Gas Chromatography

Question 1

Why is gas chromatography so called?

Answer 1

It uses a gas as the mobile phase

Question 2

What is used as the mobile phase in gas chromatography?

Answer 2

A gas

Question 3

What is used as the stationary phase in gas chromatography?

Answer 3

A non-volatile liquid (i.e. a liquid with a high boiling point such as a long-chain alkane)

Question 4

Give an example of a non volatile liquid used as the stationary phase used in gas chromatography.

Answer 4

A liquid with a high boiling point such as a long-chain alkane

Question 5

What is the stationary phase spread on?

Answer 5

It is spread on solid inert particles such as alumina or silica gel that are packed into a long cooked tube called the column

Question 6

Give an example of some solid inert particles that the stationary phase can be spread on.

Answer 6

Alumina or silica gel

Question 7

What are the solid inert particles such as alumina or silica gel packed into?

Answer 7

Into a long tube called the column

Question 8

What are packed into the column

Answer 8

The solid inert particles

Question 9

Describe the column

2

Answer 9

It is a long coiled tube of small diameter and sever metres in length

It is inside a temperature-controlled oven

Question 10

Where is the column?

Answer 10

Inside a temperature-controlled oven

Question 11

How many processes occur in gas chromatography?

Answer 11

Four

Question 12

List the processes that occur in gas chromatography

4

Answer 12

Sample is injected into column

Sample is vaporised

Components are adsorbed

Components pass through a detector

Question 13

Describe the first process that occurs in gas chromatography

Answer 13

The sample to be analysed is injected into the hot column using a syringe

Question 14

Describe the second process that occurs in gas chromatography
(2)

Answer 14

The sample is vaporised and is carried through the tube using an unreactive gas such as nitrogen, helium or argon

This gas is commonly called a carrier gas as it carries the mixture through the hot column

Question 15

What carries the vaporised sample through the tube?

Answer 15

An unreactive gas

Question 16

Give some examples of unreactive gases that carry the vaporised sample through the tube
(3)

Answer 16

Nitrogen

Helium

Argon

Question 17

What are the unreactive gases that carry the vaporised sample through the tube often called?

Answer 17

Carrier gas

Question 18

Why are the unreactive gases used in gas chromatography often called carrier gases?

Answer 18

As it carries the mixture through the hot column

Question 19

Describe the third process that occurs in gas chromatography

2

Answer 19

The components of the mixture are adsorbed to different extents on the stationary phase

Therefore, the various components in the mixture are separated out as they flow through the column

Question 20

What happens to the components of the mixture during process three?

Answer 20

They are adsorbed to different extents on the stationary phase

Question 21

When are the various components in the mixture separated?

Answer 21

They are separated as they flow through the column

Question 22

Describe the fourth process that occurs in gas chromatography
(2)

Answer 22

As each component of the mixture leaves the column, it passes into a detector that records a signal

This detector plots a chart called a gas chromatogram on which each component of the mixture shows up as a peak

Question 23

What happens as each component of the mixture leaves the column?

Answer 23

It passes into a detector that records a signal

Question 24

What part of the apparatus used in gas chromatography records a signal?

Answer 24

A detector

Question 25

What does the detector do?

Answer 25

It plots a chart called a gas chromatogram on which each component of the mixture shows up as a peak

Question 26

What is the name of the chart plotted by the detector?

Answer 26

A chromatogram

Question 27

What is the principle of gas chromatography?

Answer 27

That a gaseous mobile phase is in contact with a stationary phase (non-volatile liquid) and separation of the mixture occurs as result of selective adsorbance of the components of the mixture on the stationary phase

Question 28

What is gas chromatography commonly used for?

2

Answer 28

To measure the level of alcohol in blood or urine samples

To carry out drug tests on athletes

Question 29

What is gas chromatography often combined with to be used as an analytic tool?

Answer 29

Mass spectrometry

Question 30

What is gas chromatography combined with mass spectrometry often referred to as?

Answer 30

GC-MS

Question 31

Describe how GC-MS is carried out.

Answer 31

The separated components that come from the gas chromatography apparatus are passed into a mass spectrometer

Question 32

How is using GC-MS one of the most powerful analytical tools available.

Answer 32

It enables each individual compound to be analysed separately and identified

Question 33

What is the GC-MS technique often used to do?

4

Answer 33

Identify drugs of abuse

To monitor the performance of a particular pharmaceutical in the body

To detect gases from waste dumps and organic pollutants in plants

To analyse the atmosphere and soil from other planets

Question 34

How is GC-MS used to monitor the performance of a particular pharmaceutical in the body?

Answer 34

Volunteers are given a dose of the drug and then blood samples are taken at regular intervals and subjected to GC-MS analysis

Question 35

What does monitoring the performance of pharmaceuticals in the body through GC-MS enable?

Answer 35

It enables the researcher to follow the metabolic pathway of the drug inside the body