Chromatography

Question 1

What does GC stand for

Answer 1

Gas chromatography

Question 2

In a GC experiment, what is measured

Answer 2

Time

Question 3

If on a chromatography paper the sample travels far, what is the time recorded if the sample was tested using a GC

Answer 3

Fast time

Question 4

Reading the graph, with the time for the molecules to pass through the GC, what do the widths of the peaks show

Answer 4

Concentration of molecule

Question 5

What are the 2 things that chromatography can be used for

Answer 5

-Small scale analysis
- Bigger scale purification

Question 6

In all types of chromatography, what are the 2 phases

Answer 6

• Mobile
• Stationary

Question 7

What does TLC stand for

Answer 7

Thin Layer Chromatography

Question 8

If a component of the compound has a stronger absorption to the stationary phase, does it more or less time for the component to migrate up the plate

Answer 8

More time, it’s slower

Question 9

What is the mobile phase in gas chromatography

Answer 9

Gas, unreactive

Question 10

What is the time taken for each component of a sample to travel through the tube known as

Answer 10

The retention time

Question 11

In gas chromatography, what is the stationary phase

Answer 11

A liquid absorbed onto an inert solid support

Question 12

If a component of compound is more soluble, what happens to the retention time

Answer 12

Longer retention time as the component would spend more time in the stationary phase

Question 13

If the stationary phase is more polar, are polar or non-polar components more soluble

Answer 13

Polar

Question 14

If compounds have similar functional groups, what are their retention times like

Answer 14

Similar

Question 15

Reading a gas chromatogram, what does the area under the peak proportional to

Answer 15

The amount of each compound

Question 16

If we want to know the actual amount of a substance present in a sample, what do we have to do to the GC instrument

Answer 16

Calibrate it

Question 17

What are the steps when calibrating a GC instrument

Answer 17

• Inject a series of samples containing known concentrations
• Measure the peak area
• Plot a calibration curve
• Run the unknown sample and compare to the calibration curve.
• Concentration of sample can then be estimated

Question 18

What is a GC-MS

Answer 18

Combining Gas Chromatography with Mass Spectrometry

Question 19

What are 3 advantages of GC-MS

Answer 19

• Very good resolution
• Can operate with very tiny amounts of sample mixture
• A very large database of mass spectra, so good chance of positive identification

Question 20

What are 3 limitations of GC-MS

Answer 20

• Similar compounds often have similar retention times so difficult to separate and identify
• Unknown compounds in mixture have no reference retention time or mass spectra matching
• Equipment is relatively sophisticated and expensive

Question 21

What are some uses for GC-MS

Answer 21

• Forensic science- analysis tiny traces of matter
• Testing organic pollutants
• Airport security - detecting explosives
• Space missions - looking for life on other planets