Extraction and sample preparation Flashcards
Define menstruum
Solvent(s) used in the extraction process
Define marc
Insolube materials (waste) left after extraction
What is a galencial?
A medicinal extract or tincture derived mainly from natural sources
What are the four types of extracts?
Tinctures
Liquid extracts
Soft extracts
Dry extracts
Soft extracts are semi-solid preparations obtained by evaporation or partial evaporation of the solvent used for extraction. True or false?
True
What are the 3 main steps in the extraction process?
Comminution - physically reducing plant material to particular size
Incubation with menstruum
Separating off marc
What are the rate limiting factors of the extraction process?
Wetting of the surface of particles
Permeability of cell walls
Rate of dissolution of cell contents
Outward diffusion of the solution
What are the methods of galencial preparations?
Infusion Decoction Maceration Percolation Continuous hot extraction
What is meant by infusion?
Drug stood in hot/cold water for a short time
What is meant by decoction?
Extraction of soluble material by boiling plant in water for specified time
What is maceration?
Pronlonged infusion (days) in aq alcohol and a closed container
What is percolation?
Maceration and then flow of fresh solvent passing over ground material at a specified rate
What is continuous hot extraction?
Repeated infusion with hot solvent
What determines the method of extraction that is used?
Pharmacognosy Hard Soft Unstable to heat Cost
Why is sample preparation needed?
Isolate drugs of interest from complex matrices
Concentrate the analyte
Derivatise the analyte
Stabilise the analyte from undue degradation
Most organic solvent are lighter than water so float on top, what is the exception?
Chlorinated solvents
The aim of acid-base extractions is to get drug into aqueous layer. True or false?
False - organic layer
Phenobarbital is a basic drug. True or false?
False - acidic drug
Lowering the pH of environment of phenobarbital will make it more soluble in organic solvents. True or false?
True
Procaine is a basic drug. True or false?
True
Increasing pH in which procaine is in will lead to it being more soluble in organic solvents. True or false?
True
Aspirin is a weakly acidic drug. What is the best way to get it into organic phase?
React it with a weak acid (rather than base) so it remains unionised and gets into the organic phase
What is the best way to extract alkaloids?
They are nitrogen containing bases so treat with a base to deprotonate and extract
What is rotary evaporation?
Vacuum and heat - solute gets separated
If a sample has a high boiling point, rotary evaporation is not a good method of extraction. Why?
Because heat will degrade the drug
When is distillation used to separate miscible phases?
If the two components in the extract have different boiling points
When is crystallisation used to separate miscible phases?
Components of the extract have different solubilities
What is sublimation?
Freeze-drying
Which extraction process involves the use of a lyophiliser and how is it used?
Sublimation -
Freeze sample so mixture becomes solid
Apply vacuum to sublimate ice directly into water vapour
Keep drawing off water vapour - usually waste
Solid product recovered in flask
What is the key advantage of sublimation?
Can be used for heat-labile compounds e.g. biologicals, vaccines etc.
What are the advantages of solid-phase extraction over liquid-liquid extraction?
Less labour
Less solvent used
Quick
Easier to automate
How does solid phase extraction work?
The sample is filtered through sorbent particles
Analytes are captured from liquid matrix
Concentrated analytes are eluted with the solvent
Eluted sample is collected
