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Submitted to:
Associate professor
Department of pharmaceutics.

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Factors affecting microbial preservative

•Interaction with formulation components

•Properties of preservatives

•Effect of containers

•Types of micro-organisms

•Influence of pH

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1. Interaction with formulation components :-

•Hydrocollids such as methylcellulose, alignates, tragacanth can

interact with preservatives and diminish their activity.

• Many emulgents are used in pharmaceutical preparations to
produce elegant applications. Interaction may occur between
preservatives and emulsified oil phase and with emulgent

• Nature of oil, oil water ratio, type of concentration of emulgent,
influence the concentration of preservatives needed to protect
the system.

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2.Properties of preservatives:-

• The distribution of preservative must be homogeneous and
more solubility in the bulk phase is preferable in multi phase

• Some chemicals such as chlorobutol may hydrolyse on
storage if the pH is unfavourable.

• Preservatives may react with substances leached from the
container and lose its antimicrobial activity.

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3.Effect of containers:-

• Formulations packed in glass containers can be expected to
retain their preservative content if closure is airtight.

• Preservatives may penetrate through the plastic container and
interacts with it.

• Rubber also reacts with many preservatives but is still used for

• Containers or closures may cause contamination of pathogens.

• Screw–capped containers and corks are the common source of
mould spores.

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4. Types of micro-organisms:-

• Plants products may contain pathogenic microorganisms from
the soil. E.g Clostridium species, Bacillus anthracis.

These soil microorganisms can cause spoilage of pharmaceutical

• Many products prepared from animal sources may contain
pathogens like Salmonella typhi.

• Spores of tetanus and gas gangrene have been isolated from

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5. Influence of pH:-

• Adjustment of the pH of cosmetic may affect the chemical
stability and the activity of the preservative.

• The majority of preservatives are less dependent upon pH,
although cationic active quaternary ammonium compounds are
more active at high pH values.

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According to D&C ACT c osmeticinst oa, roer defined as,

Any article intended to be rubbed, poured, sprinkled or sprayed on
or introduced into, or otherwise applied to human body or any
part thereof for cleansing, beautifying, promoting attractiveness
or altering the appearance..

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Definition : A shampoo is a preparation of surfactant in a
suitable form- liquid solid or powder- which when used under
the specified conditions will remove surface grease, dirt & skin
debris from the hair shaft & scalp without adversely affecting
the user.

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➢ It should produce a good amount of form to satisfy
the psychological requirements of the user.

➢ It should be easily removed on rinsing with water.
➢ It should impart a pleasant fragrance to the hair.
➢ It should not cause any side effects / irritation to the

skin or eye.
➢ It should effectively or completely remove dust

or soil.
➢ It should not make the hand rough.

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Shampoos are of the following types:
Powder shampoo
Liquid shampoo
Lotion shampoo
Cream shampoo
Specialized shampoo

➢ Conditioning shampoo
➢ Anti-dandruff shampoo

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Product Ingredients:-

Surfactants are the main component of shampoo.
Mainly anionic surfactants are used.

1. Primary surfactants: Provide detergency and foam.
2. Secondary surfactants: Improve detergency,

foam & hair condition.
3. Other additives.

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Anionic surfactants :-are mostly used(good
forming properties). The hydrophilic portion carries a
negative charge which result in superior foaming &
cleaning. eg: Sodium dodecyl benzene sulfonate, Lauric
acid, stearic acid.

Non-ionic surfactants:- have good cleansing properties but do
not have sufficient foaming power. eg: Sorbitol esters (TWEENS),
Ethoxylated fatty alcohols, Lauric monoethanolamide.

Cationic surfactants :-are toxic & are hence not used. However,
they may be used in low conc. in hair conditioners.

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Ampholytics:- being expensive, are generally not used. However,
they are mainly used as secondary surfactant & good hair
conditioners. eg: β – amino acid derivatives, Asparagine

•Conditioning agents: Lanolin, mineral oil, herbal
extracts, egg derivatives.
• Foam builders: Lauryl monoethanolamide,
• Viscosity modifiers:
•Electrolytes: NaCl,
•Natural gums: Tragacanth, alginates
•Cellulose derivatives: Hydroxy ethyl cellulose, methyl
• Opacifying agents: Propylene glycol, Mg, Ca & Zn
salts of stearic acid.

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Clarifying agents:-
•solubilizing agents: ethanol, isopropanol
• Non-ionic solubilizer: polyethoxylated alcohols & esters.
• Perfumes: Herbal, fruity & floral fragrance.
• Preservatives: Methyl & propyl paraben,formaldehyde (most

Role of ingredients…
• Surfactants:-They are the compounds that lower the surface
tension b/w two liquids or b/w a liquid and a solid. They may
act as detergents, wetting agent, foaming agent & emulsifiers.

• Conditioning agents: They are intended to improve
manageability, feel & lusture of hair.
• Viscosity modifier: They are used to improve the thickness of

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• Preservatives: –

Many synthetic products are vulnerable to microbial attack, if not
preserved efficiently. Bacterial growth in shampoo can lead to
breakdown of detergent i.e. resulting in
discoloration of product. The simple & most effective antimicrobial
agent is formaldehyde.

• Perfumes:-
There are two imp. aspects which should be ascertained before final
selection of fragrance for shampoos:-

1. Fragrance must be soluble in shampoo.

2. It must be compatible with shampoo i.e. not affect the viscosity &

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➢ Liquid shampoo:-
1. Sodium lauryl sulphate 40.0%
2. Sodium chloride 2.0 – 4.0%
3. Water (to make) 100
4. Perfume, colour & preservatives q.s

➢ Cream shampoo:-
1. Sodium lauryl sulphate 40.0%
2. Cetyl alcohol 7.0%
3. Water (to make) 100
4. Perfume, colour & preservatives q.s

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✓ A toothpaste or dentifrice is a substance used with a toothbrush
for the purpose of cleaning the accessible surfaces of the teeth.

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Requirements of a toothpaste:-

• When used properly, with an efficient toothbrush, it should
clean the teeth adequately, that is, remove food debris,
plaque and stains.

• It should leave the mouth with a fresh, clean sensation.

• Its cost should be such as to encourage regular and frequent use
by all.

• It should be harmless, pleasant and convenient to use.

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Ingredients used in toothpastes:-

➢ Cleaning and polishing agents: Clearly the main purpose of the
cleaning and polishing agent is to remove any adherent layer on the

➢ Calcium carbonate: Calcium carbonate is probably one of the most
commonly used dental cream abrasives. Precipitated calcium
carbonate (chalk) is available with a white or off-white colour and
both particle size and crystalline form can be varied, depending upon
its conditions of manufacture.

Sodium bicarbonate: It is a very mild abrasive, usually used at
a 5-30% level, in combination with other abrasives such as
silica or calcium carbonate to achieve the required cleaning

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Surfactants: Surfactants are used in the toothpaste to aid in the
penetration of the surface film on the tooth by lowering the surface
tension. They also provide the secondary benefits of providing foam
to suspend and remove the debris, and the subjective perception of
toothpaste performance.

Sodium lauryl sulphate: Also known as sodium dodecyl sulphate i.e.
currently the most widely used detergent in toothpaste because it
satisfies almost all the requirements. It is a foaming & solubilizing
agent that is derived from coconut and palm oil. SLS emulsifies fats,
has a high affinity for protiens, and has mild antibacterial activity.

Humectants: Humectants are used to prevent the paste from drying
out and hardening to an unacceptable level. At the same time they
give shine and some plasticity to the paste. Generally only two
major humectants are considered for use in toothpaste.

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Some common humectants are:
• Glycerin: Glycerin is still the humectant used in greatest bulk
quantity in toothpaste. It is one of the best humectants, producing a
shiny, glossy product. It is stable, non-toxic, available from both
synthetic and natural sources, and provides a useful sweetening
function to the paste.

Sorbitol: Sorbitol syrup (approximately 70%) is also extensively used
throughout the industry and is sometimes considered superior to
glycerine depending upon the formulation. It also imparts sweetness,
and is a stable humectant.

• Sweetening agents: These are important for product acceptance,
since the final product must be neither too sweet nor too bitter. These
ingredients must always be considered in partnership with the flavour
because of their combined impact.

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Sodium saccharin. This is the sweetening agent in widest commercial
use, and is generally used at a level between 0.05% and 0.5% by

• Flavours:
Flavours are probably the most crucial part of toothpaste because of
consumer preferences. They are also the most proprietary part of
the formulation. Exotic flavours, although
available, are generally not well liked under long-term usage
conditions, since one of the primary consumer requirements of
toothpaste is the perception of freshness and cleanliness after
brushing conventionally, therefore, mint flavours tend to

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• Minor ingredients:

• Titanium Dioxide: Titanium dioxide may be added to give additional
whiteness and brilliance to the paste.

•Colours: Colours can be an integral part of the aspect of any
toothpaste that may influence consumer preference and purchase

• pH regulators: Occasionally buffering systems need to be added to
the dental cream to adjust the pH of the final finished product.

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Formulation of Toothpaste:-

Surfactant 1.0-2.0 Sodium lauryl sulphate
Humectant 10-30 Glycerin, Sorbitol
Gelling Agent 0.5-1.5 Hydroxy ethyl cellulose,
carboxy methyl cellulose
Sweetener 0.05-0.5 Sodium Saccharin
Flavour 1.0-3.0 Spearmint, Menthol,
Colour <1.0 Titanium Dioxide
Water to 100

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•Creams are defined as “a semisolid dosage form containing
one or more drug substances dissolved or dispersed in a
suitable base.”
• Semisolid emulsions of either o/w or w/o type.

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Vanishing Creams
➢ These are also called foundation creams because they disappears
when rubbed into skin.

Moisturizing creams:-
• These are the creams which restore water (moisture) to the stratum
• Water contained in the cream is lost by evaporation when the
cream is applied to the body.

Commonly used ingredients …
•ANTIOXIDANT- Oxygen is highly reactive atom that is capable of
becoming of potentially damaging molecules commonly called “free

➢ Free radicals are capable of attacking the healthy cells of the body,
causing them to loose their structure and functions.

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• To prevent this an anti oxidant are added. eg.- Ascorbic acid,
BHT(Butylated hydroxytoluene).

➢ BASE- It is one of the most important ingredient used in the
formulation of semisolid dosage form

➢ BUFFER- They are added in the preparation to maintain the pH eg.
Citrate buffer ,phosphate buffer.

➢ CHELATING AGENTS- Chelating agents are ingredients that bind
with metal ions or metallic compounds, preventing contamination or

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Role of ingredients…

➢ Chelating agents :-are used in creams and lotions, body washes,
shampoos, conditioners, cosmetics and skin care products. Chelating
Agents improve the efficacy of preservatives and antioxidants and
play a crucial role in the stability and efficacy of personal skin care
products. eg. Citric acid, EDTA (Ethylene diamine tetra acetic acid).

➢HUMECTANT- Humectants are essential cosmetic ingredients
which are hygroscopic in nature and absorb moisture from the air.

Humectants form hydrogen bonds with water molecules and help to
retain the natural moisture of the skin. Basically, humectants are
molecules with one or more hydrophilic groups attached to them.eg.
Glycerin, propylene glycol, PEG.

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➢ EMULSIFIERS- Emulsifiers are used in creams and lotions to mix
water with oils. Since water and oil do not mix but stay separated,
an additional agent (emulsifier) is necessary to form a
homogenous mixture keeping water and oil together

There are 2 types of emulsifiers. Oil-in-water (o/w) emulsifiers
keep oil drops packed in water, while water-in-oil (w/o) emulsifiers
keep water drops packed in oil. W/O emulsifiers are used for a fatty
feel (eg. night & sun protection creams). O/W emulsifiers are used
more in moisturizing products (eg. body lotions, day creams). eg.
Monoglycerides, Sulfonates, Polyoxyethylene.

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➢ PERMEATION ENHANCER-Skin can acts as a barrier with the
introduction of various penetration enhancers, penetration of the
drug through the skin can be improved. eg. Ethanol , oleic acid,

➢ PRESERVATIVE – Some bases , although, resist microbial attack but
because of their high water content, it require an anti microbial
preservative.eg. Benzoic acid, phenyl ethyl alcohol, Methyl hydroxy
benzoate, Propyl hydroxy benzoate.

➢ GELLING AGENT- Gelling agent forms a gel dissolves in a liquid
phase as a colloid mixture that forms a weakly cohesive internal
structure. eg. Cellulose, pectin, gelatin, tragacanth.

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Fragrances are complex combinations of natural or man-made
substances that are added to many consumer
products to give them a distinctive smell.

Fragrances are used in a wide variety of products to impart a
pleasant odor, mask the inherent smell of some ingredients, and
enhance the experience of using the product.eg. Lavender oil,
rose oil, lemon oil.

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➢Vanishing cream

• Stearic acid 17.0%
• Potassium hydroxide 0.7%
• Glycerine 5.0%
• Water (to make) 100
• Perfume & preservatives q.s

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➢Moisturizing cream:-

• Stearic acid 4.0 %
• Mineral oil 8.0 %
•Lanolin 1.0 %
•Glyceryl monostearate 3.0 %
• Isopropyl myristate 2.0 %
• Glycerin 4.0 %
• Propylene glycol 4.0 %
•Triethanolamine 0.2 %
• Water (to make) 100.0
• Perfume & preservative q.s

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•Poucher’s perfume cosmetics and soaps 10th edition

•Internet source

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