1.3 mass spectrometry

define atomic mass

the weighted mean mass of an atom of an element, compared to 1/12th of the mass of an atom of carbon-12

define isotopic mass

mass of an atom of an isotope compared with 1/12th of the mass of an atom of carbon-12

what are the 5 stages of mass spectrometry

1. vaporisation

2. ionisation

3. acceleration

4. deflection

5. detection

what happens in stage 1 of mass spectrometry

• vaporisation

• liquid → gas

• allows the particles to move freely into mass spectormeter

what happens in stage 2 of mass spectrometry

• ionisation

• high energy electrons are fired at particles

• an electron is knocked off the particle

• it forms a positive ion

what happens in stage 3 of mass spectrometry

• acceleration

• they are acceleration using an electric feild

• giving ions the same kinetic energy

• ions with lower mass-to-charge ration travel faster

what happens in stage 4 of mass spectrometry

• deflection

• ions pass through a magnetic feild

• they are deflected by different amounts depending on their m/z ration

• smaller m/z raito → more deflection

• larger m/z ratio —> less deflection

what happens in stage 5 of mass spectrometry

• detection

• ions hit a detector

• detector produces electrical signal

• signal is used to produce mass spectrum

• m/z values tell the masses of ions