Definitions and preparations of MonoPhasic & Biphasic Liquid Dosage Form

1. Prepared by: Dr.Harshil M Patel, Assistant Professor
Dept. of Pharmaceutics, SNLPCP, UMRAKH.

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MONOPHASIC LIQUIDS
➢The compounding of solution retains an important place in therapeutics
owing to the simplicity of preparation and rapid absorption of soluble
medicinal products. Solutions are of particular value for paediatric, geriatrics
and psychiatric patients who have difficulty in swallowing solid dosage forms
and in cases where individualized dosages are required.
➢Dosage forms meant either for internal, external or parenteral use may be
sub-classified into monophasic or biphasic liquid dosage forms. The
monophasic liquid dosage forms consist of either true or colloidal solutions or
solubilized system. All these consist of only a single phase and may have
either aqueous or non-aqueous solvents as the base.

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Gargles
➢ Gargles are aqueous solution used to prevent or treat infection. They are usually available in
concentrated form with direction for dilution with warm water for use.
➢ They are brought into intimate contact with mucous membrane of throat and allowed to remain in
contact with it for few seconds, before they are thrown out of mouth. They are used to relieve soreness
in mild throat infection.
➢ Phenol or thymol is used as antibacterial agent in gargles. Phenol or thymol may be present in low
concentrations which exert mild anesthetic effect; KCI is included in gargle preparation for its weak
astringent effect, and stimulation the flow of saliva, which released drugs. Gargle differs from mouth
washes in that they are light medicated oral mixture be diluted with water before use.
➢ For example: Phenol gargle, KCIO3 gargles.
Storage: Gargles should be dispensed in clear, fluted glass bottles. Coloured bottles are required to be
used if gargles need protection from sunlight.
Labeling: For EXTERNAL USE ONLY. NOT TO BE SWALLOWED.

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Gargles
Formula: Phenol gargle
Rx
Phenol glycerin - 5 ml
Amaranth solution - 1 ml
Purified water - q.s. to 100 ml
This gargle may be prepared by mixing amaranth solution (1% w/v in chloroform water) with a small quantity of water
and adding Phenol glycerin (16% w/w phenol and 84% w/w glycerin) to it. The solution is stirred and made up to
volume with purified water. The gargle is meant to be diluted with equal quantity of warm water before use.
Uses: Antibacterial effect, astringent effect, mild anesthetic effect.
Packaging: Pack in flip flop bottles, water proof packing.

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Mouth Wash
➢ These are aqueous solutions with a pleasant taste to clean, deodorize the buccal cavity. Mouthwashes
have refreshing, antiseptic and antibacterial activity and prevent Halitosis. They may also contain
alcohol, glycerin, synthetic sweeteners, surfactants, Flavouring and colouring agents. They may be
either acidic or basic in their reaction and in some instances are fairly effective in reducing bacterial
concentration and odors in the mouth for short periods of time.
For example: Compound sodium chloride mouth wash, Zinc chloride mouth wash, Fluoride mouth wash.
Storage: Keep in cool and dry place, Dispense in clear, fluted bottles.
Labeling:
➢ FOR EXTERNAL USE ONLY
➢ Not to be swallowed in large amount
➢ Pack in narrow mouth bottle

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Mouth Wash
Formula:
Rx
Zinc sulphate and zinc chloride mouth wash B.P.C.
Zinc sulphate - 20 g
Zinc chloride - 10 g
Oilute hydrochloride acid - 10 ml
Compound tartarzine solution - 10 ml
Chloroform water to produce - 1000 ml
➢ The preparation may be made by dissolving Zinc sulphate and Zinc chloride in small quantity of Chloroform
solution. To this is added dilute hydrochloric acid and compound tartrazine solution and the final volume is made up
with water.
➢ Zinc sulphate and Zinc chloride included in the preparation acts as astringents. Chloroform water acts as the
flavouring agent and preservative while tartrazine serves as the colour. Zinc sulphate usually contains a small
quantity of oxychloride which may make the solution turbid. This however disappears on addition of dilute
hydrochloric acid.

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Throat Paint
➢ Solution or dispersion of one or more active agents. Throat paints are viscous liquid preparations used for mouth and throat infections.
Glycerin is commonly used as a base because being viscous it adheres to mucous membrane for a long period. Glycerin prolongs the
action of medicaments. Glycerin also provides sweet taste to preparation.
For example: Boroglycerin, Phenol glycerin throat paint.
Storage: Throat paint should be stored in airtight container and in cool place.
Labeling: For EXTERNAL USE ONLY. Not to be swallowed.
Formula:
RX
Potassium iodide - 2.5 gm
lodine - 1.25 gm
Alcohol - 4 ml
Water - 2.5 ml
Peppermint oil - 0.4 ml
Glycerin - 100 ml
➢ Dissolve the potassium iodide in water. Add the iodine and stir until completely dissolved. Dissolve peppermint oil in alcohol 90% in a
small container and transfer it into iodine solution.
➢ Transfer paint into a measuring cylinder and make up the volume to q.s.
➢ Paint are applied with soft brush.
Packing: A wide mouth, fluted, light resistant, screw car glass bottle is used and dispensed in amber coloured bottle.

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Ear Drops
➢ Ear drops are liquid preparations meant for instillation into the ear. In these preparations, the drug is usually
dissolved or suspended in a suitable solvent such as propylene glycol, polyethylene glycol, glycerol alcohol and
water or a mixture of these. Aqueous vehicle is generally not preferred because the secretions in the ear are fatty in
nature and as such these do not easily mix with water.
➢ Ear drops are generally used for their cleansing, pain relieving and antiseptic actions. The main classes of drugs
include analgesics like benzo ne, antibiotics like neomycin and chloramphenicol and anti-inflammatory agents such
as cortisone and dexamethasone. Wax softening agents include hydrogen peroxide and sodium bicarbonate. Ear
drops are usually supplied in amber coloured, glass bottles with a teat and dropper closure or plastic squeeze
bottles.
➢ Example : Chloramphenicol Ear Drops
Chloramphenicol – 5 g
Propylene glycol q.s to 100 ml
➢ Chloramphenicol ear drops may be prepared by dissolving Chloramphenicol in sufficient quantity of Propylene
glycol and finally making up the final volume with it.

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Nasal Drops
➢ Nasal drops are liquid preparations intended for instillation into the nostrils usually with the help of a dropper. Nasal
drops are mostly based on aqueous vehicles although oily drops (containing liquid paraffin of suitable viscosity) are
not uncommon. Oily vehicles are generally not preferred since the oil may retard the ciliary action of the mucosa
and may even cause lipoid pneumonia if drops of the oil enter the lungs. Nasal drops are generally formulated to
resemble the nasal secretions as closely as possible. Thus, these are usually isotonic and slightly buffered to
maintain a pH of 5.5 to 7.5. Additionally, the preparation is made slightly viscous with the help of thickening agents
like methyl cellulose to match its viscosity with that of the nasal secretions.
➢ Example : Ephedrine Nasal Drops
Ephedrine Hydrochloride - 0.5 g
Chlorbutol
Sodium Chloride
Purified water q.s to 100 ml
➢ The drops may be prepared by first dissolving Chlorobutol in small quantity of hot water followed by cooling the
solution to room temperature. Other ingredients are then dissolved in the solution, which is filtered and the final
volume is made up with water. These drops are used as decongestant with Ephedrine acting as the active
medicament. Chlorobutol acts as the preservative while Sodium chloride is added to make the solution iso-osmotic
with nasal secretions.

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Nasal Sprays
➢ Nasal sprays are suspensions or solution of drugs intended for spraying in to the nostrils.
The chief uses of nasal sprays are to relieve nasal congestion and inflammation and to treat
infections. They are intended to be retained in the nasal tract, they are usually viscous and
coarse since fine droplets tend to penetrate further in to the respiratory tract. These
preparations are usually supplied in pressurized containers or plastic squeeze bottles.

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Enemas
➢ Enemas are liquid preparations meant to be introduced into the rectum for cleansing, therapeutic or diagnostic
purposes. Evacuation enemas are rectal injections employed to evacuate the bowel in constipation or before an
operation. e.g., Enema of soap, Sodium phosphate enema, Olive and arachis oil enema, etc. Retention enemas are
usually employed to influence the general system by absorption or to affect locally the seat of disease. They may
possess anthelmintic (quassia), nutritive, sedative (chloral hydrate), or anti-inflammatory (corticosteroids)
properties, or they may contain radio-opaque substances (barium sulphate) for X-ray examination.
➢ Large volume enemas are administered from a douche can and should be warmed to body temperature before use.
Small volume enemas are available in polythene or polyvinyl chloride bags sealed to a rectal nozzle and these are
more convenient for personal administration since the patient has simply to insert the nozzle and squeeze the bag.

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Enemas
➢ Enemas are liquid preparations meant to be introduced into the rectum for cleansing, therapeutic or diagnostic
purposes. Evacuation enemas are rectal injections employed to evacuate the bowel in constipation or before an
operation. e.g., Enema of soap, Sodium phosphate enema, Olive and arachis oil enema, etc. Retention enemas are
usually employed to influence the general system by absorption or to affect locally the seat of disease. They may
possess anthelmintic (quassia), nutritive, sedative (chloral hydrate), or anti-inflammatory (corticosteroids)
properties, or they may contain radio-opaque substances (barium sulphate) for X-ray examination.
➢ Large volume enemas are administered from a douche can and should be warmed to body temperature before use.
Small volume enemas are available in polythene or polyvinyl chloride bags sealed to a rectal nozzle and these are
more convenient for personal administration since the patient has simply to insert the nozzle and squeeze the bag.

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Syrups
➢ Syrups are sweet viscous concentrated aqueous solution of sucrose in purified water.
Simple syrup I.P contains 66.7%w/w sucrose in purified water (100 ml)
Simple syrup USP contains 85%w/v sucrose in purified water (100 m.)
Medicated Syrup: Contains a therapeutic or medicinal agent e.g. Cough syrup.
Flavoured Syrup: Contains Flavouring agent but no medicinal substances e.g. Cherry syrup.

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Advantages of Syrup
➢ Syrup retards oxidation because it is partly hydrolyzed into its reducing sugar such as laevulose and
dextrose.
➢ It prevents decomposition of vegetable substances. Syrup has high concentration of sugar having high
osmotic pressure which prevents the growth of bacteria, fungi, microbes. It acts as a self preservative.
➢ They are palatable due to the sweetness of sugar. It is a valuable vehicle for the administration of
nauseous and bitter substances.
➢ Syrups are good demulcents and soothing agents and hence they are of special value in cough syrup.
➢ Syrups have good patient compliance.

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Method of Preparation
➢ Hot Process
➢ Percolation
➢ Agitation Without Heat
➢ Addition of Medicating or Flavouring Liquid to Syrup

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Hot Process
➢ This method is used when active constituents is neither volatile nor heat labile.
Procedure
✓ Weighed sucrose is taken in beaker.
✓ Purified water is added.
✓ Heated on water bath (less than 70°C) till a solution is obtained.
✓ Product is filtered.
✓ Volume is made up to q.s.
✓ Excessive heat may leads to inversion of sucrose.

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Percolation
➢ Sucrose is placed in percolator.
➢ Water is passed through sucrose slowly.
➢ Neck of percolator is packed with cotton.
➢ Rate of percolation regulates rate of dissolution.
➢ After complete dissolution final volume is made up to q.s.

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Agitation Without Heat
➢ Sucrose and other ingredients are weighed properly.
➢ Dissolved in purified water.
➢ Kept in a bottle of about twice the volume of syrup followed by continuous agitation.
➢ Prepared syrup volume is made up to q.s.

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Addition of Medicating or Flavouring Liquid to Syrup
This method is used when fluid extracts, tinctures or the other liquids are to be added to syrup.
➢ Alcohol is added to dissolve the resinous or oily substances.
➢ Alcohol acts as a preservative also.

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Formulation of Syrup
Vehicle: Syrups are prepared by using purified water.
Adjuncts: The following adjuncts are generally added to improve the formulation of syrup.
Chemical Stabilizer: Glycerin, sorbitol, propylene glycol is added in small quantity to syrup to prevent the crystallization.
Colouring agent: Many syrup are attractively coloured with coal tar dyes such as amaranth, compound tartarazine and
Green S.
Flavouring agents
Tinctures: Lemon and ginger tincture
Fruit juice: Cherry, Raspberry
Essence: Vanilla, orange
Preservatives: Syrups are self preservative. Generally, Benzoic acid, Sodium benzoate, Methyl paraben etc.
Storage: Stored in well dried, completely filled and well stoppered bottle in a cool dark place. Store at a temperature not
exceeding 25°C.

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Elixir
Elixirs are defined as clear, aromatic, sweetened, hydroalcoholic liquids intended for oral us
➢ They provide a palatable means of administering potent or nauseous drugs. Elixirs are less sweet and less viscous then
syrup may contain less or no sucrose Elixirs are more stable than syrups and hence preferred over syrup Elixirs contain
4-40% of alcohol (ethanol).
➢ They may contain glycerin and syrup for increasing the solubility of medicaments or for sweetening purpose. Elixirs may
also contain suitable Flavouring and colouring agents Preservatives are not needed in elixirs as alcohol content is
sufficient to act as preservative.
Types of Elixir:
➢ Non-medicated: Not contain medicament and used as flavoring agent. For example: Aromatic elixir.
➢ Medicated: Which contain a potent drug such as antibiotics, antihistamines, sedatives.

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Method of Preparation
➢ Elixirs are prepared by simple dissolution with agitation or by mixing two or more liquids Ingredients are dissolved in their
respective solvents. For example alcohol soluble ingredients in alcohol and water soluble in water.
➢ Alcoholic strength is maintained by adding the aqueous solution to the alcoholic solution.
➢ The mixture is then made up to the desired volume (q.s.).
➢ At this stage the product may not be clear due to separation of some of the Flavouring agent because the alcoholic
strength is reduced.
➢ Then elixir allowed to stand for some time here the oil globules starts precipitating.
➢ Then elixir is filtered.
➢ Talc can be added to absorb the excess of oils.
➢ Filtration gives clear product.

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Formulation of Elixir
1. Vehicles: The elixirs are usually prepared by using water, alcohol, glycerin, sorbitol, and propylene glycol. Certain oils are
easily soluble in alcohol where alcohol is used as cosolvent. 30-40% of alcohol may be used to make a clear solution.
2. Adjuncts
(a) Chemical stabilizer: The various chemicals or special solvents are used in many elixirs to make suitable elixir. E.g. For
neomycin elixir - citric acid is added to adjust pH.
(b) Colouring agent: Amaranth, compound tartrazine dyes are used for colouring purpose.
(c) Flavouring agent: Black current syrup, raspberry syrup, lemon syrup etc.
(d) Preservatives: Alcohol 20% or more propylene glycol or glycerol as a vehicle is used as preservative. Chloroform
desirable strength, benzoic acid may also be used.
Container: Elixirs are dispense in well filled, well closed air tight or glass bottles having screw caps.
Storage: Store in cool and dry place, protected from sunlight.

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Liniments
Liquid or semi-liquid preparation meant for application to the skin. The liniments are usually applied to the skin with friction
and rubbing of skin (on the affected area).The liniment may be alcoholic or oily solution or emulsion.
In alcoholic preparation, alcohol helps in the penetration of medicament to the skin and also increases its counter irritant
effect and rubefacient action.
In oily liniments, arachis oil is commonly used which spreads more easily on the skin. Some lubricants may contain soap
which helps in easy application of liniment on skin.
Liniment should not be applied on broken skin because it may cause excessive irritation. Liniment contain medicament
possessing analgesic action, rubefacient, counter irritant properties and applied in joint pain, muscle pain etc.
Should be dispensed in colored fluted bottle.
Labelling: FOR EXTERNAL USE ONLY
Storage: Stored in tightly closed container.

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Lotions
➢ Lotions are liquid preparations meant for external use without friction.
➢ They are applied direct to the skin with the help of some absorbent material, such as cotton wool, gauze soaked in it.
Lotions are not applied to broken skin it may cause excessive irritation. The insoluble matter should be divided very finely
for preparing lotions. Bentonite as a suspending agent is added to it.
➢ Lotions are applied for antiseptic action, astringent action, germicidal action e.g. Calamine lotion.
➢ Alcohol is sometimes included in aqueous lotions for its cooling and soothing effect e.g. salicylic acid lotion.
Preparation: Lotions are prepared by triturating the ingredients to a smooth paste and then adding the remaining liquid
phase with trituration.
Storage: Lotions should be stored in well closed and in air tight container.
Labeling: FOR EXTERNAL USE ONLY

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Emulsion
➢ An emulsion is a biphasic liquid preparation containing two immiscible liquids, one of which is dispersed as
globules into the other.
➢ The liquid which is converted into globules is called the dispersed phase and the liquid in which the globules
are dispersed is called the continuous phase.
➢ Normally, two immiscible liquids cannot be dispersed for a long period. So, an emulsifying agent is added to
the system.

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Advantages
➢ Medicines having an unpleasant taste and odour can be made more palatable for oral administration in the
form of an emulsion. e.g. castor oil, cod-liver oil etc.
➢ Emulsion provides protection against drugs which are prone to oxidation or hydrolysis.
➢ Various external preparations such as, cream, lotion and foam aerosols are formulated in emulsion.
➢ The sterile stable intravenous emulsions containing fats, carbohydrates and vitamins can be administered
to the patients who are unable to take them orally.

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Types of Emulsions
➢ Primary emulsion containing one internal phase, for example,
1. oil-in-water emulsion (o/w)
2. water-in-oil emulsion (w/o).
➢ Secondary emulsion also called multiple-emulsion contains two internal phases, for instance,
1. o/w/o
2. w/o/w.
➢ It can be used to delay release or to increase the stability of the active compounds

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Identification test for Emulsion
1. Dilution test:
➢ The emulsion is diluted with water. In case the emulsion remains stable after its dilution, it is o/w emulsion.
The w/o emulsion breaks on its dilution with water but remain stable when diluted with oils.
2. Dye test:
➢ The scarlet red dye is mixed with the emulsion. Place a drop of the emulsion on a microscopic slide, cover it
with a cover-slip, and examine it under a microscope.
➢ If the disperse globules appear red and the ‘ground’ colorless, the emulsion is o/w type.
➢ The reverse condition occurs in w/o type emulsion i.e., the disperse globules appear colorless in the red
‘ground’.

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Identification test for Emulsion
3. Conductivity test:
➢ Water is a good conductor of electricity, whereas oil is non-conductor of electricity.
➢ The conductivity test can be performed by dipping a pair of electrodes connected through a low voltage bulb
in the emulsion.
➢ If the bulb glows on passing the electric current, the emulsion is o/w type, because water is in continuous
phase.
➢ Incase the bulb dose not glow, the emulsion is w/o type, because oil is in continue phase.

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Identification test for Emulsion
3. Fluorescence test:
➢ Certain fixed oils possess the physical property of fluorescing in the presence of ultraviolet radiation.
➢ On microscopic observation of emulsion under ultraviolet radiation, the whole field fluorescence indicates
that oil is present in continuous phase (w/o type emulsion) and droplets fluorescence indicates that oil is
present in dispensed phase (o/w type emulsion).

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Classification of Emulsion
1. Classification of emulsion on the basis of type of emulsifying agent:
A. Natural Gum e.g. Acacia, Tragacanth
B. Gum Substitute e.g. Cellulose & its derivatives
C. Various Soap
D. Saponins
E. Starch
F. Natural Wax e.g. Wool fat & bees wax
G. Synthetic Wax e.g. emulsifying Wax

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1. Classification of emulsion on the basis of mode of administration:
A. For Oral Administration
These are usually o/w type of emulsion and are used to administe oils having medicinal value. E.g.
Castor oil, olive oil, almond oil, cod-liver & liquid Paraffin.
B. For External use
These may be either o/w type or w/o type. However o/w emulsion are preferred over w/o type
emulsions.
C. For Parenteral use
These are used to administer fat soluble vitamins such as A,D,E & oil soluble hormones because
their absorption in this form is very rapid.

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Formulation of Emulsion
1. Emulsifying Agents
2. Preservatives
3. Antioxidants
4. Flavours

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Emulsifying Agents
➢ The emulsifying agents reduce the interfacial tension between two phase, oily phase & aqueous
phase and thus make them miscible with each other and form a stable emulsion.
➢ Emulsifying agents are also known as emulgents or emulsifiers.
❖ An ideal emulsifying agents should have the following Properties:
➢ It should be capable of reducing the interfacial tension between the two immiscible liquids.
➢ It should be compatible with other ingredients of the preparation
➢ It should be non-toxic.
➢ It should be capable to produce ad maintain the required consistency of the emulsion.
➢ It should be chemically stable.

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Classification of Emulsifying Agents
1. Natural Emulsifying agents from vegetable Source
2. Natural Emulsifying agents from animal source
3. Semi Synthetic Polysaccharides
4. Synthetic emulsifying Agents
5. Inorganic emulsifying agents
6. Alcohols

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Natural Emulsifying agents from vegetable Source
➢ These are carbohydrates which includes gums and mucilaginous substances. They are anionic in nature and produce
o/w type emulsions.
➢ The emulsions prepared from these emulsifying agents need suitable preservative to preserve them because the
carbohydrates act as a medium for bacterial growth.
1. Acacia:
✓ Acacia is considered to be the best emulsifying agents for the extemporaneous preparation of emulsion for internal use.
✓ Emulsion prepared with gum acacia are attractive in appearance, quite palatable and relatively stable over a wide range
of pH (2 to 10).
2. Tragacanth:
✓ Tragacanth alone is rarely used as emulsifying agent because it produces very coarse and thick emulsion. The
appearance and stability of the emulsion can be improved by passing the emulsion through a homogenizer.
✓ A stable emulsion can also be produced if tragacanth is used along with gum acacia as emulsifying agent.

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3. Agar:
✓ It is not good emulsifying agent, as forms a very coarse and viscous emulsion. It is used as emulsifying
agents by preparing 2% mucilage, by dissolving in boiling water and cooled at 45 C.
4. Pectin:
✓ It is used as emulsifying agents by preparing 1 % mucilage in water. It is incompatible with alkalies, strong
alcohol, tannic acid and salicylic acid.
5. Starch:
✓ Starch mucilage is rarely used because it forms very coarse emulsions. It is generally used to prepare
enemas.

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Natural Emulsifying agents from animal source
1. Wool fat:
✓ It is generally used in emulsion which are meant for external use. It produce o/w emulsion and can absorb
about 50 % of water.
2. Egg yolk
✓ It is mainly used in extemporaneous preparations meant for internal use because it gel spoiled during
transportation. The emulsion prepared with egg yolk require proper preservation and storage in a
refrigerator.
✓ It is used as emulsifying agents in the concentration of 12-15%.
3. Gelatin:
✓ It is used in the concentration of 1% as emulsifying agents. It is mainly used for the emulsification of liquid
paraffin.
✓ The emulsion prepared with gelatin is quite white and have an agreeable taste. But it needs proper
preservation because emulsions are prone to bacterial growth.

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Semi-synthetic Polysaccharides
1. Methyl cellulose:
✓ It Is a synthetic derivative of cellulose. It is widely used as suspending, thickening and emulsifying agents in
the concentration of 2%.It is commonly used for emulsification of mineral and vegetable oils but get
precipitated in the presence of large amount of electrolytes.
2. Sodium carboxymethyl cellulose:
✓ It is used as an emulsion stabilizer in the concentration of 0.5 to 1.0%. It is soluble in both cold and hot
water.

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Synthetic Emulsifying agent
1. Anionic:
✓ Various alkali soaps, metallic soaps, sulphated alcohols and sulphonates are used as anionic emulsifying
agents.
✓ Soap emulsions are used for external application. SLS is commonly used as emulsifying agents among the
sulphated alcohols. It Produces o/w emulsion.
2. Cationic:
✓ The quaternary ammonium compounds, such as benzalkonium chloride, benzethonium chloride, cetrimide
are used as cationic emulsifying agents. Cationic surface active agents bear positive charge on them.
✓ They mainly used in the preparations meant for external use such as skin lotion and cream.
3. Non-Ionic:
✓ The glyceryl esters, such as Glyceryl monostearate, sorbitan fatty acid esters such as sorbitan
monopalminate are commonly used non-ionic surface active agents.
✓ They are widely used in the preparation of pharmaceutical emulsions, because emulsions prepared with
non-ionic surfactants remain stable over a wide range of pH changes.

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Inorganic Emulsifying Agents
✓ Several inorganic substances such as milk of magnesium (10-20%), Magnesium Oxide (5-10%), and
magnesium aluminium silicate (1%) are used to prepared coarse o/w emulsion.
✓ Bentonite (5%) is used to prepare o/w or w/o emulsions. When bentonite is used to prepare o/w emulsion,
oil is added to the suspension of bentonite, where as when it is used to prepared w/o emulsion, oil phase is
placed in the container and then bentonite suspension is added to the oil with rapid stirring.

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Alcohols
1. Carbowaxes:
✓ These are Mainly used in the preparation of ointments and creams. Carbowaxes having molecular weight
between 200-700 are viscous, light colored, hygroscopic liquids.
✓ Where as carbowaxes with molecular weight 1000 and above are wax like solids.
2. Cholesterol:
✓ In this category, cetyl alcohol, stearyl alcohol, cholesterol and glyceryl monostearate are used to stabilize
the emulsion.
3.Lecithins:
✓ Lecithins which forms w/o emulsion, is rarely used as an emulsifying agents because it darkens in colour
when exposed to light and gets easily oxidised.

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Preservation of Emulsions
✓ Emulsions which are prepared by using emulsifying agents, such as carbohydrates, protiens, sterol and
non-ionic surfactants may lead to the growth of bacteria, fungi and moulds in the presence of water.
✓ The contamination of emulsions by these micro-organisms may cause unplkeasant odour, taste and
discoloration.
➢ The contamination of an emulsion may occur due to any one of the following reason:
✓ The equipment used in the preparation of emulsion are carelessly cleaned.
✓ By using contaminated natural emulsifying agents such as gums, starches and clays.
✓ The ratio of oil and water is not proper.
✓ By using not properly stored deionized and purified water.
✓ pH of the preparation.

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Antioxidants
✓ During storage of emulsion, the fats and emulsifying agents undergo oxidation by atmospheric oxygen.
✓ This can be avoided by using antioxidant such as tocopherol, gallic acid and ascorbic acid.
❖ The following are some of the qualities of an ideal anti-oxidant:
✓ It should be readily soluble in the medium.
✓ It should be effective in low concentration.
✓ It should be non toxic.
✓ It should be non irritant.
✓ It should be colorless, odorless and tasteless.

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Flavours
✓ Vanillin is a good Flavouring agent for liquid paraffin emulsion.
✓ Benzaldehyde is generally used as Flavouring agents for cod-liver oil emulsion.
✓ A combination of Flavouring and sweetening agents provides greater palatability to emulsion.

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Preparation of Emulsion
✓ The following methods are commonly used for the preparation of emulsions on small scale:
1. Dry gum Method
2. Wet gum Method
3. Bottle Method
4. Other Method

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Dry Gum Method
✓ Measure the required quantity of oil in dry measure and transfer it into a dry mortar.
✓ Add the calculated quantity of gum acacia into it and triturate rapidly so as to form a uniform Mixture.
✓ Add required quantity of water and triturate vigorously till a clicking sound is produced and the product
becomes white or nearly white due to the total internal reflection of light.
✓ The emulsion produced at this stage is known as primary emulsion.
✓ Add more of water to produce required volume.

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Wet Gum Method
✓ Calculate the quantity of oil, water and gum required for preparing the primary emulsion.
✓ Powder the gum acacia in a mortar. Add water and triturate it with gum so as to form a mucilage.
✓ Add required quantity of oil in small portions with rapid trituration until a clicking sound is produced and the
product becomes white or nearly white. At this stage the emulsion is known as primary emulsion.
✓ Add more of water in small portions to the primary emulsion with trituration to produce the required volume.
Stir thoroughly so as to form a uniform emulsion.
✓ Transfer the emulsion to a bottle, cork, label and dispense.

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Bottle Method
✓ Measure the required quantity of the oil and transfer into a large bottle. Add the required quantity of
powdered gum acacia.
✓ Shake the bottle, until the oil and gum are mixed.
✓ Add the calculated amount of water all at once.
✓ Shake the mixture to form a primary emulsion.
✓ Add more of water in small portions with constant agitation to produce the required volume.

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Stability of Emulsion
✓ An emulsion is said to be stable if it remains as such after its preparation, i.e., dispersion globules are
uniformly distributed throughout the dispersion medium during its storage.
✓ The emulsion should be chemically stable and there should not be any bacterial growth during its shelflife.
✓ The following three changes usually occurs during the storage of an emulsion:
1. Cracking
2. Creaming
3. Phase inversion

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1. Cracking
✓ Cracking means the separation of two layers of disperse and continuous phase, due to the coalescence of
disperse phase globules which are difficult to redisperse by shaking.
✓ Cracking may occurs due to following reasons:
1. By addition of emulsifying agents of opposite type
2. By decomposition or precipitation of emulsifying agents
3. By addition of a common solvent
4. By Microorganisms
5. Changes in temperature
6. By creaming

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By addition of emulsifying agents of opposite type
✓ Soaps of monovalent metals produce o/w type emulsions where as soaps of divalent metal produce w/o
type emulsions.
✓ But the addition of monovalent soap to a divalent soap emulsion or a divalent soap to a monovalent soap
emulsion leads to cracking of emulsion.
By decomposition or precipitation of emulsifying agents
✓ When an acid is added to an alkali soap emulsion, it causes the decomposition of an emulsifying agents
and thus leads to cracking of an emulsion.
✓ Similarly, when sodium chloride is added to sodium or potassium soap emulsion, it leads to the precipitation
of emulsifying agents and thus cracking of emulsion take place.

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By addition of a common solvents
✓ When a solvent is added to an emulsion which is either miscible with or dissolve the dispersed phase, the
emulsifying agent and continue phase, there is formation of one phase or a clean solution.
✓ This leads to cracking of an emulsion
By Microorganisms
✓ If emulsions are not stored properly, they may develop bacterial and mould growth. This may leads to
destruction of emulsifying agents and cause cracking of emulsion.
✓ Therefore, it is desirable that all emulsions which are required to be stored for a long period should be
suitably preserved.

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Changes in temperature
✓ When emulsion are stored for a long time, an increase in temperature may reduce the viscosity of the
emulsion and encourage creaming.
✓ When emulsions are stored at a very low temperature, freezing of its water content into ice and melting of
an ice and shaking may reform the emulsion.
By Creaming
✓ A creamy emulsion is more liable to crack than a homogenous emulsion. It is therefore, necessary to take
steps to retard creaming as far as possible.

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2. Creaming
✓ Creaming may be defined as the upward movement of dispersed globules to form a thick layer at the
surface of the emulsion.
✓ Creaming is a temporary phase because it can be re-distributed by mild shaking or stirring to get again a
homogenous emulsion.
✓ As far as possible creaming of an emulsion should be avoided because it may lead to cracking with
complete separation of two phase
✓ According to stoke’s law, the rate of creaming depends on the number of factors which can be explained by
following equation:
𝑥 =
2𝑟2 𝑑1 − 𝑑2 𝑔
9𝑛

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✓ According to stoke’s law, the rate of creaming depends on the number of factors which can be explained by
following equation:
𝑥 =
2𝑟2 𝑑1 − 𝑑2 𝑔
9𝑛
Where,
V= Rate of creaming
R= Radius of globules
D1=Density of dispersed phase
D2=density of continuous phase
G= Gravitational phase
N=Viscosity of the dispersion medium

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1. Radius of globules:
✓ The rate of creaming is directly proportional to the radius of the globules. Larger the size of globules the
more will be creaming and smaller the size of the globules, lesser will be creaming. The small globules rise
less quickly than large globules.
✓ Hence, creaming can be reduced by reducing size of globules by passing the emulsion through a
homogenizer.
2. Difference in density of disperse phase and continuous phase:
✓ The rate of creaming depends upon the difference between the densities of the disperse phase &
continuous phase.
✓ Greater the difference, more will be the creaming. This difference can be reduced but it is not desirable
because it is not required therapeutically.

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3. Viscosity of the dispersed:
✓ The rate of creaming is inversely proportional to the viscosity of the dispersed medium.
✓ The viscosity can be increased by adding tragacanth and methyl cellulose, but too much viscosity is
undesirable because it may become difficult to redisperse the materials which have settled at the bottom.
✓ Moreover, it is difficult to pour the emulsion from the container.
4. Storage condition:
✓ The emulsion should be stored in a cool place because the rise in temperature reduces the viscosity which
may leads to creaming.
✓ The freezing should be avoided because it may leads to cracking.

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3. Phase inversion
✓ Phase inversion means the change of one type of emulsion in to the other type i.e., oil in water emulsion
changes in to water in oil emulsion.
✓ It may be due to following reason:
1. By the addition of an electrolyte
2. By changing the phase volume ratio
3. By temperature change
4. By changing the emulsifying agents
✓ The phase inversion can be minimized by keeping the concentration of disperse phase between 30-60 %,
storing the emulsion in a cool place and using proper emulsifying agents in proper concentration.

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Storage of Emulsion
✓ The emulsion should be stored in containers having an adequate air space above the emulsion, so as to
permit adequate shaking before its use.
✓ The emulsion which are use for internal, should be packed in comparatively wide mouth bottle so that it is
easy to remove it without any difficulty.
✓ A secondary label “Shake Well Before use” is required to be fixed on the container.
✓ An emulsion should be stored in air tight closed container, protected from light, frrzing and excess heat.
✓ They are required to be stored in a cool place.

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EMULSION SUSPENSION
It is a heterogeneous mixture of two immiscible
liquids
It is a heterogeneous mixture
Dispersed particle do not settle on standing Dispersed particle settle on standing
Dispersed particle size 1 to 1000nm Dispersed particle size more than 1000nm
Particle are not visible through the naked eye Particle are visible through the naked eye
It can not be separated by filtration It can be separated by filtration
Dispersed in solid, liquid or gas Dispersed in liquid
Emulsifying agents are required Suspending agent are required
Freezing should be avoided during as it leads to
cracking
Freezing should be avoided during as it leads to
aggregation
DIFFERENCE BETWEEN EMULSION & SUSPENSION