Questions and Answers
What is a desirable characteristic of an ideal solvent for extraction?
Which of the following is a disadvantage of using water as a solvent?
What is a characteristic of the plant constituents that are easily extracted by water?
Why may preservatives need to be added to aqueous preparations?
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What type of compounds does alcohol dissolve?
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What is a characteristic of the compounds that are not dissolved by alcohol?
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Why is a high amount of heat needed to concentrate an aqueous extraction?
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What is an advantage of using water as a solvent?
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What is a common use of alcohol as a solvent?
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What is the minimum concentration of alcohol required to prevent microbial contamination in an alcohol solution?
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What is the primary advantage of using infusions for soft drugs?
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What is the main disadvantage of using decocations for extraction?
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What is the purpose of stirring during the infusion process?
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Why is boiling water commonly used as a solvent in infusion?
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What is the primary advantage of using ABBA Anas?
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What type of crude drugs are typically extracted using decocations?
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What is the duration of the infusion process?
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What is the result of the infusion process?
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What is the primary purpose of boiling the crude drug with water in the extraction process?
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What type of equipment is used in the digestion process of extraction?
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What is the main advantage of using digestion over other extraction methods?
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What type of maceration process is used for tinctures made from unorganised drugs?
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What is the purpose of shaking the mixture in the simple maceration process?
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What is the typical duration of the simple maceration process?
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What is the purpose of pressing the marc in the simple maceration process?
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What type of solvent is typically used in the simple maceration process?
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What is the purpose of using a closed vessel in the simple maceration process?
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What is the primary difference between simple distillation and fractional distillation?
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Which separation technique is based on the difference in physical properties of the components?
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What is the purpose of the glass beads in a fractionating column?
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What is the term for the process of a substance changing directly from a solid to a gas?
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Which of the following is an example of a substance that sublimes on heating?
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What is the purpose of using an inverted funnel in the sublimation process?
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Which separation technique is used to separate a mixture of a soluble substance and a solvent?
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What is the main limitation of the sublimation process?
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What is the purpose of decantation in separating a mixture?
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What is the principle behind fractional distillation?
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Which of the following is an example of a product obtained through crystallization?
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What happens to the dissolved substance during crystallization?
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What is the primary basis for separation in chromatography?
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What happens to the components with the strongest attraction for the paper in chromatography?
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What is the result of evaporation in crystallization?
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Which separation technique is used to separate ethanol from glucose solution?
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What is the purpose of fractional distillation in the separation of crude oil?
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What is the result of fractional distillation of liquid air?
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What is the primary function of a menstruum in extraction?
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Which of the following solvents is considered polar?
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What is the result of the extraction process?
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What is the advantage of using a polar solvent?
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What is the purpose of evaporation in the preparation of extractives?
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Which of the following is a characteristic of non-polar solvents?
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What is the term for the concentrated preparation of vegetable or animal drugs obtained by removal of the active constituents?
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What is the primary purpose of the 'extractive solvent' in liquid-liquid extraction?
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What is the main characteristic of solid-liquid extraction?
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What is the primary purpose of galenicals?
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What is the main difference between tinctures and galenicals?
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What is the primary advantage of using liquid-liquid extraction?
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What is the primary purpose of menstruum in extraction?
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What is the primary characteristic of expression as a method of fragrance extraction?
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Which of the following extraction methods involves the use of heat and pressure?
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What is the primary purpose of using a closed vessel in the simple maceration process?
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Which type of solvent is most suitable for extracting thermolabile compounds?
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What is the primary advantage of using digestion over other extraction methods?
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Which of the following is NOT a type of maceration process?
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What is the purpose of pressing the marc in the simple maceration process?
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What is the primary purpose of shaking the mixture during the simple maceration process?
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Which type of maceration process is used for tinctures made from unorganised drugs, where the final volume is made up by passing the remaining menstruum through the filter?
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What is the primary purpose of percolation process?
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What is the purpose of shaking the mixture in the simple maceration process?
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What is the primary difference between multiple maceration and maceration with adjustment?
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What type of percolator is used for tinctures and other preparations?
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What is the primary advantage of using multiple maceration over simple maceration?
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What is the primary purpose of the filter in the tincture preparation process?
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What is the primary advantage of using infusions for soft drugs?
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Which of the following is NOT an advantage of using alcohol as a solvent?
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What is the primary purpose of decocations?
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What is the minimum concentration of alcohol required to prevent microbial contamination in an alcohol solution?
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What is the result of the infusion process?
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What is the primary function of a menstruum in extraction?
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What is the primary advantage of using alcohol as a menstruum?
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Which of the following is a crucial consideration when selecting a solvent for extraction?
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What is the primary reason why water is not an ideal solvent for extracting active plant constituents?
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Alcohol is a good solvent for which of the following compounds?
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What is the primary advantage of using a solvent with high selectivity?
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Which of the following is a characteristic of a good menstruum?
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What is the primary reason why preservatives are added to aqueous preparations?
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Which of the following is a disadvantage of using water as a solvent?
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What is the primary purpose of heating during the extraction process?
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Which of the following is a characteristic of the compounds extracted by alcohol?
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What is the primary advantage of using a solvent with high capacity for extraction?
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Study Notes
Liquid-Liquid Extraction
- Ideal solvents for extraction should be highly selective, have high capacity, not react with the compound or other plant material, be inexpensive, and harmless to humans and the environment.
- Commonly used solvents include water, ether, alcohol, and chloroform.
Advantages of Water as a Solvent
- Readily available and inexpensive
- Good solvent action for many plant constituents
- Can be used with other solvents
Disadvantages of Water as a Solvent
- Many active plant constituents are less soluble in water
- Water can extract undesirable components like sugars, gums, and tannins
- Aqueous preparations can support microbial growth, requiring preservatives like alcohol
- Requires a large amount of heat to concentrate the extraction
Alcohol as a Solvent
- Solvent for alkaloids, glycosides, volatile oils, and resins
- Dissolves many forms of coloring matter, tannins, and organic acids and salts
- Does not dissolve albuminous matter, gums, waxes, fats, or sugars
Advantages of Alcohol as a Solvent
- No microbial contamination in solutions with 20% or more concentration
- Requires minimal heat to concentrate the preparation
- Non-toxic and dissolves selected active constituents of drugs
Disadvantages of Alcohol as a Solvent
- Expensive
- Flammable
Extraction Processes
Infusion
- Process of extracting chemical compounds or flavors from plant material in a solvent
- Involves steeping the material in the solvent, then filtering off the liquid
- Used for soft drugs with water-soluble active constituents
Decoction
- Process of extracting water-soluble and heat-stable constituents from hard and woody crude drugs
- Involves boiling the drug in water for a specified time
Concoction
- Process of heating a mixture of two or more drugs for a specified period
Digestion
- Process using heat and pressure for extraction
- Involves using equipment like a pressure cooker or autoclave
- Efficient for extracting non-thermolabile materials due to high pressure and temperature
Maceration
- Various types include simple maceration, maceration with adjustment, and double and triple maceration
- Simple maceration involves mixing the drug with a menstruum, allowing it to stand for 7 days, then straining and pressing the liquid
General Separation Techniques
Decantation
- Involves pouring off the upper liquid layer to separate a liquid from an insoluble solid
Filtration
- Uses a porous barrier to separate a solid from a liquid
- Liquid passes through, leaving the solid in the filter paper
Sublimation
- Process of separating a solid that sublimes on heating from another substance with a high melting point
- Limited uses, as very few solids will sublime on heating
Distillation
- Used to separate homogeneous mixtures based on differences in boiling points
- Types include simple distillation and fractional distillation
Crystallization
- Technique that results in the formation of pure solid particles from a solution containing the dissolved substance
- Produces highly pure solids
Chromatography
- Separates components of a mixture based on their ability to be drawn across the surface of another material
- Components with the strongest attraction for the material travel the slowest
Extraction Processes
- Tinctures: Alcoholic or hydroalcoholic solutions prepared from vegetable material or chemical substances (e.g. belladonna tincture)
- Expression: A method of fragrance extraction where raw materials are pressed, squeezed, or compressed, and the oils are collected
- Galenicals: Extracts initially obtained by leaching vegetables or animal tissues with suitable solvents, concentrated, and converted into dry extracts
- Some extraction products include:
- Fixed oils from seeds
- Alkaloids (e.g. quinine from Cinchona bark)
- Morphine from opium
- Reserpine from Rauvolfia serpentina
Classification of Extraction
- Solid-Liquid Extraction (Leaching):
- Separation of soluble constituents from a solid by extraction with a solvent
- Two stages: contact of solute with the liquid phase, and separation of the liquid phase from the solid phase
- Liquid-Liquid Extraction (Solvent Extraction or Partitioning):
- Separation of compounds based on their relative solubilities in two different immiscible liquids (usually water and an organic solvent)
- Performed using a separatory funnel, where an extractive solvent is brought into contact with a solute-bearing solvent
Definitions
- Extraction: Treatment of plant or animal tissues with a solvent to dissolve medicinally active constituents, leaving behind inert matter
- Menstruum: Solvent used for extraction (e.g. water, alcohol, ether, acetone, etc.)
- Marc: Inert, fibrous, and insoluble materials remaining after extraction
- Extractives: Concentrated preparations of vegetable or animal drugs obtained by removal of active constituents with a suitable menstruum and evaporation of the solvent
Maceration with Adjustment
- Unorganised drug is placed with 4/5th of menstruum in a closed vessel for 2-7 days
- Shaking is done occasionally
- Liquid is filtered, and the final volume is made up by passing the remaining 1/5th of the menstruum through the filter
Multiple Maceration
- Used to establish maximum extraction by dividing the total quantity of menstruum into multiple macerations
- Repeating the process 2-4 times to make the extraction process more effective
Percolation
- Continuous flow of a solvent through a bed of drug material to obtain the extract
- Types of percolation:
- Simple percolation for tinctures
- Reserve percolation process
- Modified percolation process
- Continuous hot percolation or soxhelation
- Apparatus used: Conical Percolator, Cylindrical Percolator, Stem jacketed percolator
Concoction
- Heating a mixture of two or more drugs for a specified period of time
Digestion
- Using heat and pressure to extract non-thermolabile materials
- Equipment used: Pressure cooker or autoclave (called a digester)
Maceration
- Various types of maceration processes:
- Simple Maceration for tinctures made from organized drugs (e.g. roots, stems, leaves)
- Maceration with adjustment for unorganised drugs (e.g. oleo resins and gum resins)
- Double and triple maceration process for concentrated preparations
Advantages and Disadvantages of Solvents
- Advantages of water as a solvent:
- Readily available
- Cheap
- Good solvent action for many plant constituents
- Can be used with other solvents
- Disadvantages of water as a solvent:
- Most active plant constituents are less soluble in water
- Plant constituents like sugars, gums, starches, and tannins are easily extracted but may interfere with clarity of preparations
- Aqueous preparations serve as an excellent growth medium for microorganisms
- Advantages of alcohol as a solvent:
- Solvent for alkaloids, alkaloid salts, glycosides, volatile oils, and resins
- Does not dissolve albuminous matter, gums, waxes, fats, and sugars
- Disadvantages of alcohol as a solvent:
- Costly
- Flammable
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Description
Learning about different separation techniques and extraction processes.