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Pharmaceutics II > Disperse Systems > Flashcards

Disperse Systems Flashcards

1
Q

When is the term “surface” used?

A

When talking about gases.

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2
Q

When is the term “interface” used?

A

When talking about solids and liquids.

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3
Q

What does heterogenous mean?

A

Not all units are the same throughout

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4
Q

What does homogenous mean?

A

When each unit of a system is looked at under a microscope, it is completely the same as another unit of the system.

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5
Q

How many phases does an emulsion have?

A

2 or 3

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6
Q

What types of phases are found in suspensions?

A

A solid and a liquid phase.

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7
Q

What are some examples of heterogenous mixtures?

A
  • blood
  • salad dressing
  • Tylenol suspension
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8
Q

When is a unit called the dispersed, discontinuous, or internal phase?

A
  • in a suspension–when the solid phase is discrete units

* one homogenous phase

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9
Q

What is a dispersion?

A

An emulsion is a dispersion. It is a liquid in a liquid–one liquid is discrete units that are immiscible in the liquid medium.

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10
Q

Disperse system encompass a variety of…

A

…heterogenous, multiphase systems in which one homogenous phase is intimately distributed, in discrete units, within the second phase.

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11
Q

What is the second phase called in a dispersion?

A

Dispersing or continuous

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12
Q

What is a solution?

A

A liquid preparation when the drug or AI is in a molecular form dissolved in the solvent system.

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13
Q

What is a two phase system or dispersion?

A

Liquid preparations when the drug or AI is undissolved, insoluble, or immiscible and is distributed throughout the vehicle.

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14
Q

What is the dispersed phase?

A

The AI or drug

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15
Q

What is the dispersing phase or medium?

A

The vehicle

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16
Q

What a dispersion?

A

The dispersed phase and the dispersing phase or medium mixed together.

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17
Q

Are solutions dispersions?

A

NO–they are not. They are liquid dosage forms and are homogenous systems with the dissolved solid ingredient in molecular form.

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18
Q

Describe the AI in dispersions.

A

It is not dissolved or it is immiscible–not in molecular form.

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19
Q

What are some examples of dispersions?

A
  • suspensions

* emulsions

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20
Q

To act in the body, what does a drug and dosage form need to be?

A

Both physically and chemically stable–distributed uniformly throughout

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21
Q

What is the dispersed phase and dispersing phase of a liquid aerosol?

A

dispersed phase: liquid

dispersing phase: gas

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22
Q

What is the dispersed phase and dispersing phase of a solid aerosol?

A

dispersed phase: solid

dispersing phase: gas

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23
Q

What is the dispersed phase and dispersing phase of an emulsion?

A

dispersed phase: liquid

dispersing phase: liquid

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24
Q

What is the dispersed phase and dispersing phase of a suspension?

A

dispersed phase: solid

dispersing phase: liquid

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25
Q

What is the most common way to classify dispersions?

A

Based on the particle size of the dispersed phase (varied particle size to large visible particles to colloidal dimension)

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26
Q

What size are coarse dispersions? What are some examples of dosage form?

A
  • 10 to 50 um

* suspensions and emulsions

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27
Q

What size are fine dispersions? What are some examples of dosage form?

A
  • 0.5 to 10 um

* magmas and gels

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28
Q

What size are colloidal dispersions?

A

1 nm to 0.5 um

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29
Q

Describe a successful and proper dispersion.

A

Upon moderate agitation, they result in a uniform and complete redistribution of the dispersed phase throughout the dispersion

30
Q

What size dispersion has a greater tendency to separate from the dispersing medium? Why?

A
  • Coarse dispersions
  • suspensions: denser than water, solids tend to settle down
  • emulsions: less dense than water, oils tend to float or cream on top
31
Q

Lyophobic dispersions are…

A

…solvent fearing.

32
Q

Lyophilic dispersions are…

A

…solvent loving.

33
Q

What type of dispersion system has greater stability?

A

Lyophilic dispersions

34
Q

What is a molecular dispersion?

A

Units of dispersed phase are composed of single macromolecules (drug exists in molecular form, but is really a solution)

35
Q

What are micellar dispersions?

A

Units of dispersed phase are composed of micelles or association of several molecules (surfactant is more concentrated, thus a micelle is formed–not a true dispersion, usually has AI of surface active agent)

36
Q

What are the 5 principles of surface phenomena?

A
  • surface and interface
  • surface tension and interfacial tension
  • electrical properties at the interface
  • surfactants
  • wetting and contact angle
37
Q

How would a boundary between two homogenous phases be described as?

A

As a film of a characteristic thickness (NOT as a simple geometric plane)

38
Q

What is a surface, or an interface?

A

The boundary of separation of two phases

39
Q

What is a phase?

A

A mass of substance (solid, liquid, gas) that possesses a well defined boundary.

40
Q

Describe the molecules on the surface of a liquid.

A

The potential energy of the molecules on the surface have a net force that pulls towards the bulk.

41
Q

Describe the molecules in the bulk of a liquid.

A

The molecules are being pulled in all directions with a net force of ZERO

42
Q

Why do droplets want to have a spherical shape?

A

Because a sphere has the minimum surface area possible–all other shapes have a larger surface area. (the molecules on the outer edge are being pulled towards the bulk to make it smaller)

43
Q

What does interfacial tension cause in a suspension?

A

caking

44
Q

What happens when you decrease the interfacial tension?

A

increase stability

45
Q

How do you decrease interfacial tension?

A

Surfactant binds to the solid internal phase and has association with the dispersion medium (solid in a suspension has a coating that interacts with the liquid medium)

46
Q

Molecules forming the surface of a liquid behave differently from those in the bulk of each phase. This is manifested in what 3 ways?

A
  • capillary action
  • wetting
  • adsorption
47
Q

Describe the binding forces in the bulk of the phase.

A

The binding forces between molecules are equivalent in all directions. (decreases surface area)

48
Q

What are molecules on the surface subjected to?

A

Intermolecular forces in the direction of the interface and towards the bulk (decreases surface area)

49
Q

What is required to bring molecules from the bulk to the surface?

A
  • work

* think about grinding powder in a mortar–you have to put energy into the grinding

50
Q

What is surface tension, or surface free energy per unit area?

A

It is the amount of work required to bring the molecules from the interior to the surface (to expand by unit area)

51
Q

When you reduce the drop size of an oil to make an emulsion…

A

…you are increasing the surface area.

52
Q

What liquid has the highest surface tension?

A

Water

53
Q

What describes the interface between two liquids or a solid and a liquid?

A

Interfacial tension

54
Q

What is present at the interface between two condensed matters (ex: liquid-liquid interface)?

A

Tension or excess energy

55
Q

Which is greater, the interfacial tension between two liquids or a solid and a liquid? Why?

A

The solid and liquid have a greater interfacial tension because the adhesive forces between the two liquid phases forming the interface are greater than when a liquid and a gas phase or a solid and a liquid exist together.

56
Q

What is cohesion?

A

The force of attraction between like molecules.

57
Q

What is adhesion?

A

The force of attraction between different molecules.

58
Q

What force of attraction does a suspension have?

A

adhesion

59
Q

True/False

The adhesive forces between a liquid and a liquid are stronger than the adhesive forces with a solid in a liquid.

A

True

60
Q

When adhesive forces are stronger, the tension is…

A

…weaker.

61
Q

True/False
In an emulsion, the adhesive forces are stronger than in a suspension so the adhesive forces cause the tension to be weaker in an emulsion.

A

True

62
Q

What needs to be applied to a system to make a dispersion make states of matter coexist?

A

Energy needs to be provided–mixing in a mortar and pestle.

63
Q

True/False

Within the same same of matter, adhesive forces are stronger.

A

True

Different states of matter have weaker adhesion forces

64
Q

How is interfacial tension defined?

A

The force per unit length existing at the interface between two liquid immiscible phases or between solid and liquid phase. (units: dyne/cm)

65
Q

What are the units for surface tension?

A

dyne/cm (same as interfacial tension)

66
Q

What is an important part of the surface’s physical chemistry?

A

Knowing the influence of electrical charges on a surface. Aqueous suspensions are not only influenced by the interfacial properties, but also by attraction and repulsion caused by electrostatic charges.

67
Q

What can happen when a particle is dispersed in a surrounding liquid environment? (like in suspensions)

A

The dispersed particles in the liquid may become charged. (ion adsorption, ionization, and ion dissolution)

68
Q

The net charge at the particle surface affects what?

A

It affects the ion distribution in the nearby region, increasing the concentration of counter-ions close to the surface.

69
Q

What is formed in the region of the particle-liquid interface?

A

an electrical double layer

70
Q

Assume a CaCO3 particle is positively charged. As soon as you add a neutral molecule to water or any liquid, it can obtain a charge based on what?

A
  • ion adsorption
  • ionization
  • ion dissolution

(CaCO3 can adsorb ions from water/liquid medium or undergo ionization and get a charge)

71
Q

As soon as you put a positive charge on a drug particle in water, what happens?

A

The positive particle will combine with the anions in the water.

(vice versa: if you have a negative charged drug particle, it will have cations gather around it–these are counter ions)

72
Q

What is a counter ion?

A

When the charge is opposite to that of the drug particle.

Pharmaceutics II (2 decks)

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