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Compounding Exam 2 > Emulsions > Flashcards

Emulsions Flashcards

1
Q

emulsions are ____ in ___ dispersions

A

liquid in liquid

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2
Q

true or false

emulsions are thermodynamically stable

A

FALSE

like suspensions, they’re thermodynamically unstable

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3
Q

how are emulsions stabilized?

A

by an emulsifying agent - lowers interfacial tension

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4
Q

range of droplet size diameter for emulsions

A

1-100 micrometers

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5
Q

how can delayed onset be achieved for emulsions?

A

for ex:

oil soluble drug in an o/w emulsion

the drug will be in the center oil phase. takes time to pass the outer water phase and get into the GI fluid

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6
Q

emulsions are made by _____ equipment that is capable of….

A

high energy ( ie - homogenizer, blender)

breaking the dispersed phase into very tiny droplets

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7
Q

the addition of _____ makes the emulsion stable

A

emulsifying agent (emulsifier)

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8
Q

true or false

emulsifying agents are surfactants

A

TRUE

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9
Q

for an emulsifying agent/surfactant, what way will the hydrophilic head face and the lipophilic tail face BEFORE cmc is reached?

A

hydrophilic head will face water and lipophilic tail will face air (relatively lipophilic)

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10
Q

**O/W emulsions are formed with what kind of emulsifier?

A

A HYDROPHILIC EMULSIFIER (with high HLB)

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11
Q

true or false

a high HLB means a lipophilic surfactant

A

FALSE

high HLB means hydrophilic surfactant

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12
Q

what is the most common emulsion type and is preferred for oral products?

A

O/W emulsions

bc oily feel in the mouth is objectionable

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13
Q

when are O/W emulsions used as external products?

A

when a non-greasy feeling and easy to remove/wash is desired

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14
Q

name a food that is an O/W emulsion

A

mayo

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15
Q

true or false

o/w emulsions are made with hydrophilic emulsifiers

A

TRUE

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16
Q

true or false

W/O emulsions are formed if a lipophilic emulsifier with a low HLB is used

A

TRUE

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17
Q

when are w/o emulsions used as external products rather than o/w emulsions?

A

when emollient, lubricating, or protective properties are desired

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18
Q

true or false

many ointments are emulsions with o/w emulsions

A

FALSE

W/O - it’s greasy

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19
Q

differentiate between the type of emulsion: cream vs butter

A

butter is w/o (more greasy!)

cream is o/w

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20
Q

butter is mostly fat or water

A

fat (W/O emulsion)

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21
Q

HLB of egg yolk

A

10 - so hydrophilic

that why it’s emulsifer for mayo which is a o/w emulsion

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22
Q

4 ways that we can distinguish types of emulsions and figure out what they are

A

-feel on the skin

-dye solubility test

-conductivity test

-dilution test

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23
Q

explain the dye solubility test to determine the type of emulsion

A

a water soluble dye (like methylene blue/brilliant blue) can be dusted on the emulsion

if only the internal drug gets blue - you know that it’s w/o

if the external medium becomes blue, it’s o/w

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24
Q

explain the conductivity test to distinguish the types of emulsions

A

electrodes are placed in the emulsion

o/w WILL carry a current and w/o will not

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25
Q

explain the dilution test for distinguishing the types of emulsions

A

O/W emulsions can be diluted with water – will dilute nicely

If you add extra water to a W/O emulsion, it will make phase separation!!

W/O emulsions can be diluted with oil

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26
Q

name a LIPOPHILIC dye that can be used in the dye solubility test to distinguish the types of emulsions

A

Sudan IV
will stain LIPIDS clear red

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27
Q

emulsifying agents will _____ at the interface between the 2 phases and do what?

A

ADSORB

REDUCE THE INTERFACIAL TENSION

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28
Q

Name 2 types of emulsifying agents

A

ionic emulsifiers and non-ionic emulsifiers

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29
Q

when IONIC emulsifers are placed in an o/w emulsion, what will happen?

A

a charged layer will be formed around the oil droplet

this will create an electrostatic repulsion and will reduce the tendency of adjacent particles to coalesce (join together)

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30
Q

explain how non-ionic emulsifiers work and name 3

A

there are repulsive effects in the continuous phase due to the long chains

they can also increase the viscosity by forming multimolecular films. they are generally high in MW, and thus can increase the viscosity of the continuous phase and reduce the mobility of the dispersed particles, stabilizing them

acacia, tragacanth, cellulose

31
Q

emulsifying agents should be adsorbed _____ around the _____ and wetted by _____

A

QUICKLY around the dispersed phase droplets and wetted by both WATER AND OIL

32
Q

true or false

an emulsifier film should be formed RAPIDLY during the emulsification process

A

true

33
Q

an emulsifer film must be _____

explain

A

elastic – enough so they can bounce off each other and don’t aggregate

34
Q

name the 2 types of films that can be formed and which emulsifying agent does what

A

monomolecular film (ionic)

multimolecular film (non-ionic)

35
Q

emulsifiers reduce the interfacial tension below…..

A

10 dynes/cm

36
Q

true or false

emulsifiers decrease the viscosity of the emulsion

A

FALSE

increase

37
Q

emulsifiers must be effective at what concentration

A

LOW, non-toxic concentrations

38
Q

name 6 hydrophilic emulsifying agents

what kind of emulsions do they form?

A

acacia
tragacanth
pectin
microcrystalline cellulose
glyceryl monostearate
bentonite

O/W EMULSIONS —— EMULSIFYING AGENT MATCHES WITH THE EXTERNAL MEDIUM!!!!

39
Q

Name 6 lipophilic emulsifying agents and what type of emulsions they can make

A

cholesterol
wool fat
carbon black
talc
calcium palmitate
some spans (sorbitan esters)

W/O EMULSIONS — EMULSIFYING AGENT GOES WITH EXTERNAL PHASE

40
Q

True or false

hydrophilic emulsifying agents favor to create an O/W emulsion

A

TRUE

41
Q

true or false

the higher the HLB of an emulsifier, the more lipophilic it is

A

FALSE - more hydrophilic

42
Q

which have higher HLB - spans or tweens?

A

TWEENS have high HLB values – thus favor o/w emulsions over spans

43
Q

**span 80 vs span 20

A

span 80 - has 18 carbons in the fatty acid chain

span 20 - has 12 carbons in the fatty acid chain

ZERO — MEANS NO DOUBLE BONDS IN THE CHAIN

LONGER FATTY ACID CHAIN = MORE HYDROPHOBIC. THUS SPAN 80 IS MORE HYDROPHOBIC THAN SPAN 20**

44
Q

***SPAN 80 VS TWEEN 80

A

TWEEN 80 always has much higher HLB bc it has PEG attached which is HYDROPHILIC

EVEN WITH SAME CHAIN LENGTH — TWEEN IS MORE HYDROPHILIC BC HAS PEG AS PART OF THE HEAD

45
Q

What is “creaming” and in which emulsions does it happen?

A

upward movement of the dispersed droplets (OIL)

happens in O/W emulsions

associated with physical instability of emulsions

46
Q

what is sedimentation

A

the downward movement of dispersed droplets (water)

47
Q

both creaming and sedimentation pose the risk of what?

A

coalescence — bc they bring particles together

48
Q

true or false

creaming or sedimentation always results in the breakdown of the emulsion

A

FALSE - not necessarily

the dispersed droplets can be re-dispersed with mild agitation (shaking). the droplets still maintain their individuality

49
Q

when ____ occurs to an emulsion, simple mixing fails to resuspend the globules in the stable emulsified form

A

BREAKING

50
Q

why does mixing not fix a emulsion that has broken

A

bc the film surrounding the particles is destroyed. the oil will coalesce together, and there will be phase separation

51
Q

TRUE OR FALSE

breaking of an emulsion is irreversible

A

TRUE

52
Q

irreversible coalescence of emulsion droplets can be called ___ or ____

A

breaking or cracking

53
Q

name and explain 2 ways that emulsions can undergo phase inversion***

A

-adding an electrolyte (ie - o/w emulsion has sodium stearate (Hydrophilic) as the emulsifier. when calcium chloride is added, CALCIUM STEARATE (lipophilic emulsifier) will be formed — WHICH FAVORS W/O EMULSION!!!)

-changing the phase volume ratio

IE - adding a lot of water to a w/o emulsion will result in phase inversion to o/w emulsion (if more than 70% of the total emulsion volume is added)

54
Q

name 2 things that can DESTABILIZE emulsions

A

excessive heat or freezing/thawing

presence of light, air, contaminating microorganisms that decompose emulsifying agents

55
Q

which particular emulsifiers can microorganisms decompose? what can be done to prevent this?

A

nonionic and anionic emulsifiers, glycerin, and vegetable gum thickeners

ADD PRESERVATIVES!! Also, make sure they get into the water phase because this is where the bacteria tend to grow

56
Q

most emulsions exhibit what flow? what is an exception?*****

A

NON-NEWTONIAN FLOW

EXCEPT extremely dilute ones

57
Q

internal phase of the emulsion has less than 5% concentration.

what is the flow pattern?

A

NEWTONIAN – it’s so diluted

behaves like pure water or oil

58
Q

as mentioned, when the volume of the dispersed phase is less than 5% of the system, the emulsion exhibits newtownian flow.

when will it exhibit pseduoplastic (non-newtonian) flow??

A

when the dispersed phase volume concentration increases

if increased even MORE—- will ehibit PLASTIC FLOW (have to shake a lot to yield value to flow) and behave like a semisolid

if increased MORE – GREATER THAN 75% — phase inversion will occur and the viscosity changes – possibly newtonian flow

59
Q

which are generally preferred by the patients - oral emulsions or solutions/suspensions

A

solutions/suspensions bc they dont have the oily feeling in the mouth

60
Q

____ emulsions can include TPN

A

parenteral

61
Q

for topical emulsions, what is likely the external medium?

A

oil

62
Q

true or false

coalescence can be reduced by increasing the droplet size of the dispersed phase

A

FALSE

63
Q

true or false

increasing the viscosity of the medium can reduce coalescence

A

TRUE

64
Q

decreasing the difference between _________________ can reduce coalescence*****

A

decreasing the difference between the density of the dispersed phase and the density of the medium

65
Q

name 2 methods of preparing primary emulsions

A

continental gum method (dry gum)

english gum method (wet gum)

66
Q

***primary emulsion ratios
(for both wet and dry gum)

A

same for both

4 parts oil: 2 parts water: 1 part emulsifier

4mL:2mL:1g

67
Q

explain the dry gum method of preparing primary emulsion

A

levigate 1 part of the gum-like emulsifer (acacia) with 4 parts of the oil

then, add the water ALL AT ONCE and triturate until you hear cracking and the mixture is creamy white

ass other ingredients by 1st DISSOLVING THEM IN SMALL AMT WATER and QS water to final volume

68
Q

explain the english gum/wet gum method of preparing primary emulsion

A

same 4:2:1 ratio

triturate gum and WATER together to form mucilage (slurry) and add the oil SLOWLY while triturating to form the emulsion

69
Q

*acacia always forms what kind of emulsion

A

o/w

70
Q

rate of sedimentation decreased if the particle size of the dispersed phase _______

A

decreases

71
Q

rate of sedimentation increases if the viscosity of the dispersion phase _______

A

decreases

72
Q

true or false

irreversible aggregation of emulsions is creaming

A

FALSE

can be redispersed

breaking and cracking are irreversible

73
Q
A

Compounding Exam 2 (9 decks)

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