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Stage 1: Ionisation - Electrospray Ionisation
-Sample is dissolved in a solvent
-Injected through a needle at high voltage
-Gains a proton
Solvent, Needle & Proton
Stage 1: Ionisation - Electron Impact (Electron Gun)
-High energy electrons from an electron gun
-Fired at the sample and knock off an electron
The Lion King
Stage 2: Acceleration
-The positive ions are accelerated by an electric field to a constant kinetic energy
-The rate at which they are accelerated is dependent on their masses
-Ions with a lower mass will travel faster and will have a higher velocity
-Ions with a higher mass will travel slower and will have a lower velocity
Electric Field, Kinetic Energy, Mass & Velocity
Stage 3: Ion Drift
-Ions will separate (All Ions have a constant kinetic energy)
-Ions are allowed to drift in a flight tube and the time it takes for the Ions to reach a detector at a known distance in measured
-This time will depend on the mass of the ion
-Lighter Ions reach higher velocities, therefore Ions with a low mass will reach the detector first and those with a high mass will arrive last
-The mass of the Ion can be determined from the time taken for the Ion to reach the detector
Separate, Time, Distance, Mass & Velocity
Stage 4: Ion Detection
-Positive Ions hoy the detector (a negatively charged plate) and pick up electrons
-A current is generated when the Ions gain an electron
-The greater the abundance of the Ions hitting the detector, the bigger the current produced
Detector, Current & Abundance
Stage 5: Data Analysis
-The detector is linked to an amplifier and recorder, which converts the current into a peak and that is shown in a mass spectrum
-The height of the peak is proportional to the size of the current generated and therefore proportional to the abundance of the Ion
-Flight times are analysed and recorded as a plot of abundance v mass/charge ratio or m/z
Peak, Height, Current and Ratio
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