside and outside the cell

hypotonic

• causes blood cells to swell and burst = hemolysis
• high solute concentration inside the cell
• can use NaCl, glucose or mannitol to make it isotonic

hypertonic

• causes the blood cells to shrink = crenated
• low solute concentration inside the cell
• can be diluted to make it isotonic

Question 3

What are the methods for measuring tonicity?

Answer 3

haemolytic method

• the effect of solutions of the drug is observed on the appearance of red blood cells suspended in the solutions
• in hypotonic solutions, the oxyhemoglobin is liberated from the RBCs through lysis - liberation is directly proportional to the number of hemolysed cells

colligative properties methods

• vapour pressure lowering
• boiling point elevation
• depression of freezing point
• osmotic pressure

Question 4

What is the effect of vapour pressure lowering on?
boiling point elevation
depression of freezing point

Answer 4

vapour pressure lowering causes

boiling point to be increases

depression of freezing point decreases to reestablish equilibrium
- freezing point depression is proportional to the concentration of the solute

Question 5

What is normal freezing point?

Answer 5

the T at which solid and liquid phases are in equilibrium at P=1atm

Question 6

How can tonicity be adjusted?

Answer 6

NaCl method

- find out the amount of NaCl needed to make a hypotonic solution become isotonic