3.16 Chromatography

Question 1

Give the definition of chromatography.

Answer 1

Chromatography is an analytical technique that separates components in a mixture between a mobile phase and a stationary phase.

Question 2

What are 3 types of chromatography?

Give a brief explanation of each.

Answer 2

• Thin-layer chromatography (TLC)
  A plate is coated with a. solid and a solvent moves up the plate.
• Column chromatography (CC)
  A column is packed with a solid and a solvent moves down the column.
• Gas chromatography (GC)
  A column is packed with a solid or with a solid coated by a liquid, and a gas is passed through the column under pressure at high temperature.

Question 3

What states will the mobile phase be in?

Answer 3

Gas or liquid

Question 4

What states will the stationary phase be in?

Answer 4

Solid (as in thin-layer chromatography, TLC) or either a liquid or solid on a solid support (as in gas chromatography, GC)

Question 5

In gas chromatography, what is the mobile phase and what is the stationary phase?

Answer 5

Mobile phase - An inert gas, eg. nitrogen, helium, argon.

Stationary phase - Liquid on an inert solid.

Question 6

Separation by column chromatography depends on the balance between the ________ in the moving phase and _______ in the stationary phase.

Answer 6

Separation by column chromatography depends on the balance between the solubility in the moving phase and retention in the stationary phase.

Question 7

A solid stationary phase separates by __________

Answer 7

A solid stationary phase separates by absorption.

Question 8

A liquid stationary phase separates by _________

Answer 8

A liquid stationary phase separates by relative solubility.

Question 9

What would happen if the stationary phase was polar and the moving phase was non-polar?

Answer 9

(see page 1 in the chemrevise revision guide)

Question 10

___________ and _________ are used to identify different substances.

Answer 10

Retention and Rf values are used to identify different substances.

Question 11

When is a UV lamp used in TLC?

Answer 11

If the spots are colourless and not visible.

Question 12

Describe the method for Column chromatography (CC)

Answer 12

(see page 2 in the chemrevise revision guide)

Question 13

What does HPLC stand for?

Answer 13

High performance liquid chromatography

Question 14

In Column chromatography (CC) what is the mobile phase and the stationary phase?

Answer 14

Stationary phase - solid silica

Mobile phase - liquid, suitable solvent that moves downwards.

Question 15

Draw and label the apparatus for Column chromatography (CC)

Answer 15

(see page 2 in the chemrevise revision guide)

Question 16

What does Column chromatography (CC) allow you to do to samples?

Answer 16

Enables you to separate and prepare a pure compound.

Question 17

What is gas chromatography (GC) used for?

Answer 17

Used to separate mixtures of volatile liquids.

Question 18

Describe how gas-liquid chromatography (GC) works.

Answer 18

(see page 2 in the chemrevise revision guide)

Question 19

What is GC-MS used in?

Answer 19

Analysis, in forensics, environmental analysis, airport security and space probes.

Question 20

Draw the apparatus for gas-liquid chromatography (GC)

Answer 20

(see page 2 in the chemrevise revision guide)

Question 21

What is the retention time in gas-liquid chromatography (GC)?

Answer 21

The time taken for a particular compound to travel from the injection of the sample to where it leaves the column to the detector.

Question 22

What is the mobile phase and stationary phase in gas-liquid chromatography (GC)?

Answer 22

Mobile phase - gas, eg. helium

Stationary phase - high boiling point liquid absorbed into a solid