U1S1 mass spectrometer Flashcards
1
Q
What does a mass spectrometer do
A
- gives information about the relative atomic mass of an element and the relative abundance of isotopes
2
Q
Ionisation
A
- step one
- sample ionised before it enter mass spectrometer
- either done through electrospray ionisation or electron impact ionisation
3
Q
Electrospray ionisation
A
- sample dissolved in a solvent and pushed through a small nozzle at high pressure
- high voltage is applied to it, causing each particle to gain a H+ ion
- solvent removed leaving a gas made of positive ions
4
Q
Electron impact ionisation
A
- sample vaporised and an electron gun used to fire high energy electrons at it
- knocks one electron off each particle, so they become +1 ions
5
Q
Acceleration
A
- stage two
- positive ions accelerated by an electric field
- electric field gives same kinetic energy to all ions
- lighter ions experience greater acceleration
6
Q
Ion drift
A
- stage three
- ions enter a region with no electric field
- drift through it at the same speeds as they left field
7
Q
Detection
A
- stage four
- detector detects current created when ions hit and record how long they took to pass through spectrometer
8
Q
What is a mass spectrum
A
- a chart produced by a mass spectrometer
- y axis gives abundance of ions
- each line represents a different isotope
- x axis units given as mass/charge ratio
