Mass spectrometer Flashcards
What is the atomic mass unit(amu)
1/12th the mass of a C-12 atom
What is Ar (relative atomic mass)
Mean mass of an atom relative to 1/12th the mass of an C-12 atom
What is relative isotopic mass
Mass of an isotope relative to the 1/12th the mass of an C-12 atom
What is Mr (relative molecular mass)
Average mass of molecule relative to the 1/12th of the mass of an C-12 atom
What are the 2 possible ionisation methods
Electro spray and electron impact
What is a Mass Spectrometer.
Allows to measure mass of molecules, also gives abundance and masses of isotopes. Can be used to identify molecules and give Mr value
What is electro spray
Sample dissolved in polar solvent and vaporised, pushed through a fine needle which has a high charge
What does a solvent gain in electro spray
Sample gains a proton
What is electron impact
Vaporised sample is bombarded with high speed electrons from electron gun. These knock out electrons from sample leaving positive charged ions
What is electron impact prefered for
Molecules
What is acceleration in the mass spectrometer
Positive charged ions accelerated by negative electric field.
What is the drift region
The ions drift through the drift region after being accelerated until it reaches the detector
Why will the positively charged ions have different velocity.
Even though all the ions will have the same energy some will have different velocity due to there mass. As the lighter ones will drift faster therefore detected first.
What does the mass spectrometer measure
Mass to charge ratio. M/Z
How are the ions detected
Ions hit the detector and gain a electron this induces a current, the magnitude of the current gives the abundance.
