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Pharmaceutics Spring 2016 > Dispersed Systems > Flashcards

Flashcards in Dispersed Systems Deck (74)
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1

dispersed system

fine particles, evenly distributed in a vehicle/dispersion medium

2

T/F In a dispersion system, the particles are NOT aggregated

FALSE; are

3

What are the 3 types of dispersion systems?

-molecular dispersion
-colloidal dispersion
-coarse dispersion

4

dispersion system?
-true solution
-less than 1 nm

molecular dispersion

5

dispersion system?
-generally can not be seen with the eye
-1 nm- 0.5 um

colloidal dispersion

6

dispersion system?
-BIG
-greater than 0.5 um

coarse dispersion

7

In dialysis, the blood cells and plasma proteins fall in the ____ size and will be retained

colloidal

8

What are the 3 types of colloidal systems?

-lyophilic system
-lyophobic system
-association/amphiphilic colloid

9

lyophilic system

loves the solvent (example water)

10

lyophobic system

need special dispersion or condensation method
-dislikes solvent

11

surfactants are an example of ____ colloids

association/ amphiphilic

12

surfactant (2)

-lowers the surface tension
-have a certain affinity for both polar and non polar solvents (does not allow water and oil to separate)

13

at a concentration that is characteristic of each amphiphile, these molecules will aggregate to produce____

micelles (hydrophilic on the outside and lipophilic on the inside)

14

CMC?

critical micelle concentration

15

Critical Micelle concentration involves....

blocking the surface and adding surfactant passed the concentration leading to a micelle being formed

16

Colloids have properties such as ____, _____, and _____

optical
kinetic
electrical

17

What is an example of a natural colloid?

protein

18

What is an example of a coarse dispersion?

suspension

19

T/F Suspension may be for oral, ophthalmic, parenteral, or topical use

TRUE

20

advantages of suspension (4)

-greater flexibility in the administration
-can better mask the taste of the drug
-some drugs are more stable as a suspension
-drugs not soluble in common vehicles

21

What are the 3 desired features of a suspension?

-pour readily and evenly
-particle size should remain constant
-uniform dispersion/ settle slow

22

T/F The bigger the particle, the better it dissolves

TRUE

23

Stoke's law

factors involved in the rate of velocity of SETTLING of the particles in a suspension

24

T/F Stokes equation applies to uniform, perfectly spherical particles settling in a very dilute suspension WITH hindrance or turbulance

False; without

25

What are ways to slow settling in a suspension? (3)

-small particle size
-increase density of vehicle
-increase viscosity of vehicle

26

How can particles dispersed in a liquid media become charged? (2)

-selective adsorption of ionic species present in solution
-ionization of groups situated at the surface of the particle

27

The electrical double layer is known as the .....

Nernst and Zeta potential

28

T/F There is ALMOST ALWAYS charges surrounded by particle size particles in a suspension

TRUE

29

11' is known as

nernst potential : true potential

30

22' is known as

electrokinetic: zeta potential