Extraction and sample preparation

Question 1

Define menstruum

Answer 1

Solvent(s) used in the extraction process

Question 2

Define marc

Answer 2

Insolube materials (waste) left after extraction

Question 3

What is a galencial?

Answer 3

A medicinal extract or tincture derived mainly from natural sources

Question 4

What are the four types of extracts?

Answer 4

Tinctures
Liquid extracts
Soft extracts
Dry extracts

Question 5

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

Answer 5

True

Question 6

What are the 3 main steps in the extraction process?

Answer 6

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

Question 7

What are the rate limiting factors of the extraction process?

Answer 7

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

Question 8

What are the methods of galencial preparations?

Answer 8

Infusion
Decoction
Maceration
Percolation
Continuous hot extraction

Question 9

What is meant by infusion?

Answer 9

Drug stood in hot/cold water for a short time

Question 10

What is meant by decoction?

Answer 10

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

Question 11

What is maceration?

Answer 11

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

Question 12

What is percolation?

Answer 12

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

Question 13

What is continuous hot extraction?

Answer 13

Repeated infusion with hot solvent

Question 14

What determines the method of extraction that is used?

Answer 14

Pharmacognosy 
Hard
Soft
Unstable to heat
Cost

Question 15

Why is sample preparation needed?

Answer 15

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

Question 16

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

Answer 16

Chlorinated solvents

Question 17

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

Answer 17

False - organic layer

Question 18

Phenobarbital is a basic drug. True or false?

Answer 18

False - acidic drug

Question 19

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

Answer 19

True

Question 20

Procaine is a basic drug. True or false?

Answer 20

True

Question 21

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

Answer 21

True

Question 22

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

Answer 22

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

Question 23

What is the best way to extract alkaloids?

Answer 23

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

Question 24

What is rotary evaporation?

Answer 24

Vacuum and heat - solute gets separated

Question 25

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

Answer 25

Because heat will degrade the drug

Question 26

When is distillation used to separate miscible phases?

Answer 26

If the two components in the extract have different boiling points

Question 27

When is crystallisation used to separate miscible phases?

Answer 27

Components of the extract have different solubilities

Question 28

What is sublimation?

Answer 28

Freeze-drying

Question 29

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

Answer 29

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

Question 30

What is the key advantage of sublimation?

Answer 30

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

Question 31

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

Answer 31

Less labour Less solvent used Quick Easier to automate

Question 32

How does solid phase extraction work?

Answer 32

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