A vaporised sample is exposed to a beam of electrons, resulting in abstraction or addition of electrons. The radical ions are very reactive and have a low stability, leading to a high degree of fragmentation (hard ionisation)
Electron ionisation
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A vaporised sample is exposed to chemical ions (e.g. CH3+, CH4+, CH5+) formed by EI. Can result in protonation, abstraction, adduct formation or charge exchange
Chemical ionisation
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Solution of a sample is brought into contact with a high voltage which leads to formation of aerosol comprised of small, highly ionic droplets which expel stable ions, e.g. MH+ or MNa+. Fragmentation is seen but this is a soft technique
Electrospray ionisation
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Machine which separates the ions
Analyser
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A magnetic or static field electric field is used to deflect ions. Smaller and more highly charged ions are deflected more (m/z)
Sector
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These analysers accelerate ions using an electrostatic field of known strength. Smaller and more highly charged ions accelerate faster. m/z is determined by the time taken to reach the detector
Time of flight
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Ions pass through an oscillating electrostatic field generated by charged rods - the path of the ions is altered by the field depending on the m/z ratio. By altering the field strength, the spectrometer can detect different m/z ratios
Quadrupole
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This type of mass spec can be used to determine the mass of an ion up to 4 decimal places. This means the ion can be linked to a single molecular formula (not useful for isomers)
High resolution
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This type of mass spec involves fragmenting the fragments to identify any peaks that may come from impurities.
Tandem
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Other cards in this set
Card 2
Front
A vaporised sample is exposed to chemical ions (e.g. CH3+, CH4+, CH5+) formed by EI. Can result in protonation, abstraction, adduct formation or charge exchange
Back
Chemical ionisation
Card 3
Front
Solution of a sample is brought into contact with a high voltage which leads to formation of aerosol comprised of small, highly ionic droplets which expel stable ions, e.g. MH+ or MNa+. Fragmentation is seen but this is a soft technique
Back
Card 4
Front
Machine which separates the ions
Back
Card 5
Front
A magnetic or static field electric field is used to deflect ions. Smaller and more highly charged ions are deflected more (m/z)
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