emulsions/dvlo theory

Question 1

what 3 factors does the degree of steric effects depend on

Answer 1

-non ionic surfactant chain length
-number of chains per unit area of -interacting surface
chain/solvent interactions

Question 2

types of emulsions

Answer 2

o/w
w/o
w/o/w
o/w/o

Question 3

what is an emulsion

Answer 3

dispersion of a liquid in another liquid which are immiscible

Question 4

basic types of emulsifiers and examples

Answer 4

(-)anionic- sodium dodecyl sulphate
(+)cationic- cetrimide
non ionic- cetostearly alcohol

Question 5

what do emulsifying agents do

Answer 5

stabilises emulsions and prevents liquids from separating

Question 6

describe surfactants as emulsifying agents

Answer 6

accumulate at water oil interface, forms interfacial barrier, not very good, charged molecules repel

Question 7

why are mixed emulsifiers better than surfactants

Answer 7

mix of hydrophilic and lipophilic amphiphiles, denser interfacial film, v good for stabilising emulsions, mostly used in creams

Question 8

what is amphiphilic

Answer 8

both hydrophobic and hydrophilic

Question 9

polymers and proteins as emulsifying agents

Answer 9

amphiphilic, adsorb at interface, good emulsifying agents, can bridge between droplets to connect multiple oil droplets so also acts as flocculating agents

Question 10

example of a natural emulsifier in food

Answer 10

lecithin (egg yolk) (phospholipid)

Question 11

what are creams

Answer 11

emulsions which one phase is semisolid/wax

Question 12

signs of instability in emulsions

Answer 12

creaming- disperse phase droplets increase in size and collect near the surface

cracking- phase separation, disperse phase forms large globules or a separate layer on surface

Question 13

emulsions are unstable and cant be reformed by shaking so what to do

Answer 13

stabilise using a good emulsifying agent to prevent coalescence of oil particles in liquid emulsions/creams

Question 14

what is coalescence of droplets

Answer 14

droplets increasing in size

Question 15

factors that cause emulsions to crack

Answer 15

incompatible chemicals- opposite charged surface active agents (cationic to anionic), addition of electrolytes

bacterial growth- protein and non ionic emulsifying agents are good growth medium

temperature changes- freezing disrupts interfacial film and heating denatures protein emulsifying agents and solubility changes in non ionic ones

Question 16

physical processes that cause instability

Answer 16

flocculation of oil droplets- loosely held together by interactive forces of attraction/repulsion, can be redispersed but can coalesce into bigger droplets

phase inversion- (ow into wo) caused by excess amounts of disperse phase

creaming- emulsion creams on standing for long time, disperse phase rises/sinks

Question 17

how to keep globules suspended

Answer 17

reduce globule size of dispersed phase, decrease density difference between two phases, increase viscosity of continuous phase

Question 18

how to reduce microbial growth in emulsions as the water vehicle in liquids/semisolids support microbial growth and contamination

Answer 18

sterilise by filtration/autoclaving, preservatives, fridge storage

Question 19

how to choose a preservative to prevent microbial growth

Answer 19

base on delivery route, stability of shelf life, non toxic, compatible with excipients, effective against wide spectrum of organisms, optimum pH

Question 20

3 types of emulsion applications

Answer 20

intravenous- total parental nutrition (TPN) (administration of fats), fat absorbed from GI tract circulates as chylomicrons

oral

intramuscular- w/o for sustained release

Question 21

examples of acceptable excipients for emulsions

Answer 21

oil phase- soya bean oil, medium chain triglycerides

emulsifiers- phospholipids, egg yolk

some hydrophilic pluronics

Question 22

emulsions for drug delivery

Answer 22

hydrophobic oil and soluble drug- dissolved in oil then emulsified

surface active drugs- adsorb at interface

Question 23

3 types of formulations of self emulsifying microemulsions classified by how it disperses in vitro

Answer 23

lipid+drug

SEDDS= self emulsifying drug delivery system= drug+lipid+ssurfactant

SMEDDS= self microemulsifying drug delivery system+ drug+lipid+surfactant+cosurfactant/solvent

Question 24

what does SEDDS and SMEDDS stand for

Answer 24

self emulsifying drug delivery system

self microemulsifying drug delivery system

Question 25

2 classifications of self emulsifying microemulsions

Answer 25

liquid lipidic- liquid at room temp, final dosage form fills soft gelatin capsule

semi solid lipidic- semi solid at room temp, final dosage form is capsule/pellet/tablet

Question 26

what excipients are used in self emulsifying emulsions

Answer 26

lipids- mono/di/triglycerides
-castor oil, sesame oil, peceol

emulsifiers- polyglycolised oils- labrasol, labrafil
-polyglycolised solids- gelucire 44

non ionic surfactants- tween 80, span 80

fatty acids- oleic acid, capric acid

co solvents- glycerol, peg 400

Question 27

what do co-solvents do

Answer 27

aid dispersion and solvation

Question 28

what do non ionic surfactants do

Answer 28

aid solubilisation

Question 29

types of in vitro test

Answer 29

-measurement of emulsion droplet size
-phase diagram
-visual dispersion test
-digestion assay
-dissolution