health, medicine and pharmaceutics

PRESENTED BY : Md. Sohanur Rahaman.A presentation Submitted to:

Bishwajit BokshiAssistant Professor, Pharmacy Discipline,

Khulna University, Khulna.9th September 2015

Presentation on Mixing and Homogenization

Definition of The Mixing

Mixing may be defined as the process in which two or more than two components in a separate or roughly mixed condition are treated in such a way so that each particle of any one ingredient lies as nearly as possible to the adjacent particles of other ingredients or components. It is not only done in pharmaceutical industries but it has been widely used in food, plastic, glass, paint, paper, pesticides and fertilizer industries.

Types of Mixing

When two gases or miscible liquids are mixed together by means of diffusion process. In this case no energy is required and no problem is formed.

When insoluble solids are mixed with a vehicles to form a suspension or when two immiscible liquids are mixed to form an emulsion. A higher degree of mixing energy is required and these mixtures are very difficult to prepare.

The components of such products

do not have any tendency to mix spontaneously but once mixed, they do not separate out easily. They are static in behavior. Pastes, ointments and mixed powders are the examples of neutral mixing.

Negative Mixture Neutral

MixturePositive Mixture

Mechanism of Mixing

o Transfer of groups of particles in bulk take place from one part of powder bed to another.

o The materials are tilted so that gravitational forces cause the upper layers to slip and diffusion of individual particles take place over newly developed surfaces.

o Shear forces are created

within the mass of the

materials by using

agitator.

Diffusive

mixingShear

mixingConvection

Mixing

Objects of Mixing• To ensure uniformity of composition

between the mixed ingredients.• To initiate or to enhance the physical or

chemical reactions e.g. diffusion, dissolution etc.

Generally mixing is carried out to obtain following types of products.

A miscible liquid + A miscible liquid = A true solution.

An immiscible liquid + An immiscible liquid + Emulsifying agent = An emulsion.

A solid + A vehicle = A solution.

An insoluble Solid + A vehicle = Suspension

A solid/ A liquid + A semisolid base = An ointment/ A suppository.

A solid + A solid = A powder.

Homogenous mixture.

Occurs by diffusion.

It is quite easy to perform and does not create any problem.

It is done by simple shaking or stirring.

Example: solutions.

Mixing of two miscible liquids

Heterogeneous mixtures.

The liquids are mixed together by emulsifying agents.

The mixing must be very efficient.

Example: emulsion.

Liquid Mixing A. Mixing of Liquids and Liquids

Mixing of two immiscible liquids

Homogenous mixtures.

Done by stirring.

It is a physical change, i.e. a soluble solid is converted to a solution.

Examples: solution.

Mixing of liquids and soluble solids

Heterogeneous mixtures.

A suspension, an unstable system, is formed.

A suitable suspending agent is required.

Liquid Mixing A. Mixing of Liquids and Solids

Mixing of liquids and insoluble solids

Run at 8000rpm.

Provides longitudinal movement of liquid.

It is used for low viscosity liquids.

Disadvantage: little shear is not suitable for emulsification.

Propeller 4, 6 or 8 blades…(axial turbine or radial

turbine).

Diameter is 30-50%of vessel.

Rotates at lower speed 50-200rpm.

More shear force suitable for viscous liquids.

Equipments for Liquid Mixing Turbine

2 or 4 blade paddles are common.

They have large surface area.

Rotate at 100rpm.

Useful for viscous and semisolid preparations.

Paddles The liquid to be mixed are pumped

separately into a jet mixer at different velocities.

And thus mixing is achieved.

Equipments for Liquid Mixing Jet mixing

Homogenization and HomogenizerHomogenization is a process in which a coarse emulsion is

converted into a colloidal state ofuniform composition by reducing the size of the particles. This

process is used in the preparation ofsuspensions and emulsions. A various types of homogenizers

are used for this purpose.

Suitable for making small batches of emulsion.

Mixing action is quite effective. Different types of beaters and whisks are

available for this mixture. The beaters produce a planetary action on

the central part of the liquid as well as on the whole part.

Knewood Mixture Consist of an emulsifying head to which

blades are attached, surrounded by a fine mesh sieve made up of stainless steel.

The emulsifying head is emerged into liquids to be emulsified.

The head is rotated by means of a small motor which rotate the blades at high speed.

Mixing capacity 9 liters to 9000 liters.

Homogenization and HomogenizerSilverson Mixture-

Emulsifier

Useful only for liquids of low viscosity and small scale preparation.

The liquid is subjected to ultrasonic vibrations, alternate regions of compression and rarefaction are produced which leads to the formation of cavities in the rarefaction region.

Ultrasonic Emulsifier Useful for the production of colloidal

dispersion and are quite suitable for the preparation of emulsion.

Continuous production can be possible.

Homogenization and HomogenizerColloid Mills

Homogenization and HomogenizerHand homogenizer:

Most commonly used hand homogenizer on laboratory. Consists of a hopper, small orifice, handle and a heavy base.

Process:

•The preformed emulsion is placed in the hopper of the emulsifier

•The emulsion is then forced to pass through a narrow orifice by up and downward movement of the handle which reduces the size of the oil globules.

•This reduction in size increases with the speed of pumping.

Powder MixingA process in which, two or more than two solid substances, is mixed thoroughly bycontinuous movement of particles. The objects of mixing is to produce a bulk mixture which when divided into different doses, every unit of dose must contain the correct proportion of each ingredients. An important operation in pharmaceuticals to prepare tablets,powder, and capsules.

Mixing Factors

The mixture must not be filled to the brim.

Sufficient empty space should be provided for dilation.

Overfilling may reduce efficiency or prevent the mixing.

Volume

Mixing of powders is done for optimum time.

The degree of mixing increases with length of time.

Duration of Mixing

Mixing Factors

After mixing the powder should be handled in such a way that the separation of ingredients is minimized due to transport, subsequent manipulation, handling etc.

Handling of The Mixed Powders

Must apply suitable shear forces and connective movement.

Mixing Mechanism

Physical propertiesHigh density Greater difficulty in mixing, because heavier material moves downward through the lighter materials.

Different particle size Difficulty in mixing because the smaller particles can move downward through the spaces between the larger particles.

Spherical shape of particles/ Irregular shape of particles Ideal for mixing.

Small particlesGreater electrostatic chargeAggregation of particles.

Equal amount of materialsEasy to mix.

Equipments for Powder Mixing

Pestle and mortar Spatula. Sieves. Agitator

mixture( Ribbon Blender)

Tumbler mixer

V Shaped Mixture

Y Shaped Mixture

Double Cone Mixture

Cylindrical mixture

The most commonly used agitator is sigma arm mixture.

The arms of the mixture produce pulling and kneading action.

The two blades rotate towards each other but at different speeds.

The mixture is fitted with 7 to 10 horsepower electric motor.

The major problem is the entrainment of air. This problem can be overcome by performing

the mixing operation under reduced pressure. Special care must be taken for volatile

substances.

Agitator

Mixing is done by reducing particle size.

The particle size depends on the gap between the rollers and their speed.

The three rollers rotate at different speed.

Equipments for Mixing of Semisolid Triple Roller Mill

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