Mass Spectromety Flashcards
What was mass spectrometry initially used for?
To show the identity of isotopes
What is mass Spectromety used for now?
To calculate molecular masses, characterise new compounds, identify unknown compounds
What does a mass spectrometer consist of?
An ion source, an analyser and a detector
Why must particles be ionised?
So they can be accelerated and deflected
What is the 1st stage of a mass spectrometer?
Ionisation - gaseous atoms are bombarded by electrons from an electron gun and are ionised. Sufficient energy is given to from ions of 1+ charge
What is the 2nd stage of a mass spectrometer?
Acceleration - ions are charged so can be accelerated by an electric field
What is the 3rd stage of a mass spectrometer?
Deflection - charged particles will be deflected by a magnetic or electric field
What is the 4th stage of a mass spectrometer?
Detection - by electric or photographic methods
What does the radius of the path of an ion depend on?
The value of the mass/charge ratio (m/z)
What is the radius path of ions of heavier isotopes?
They have larger m/z values so follow a larger radius curve
What does the amount of seperation of an ion depend on?
It’s mass as most ions are 1+ charged
What will happen if an ion acquires a 2+ charge?
It will be deflected more ; its m/z value is halved
Define details of a mass spectrum
- Positions of peaks give atomic mass
- Peak intensity gives the relative abundance
- Highest abundance is scaled to 100% and other values are adjusted accordingly
What happens when a molecule is ionised?
It forms a molecular ion which can also undergo fragmentation or re-arrangement to produce particles of smaller mass
Which particles will be deflected and detected?
Only particles with a positive charge
