Test #2 Flashcards
Coarse Dispersion
Greater than 500nm
Colloidal Dispersion
Less than 500nm
Phase separation depends on:
Temperature and composition
Common Solvents
- Purified water
- Alcohol
- Dehydrated alcohol
- Rubbing alcohol
- Glycerin
- Propylene glycol
- Oils
Common Solutes include:
- Drugs
- Flavors and Sweeteners
- Colorants
- Preservatives
- Stabilizers
Solutions include:
- Syrups
- Elixirs
- Tinctures
- Spirits
- Aromatic Waters
- Injectables
- I.V. Drug infusion
- Oral drug solutions
Colligative Properties
- Osmotic pressure
- Vapor pressure
- Boiling point
- Freezing point
Additive properties:
- Molecular weight
- Mass of a solution
- Volume
Constitutive properties:
- Solubility
- Interfacial energy
Properties of an ideal solution:
- Intermolecular bonding is equivalent
- No heat absorbed or evolved when mixed
- No change in volume when mixed
- Vapor pressure is proportional to molar fraction
Raoults Law:
Partial pressure of a volatile solution is equal to VAPOR PRESSURE OF PURE CONSTITUENT (Po) * MOLE FRACTION (X)
Pi=PioXi
Non-ideal solutions:
- In vapor: intermolecular interaction is negligible
- For real solutions (A-A, B-B, A-B) activity coefficient is 1
High activity coefficient =
Weaker interaction with solvent
Low activity coefficient=
Stronger interactions with solvent
Activity =
Activity coefficient (Yi) * Mole fraction (Xi)
Henry’s Law:
Psolute = kCsolute
k=Henry’s law constant
Csolute=Concentration of solute
Dissolution Enhancement Methods:
- Gentle heating
- Particle size reduction
- Using solubilizing agents
- Using agitation
Molarity:
Moles/liter
Temperature dependent
Molality:
Moles/kilogram
NOT temperature dependent
Percent by weight (w/w)%:
Grams of solute/100g of solution
Percent by volume (v/v)%:
Milliliters of solute/100ml of solution
Percent weight by volume (w/v)%:
Grams of solute/100ml of solution
Ratio strength:
Grams/ml
Pharmaceutical advantages of a salt compared to it’s parent drug:
- Solubility
- Bioavailability
- Physical stability
- Chemical stability
- Mechanical properties
- Ease of crystallization
- Taste
- Melting point
Ph=pKa where on ionization curve?
At 50%
At 1 unit above or below pH on ionization curve you are at:
91%, 9%
At 2 units above or below pH on ionization curve you are at:
99%, 1%
Solubility:
Amount of solute that can be dissolved in a unit volume of a solvent to for a saturated solution
Unsaturated solution:
Solution with concentration below equilibrium solubility
Supersaturated solution:
Solution that contains a solute at a concentration higher than that of a saturated solution
*It is unstable - excess solute tends to leave solution in bubbles or crystals, etc…
Intrinsic Solubility:
Equilibrium solubility of the drug molecule
Apparent solubility:
Sum of all species of the drug in solution
Solubility of a gas:
Concentration of gas that is in equilibrium with the pure gas
Solubility of gases change with what?
- Decrease in pressure
- Increase in temperature
What happens when you add an electrolyte like NaCl to an aqueous solution of a gas?
You decrease it’s solubility - it salts out
Activity of a drug can be thought of as:
Effective concentration
What affects activity?
- Melting temperature
- Heat of fusion
What does NOT affect activity?
-Solvent
Does Hsoln depend on the solvent in the Van’t Hoff equation?
YES!
Does Hf in the Van’t Hoff equation depend on solvent?
No!
Can Hsoln in Van’t Hoff equation be a negative value?
Yes!
Can Hf in the Van’t Hoff equation be a negative value?
No, it is always positive
What do co-solvents do?
- Increase solubility of drugs with poor aqueous solubility
- Reduce the H-bond density of water
What factors affect solubility?
- pH
- Temperature
- Solid form
- Particle size
- Solvent
- Pressure
Acidic drugs precipitate out where?
In the stomach
Basic drugs precipitate out where?
In the intestine
Drugs in a co-solvent precipitate out where?
In the blood
Salting out:
Ions STRENGTHEN solvent structure to make it more difficult to insert drug
Salting-In:
Ions WEAKEN solvent structure to make it easier to insert drug molecules
Solubility of a drug depends on:
- Salt concentration
- Type of salt
Effects related to Ionic Strength:
- Solubility (salting-in/salting-out)
- Activity of ions (Ksp of salt, pH of solution, etc…)
The state of a solvent can be:
- Solid
- Liquid
- Super critical fluid
- Gas
True or False: Mole fraction and molality are both independent of temperature.
TRUE!
True or False: For dilute aqueous solutions molarity and molality values are essentially equivalent.
TRUE!
