M7. Emulsions Flashcards
Define emulsions.
- dispersed systems w/ at least two immiscible liquids
One of the liquids (internal phase) uniformly distributed as droplets through the external phase
What are the types of emulsions
Simple emulsions: o/w, w/o
Multiple emulsions: o/w/o, w/o/w
*small waer drops enclused in large oil drop which disperesed in water
Microemulsions (1 nm - 1 microm)
How do you prepare an o/w and w/o emulsion
classical gym methods: dry and wet gum
in situ soap formation
what is the method for in situ soap method
* Emulsion preparation with synthetic surfactants with HLBs ranging 1-20 (or up to 50)
- devide into an oil phase and aq phase ingredients -> ingredients idssolve in their proper phases
- dissolve oil soluble ingredients and low HLB emulsifier in oil phase
2a. heat to 5010 C over melpting point of highest melting point ingredient - dissolve water soluble ingrediats and high HLB emulsifier in water phase
- heat to temp 3-5 C higher than that of oil phase
- add aq phase to oil with agitation
- stir until congealed or colled to room temp
what is a microemulsion
An emulsion where the dispersed globules are of colloidal dimensions (1 nm - 1 μm); the preparation is frequently transparent
How would you determine emulsion type?
dilution test
conductivity test
dye solubility test
describe the dilution test for emulsions
* test for emulsion type
- relies on fact thato/w emulsions can be diluted w/ water and vice vera
- if dultion is attempted with itnernal phase and see separation you know what you added wasnt teh internal phase
what is the conductivity test
* for determining emulsion type
- water is more onductive -> so if o/w emulsion will conduct electricity better
*Conduction of an electrical current between two immersed electrodes is indicative of a o/w emulsion.
describe teh Dye solubility test
- suing oil or water soluble dyes
- microscopic examination -> if water soluble dye has been taken up by continuous phase and excluded from internal its o/w
- if contonious phase not stained, test with oil sobilble dye to confirm w/o
What type of emulsion is used for i.v. administration?
Always o/w
What type of emulsion is used for oral and i.m. administration?
Oral: mostly o/w
i.m: w/o for sustained release
What are the necessary components of an emulsion?
Oil phase, water phase and an emulsifying agent (s)
What additives are used for emulsions?
Antioxidants, preservatives, humectants
Explain the restrictions for using oil components for i.v. administration. Give examples of suitable oils for i.v. use.
Only selected oils are suitable for i.v. use
cottonseed oil, soybean oil safflower oil
Name the suitable surfactants for parenteral injections.
Only certain types of non-ionic surfactants may be used
lecithin, polysorbate 80 (tween80) , poloxamers
*do o/w (idk about lecithin for sure i dont see it on the emulsifying agents table)
Define ‘in situ emulsifier’and provide four examples.
Emulsifier formed upon mixing of separate components during the compounding process:
Calcium oleate (lime water aka (Ca(OH)2) + oleic acid)
Triethanolamine stearate
Sodium or Potassium stearate
Borax-beeswax system – see this in semisolid section
what ype of emulsions is formed when soaps of divalent metals are used
w/o
what ype of emulsions is formed when alkali and ammonium soaps are used
o/w
What type of emulsifying agent is triethanolamine stearate?
what type of emulsion does it form
In situ emulsifier o/w
Describe the quaternary ammonium compounds: properties, specific uses and examples.
- cationic surfactant
- unstable at high pH (best pH 4-6)
- incompatible with anionic surfactants and polyvalent anions
- also has antimicrobial properties (disinfectant, antiseptic)
ex: benzalkonium chloride, cetylpyridinium chloride, cetrimide
*weak O/w
oil phase for oral admin
liquid paraffin
castor oil
cod liver oil
peanut oil
define amphipatic
Both hydrophilic and hydrophobic parts within the same molecule
What are “Spans”? Indicate structure, HLB ranges, solubility, and type of emulsion formed.
- Sorbitan esters
e. g. hydroxyl groups of sorbitan esterified with lauric, palmitic or stearic acid (Spans – hydrophobic)
HLB range 2-10
w/o emulsions
What are “Tweens”?
Indicate structure, HLB ranges, solubility, and type of emulsion formed.
Polysorbates
e.g. polyethylene glycol derivatives of sorbitan esters
(Tweens - hydrophilic)
HLB range 10-18
o/w emulsions
What are the advantages of polysorbates as surfactants?
Versatile, can be used in all dosage forms, safe, non-toxic, non-irritating
What are the disadvantages of naturally occurring emulsifying agents?
batch-to-batch variation in composition and emulsifying properties
susceptible to bacterial or mold growth not appropriate for products requiring long shelf-lives
List a few semisynthetic polysaccharides.
Cellulose derivatives: methycellulose, hydroxypropylmethylcellulose
route of administration for ionic emulsifieers
- shoud not be given orally
- Cationic: toxic at low conc 0> limtied to external use when antiseptic properties are req
- Anionic: high high pH (alkaline) -> suitable for broken skin
what are the types of anoinic surfacants
- alakli metal and ammonium soaps (metal + ammonium salt in situ)
- O/w
- sodium stearate
- soaps of divalent and trivalent metals
- usually formed in situ
- w/o
- calcim oleate
- amine soaps (in situ)
- o/w
- triethanolamine stearate
- Sulfated and sulfonated compoiunds
- o/w
- sodium lauyl sulfate
- v water soluble
finely divided solids
form particulate films around dsipersed droplet -> coatse grained stable emulsions
- stability results form strength of interfacial film
e: colloidal clays (o/w or w/o), bentonite, veegum
role of antioxidants in emulsions
- Cellulose derivatives: methycellulose, hydroxypropylmethylcellulose
ex: BHA and BHT (true oxidizing agents) - can be synergistic w/ chelating agrens (citric acid, EDTA, tartaric acid
ex: BHA, BHT, alpha-tocopherol, alkylgallates (Propyl Gallate B.P.), ascorbic acid, ascorbyl palmitate
role of preservatives in emulsions
- prevent microorganism growth
- usually combine lipid and water soluble preservatives
Methylparaben (water phase) propylparabens (oil phase)
* emulsion ingredients may inactivate preservates bc micellar binding with surfactants (parabens + tweens)
humectants
- compounds capable of absorbing water from air
- used to reduce evaporation of water phase (preent drying)
ex: propylene glycol, glycerol and sorbitol
