here we gonna study emulsion from subject pharmaceutics 2 and chapter Emulsion in an easy way like a full chapter with easy language easy to understand and important for examinations in MSBTE as well as others. the first is only emulsion suspension is in another part. so let’s get started.
Emulsion and Suspension
An Emulsion is a biphasic liquid preparation containing two immiscible liquids, one of which is dispersed as minute globules into the other. The liquid which Is converted into minute globules is called the “dispersed phase” and the liquid in which the globules are dispersed is called the “continues phase “
1.medicines having an unpleasant taste and order can be made more palatable for oral administration in the form of an emulsion.
e.g castor oil, cod liver oil.
2.emulsion provide protection against drugs that are responsible for oxidation and hydrolysis.
3.many preparations such as creams, lotions is formulated in the emulsion.
4.intravenous emulsion containing fats, carbohydrates and vitamin can be administered to the patient who is unable to take orally.
Types of emulsion
1.oil in water emulsion-(o/w)
2.water in oil emulsion-(w/o)
Oil in water
In this type of emulsion oil is dispersed phase and water is in the continuous phase. this type of emulsion mostly used for internal use.
Gum acacia, tragacanth, methylcellulose, synthetic substance and soaps are used and as emulsifying agent.
Water in oil
In this water is dispersed phase and oil is in the continuous phase
Wool fat, resins, beeswax, and soaps from divalent bases are used as emulsifying agent.
This type of emulsion mainly used externally as lotions and creams.
Tests for identification of the type of emulsion
The following test is used to differentiate between o/w and w/o.
the emulsion is diluted with water if the emulsion remains stable after dilution it is o/w emulsion. If emulsion breaks on dilution it is w/o type.
the scarlet dye is used in this test this dye is mixed with emulsion then place a drop of it on a microscopic slide and cover with a cover of sleep. And examine under the microscope. If dispersed globule appear red and the ground is colourless then it is the o/w type of emulsion and if dispersed globules are colourless and the ground is red then it is w/o type.
water is a good conductor of heat and electricity.
To perform a conductivity test dipped pair of electrodes and connect a low voltage bulb in it. If the bulb glows current then it is w/o type.
Formulation of emulsion
- Emulsifying agents- the emulsifying agent used to reduce the interfacial tension between two phases that is the liquid and oil phase.
Emulsifying agents are also known as emulgents or emulsifiers.
There are a lot of emulsifying agents available to form or prepare a stable emulsion but it is very difficult to select a proper emulsifying agent for the development.
No single emulsifying agent can fulfil all the properties required for the preparation of stable emulsion, therefore, they have to use 2 or more emulsifying agents.
DEFINE OR EXPLAIN HLB METHOD
Griffin device is a useful method for calculating a balanced mixture of emulsifying agents to form a particular type of emulsion, it is called hydrophile lipophile balance or HLB method.
All emulsifying agents have a given no on the HLB scale which is divided into 18 units. Emulgents with high no(8-18) indicate hydrophilic properties and they produce an o/w type of emulsion.
And opposite emulgent with lower no (3-6) indicates lipophilic properties and produce w/o type of emulsion.
Write down the Classification of an emulsifying agent?
1.natural- a) vegetable source– gum acacia, tragacanth, agar, pectin, starch, Irish moss.
- b) animal source-wool fat, egg yolk, gelatin.
2.semisynthetic polysaccharides– methylcellulose, carboxymethylcellulose.
3.synthetic – anionic, cationic, non-ionic.
4.inorganic– milk of magnesia, magnesium oxide, magnesium trisilicate, magnesium aluminium silicate, bentonite.
5.alcohols– carbowaxes, cholesterols, lecithins.
Properties of ideal emulsifying agents
1.It should be capable of reducing the interfacial tension between two immiscible liquids.
2.It should be compatible with other ingredients.
3.It should be non-toxic.
4.It should produce and maintain consistency of the emulsion.
5.It should be chemically stable.
Preparation of emulsions.
The following methods used for preparation on small scale.
Dry gum methods-(what is mean by primary emulsions)
1.measure the required quantity of oil in a dry measure and transfer it to a dry morter.
2.add a calculated quantity of gum acacia and triturate rapidly to form a uniform mixture.
3.add the required quantity of water and triturate vigorously till a clicking sound is produced product become white or nearly white is produce at this stage are called primary emulsion.
4.add more water for the required volume
|Sr no.||Type of oil||Ratio of
Oil: water: gum
|1||Fixed oil||4: 2: 1||Castor oil,
cod liver oil,
|2.||Mineral oil||3: 2: 1||Liquid paraffin|
|3||Volatile oil||2: 2: 1||Turpentine oil,
2.wet gum method
In his method, the proportion of oil-water gum required for preparing in the primary emulsion is given above.
1.calculate the quantity of oil-water and gum required to prepare a primary emulsion.
2.powder the gum acacia in a mortar. add water and triturate it with gum.
3.add the required quantity of oil in small portion rapid trituration.
4.add more water to produce a uniform emulsion
5.transfer it to a bottle or container.
This method is used for volatile and other viscous oils.
The proportion of oil-water gum is 2:2:1
1.take required quantity of oil and transfer into bottle .add gum acacia in it
2.shake the bottle vigorously until they mixed with each other
3.add a calculated amount of water all at once.
4.shake the mixture to form a primary emulsion.
5.add more water to make require a volume.
In these various blenders and homogenizers are used for preparing emulsions.
Hand homogenisers, silver son mixer homogeniser and colloidal mill are used for preparing emulsion.
These homogenizers are bases on the principle that the large globules in coarse are converted into smaller globules by passing through a narrow orifice
The coarse product is produced in a mortar and transferred into the homogenizer until the desired product gets.
The emulsion is nothing but a combination of water and oil which having therapeutics activity. These are some of the points we are clear now if you want to know more about emulsion you can check on this WIKIPEDIA
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