Pharmaceutical Equipment and Processes
Theory of filtration
The flow of any liquid through a filter follows a basic rule that govern the flow of any liquid through a medium. The rate of flow may be expressed in volume/time. The theory of filtration gives an idea about the factors that affect the rate of filtration through a filtering medium.
The scientist which gives the theory of filtration is darcy and this is also known as darcy’s law. They give an equation about the theory of filtration.
V=KAΔP/ηtWhere v is the viscosity, K = permeability of filter medium, A = surface area, ΔP =pressure, η = volume of the filtrate. t = thickness of the filtrate
Extraction
Extraction is a method of removing the active constituents from the solid or liquid by the means of liquid solvent the separation of medicinally active constituents of plants or animal tissue from the inactive components by using suitable solvent. In this method the wanted components are dissolved by the use of suitable solvent known as menstruum and the undissolved part is marc.
Methods of extraction
Infusion, decoction, digestion, maceration, percolation
Infusion– fresh infusion are prepared by macerating the crude drug for short period of time with cold or boiling water. Example- infusion of Quassia
decoction– in this process the crude drug is boiled in a specified volume of water for a given period of time. It is then cooled and then strained or filtered. example – extraction of neem, ginger, tea and coffee.
Digestion – It is a form of maceration in which gentle heat is used during the process of extraction. In this high temperature is not provided to the crude drug the solvent. Example- extraction of morphine
Fluidized bed dryer
Principle – The equipment works on the principle of fluidization of the materials. In this process hot air is introduced at high pressure through a perforated bed of moist solid particles. The wet solid is then lifted up by the process of air. The hot air surrounding the energy helps the granule to dry thus the materials and granules are uniformly dried.
Construction– The dryer is made up of stainless steel. To this a detachable bowl is placed at the bottom of the dryer. The bowl has perforated bottom with a wire mesh for placing the material to dry. A fan is mounted in the upper part for circulating the hot air. Fresh air inlet and air heaters are connected to heat to require temperature. Temperature of hot air and exit air are monitored. Back filters are placed above the drying bowl for circulation of air.
Working – The wet granules to be dried are placed in a detachable bowl and inserted in the dryer.
Fresh air is passed through inlet by using air filters to convert it into hot air.
Hot air flows through the bottom of the bowl. At the same time fans start rotating the granules move up and down due to high pressure of air. The gas surrounds to each granule, dry them completely and pass through the filter bags for removal of air.
Advantages
1)Take less time to complete drying.
2)Handling time is short. 3)More thermal efficiency.
Disadvantages
Many organic powders get attached to the filter bags during drying.
Standards of sieves
Common standards are used for sieve which are as follows-
US standard sieve (USA)
British standard sieve (UK)
German standard sieve (Germany and Europe)
IP standard sieve (India)
International test sieve (worldwide)
There are some specifications of sieve used for pharmacopeial testing.
Sieve number– according to pharmacopoeia the sieve size which is mostly used in sieve number 125.
Aperture size– this is the distance between the two wires.
Membrane Filter
Principle of Membrane Filter- It consist of microporous plastic film of a specific pore size which is known as microporous filter. These membrane filter retain the particles or microorganisms.
Construction-It consist of membrane of cellulose acetate, cellulose nitrate and cellulose ester. The pore size of filter is 150 μm.
Working- It is used as a filter to remove the particles. The particle are 5 mm pore size which is used to remove the microbes or insoluble particles present in the liquid.
Uses –
it is used for clarifying the aqueous and organic solvent.
It is suitable for the filtration of enzyme solution.
Double Cone Mixer
Double cone mixer is also known as double cone blender in which there is a uniform blending of the granules and dry powders occurs. It is made up of stainless steel. It is available in a wide range of working capacity ranging from 5 to 500 litres.
Principle– Double cone blender produce a homogeneous solid-solid mixture. This equipment moves the powder in different sections. This blender provides a complete mixing of powders by the speed of rotation.
Hammer mill
Principle-it works on the principle of impact that is the material is more or less stationary and is hit by an object moving at high speed. It consist of a metal casing, enclosing a dental shaft to which four or morehammers are attached. The lower part of the casing consists of a screen through which the material can pass and collected in a suitable receiver, when the degree of size reduction will occur.
working – the material is put into the hopper which is connected to the mill the material is powdered to a desire size due to fast rotation of hammers and is collected under the screen due to high speed. The materials get damage to the mill due to the generation of heat. So, the rotation of hammers will be at correct speed and the fine material are collected in the product collector.
Cyclone Separator
This method is used to remove the unwanted particles with the help of air and the filters with the process of vortexing . It is used for the separation of solid mixture from the fluid particle.
Principle– Cyclone separator is a type of is a type of sedimentation technique which works by vortexing the particles. Thus, the fluid particle will remove out from the solid particles leaving behind the fine behind the fine particles with the help of sieve.
Construction– It consists of a short vertical, cylindrical vessel with a conical base. The upper part of the vessel is fitted with a tangential inlet. The outlet (solid outlet) is arranged at the base. A fluid outlet is provided at the center of the top portion, which extends inwardly into the separator. Such an arrangement prevents the air from short-circuiting directly from the inlet to the outlet of the fluid.
Working-The solids to be separated are suspended in a stream of gas (usually air). Such a feed is introduced tangentially at a very high velocity so that rotary movement takes place within the vessel. The centrifugal force and vortexing throw the solids to the walls. As the speed of air diminishes, the particles fall to the conical base and are discharged through the solid outlet. The fluid (air) can escape from the central outlet at the top.
Uses-
- It is used to separate the solids from gases.
- It is also used for the size separation of solids in liquids.
- It is used for separating the heavy or coarse fraction from fine dust.
Freeze Dryer
Freeze drying is also called lyophilization (Lyophilization works by freezing the material, then by allowing the heat to allow the frozen water in material to sublimate). It is a process in which water is frozen followed by its removal from the sample.
Principle- The main principle involved in this process is lyophilization which is then sublimate by the process of sublimation. The water passes directly from the solid state to vapour state without passing through liquid state. Water is removed from the frozen solid with the help of heat and converted directly into the vapour.
Construction- it consists of a drawing chamber in which layer are used to place the material. In this freeze layer and dry layer are used to freeze the material. A condenser is also attached which is used to convert the frozen state into vapour state.
Heating sources provided inside the freeze dryer to condense the vapour form and dry the solid particle.
Working–
Following steps is involved in working of freeze dryer-
Preparation → Freezing (primary drying) → Secondary drying→ packaging
Advantages – Cost is reduced as compared to fluidized bed dryer.
Takes less time to complete drying.
Disadvantages– It requires high energy consumption.
Tablets
According to I.P. pharmaceutical tablets are solid, flat, unit dosage form which is prepared by compressing drugs or a mixture of drugs with or without excipients.
Types of tablets
The tablets are classified as follows-
1)Oral Tablets-These are the tablets which can swallow orally with the help of some suitable fluids. They are designed to disintegrate in the stomach or small intestine if they are coated.
2)Chewable tablets-These are the tablets which are designed to chew before ingestion of chewed particles. They are meant for children and such person who may find difficulty in swallowing the tablets.
3)Buckle aur sub lingual tablets -these tablets are designed to kept under the tongue. These tablets released the drug which are absorbed through oral mucosa in the G.I. track and then into the blood circulation. They give rapid on set of action when compared to the oral tablets. They are dissolved completely in about 15 to 30 minutes.
4)Lozenges– the purpose of making such a tablet is to treat the throat infection. It is necessary to design the tablet in such a manner that they get dissolved in the oral cavity to prolong the duration of action of the medicine. They do not require any disintegrating agent because instead of disintegration that dissolution is required. Usually they dissolve completely in about 15 minutes.
5)Solution tablets– these tablets are prepared to dissolve in a specified volume of fluid to produce a solution of definite concentration.
6)Entric coated tablets– these tablets are coated with entric coated material which resist the dissolution in the stomach but dissolve in the intestine .it is also used to delay the release of the drug.
7)layer tablet– These tablets consists of two or more layers of materials compressed in the same tablet. They are also known as laminated tablet which are designed to mask the incompatibility of the drug in a single tablet.
8)Time release or Prolong release tablet -these tablets are designed to provide medication for longer period of time in a controlled manner.
Formulation of tablet
there are three methods which has been employed for the preparation of compressed tablet-
1)direct compression method
2) wet granulation method
3) dry granulation method
Direct compression method
It is suitable for the powders that are easily compressible. They contain API as well as excipients.
Solution -when two or more substances are mixed together they form a homogeneous mixture this mixture is known as solution.
Suspension -suspension are the biphasic liquid dosage form of medicament in which the finely divided solid particles ranging from 0.5-5 micron are dispersed in a liquid medium. In this the solid particles act as dispersed phase whereas the liquid particles act as dispersing medium.
Emulsion– an emulsion is a biphasic liquid dosage form containing two immiscible liquid one of which is dispersed as fine globules into another.
Emulsifying agents -the emulsifying agents reduce the interficial tension between the two phases that is oil and water and thus them miscible with each other. Emulsifying agents are also known as emulsifiers.
Dilute solution– it contains very small amount of solute in the solution.
Concentrated solution– it contains large amount of solute in a solution.
Saturated solution -it contains maximum amount of solute in a solution.
Unsaturated solution– it is a solution that contain less amount of solute that is capable of being dissolved.
supersaturated solution- it contains more than the maximum amount of solute in which heating is provided to make the solution stable.
Types of emulsions
1)Oil and water emulsion
2)water in oil emulsion
oil in water emulsion-in this type of emulsion oil phase is dispersed in fine granules in the water phase they are referred in oil in water type of emulsion.
Water in oil emulsion– in these types of emulsions the water fees is dispersed as fine globules in the liquid phase they are referred as water in oil emulsion.
Test for identification of emulsions
Dilution test -the emulsion is diluted with water in case the emulsion remain stable after dilution it is oil in water emulsion. the water in oil emulsion breaks on its dilution with water but remain stable when diluted with oil.
Elixirs – they are hydro alcoholic solution of medicinal substance that is sweet and flavored. They are used as an excellent solvent for many drugs and mask the odor as well as taste of any substances dissolve in them. Typically, alcohol and water are used as a solvent when the drug will not dissolve alone.
example -aromatic elixirs, orange elixirs, benzaldehyde elixirs, phenobarbital elixirs.
Powders– powder is defined as a uniform and dry mixture of one or more finely divided material.
Example -dusting powder, tooth powder, aerosols
ointments – an ointment is a homogenous viscous semi solid preparation most commonly greasy thick oil with the high viscosity that is extended for external application to the skin or mucous membrane.
Paste -paste combine three agents oil water and powder.it is an ointment in which a powder is suspended. Paste typically consist of suspension of granular material which contain a liquid.in this the quantity of water and oil is same 50% in which the solid substances are suspended or dispersed.
Gels – gels are also known as jellies. they are semi solid preparation having suspension containing either small particles or large molecules inter penetrated by a liquid. In gels a liquid is held inside a three-dimensional polymeric liquid or Matrix with the high degree of physical or chemical cross linking. They are non-greasy in nature.
Ball mill
principle – it works on the principle of combined effect of impact and attrition (impact means the pressure exerted by the heavy objects).
Attrition- it reduced the size of materials when they collide by the heavyweight (ball). It is made up of stainless steel. it consists of a cylinder which is mounted on a metallic frame which contain the balls that occupied 30 to 50% of mill volume. The weight of the balls is kept constant. The ball size depends upon the size of feed material. The balls are made up of stainless steel or porcelain.