Gas Chromatography Flashcards
Why is gas chromatography so called?
It uses a gas as the mobile phase
What is used as the mobile phase in gas chromatography?
A gas
What is used as the stationary phase in gas chromatography?
A non-volatile liquid (i.e. a liquid with a high boiling point such as a long-chain alkane)
Give an example of a non volatile liquid used as the stationary phase used in gas chromatography.
A liquid with a high boiling point such as a long-chain alkane
What is the stationary phase spread on?
It is spread on solid inert particles such as alumina or silica gel that are packed into a long cooked tube called the column
Give an example of some solid inert particles that the stationary phase can be spread on.
Alumina or silica gel
What are the solid inert particles such as alumina or silica gel packed into?
Into a long tube called the column
What are packed into the column
The solid inert particles
Describe the column
2
It is a long coiled tube of small diameter and sever metres in length
It is inside a temperature-controlled oven
Where is the column?
Inside a temperature-controlled oven
How many processes occur in gas chromatography?
Four
List the processes that occur in gas chromatography
4
Sample is injected into column
Sample is vaporised
Components are adsorbed
Components pass through a detector
Describe the first process that occurs in gas chromatography
The sample to be analysed is injected into the hot column using a syringe
Describe the second process that occurs in gas chromatography
(2)
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
What carries the vaporised sample through the tube?
An unreactive gas
Give some examples of unreactive gases that carry the vaporised sample through the tube
(3)
Nitrogen
Helium
Argon
What are the unreactive gases that carry the vaporised sample through the tube often called?
Carrier gas
Why are the unreactive gases used in gas chromatography often called carrier gases?
As it carries the mixture through the hot column
Describe the third process that occurs in gas chromatography
2
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
What happens to the components of the mixture during process three?
They are adsorbed to different extents on the stationary phase
When are the various components in the mixture separated?
They are separated as they flow through the column
Describe the fourth process that occurs in gas chromatography
(2)
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
What happens as each component of the mixture leaves the column?
It passes into a detector that records a signal
What part of the apparatus used in gas chromatography records a signal?
A detector
What does the detector do?
It plots a chart called a gas chromatogram on which each component of the mixture shows up as a peak
What is the name of the chart plotted by the detector?
A chromatogram
What is the principle of gas chromatography?
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
What is gas chromatography commonly used for?
2
To measure the level of alcohol in blood or urine samples
To carry out drug tests on athletes
What is gas chromatography often combined with to be used as an analytic tool?
Mass spectrometry
What is gas chromatography combined with mass spectrometry often referred to as?
GC-MS
Describe how GC-MS is carried out.
The separated components that come from the gas chromatography apparatus are passed into a mass spectrometer
How is using GC-MS one of the most powerful analytical tools available.
It enables each individual compound to be analysed separately and identified
What is the GC-MS technique often used to do?
4
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
How is GC-MS used to monitor the performance of a particular pharmaceutical in the body?
Volunteers are given a dose of the drug and then blood samples are taken at regular intervals and subjected to GC-MS analysis
What does monitoring the performance of pharmaceuticals in the body through GC-MS enable?
It enables the researcher to follow the metabolic pathway of the drug inside the body
