Physioco -Chemical Processes Flashcards
Precipitation
Methods
- Organic solvent nethod
- pH change method
- Double decomposition reaction
Precipitation
Ppt maybe amorphous or crystalline
Crystal
A solid with an ordered internal arrangement of molecules
Evaporation
Affected by
1. Temperature
2. Atmospheric pressure
3. Surface area
4. Agitation
Distillation
Process of separating a liquid from a solid
Distillation is useful in
- Preparation of aromatic water.
- Preparation of distilled water.
- Preparation of water for injection.
Efflorescence
Lose of water from a hydrate
Vapour pressure
Pressure that results in the release of vapour
Hydrates
Exert vapour pressure because of water of hydration or water of crystallisation
Hydrates
Exert vapour pressure because of water of hydration or water of crystallisation
Vapour pressure > atmospheric pressure =
Efflorescence
Delinquensce = opposite of efflorescence
Vapour pressure < atmospheric pressure
Atmospheric pressure
Pressure that will lead hydration, deliquescence
Exsication
International accelerated efflorescence
Applications if exsication
- Carried out to reduce the bulk and weight of certain drugs for administration.
- Production of anhydrous product required in the formulation of another drug
Exsication
Usually produce fine powder
Dessication
Removing water molecules from a substance using a dessicant
Desiccant
Hygroscopic material that induces or sustains a state of dryness . It is usually an adsorbent .
Examples of desiccant
- Phosphorus pentoxide
- Conc. H2SO4
- Exsicated CaCl2
- Silica gel
Substances that sublime
1.Carbon dioxide
2. Ammonium chloride
3. Naphthalene
Sublimation
- Cp- critical point
- Tp- triple point
- SCF- Super critical fluid
Sublimation
Occurs when vapour pressure is equal to that of the gas phase
Sublimation
Can only occur at temperature below critical point temperature
But at a pressure above critical point pressure.
Eg. CO2 sublimes at pressure 517kPa and tep.-78.5°C
Applications of sublimation
- Purification
- Freeze drying
Freeze drying (lypholisation)
Works as sublimation.
Stages of freeze drying
- Freeze the solution
- Reduce atmospheric pressure to below that of the TP.
- Add heat of sublimation
Advantages and of freeze drying
- Heat sensitive materials are not damaged
- Freeze-dried materials are porous and facilitate easy re-dispersing in water.
- Denaturation of proteins is avoided.
- Sterility may be maintained during process.
Disadvantages of freeze drying
The product is prone to oxidation due to high porosity
2. Some materials are not cryo- stable and may require cryo protectants.
Examples of cryo protectant
- Mannitol
- Sucrose
- Glucose
- Trehalose
Elutriation
Process of moving water in the opposite direction of sedimentation
Methods of elutruation
- Gravitational
- Centrifugal
Advantages of elutriation
- It’s a continuous process
- It’s faster than sedimentation.
Disadvantage of elutriation
Dilute products may be required for the process .
Applications of elutriation
- Separation of particles into different sizes. Eg. Light and heavy kaolin
Ignition
Burning substances at elevated temperatures to cause escape of carbonaceous component( organic component) leaving behind ash(inorganic component).
Application of ignition
Used in determining the quality and purity of a product
Fusion
Putting 2 subs together and applying heat to melt them.
Fusion
Used in the preparation of ointment ( especially when they contain solids and semi-solids)
Used in preparing suppositories
Used in purification of some solid and semi solid subs. Eg. Paraffin (hard and soft, wool fat and beeswax)
Calcination
Intensely heating inorganic substances to eliminate their volatile components and produce a fixed residue
Usually carried out for 3 hrs.
Calcination ( the oxides man)
Useful in producing MgO( both hesvy and light)
, ZnO, CaO
Adsorption
Accumulation at an interface
Occurs when liquid or gas accumulates on the surface of a solide for an adsorbate.
Absorption
Movement of water or gas into a solide to form a mixture or solution.
Types of adsorption
- Physisorption - adsorbate adheres to the surface only through Van der Waals forces
- Chemisorption - adsorbate adheres to the surface through chemical bonds
Applications of adsorption
1.Decolouration - use of activated charcoal to remove colour from water.
2. Desiccation and freeze drying.
3. Medical application
4. Purification of water
5. Adsorption chromatography.
Centrifugation
Factors that affect it
- Viscosity of medium
- Rotor speed.
Centrifugation
Separation occurs due to differences in size and shape of substances in the mixture
Application of centrifugation
- Evaluation of suspension and emulsions
- Production of bulk drugs.
- Production of biological drugs.
- Determination of molecular weight of colloids
Dialysis
Separation is based on unequal rates of passage btwn substances through a pore
Application of dialysis
- Purification of protein
- Medical application
- Drug permeation studies
Maceration
Occasional agitation.
Infusions( cold)
Menstrum may be cold or boiling water.
They produce dilute solutions.
Prepared by steeping the drug into a cold or boiling water.
Decoction ( concotion)
Produces concentrated solutions.
Useful for extracting water soluble or heat soluble substances
Digestion ( gentle heat)
Gentle heat is applied in the process of extraction.
Used when moderate temperature is unquestionable and solvent efficiency is increased thereby.
Percolation
Continuous downward displacement of menstrum through drug in a percolator
Steps in percolation ( SIPMP)
- Size reduction
- Imbibition
- Packing
- Maceration
- Percolation