Time Of Flight Mass Spectrometry

Question 1

What is mass spectrometry ?

Answer 1

A powerful instrument method of analysis

Question 2

Mass spectrometry can be used for : ?

Answer 2

• Find the abundance & mass of each isotope.

* Fond the relative molecular mass of substances made of molecules.

Question 3

What Is electron impact ionisation ?

Answer 3

•Sample is vaporised.
•Electron is fired at sample at high speed from electron gun.
•Electron is knocked off.
•Positive ions are attracted to a negative electric plate where they are accelerated.
Sample hits the negative plate gaining an electron creating a current.

Question 4

What is electron spray ionisation ?

Answer 4

• Sample is dissolved in a volatile solvent.
• Injected through hypodermic needle to give a mist.
• Tip of needle attached to positive terminal of high voltage power supply.
• Particles gain a proton from solvent producing XH+ ions.
• Solvent evaporates while XH+ ions are attracted towards the negative plate where they are accelerated.

Question 5

What is the ratio of relative abundance 35Cl and 37Cl isotopes.

Answer 5

3:1

Question 6

What is the ratio of relative abundance of 79Br and 81Br isotopes ?

Answer 6

1:1

Question 7

What are the key principles of TOF ?

Answer 7

• All particles enter the flight tube with the same energy.
• All particles travel the same distance.
• Heavier particles travel slower than lighter particles.