Colloids

Question 1

Particle size range for colloids

Answer 1

less than 0.5 microns or 500 nm

Question 2

Colloid drug delivery systems that improve performance of dosage forms

Answer 2

Large surface area
drive to decrease surface energy
tendency for aggregation
unequal distribution of phases

Question 3

consideration of surface and interfacial phenomena for colloids

Answer 3

if a cube is subdivided in smaller particles, volume will stay the same but surface area will increase by 10^5 fold.

Question 4

Lyophillic colloids

Answer 4

solvent liking, hydrophillic
strong extensive interactions between dispersed phase and dispersion medium
thermodynamically stable

Question 5

Lyophobic colloids

Answer 5

solvent hating, hydrophobic

little interaction of the dispersed phase and medium. low adhesion forces. thermodynamically unstable

Question 6

assoication colloids (detergents)

Answer 6

Thermodynamically stable. Dispersed phase consists of aggregates of amphiphilic molecules or ions (micelles), lower concentration, they exist in true solution. At higher concentrations, Micelles.

Question 7

Tyndall effect

Answer 7

light may be absorbed, scattered, polarized or reflected by the dispersed phase of a colloid.

Question 8

Brownian Motion

Answer 8

how colloids are small enough to be influenced by the collision with molecules of the dispersion system. When observed, seem to be in a random manner.

Question 9

Ficks Law

Answer 9

D is diffusion coefficient
K- Boltzmann Constant
T- absolute temperature
N- viscosity of the solution
R- hydrodynamic radius of the particle

Question 10

Strokes einstein equation calculates

Answer 10

ficks law in how far a particle will travel per a certain amount of time

Question 11

If size increases, what does it do to the diffusion coefficent?

Answer 11

Inversely proportional to D

Question 12

If temperature increases, what does it do to the diffusion coefficent?

Answer 12

Proportional to D

Question 13

If viscosity increases, what does it do to the diffusion coefficent?

Answer 13

Inversely proportional to D

Question 14

Counterions

Answer 14

cations in solution

Question 15

similions

Answer 15

anions in a solution

Question 16

Which electrical region next to the particle surface neutralizes the charge on the particle?

Answer 16

The diffuse layer: with excess of counterions will neutralize surface charge. This would also be the adsorbed ions on the surface of the colloid.

Question 17

What does the zeta potential measure and how is it important for stability of colloidal systems

Answer 17

Zeta potential measures the voltage difference between double diffuse layer and the neutral region of the soln. measurement degree of attraction/ repulsion between adjacent particles.

Question 18

Steric Stabilization

Answer 18

Polymers adsorbed to the surface make it difficult for particles to approach each other.

Question 19

Polymer bridging

Answer 19

adsorbed polymers at very low concentrations promote the opposite effect of steric stabilization. instead of stablizing particles, promotes flocculation ( loosely clumped mass of fine particles)

Question 20

Hydrogels

Answer 20

water dispersion in the medium. Primary used in wound healing, tissue engineering and drug delivery systems

Question 21

Microparticles

Answer 21

0.2 to 0.5 microns loaded with drug, usually contain polymers and used in vaccines, chemotherapy, improve release profiles and drug targeting.

Question 22

Liposomes

Answer 22

consist of an outer membrane and liquid core. Can be filled with lipophilic drugs or hydrophilic drugs.

Question 23

Micelles

Answer 23

similar to liposomes but do not have inner fluid structure. Used as microcontainers for poorly soluble hydrophobic drugs. The surface can be modified such like liposomes.

Question 24

Nanoparticles

Answer 24

particles that are less than 1 nanometer.