TOF mass spectrometer

• Electron impact ionisation


  High energy electrons fired at sample from electron gun, knocking off an outer electron to form a 1+ ion
• Electrospray ionisation 


  A method good for high molecular weight substances, such as proteins, where the sample is dissolved in a volatile solvent and injected through a fine needle to create a mist.
• Ionisation necessity in TOF mass spectrometer.?


  Only positive ions will interact with and be accelerated by an electric field and create a current when hitting the detector.
• TOF mass spectrometer isotope separation


  Positive ions are accelerated by an electric field to a constant kinetic energy, with ions of smaller m/z having higher velocity and arriving at the detector first.
• Detector function in mass spectrometer

  Ions hit the negative plate of the detector, accepting an electron and generating a current, where the size of the current is proportional to the abundance of the isotope.
• Relative atomic mass


  Average mass of 1 atom (of an element) divided by 1/12 mass of an atom of 12C.
• Mass number of an isotope


  Total number of protons and neutrons in the nucleus of an atom.
• Atomic number


  Number of protons in the nucleus.
• Formation of XH+ ion


  X(g) + H²(g) → XH+(g) where the particle gains H+ ion from solvent, resulting in a mass of Mr +1 and +1 charge.
• Isotopes chemical properties


  Isotopes have the same electron configuration, leading to the same chemical properties