Colloids

Question 1

What is a Solution?

Answer 1

Particles are small and evenly dispersed

Question 2

What is a colloid?

Answer 2

Particles are small (invisible) and dispersed but do not settle

Question 3

What is a suspension?

Answer 3

Particles are larger and settle out

Question 4

What is the defn of a dispersed system?

Answer 4

A disperse system may be defined as a system in which one substance – the disperse phase – is distributed as particles throughout another phase – the dispersion medium or continuous phase

Question 5

What are the two different parts of a disperse system?

Answer 5

Disperse phase, disperse medium

Question 6

What is molecular dispersions?

Answer 6

Solute molecules are homogenously distributed
throughout the solvent

Question 7

What are examples of other dispersed systems?

Answer 7

-Colloid
-Gels
-Suspensions
-Emulsion
-Lotion, ointments and creams

Question 8

Which physicochemical feature is most important to define the type of the dispersed system?

Answer 8

Size of the dispersed particles

Question 9

What is the particle size of a colloidal system?

Answer 9

The particle size of 1-500nm (too small to see)

§ Excellent candidate for research regarding novel nano-drug delivery systems
§ Large surface area

Question 10

What are the unique properties of a colloidal system?

Answer 10

It is the ability to deliver drugs via a nanoparticle that can readily cross the membrane and be protected from degradation

Pt for example cannot be delivered unless it is in colloidal form

Question 11

Why are colloidal dispersions made in pharmacy practice? (3)

Answer 11

Increase surface area of absorption

Reduce side effects

Drug Stability

Question 12

What are the three types of colloids?

Answer 12

Lyophillic or Hydrophilic colloids
Lyophobic or Hydrophobic colloids
Association or amphiphilic Colloids

Question 13

What is the Critical Micelle Concentration (CMC)

Answer 13

The concentration of the surfactant at which micelles are formed. Below that concentration, the surfactant remains at the surface as monomers.

Question 14

What is the Most common form of colloidal dosage form of a semi solid or semi-rigid systems

Answer 14

Gels

Question 15

What are Inorganic Colloids?

Answer 15

particulate colloids, magmas or milk. Contain small discrete particles (two phase system) e.g. milk of magnesia - thixotropic

Question 16

What is thixotropic?

Answer 16

Meaning it is solid when it sits, but when you shake it gets runny and less viscous

Question 17

What is an organic colloid?

Answer 17

polymer macromolecules that dissolve in water like tragacanth, carbomer, poloxamer, methyl cellulose (single phase system) e.g. Clindoxyl gel

Question 18

What is a hydrogel colloid?

Answer 18

dispersible in water

Question 19

What is a organogel colloid?

Answer 19

not dispersible in water include vegetable and animal fat, soap base greases, hydrocarbons e.g.

Question 20

What is a Jelly?

Answer 20

Rich in liquid and formed with thickening agents like carboxymethylcellulose.
Bacterial contamination can occur easier

Question 21

What is Xerogel?

Answer 21

If the liquid is removed from a gell forms a xerogel

Question 22

What is the main difference between colloids and suspensions?

Answer 22

Colloids do not settle while suspensions settle

Question 23

What is the typical concentration of gelling agents within the gel?

Answer 23

0.5 to 5%

Question 24

What is a natural gelling agent? Alginic Acid

Answer 24

*Obtained from seaweed
Used in 1-5% and takes about 30 minutes to get
*dispersed in water
*Sodium alginate 10%
*prone to microbial growth must have preservatives like parabens

Question 25

What is a natural gelling agent? Tragacanth

Answer 25

*Used for gels that are stable at pH 4-8 *Requires addition of preservatives *Powdered tragacanth tends to form lumps in water aqueous dispersions are prepared or wetting agents like glycerin are used

Question 26

What is the gelling agent methylcellulose?

Answer 26

Thins gels and hydrates in HOT water Good solvent compatibility with water alcohol

Question 27

What is the gelling agent Hydroxypropylmethyl cellulose (HPMC)?

Answer 27

*makes thicker gels *Good-gelling agent for time-release preparations

Question 28

What is the gelling agent carbomers?

Answer 28

They make an acidic pH that NEEDS a stabilizer*** Different levels of viscosity that determine pureness Synthetic gelling agent

Question 29

What is PLO gel

Answer 29

Combination of poloxamers and another ingredient

Question 30

How do you use PLO Gel? Lipophilic

Answer 30

Solubilize drug in organic phase Add aqueous phase Formed

Question 31

How do you use PLO Gel? Hydrophilic

Answer 31

Solubilize drug in aqueous phase Add organic phase Formed

Question 32

What is the gelling agent PLO gel?

Answer 32

Comes in a kit and that is convenient to use

Question 33

Should the gel first be formed and then the active drug added, or should the active drug may be added and then the gel should be formed?

Answer 33

The active drug may be added before or after the gel is formed. Two things to consider: *Drug does not interfere with the gelling process *Drug is stable at the conditions of temperature and pH changes induced. Preference is generally prior to forming the gel as its easier to get uniform dispersion

Question 34

Particles in a liquid medium may become charged by

Answer 34

* Selective adsorption of a particular ionic species present in the dispersion * Ionization of groups on the particle surface (e.g. COO ̄) * Adsorption of ionic surfactant molecules to the particle

Question 35

What does the electrical double layer determine?

Answer 35

The distance between other particles which affects the stability of the system

Question 36

What is the order of layers in a particle?

Answer 36

Negative charge particle Stern layer slipping plane

Question 37

What is the potential called on the particle

Answer 37

Surface potential

Question 38

What is the potential called at the stern layer

Answer 38

Stern potential

Question 39

What is the potential called on the slipping plane?

Answer 39

Zeta potential

Question 40

What does the DLVO theory describe?

Answer 40

a quantitative approach to estimating the stability of hydrophobic sols. This theory reflects a balance between net attractive and repulsive forces.

Question 41

The Secondary minimum is?

Answer 41

Easy dispersion

Question 42

The primary maximum

Answer 42

Ideal state of dispersion as the repulsion is greater than attraction and the particles are going to avoid each other

Question 43

The primary minimum?

Answer 43

indicates that the aggregated state is of the lowest-energy condition and this is where we would expect the particles to reside

Question 44

What is Coagulation

Answer 44

Particles cannot be re-dispersed

Question 45

What is Flocculation

Answer 45

A loose aggregation

Question 46

What are some examples of protective colloids?

Answer 46

Gelatin and Methylcellulose

Question 47

What are some other ways of stabilizing a dispersed system? (3) VPE

Answer 47

Change viscosity Add buffer salts to maintain pH Add electrolytes

Question 48

The charge of the stern layer is?

Answer 48

Positive

Question 49

Which type of colloids do we prefer?

Answer 49

Unstable colloids as it is easier to redisperse as compared to stable colloids

Question 50

Unique properties of colloidal systems

Answer 50

Platinum is effective as a catalyst Cellular uptake of nanoparticles is different from true molecular disersions. Lipid Nanoparticles help with delivery of the drugs to the site of action

Question 51

The only colloid based on a state of matter that does not exist

Answer 51

Gas in a Gas

Question 52

What are Micelles?

Answer 52

The polar head groups are on the outside

Question 53

What are inverse micelles?

Answer 53

Polar head groups are on the inside (Oils)

Question 54

What are surfactants

Answer 54

Polar head and a long non-polar chian

Question 55

What happens when you over saturate with surfactants?

Answer 55

You will see the formation of micelles and you will reach the critical micelle concentration

Question 56

What happens when you shine a light in a colloid?

Answer 56

It refracts light

Question 57

What is the tyndall effect?

Answer 57

The light is scattered by small molecules

Question 58

What is the most common inorganic colloid?

Answer 58

milk of magnesia

Question 59

Two phase system

Answer 59

Mostly inorganic gels and they have a tendency to separate when left

Question 60

Whenever you are dealing with a natural gelling agent what do you always need?

Answer 60

Preservative

Question 61

Which gel agent could be used for a time release?

Answer 61

HPMC

Question 62

Brownian movement

Answer 62

Uneven collisions betweek particles Smaller particles are faster and larger decreases speed Viscosity decreases brownian movement

Question 63

What are the potentials of a particle?

Answer 63

Surface potential Stern potential Zeta Potential

Question 64

What is the stern plane?

Answer 64

It is a positive layer that surrounds the negatively charged particle

Question 65

Where is the zeta potential located/measured?

Answer 65

Measured basd off of hte slipping plane

Question 66

Electric double layer is the

Answer 66

Stern and slipping plane

Question 67

As two particles are close together what is that?

Answer 67

Primary Minimum

Question 68

Repulsion is greater then attraction?

Answer 68

Primary maximum

Question 69

In pharmacy what is our ideal formulation?

Answer 69

Flocculated that is distributed or unstable colloid

Question 70

Caking occurs at the?

Answer 70

primary minimum (Deflocculated)

Question 71

What are protective colloids?

Answer 71

Where we add another polymer like gelatin and methylcellulose that will help with stabilizing. Stabilizes lyophobic to lyophilic

Question 72

What are the two heterogenous systems?

Answer 72

Colloids and suspensions

Question 73

What is the one homogenous system?

Answer 73

Solution

Question 74

What defined the flow of a colloid?

Answer 74

Shape and size of particle

Question 75

What are some general properties of a lyophilic colloid?

Answer 75

Has an affinity for the medium Becomes hydrated when dispersed thermo stable

Question 76

What are the two nature of the colloid?

Answer 76

Inorganic and Organic

Question 77

High the gelling agent?

Answer 77

Stiffer or more viscous the gel