Extraction and sample preparation Flashcards Preview

The Medicine (Y2) > Extraction and sample preparation > Flashcards

Flashcards in Extraction and sample preparation Deck (32)
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1
Q

Define menstruum

A

Solvent(s) used in the extraction process

2
Q

Define marc

A

Insolube materials (waste) left after extraction

3
Q

What is a galencial?

A

A medicinal extract or tincture derived mainly from natural sources

4
Q

What are the four types of extracts?

A

Tinctures
Liquid extracts
Soft extracts
Dry extracts

5
Q

Soft extracts are semi-solid preparations obtained by evaporation or partial evaporation of the solvent used for extraction. True or false?

A

True

6
Q

What are the 3 main steps in the extraction process?

A

Comminution - physically reducing plant material to particular size
Incubation with menstruum
Separating off marc

7
Q

What are the rate limiting factors of the extraction process?

A

Wetting of the surface of particles
Permeability of cell walls
Rate of dissolution of cell contents
Outward diffusion of the solution

8
Q

What are the methods of galencial preparations?

A
Infusion
Decoction
Maceration
Percolation
Continuous hot extraction
9
Q

What is meant by infusion?

A

Drug stood in hot/cold water for a short time

10
Q

What is meant by decoction?

A

Extraction of soluble material by boiling plant in water for specified time

11
Q

What is maceration?

A

Pronlonged infusion (days) in aq alcohol and a closed container

12
Q

What is percolation?

A

Maceration and then flow of fresh solvent passing over ground material at a specified rate

13
Q

What is continuous hot extraction?

A

Repeated infusion with hot solvent

14
Q

What determines the method of extraction that is used?

A
Pharmacognosy 
Hard
Soft
Unstable to heat
Cost
15
Q

Why is sample preparation needed?

A

Isolate drugs of interest from complex matrices
Concentrate the analyte
Derivatise the analyte
Stabilise the analyte from undue degradation

16
Q

Most organic solvent are lighter than water so float on top, what is the exception?

A

Chlorinated solvents

17
Q

The aim of acid-base extractions is to get drug into aqueous layer. True or false?

A

False - organic layer

18
Q

Phenobarbital is a basic drug. True or false?

A

False - acidic drug

19
Q

Lowering the pH of environment of phenobarbital will make it more soluble in organic solvents. True or false?

A

True

20
Q

Procaine is a basic drug. True or false?

A

True

21
Q

Increasing pH in which procaine is in will lead to it being more soluble in organic solvents. True or false?

A

True

22
Q

Aspirin is a weakly acidic drug. What is the best way to get it into organic phase?

A

React it with a weak acid (rather than base) so it remains unionised and gets into the organic phase

23
Q

What is the best way to extract alkaloids?

A

They are nitrogen containing bases so treat with a base to deprotonate and extract

24
Q

What is rotary evaporation?

A

Vacuum and heat - solute gets separated

25
Q

If a sample has a high boiling point, rotary evaporation is not a good method of extraction. Why?

A

Because heat will degrade the drug

26
Q

When is distillation used to separate miscible phases?

A

If the two components in the extract have different boiling points

27
Q

When is crystallisation used to separate miscible phases?

A

Components of the extract have different solubilities

28
Q

What is sublimation?

A

Freeze-drying

29
Q

Which extraction process involves the use of a lyophiliser and how is it used?

A

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

30
Q

What is the key advantage of sublimation?

A

Can be used for heat-labile compounds e.g. biologicals, vaccines etc.

31
Q

What are the advantages of solid-phase extraction over liquid-liquid extraction?

A

Less labour
Less solvent used
Quick
Easier to automate

32
Q

How does solid phase extraction work?

A

The sample is filtered through sorbent particles
Analytes are captured from liquid matrix
Concentrated analytes are eluted with the solvent
Eluted sample is collected