Process Of Mass Spectrometry

Question 1

What are the four stages of mass spectrometry

Answer 1

-ionisation
-acceleration
-deflection
-detection

Question 2

Why are air molecules pumped out of mass spectrometer

Answer 2

So the ions produced are able to pass through the machine without hitting air molecules

Question 3

In what state do molecules need to be in when they enter the mass spectrometer and how do you make some of the molecule to be in that star

Answer 3

Gaseous
Need to heat up the sample till sufficient number of gaseous particles are made

Question 4

What happens in the first stage and what does it form

Answer 4

The sample in the gaseous form is injected into the mass spectrometer and is bombarded by high energy electron s from electron gun to form high positive ions

Question 5

What happens I the second stage of mass spectrometry

Answer 5

Positive ions are accelerated by electric field to give them specific kinetic energy

Question 6

What happens in the third stage of mass spectrometry

Answer 6

The ions are deflected by a powerful magnetic

Question 7

What does angle of deflection depend upon

Answer 7

M/Z ratio and strength of magnetic field

Question 8

What type of ions are deflected less than those with smaller mass

Answer 8

Ions with same charge but different masses

Question 9

What happens in the last stage of mass spectrometry

Answer 9

Ions with lowest mass are detected first
The magnetic field increases and ions of greater mass are then detected
The detector is connected to a computer which calculates m/Z ratio of each positive ion and it’s percentage abundance compared with most abundant particles

Question 10

How do you work out molecular mass on a mass spectrum

Answer 10

The largest m/Z value is the

Question 11

Why are M+1 peaks ignored

Answer 11

Because of the presence of any carbon 13 atoms

Question 12

What is time of flight

Answer 12

The time between ionisation and detection

Question 13

Why is time of flight calculated

Answer 13

Although the ions have the same kenetic energy the heavier ones move slower and so reach the detector later then the lighter ones

Question 14

Why is electrospray ionisation used

Answer 14

To identify complex molecules but no fragment ion occurs

Question 15

What is the process of electrospray ionisation

Answer 15

Sample is dissolved in volatile solvent containing little Ethanioc acid
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