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PHAR 124 > Colloids > Flashcards

Colloids Flashcards

1
Q

What is a Solution?

A

Particles are small and evenly dispersed

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2
Q

What is a colloid?

A

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

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3
Q

What is a suspension?

A

Particles are larger and settle out

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4
Q

What is the defn of a dispersed system?

A

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

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5
Q

What are the two different parts of a disperse system?

A

Disperse phase, disperse medium

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6
Q

What is molecular dispersions?

A

Solute molecules are homogenously distributed
throughout the solvent

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7
Q

What are examples of other dispersed systems?

A

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

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8
Q

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

A

Size of the dispersed particles

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9
Q

What is the particle size of a colloidal system?

A

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

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

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10
Q

What are the unique properties of a colloidal system?

A

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

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11
Q

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

A

Increase surface area of absorption

Reduce side effects

Drug Stability

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12
Q

What are the three types of colloids?

A

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

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13
Q

What is the Critical Micelle Concentration (CMC)

A

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

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14
Q

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

A

Gels

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15
Q

What are Inorganic Colloids?

A

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

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16
Q

What is thixotropic?

A

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

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17
Q

What is an organic colloid?

A

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

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18
Q

What is a hydrogel colloid?

A

dispersible in water

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19
Q

What is a organogel colloid?

A

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

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20
Q

What is a Jelly?

A

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

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21
Q

What is Xerogel?

A

If the liquid is removed from a gell forms a xerogel

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22
Q

What is the main difference between colloids and suspensions?

A

Colloids do not settle while suspensions settle

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23
Q

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

A

0.5 to 5%

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24
Q

What is a natural gelling agent? Alginic Acid

A

*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

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25
Q

What is a natural gelling agent? Tragacanth

A

*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

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26
Q

What is the gelling agent methylcellulose?

A

Thins gels and hydrates in HOT water

Good solvent compatibility with water alcohol

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27
Q

What is the gelling agent Hydroxypropylmethyl cellulose (HPMC)?

A

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

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28
Q

What is the gelling agent carbomers?

A

They make an acidic pH that NEEDS a stabilizer***

Different levels of viscosity that determine pureness
Synthetic gelling agent

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29
Q

What is PLO gel

A

Combination of poloxamers and another ingredient

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30
Q

How do you use PLO Gel? Lipophilic

A

Solubilize drug in organic phase
Add aqueous phase

Formed

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31
Q

How do you use PLO Gel? Hydrophilic

A

Solubilize drug in aqueous phase
Add organic phase

Formed

32
Q

What is the gelling agent PLO gel?

A

Comes in a kit and that is convenient to use

33
Q

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?

A

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

34
Q

Particles in a liquid medium may become charged by

A
  • 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
35
Q

What does the electrical double layer determine?

A

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

36
Q

What is the order of layers in a particle?

A

Negative charge particle
Stern layer
slipping plane

37
Q

What is the potential called on the particle

A

Surface potential

38
Q

What is the potential called at the stern layer

A

Stern potential

39
Q

What is the potential called on the slipping plane?

A

Zeta potential

40
Q

What does the DLVO theory describe?

A

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

41
Q

The Secondary minimum is?

A

Easy dispersion

42
Q

The primary maximum

A

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

43
Q

The primary minimum?

A

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

44
Q

What is Coagulation

A

Particles cannot be re-dispersed

45
Q

What is Flocculation

A

A loose aggregation

46
Q

What are some examples of protective colloids?

A

Gelatin and Methylcellulose

47
Q

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

VPE

A

Change viscosity
Add buffer salts to maintain pH
Add electrolytes

48
Q

The charge of the stern layer is?

A

Positive

49
Q

Which type of colloids do we prefer?

A

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

50
Q

Unique properties of colloidal systems

A

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

51
Q

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

A

Gas in a Gas

52
Q

What are Micelles?

A

The polar head groups are on the outside

53
Q

What are inverse micelles?

A

Polar head groups are on the inside (Oils)

54
Q

What are surfactants

A

Polar head and a long non-polar chian

55
Q

What happens when you over saturate with surfactants?

A

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

56
Q

What happens when you shine a light in a colloid?

A

It refracts light

57
Q

What is the tyndall effect?

A

The light is scattered by small molecules

58
Q

What is the most common inorganic colloid?

A

milk of magnesia

59
Q

Two phase system

A

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

60
Q

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

A

Preservative

61
Q

Which gel agent could be used for a time release?

A

HPMC

62
Q

Brownian movement

A

Uneven collisions betweek particles

Smaller particles are faster and larger decreases speed

Viscosity decreases brownian movement

63
Q

What are the potentials of a particle?

A

Surface potential
Stern potential
Zeta Potential

64
Q

What is the stern plane?

A

It is a positive layer that surrounds the negatively charged particle

65
Q

Where is the zeta potential located/measured?

A

Measured basd off of hte slipping plane

66
Q

Electric double layer is the

A

Stern and slipping plane

67
Q

As two particles are close together what is that?

A

Primary Minimum

68
Q

Repulsion is greater then attraction?

A

Primary maximum

69
Q

In pharmacy what is our ideal formulation?

A

Flocculated that is distributed or unstable colloid

70
Q

Caking occurs at the?

A

primary minimum (Deflocculated)

71
Q

What are protective colloids?

A

Where we add another polymer like gelatin and methylcellulose that will help with stabilizing.

Stabilizes lyophobic to lyophilic

72
Q

What are the two heterogenous systems?

A

Colloids and suspensions

73
Q

What is the one homogenous system?

A

Solution

74
Q

What defined the flow of a colloid?

A

Shape and size of particle

75
Q

What are some general properties of a lyophilic colloid?

A

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

76
Q

What are the two nature of the colloid?

A

Inorganic and Organic

77
Q

High the gelling agent?

A

Stiffer or more viscous the gel

PHAR 124 (6 decks)

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