Emulsifying agents and Emulsions MCQs for GPAT, NIPER, Pharmacist and Drug Inspector exam

EMULSIFYING AGENTS: Emulsifying agents are substance that are soluble in both water and fat and enable fat to be uniformly dispersed in water as an emulsion.

CLASSIFICATION OF EMULSIFYING AGENT:

Table 1 – Classification of emulsifying agents

Examples – Carbomer, Carrageenan, Lanolin, Lecithin, Mineral Oil, Oleic Acid, Oleyl alcohol, Pectin, Poloxamer, Polyoxyethylene Sorbitan Fatty Acid Esters, Sorbitan Esters, Triethanolamine

1.Carbomer:

INN: Carbomer; Carbomera

Synonyms: Acrylic acid polymer; carboxyvinyl polymer, carboxy polymethylene; polyacrylic acid

Molecular Formula: A synthetic high-molecular-weight crosslinked polymer of acrylic acid; contains 56–68% of carboxylic acid (COOH) groups. The viscosity of a neutralized preparation of carbomer 934P (2.5 g/500 mL water) is 30,000–40,000 mPa.s.

Description—White, fluffy powder with a slight, characteristic odor; hygroscopic.

Properties: Dissolves in water, alcohol, or glycerin, when neutralized with alkali hydroxides or amines; 0.5% dispersion pH 3; specific gravity about 1.41; moisture content 2%; viscosity varies depending upon grade, salt type and concentration, and pH of solution.

Incompatibilities: Resorcinol, phenol, cationic polymers, strong acids, and high levels of electrolytes.

Uses: As a thickening, suspending, dispersing, emulsifying agent and gel former.

2.Carrageenan:

INN: Carrageenan

Synonyms: Chondrus crispus, Irish moss, pearl moss

Chemical Name & CAS Number: λ-Carrageenan (9064-57-7) κ-Carrageenan (11114-20-8) ι-Carrageenan (9000-07-1)

Molecular formula: It is a variable mixture of potassium, sodium, calcium, magnesium, and ammonium sulfate esters of galactose and 3,6-an-hydrogalactose copolymers, the hexoses being alternately linked at the α-1,3 and β-1,4 sites in the polymer chain.

Description: Yellow-brown to white, coarse to fine powder; odorless; tasteless. The three main types of copolymers present are kappa-carrageenan, iota-carrageenan, and lambdacarrageenan, which differ in the composition and manner of linkage of monomeric units and the degree of sulfation (the ester sulfate content for carrageenans varies from 18% to 40%). Kappa carrageenan and iota-carrageenan are the gelling fractions; lambda-carrageenan is the non gelling fraction.

Properties: All carrageenans hydrate rapidly in cold water, but only lambda-carrageenan does not require the presents of cations to initiate functionality. Gelling carrageenans require heating to about 80°C for complete solution when potassium and calcium ions are present.

Incompatibilities: All carrageenans are reactive with cationic materials, resulting in complexation.

Uses: As an emulsifying, suspending, and gelling agent.

3.Lanolin:

INN: Wool Fat; Purified lanolim; Adeps lanae; Lanolin

Synonyms: Lanolin anhydrous, purified lanolin, refined wool fat

Chemical Name & CAS Number: Anhydrous Lanolin(8006-54-0)

Description: Yellowish white, ointment-like mass, with a slight, characteristic odor.

Properties: Insoluble in water; soluble in chloroform or ether with separation of its water of hydration; density 0.932-0.945 g/cc at 15°C.

Uses: As an emulsifying agent, ointment base.

4.Lecithin:

INN: Lecithin

Synonyms: Egg lecithin, mixed soybean phoisphatides, ovolecithin, soybean phospholipids

Chemical Name & CAS Number: Lecithin (8002-43-5)

Description: Varies greatly, depending on the free fatty acid content; could be a free flowing powder or a viscous dark brown to black syrup-like liquid; changes color (oxidation) quickly when exposed to air.

Properties: Powder: density of 0.5g/cc, insoluble in water and polar solvents; liquid: density 0.97 g/cc.

Incompatibilities: Will oxidize when exposed to air; hydrolyzes when exposed to esterases.

Uses: As an emollient, emulsifying agent, and solubilizing agent.

5.Mineral oil:

INN: Liquid paraffin; Paraffin liquidum; Mineral oil

Synonyms: Mineral hydrocarbons, heavy mineral oil, liquid petrolatum, paraffin oil, white mineral oil

Chemical name & CAS Number: Mineral oil (8012-95-1)

Molecular Formula: A refined mixture of liquid hydrocarbons (C14 to C18) obtained from petroleum

Description: Colorless, transparent, oily liquid, odorless and tasteless when cold, and develops not more than a faint odor of petroleum when heated.

Properties: Insoluble in water, glycerin, or alcohol; miscible with most fixed oils, but not with castor oil; soluble in volatile oils; specific gravity 0.818-0.880; kinematic viscosity not more than 33.5 centistokes at 40°C.

Incompatibilities: Strong oxidizing agents.

Uses: As an emulsifying agent and emollient in topical formulations mostly ointments.

6.Oleic Acid:

INN: Oleic acid; Acidum oleicum

Synonyms: Elaic acid, cis-9-octadecenoic aci,; 9,10-octadecenoic acid, olenic acid

Chemical Name & CAS Number:(Z)-9-Octadecenoic acid(112-80-1)

Molecular Formula: C18H34O2

Description: Colorless to pale yellow, oily liquid; lard-like odor and taste.

Properties: Specific gravity 0.889-0.895; congeals at a temperature not above 10°C; pure acid solidifies at 4°C; at atmospheric pressure, it decomposes when heated at 80–100°C; on exposure to air, it gradually absorbs oxygen, darkens, and develops a rancid odor; practically insoluble in water; miscible with alcohol, chloroform, ether, benzene, or fixed and volatile oils.

Incompatibilities: Reacts with alkali to form soaps. Heavy metals and calcium salts form insoluble oleates. Iodine solutions are decolorized by formation of the iodine addition compound of the acid. It is oxidized to various derivatives by nitric acid, potassium permanganate, and other agents.

Uses: As an emulsifying agent for topical; a penetration enhancer for poorly soluble actives (both topical and oral); a vehicle in soft gelatin capsules.

7.Oleyl Alcohol:

INN: Alcohol oleicus

Synonyms: cis-9-octadecen-1-ol, oleic alcohol, oleo alcohol, oleol

Chemical name & CAS Number: (Z)-9-Octadecen-1-ol(143-28-2)

Molecular Formula: C18H36O

Description: Clear, colorless to light yellow, oily liquid; faint characteristic odor and bland taste; iodine value between 85 and 90; hydroxyl value between 205 and 215.

Properties: Soluble in alcohol, ether, isopropyl alcohol, or light mineral oil; insoluble in water; boiling point 182–184°C.

Use: As an emollient, emulsifying agent.

8.Pectin:

INN: Pectin

Synonyms: Citrus pectin, methopectin;methyl pectin, methyl pectinate, pectinic acid

Chemical Name & CAS Number: Pectin (9000-65-5)

Molecular Formula: Repeating linear units of (1-4)-linked α-D-galactopyranosyluronic acid units with some carboxyl groups esterified with methanol.

Description: Off-white, odorless powder that has a mucilaginous feel when moistened.

Properties: Soluble in water; insoluble in most organic solvents; slightly acidic in solution; solubilizes more easily when mixed with glycerin or 1:3 parts of sucrose to prevent clumping.

Incompatibilities: High concentration of alcohol cause precipitation; hydrolysis in the presence of alkalis; high temperatures promotes hydrolysis.

Uses: As an emulsifying agent, thickening agent for suspensions.

9.Poloxamer:

INN: Poloxamer

Synonyms: Poloxalkol, polyethylene-propylene glycol copolymer, polyoxyethylene polyoxypropylene copolymer

Chemical Name & CAS Number: α-Hydro-ωhydroxypoly(oxyethylene)poly(oxypropylene) poly(oxyethylene) block copolymer (9003-11-6)

Molecular Formula: HO(C2H4O)a(C3H6O)b(C2H4O)aH

Description: Waxy appearing, white colored, freely flowing prilled granules.

Properties: 2.4% aqueous solution pH of 5.0–7.4; density 1.06 g/cc; HLB value 0.5–30, depending on grade; moisture content approximately 0.5%; all grades are freely soluble in water, solubility in other solvents is grade dependent.

Incompatibilities: Phenols and parabens.

Uses: As nonionic emulsifiers and solubilizing agents; tablet binders and coating agents; thermally inverse gelling agents (grade dependent).

10.Polyoxeythylene SorbitanFatty Acid Esters:

INN: Polysorbate; Polysotbatum

Synonyms: Crillet, Alkamuls, Atlas, Tween

Chemical Name & CAS Number: Polyoxyethylene 20 Sorbitan monolaurate (9005-64-5) Polyoxyethylene 20 Sorbitan monopalmitate (9005-66-7)

Polyoxyethylene 20 Sorbitan monostearate (9005-67-8)

Polyoxyethylene 20 Sorbitan monooleate (9005-65-6)

Description: All polysorbates (20,40,60 & 80) are slightly yellow, oily liquids exhibiting a faint, characteristic odor; and somewhat bitter taste.

Properties: Very soluble in water, producing an odorless and nearly colorless solution; soluble in alcohol, cottonseed oil, corn oil, ethyl acetate, methanol, or toluene; insoluble in mineral oil; specific gravity 1.07-1.09; pH (1:20 aqueous solution) 6–8; viscosity range 400–600 mPa s.

Uses: As emulsifying agents, forming O/W emulsions; wetting agents in coating applications; solubilizing agents for oil-soluble APIs.

11.Sorbitan Esters:

INN: Sorbitan; Sobritani

Synonyms: Spans

Chemical Name & CAS Number: Sorbitan esters (monolaurate [1338-39-2]; monooleate[1338-43-8]; monopalmitate[26266-57-9]; monostearate [1338-41-6]; trioleate [26266-58-0]; tristearate [26658-19-5])

Description:

• Monolaurate: Amber, oily liquid.
• Monooleate: Amber liquid.
• Monopalmitate: Tan, granular waxy solid.
• Monostearate: Cream to tan beads.
• Trioleate: Amber, oily liquid.
• Tristearate: Tan, waxy beads.

Properties:

Monolaurate:

• Soluble in methanol or alcohol
• Dispersible in distilled water and hard water (200 ppm)
• Insoluble in hard water (20,000 ppm)
• Viscosity – 4250 cps
• HLB number is 8.6
• Acid number is 7.0

Monooleate:

• Soluble in most mineral or vegetable oil
• Slightly soluble in ether
• Dispersible in water
• Insoluble in acetone
• Viscosity approximately 1000 cps
• HLB number is 4.3
• Acid number is 8.0

Monopalmitate:

• Dispersible in distilled water or hard water (200 ppm)
• Soluble in ethyl acetate
• Insoluble in cold distilled water or hard water (20,000 ppm)
• HLB number is 6.7
• Acid number is 7.5

Monostearate:

• Soluble (above melting point) in vegetable oils or mineral oil
• Insoluble in water, alcohol, or propylene glycol
• HLB number is 4.7
• Acid number is 5–10

Trioleate:

• Soluble in mineral oil, vegetable oils, alcohol, or methanol
• Insoluble in water
• HLB number is 1.8
• Acid number is 15
• Viscosity approximately 200 cps

Tristearate:

• Soluble in isopropyl alcohol
• Insoluble  in water
• HLB number is 2.1
• Acid number is 12–15

Uses: As a nonionic surfactant used as emulsifying agents.

12.Triethanolamine:

INN: Triethanolamine; Trolaminum; Trolamine

Synonyms: Triethylolamine, trihydroxytriethylamine, tris(hydroxyethyl)amine, TEA

Chemical Name & CAS Number: 2,2’,2”-Nitrilotriethanol(102-71-6)

Molecular Formula: C6H15NO3

Description: Colorless to pale yellow, clear viscous liquid with a slight odor of ammonia.

Properties: Miscible with water; 0.1N solution pH 10.5; freezing point 21.6°C

Incompatibilities: Higher fatty acids; mineral acids; heavy metal salts; if hydroxyl groups are replaced with halogen, the resultant product is toxic similar to mustard gas.

Use: As a polymer plasticizer; humectants; emollient.

Note: Emulsifying agents are also discussed in ‘Dosage form necessities and additives: Emulsifying agents and MCQs for GPAT, NIPER, Pharmacist and Drug Inspector exam’ article. Refer this article for more details and structures.

Multiple choice questions:

1.Emulsifying agents are substance that are soluble in both water and fat and enable fat to be uniformly dispersed in water as an emulsion.

a)true

b)false

2.Anionic emulsifying agents have pH

a)> 8

b)<8

c)3-7

d)5-6

3.Which of the following is not an anionic type of emulsifying agent?

a)Potassium laurate

b)Sodium lauryl sulfate

c)Dioctyl sodium sulphosuccinate

d)Quaternary ammonium salt

4.Which of the following is soap type of anionic emulsifying agent?

a)Potassium laurate

b)Sodium lauryl sulfate

c)Dioctyl sodium sulphosuccinate

d)Quaternary ammonium salt

5.Which of the following is sulfate type of anionic emulsifying agent?

a)Potassium laurate

b)Sodium lauryl sulfate

c)Dioctyl sodium sulphosuccinate

d)Quaternary ammonium salt

6.Which of the following is sulfonate type of anionic emulsifying agent?

a)Potassium laurate

b)Sodium lauryl sulfate

c)Dioctyl sodium sulphosuccinate

d)Quaternary ammonium salt

7.Which of the following is not synthetic (surface active agent) emulsifying agent?

a)Anionic

b)Cationic

c)Non ionic

d)Hydrophilic colloids

8.Cationic emulsifying agents have pH

a)> 8

b)<8

c)3-7

d)5-6

9.Which of the following is cationic type of emulsifying agents?

a)Potassium laurate

b)Sodium lauryl sulfate

c)Dioctyl sodium sulphosuccinate

d)Quaternary ammonium salt

10.Which of the following is non ionic type of emulsifying agent?

a)Polyoxyethylene fatty alcohol ethers

b)Sorbitan fatty acid esters

c)Magnesium hydroxide

d)a and b

11.Natural emulsifying agent is

a)Anionic

b)Cationic

c)Non ionic

d)Hydrophilic colloids

12.Natural emulsifying agent are

a)Acacia

b)Gelatin

c)Lecithin

d)All of these

13.Which of the following is/are finely dispersed solid type emulsifying agents?

a)Bentonite

b)Veegum

c)Magnesium hydroxide

d)All of these

14.Bentonite is a

a)Hydrophilic colloid

b)Colloidal clay

c)Metallic hydroxide

d)None of these

15.Magnesium hydroxide is

a)Hydrophilic colloid

b)Colloidal clay

c)Metallic hydroxide

d)None of these

Solutions:

1. a)true
2. a)> 8
3. d)Quaternary ammonium salt
4. a)Potassium laurate
5. b)Sodium lauryl sulfate
6. c)Dioctyl sodium sulphosuccinate
7. d)Hydrophilic colloids
8. c)3-7
9. d)Quaternary ammonium salt
10. d)a and b
11. d)Hydrophilic colloids
12. d)All of these
13. d)All of these
14. b)Colloidal clay
15. c)Metallic hydroxide

References:

1. Remington Essential of Pharmaceutics, 1st edition 2013, page no. 688, 689, 695, 696, 697, 698, 700,702.
2. Raymond C Rowe Handbook of Pharmaceutical excipients, 6th edition, page no. 110-114, 122-126, 378-380, 385-387, 445-447, 468-470, 478, 479,  506-509, 549-553, 675-678, 754, 755.

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