Atomic Structure- TOF Mass Spectrometry Flashcards
What charge is on the ions?
Positive
Why is it necessary to ionise the mixture?
Acceleration and detection
How are the ions accelerated?
The positive ions accelerate towards the negatively charged plate.
Why do the different ions separate in the flight tube?
Same kinetic energy, different velocities.
Heavier particles travel slower, lighter particles travel faster.
Why is the inside of the machine a vacuum?
So other particles can’t interfere with the ion beam made from the sample
How are the ions detected and how is their abundance measured?
Ions hit the detector and gain an electron. This generates a current proportional to the abundance.
Name the ionisation method when a particle gains a proton to form an ion.
Electrospray
What are the two measurements made by the mass spectrometer?
M/Z ratio and relative abundance
Why would a fluoride ion not be detected?
Because it has a negative charge
How are ions formed?
By electrospray or electron impact
How are ions form via electron impact ionisation?
- Sample is vapourised
- High-energy electrons are fired at sample
- from an electron gun
- One electron is knocked off each particle
How are ions form via electrospray ionisation?
- Sample is dissolved in a volatile solvent
- Sample is injected through a needle at high voltage
- Sample is ionised by gaining a proton
Which ionisation method knocks off an electron to form an ion?
Electron impact
All particles have the same kinetic energy. How are they separated in the flight tube?
Different velocities.
Heavier particles travel slower, lighter particles travel faster.
When an ion hits the detector, how is a current generated?
Ions hit the detector and gain an electron. This generates a current proportional to the abundance.
