Mass Spectrometry Flashcards
What is the time of flight mass spectrometer?
An instrument used for measuring the masses of atoms and molecules.
What are the 4 stages of the mass spectrometer?
Electrospray ionisation, acceleration, ion drift and detection
What happens in electrospray ionisation?
1) The sample is dissolved in water and pushed through the small nozzle at high-pressures.
2) An electric current is passed through causing particles to become ionised.
3) The particles are separated from the solvent, leaving a gaseous sample of ions.
What happens during the acceleration stage?
The positive ions are accelerated by an electrical field. Smaller ions have a higher speed than larger ions.
What happens during the ion drift stage?
The ions leave the electric field at different speeds depending on their mass/charge ratio. The heavier particle, the lower the speed and the greater the time taken to reach the detector.
What happens in the detection stage?
The electrons on the detector move towards the ions which creates a current. The detector records the time taken to reach it and the current. The larger the current, the greater the abundance of that isotope.
Which two stages of time of flight mass spectrometry needs the sample to be ionised?
Acceleration and detection.
What can be calculated from the mass spectrum of an element?
The relative atomic mass of that element.
What is the mass spectrum of an element?
The graph produced when that element is passed through a (TOF) mass spectrometer.
How is the relative molecular mass of a molecule obtained by looking at the graph?
By looking at the peak in the spectrum with the largest m/e ratio. The peak that is furthest to the right.
