Chromatography 1

Question 1

What is Quality control?

Answer 1

Checking that the right ingredients are present at the right quantity

Question 2

What is Quality Assurance?

Answer 2

Checking that the SOPs are such that the quality of the products can be assured

Question 3

Define Chromatography?

Answer 3

Chromatography is a process in which a chemical mixture (e.g. a medicine) is carried (by a liquid or gas) around or over a stationary liquid or solid phase. Components of the mixture are separated as a result of differential distribution of the solutes between the carrier phase (mobile phase), and the stationary phase.

Question 4

What is a stationary phase?

Answer 4

The stationary phase is a solid or liquid material that is either coated onto a thin layer of inert material such as plastic (Thin Layer Chromatography), or packed or coated around the edge of a column (Column Chromatography

Question 5

What is a Mobile phase?

Answer 5

The mobile phase, is a gas or a liquid that is allowed to flow over or through the stationary phase carrying the analyte with it.

Question 6

State the general principles of Separation

Answer 6

1. When the mixture is introduced onto the stationary phase it has the choice of either staying with the stationary phase or moving with the mobile phase.
2. Most components will partition between both phases.
3. The amount of time a component of a mixture spends in each phase is dependant on the differing affinities it has for each phase. This in turn is dependant on its individual physical and chemical properties.
   As the mobile phase passes through the stationary phase, the components of the mixture travel at different rates over or through the stationary phase and become separated.

Question 6

State the general principles of Separation

Answer 6

1. When the mixture is introduced onto the stationary phase it has the choice of either staying with the stationary phase or moving with the mobile phase.
2. Most components will partition between both phases.
3. The amount of time a component of a mixture spends in each phase is dependant on the differing affinities it has for each phase. This in turn is dependant on its individual physical and chemical properties.
4. As the mobile phase passes through the stationary phase, the components of the mixture travel at different rates over or through the stationary phase and become separated.

Question 7

If given the choice, a molecule made mainly of carbon and hydrogen is likely to dissolve best in?

Answer 7

A non-polar phase

Question 8

Polarity is due to ……….

Answer 8

to an uneven distribution of electrons in a molecule

Question 9

Methanol is relatively less polar than water . True or false?

Answer 9

True

Question 10

Why is methanol relatively less polar than water?

Answer 10

Methanol (CH3OH) is also considered to be a polar solvent however it is relatively less polar than water. As you increase the ratio of carbon to electronegative atom compounds generally become less polar

Question 11

OH, NH2 are very polar. true or false?

Answer 11

True

Question 12

Which of the following solvents is most polar?
Dichloromethane
Hexane
Methanol
Ethanol
Chloroform (CHCl3

Answer 12

Methanol

Question 13

Facts about column chromatography

Answer 13

In column chromatography, the stationary phase is held in a tube (column) and the mobile phase is forced through the column under pressure or by gravity.

Question 14

Many different types of column chromatography differ according to ……..

Answer 14

the nature of the mobile phase, and stationary phase.

Question 15

List the two types of column chromatography

Answer 15

1. Liquid Chromatography

2. Gas Chromatography

Question 16

State the type of mobile phase in liquid chromatography?

Answer 16

Liquid

Question 17

List the 4 common types of liquid chromatography

Answer 17

Adsorption chromatography (stationary phase is an adsorbent solid e.g. charcoal, silica).

Partition chromatography (stationary phase is a liquid coated solid, partition occurs)

Ion exchange chromatography (stationary phase has ionic bonded phase)

Gel permeation chromatography (stationary phase is a porous solid)

Question 18

Facts about Adsorbent Chromatography

Answer 18

Adsorbent solid stationary phases have polar groups on their surface e.g. SiO2, Al2O3.

Molecules are attracted to the surface by dipole, dipole forces, hydrogen bonding, or week van der Waals forces. All of these interactions are weak, since in chromatography you must be able to displace the molecules from the adsorbent.

Question 19

What is the stationary phase in Partitioned Chromatography?

Answer 19

It is an inert solid, coated with a liquid e.g. SiO2/H2O.

Question 20

What is the stationary phase in a normal phase chromatography?

Answer 20

The STATIONARY phase is POLAR

Question 21

What is the mobile phase in a normal chromatography phase?

Answer 21

Mobile phase is relatively non-polar

Question 22

In reverse-phase chromatography, the stationary phase is ……

Answer 22

Non-polar

Question 23

In reverse phase chromatography, the mobile phase is…..

Answer 23

relatively polar

Question 24

Separation occurs in a partitioned chromatography due to........

Answer 24

the differences in solubility of the solute between the stationary and mobile phase liquids

Question 25

In partitioned chromatography, The solute is partitioned between the two phases, the amount of time spent in each is dependant on solubility. True or false?

Answer 25

True

Question 26

if the stationary phase is very polar, and the mobile phase is very non-polar, then polar compounds will spend more time on which of the phases?

Answer 26

the polar compounds will spend more time on the stationary phase than non-polar ones, and separation according to polarity may occur.

Question 27

In normal phase chromatography, what type of bonds are most likely to account for the attraction of an analyte to the stationary phase?

Answer 27

Polar-polar interactions e.g. hydrogen bonding

Question 28

In reverse phase chromatography, what kind of bonds are most likely to account for the attraction of an analyte to the stationary phase

Answer 28

Van der Waals

Question 29

What is the stationary phase in an ion-exchange Chromatography?

Answer 29

The stationary phase is a coated solid. The coating is a solid resin with ions (cations and anions) covalently bonded to it. Ions of opposite charge are bonded electrostatically (ionically) onto these ions e.g. SEE SLIDE 20

Question 30

State what happens when the eluent containing ions is eluted through the column in an ion-exchange chromatography?

Answer 30

When the eluent-containing ions is eluted through the column, the electrostatically bound ions are released as others are preferentially bound.

Question 31

Separation occurs in ion-exchange chromatography because of ......

Answer 31

Separation occurs because, the smaller and more highly charged an ion is, the stronger it will be retained in the column, and therefore the longer it will take to elute.

Question 32

State why Gel Permeation Chromatography differs from others..

Answer 32

This differs from the others in that no equilibrium exists between the solute and the stationary phase. Instead, the solute (in solution) passes through a porous gel.

Question 33

State how separation occurs in a Gel Permeation Chromatography?

Answer 33

Separation thus occurs according to the size of the solutes Depending on the pour size, smaller molecules are allowed in the pours and therefore have to travel through the entire volume of the column. Larger molecules are excluded from the pours and therefore have less volume to travel through and elute more quickly.

Question 34

Mobile phase is a liquid, stationary phase is usually a solid in a liquid chromatography. True or false?

Answer 34

True

Question 35

Define a preparative column chromatography

Answer 35

This involves a column packed with quite large stationary phase molecules (e.g. silica or alumina). The sample mixture is coated onto the top and the eluent is flushed down by the liquid mobile phase, taking the sample witnot for analytical determinations.

Question 36

What is a High-Performance Liquid Chromatography?

Answer 36

High-performance liquid chromatography (HPLC) is an extension of liquid column chromatography where particle size is smaller and the eluent is pumped around the column under pressure rather than relying on gravity