Mass Spectrometer

How many types of ionisation are there?

Electron impact - used for elements and low Mr compounds

Electrospray ionisation - compounds with high Mr

What are the steps of Electron Impact?

1. Fire high energy electrons from an electron

2. Knock off one electron per atom to form 1+ ion

What are the steps of Electrospray ionisation?

1. Sample is dissolved in volatile solvent

2. injected through hypodermic needle as a fine spray

3. into vacuum in the ionisation chamber

4. a very high voltage is applied to end of needle

5. particles gain a proton and become ions as a fine mist

6. leave as 1+ ions

What is the second stage of mass spectrometer?

Acceleration of ion

How does acceleration occur?

ions are accelerated using an electric field so all ion have same kinetic energy

Equation for kinetic energy

0.5 x mass x velocity²