The Mass Spectrometer - CGP

• What is a mass spectrometer used for?

  To analyse elements or compounds
• What information can a mass spectrometer provide about an element?

  Relative atomic mass and isotopic abundance
• What happens first when a sample enters a TOF mass spectrometer?

  The sample is ionised
• What are the two methods of ionisation in a mass spectrometer?

  • Electrospray ionisation
  • Electron impact ionisation
• How does electrospray ionisation work?

  Sample is dissolved and pushed through a nozzle
• What happens to particles during electrospray ionisation?

  Each particle gains an H+ ion
• What is the role of the electron gun in electron impact ionisation?

  It fires high energy electrons at the sample
• What is the effect of the electric field on positive ions in a mass spectrometer?

  It accelerates them with the same kinetic energy
• Why do lighter ions accelerate more than heavier ions?

  They have less mass but same energy
• What happens to ions in the drift region of a TOF mass spectrometer?

  They drift at the same speed as they left
• How does the speed of lighter ions compare to heavier ions in the drift region?

  Lighter ions drift at higher speeds
• What does the detector in a mass spectrometer measure?

  The time ions take to reach it
• What does a mass spectrum represent?

  Information about the sample analyzed
• What does the y-axis of a mass spectrum indicate?

  The abundance of ions as a percentage
• What does the x-axis of a mass spectrum represent?

  The mass/charge ratio of ions
• How does the mass/charge ratio relate to isotopes in a mass spectrum?

  It equals the relative mass of each isotope
• What happens to the mass/charge ratio when electrospray ionisation is used?

  It is one unit greater than the relative mass
• How can mass spectrometry be used to identify elements?

  By producing characteristic patterns in spectra
• What does the presence of multiple lines in a mass spectrum indicate?

  Different isotopes of an element are present
• What does the height of each peak in a mass spectrum represent?

  The relative isotopic abundance of isotopes
• What is the significance of the mass spectrum produced using electron impact ionisation?

  It shows the mass/charge ratio of isotopes
• How does the mass spectrum differ when using electrospray ionisation compared to electron impact ionisation?

  Electrospray adds an H+ ion, shifting ratios
• What is the charge of lithium ions produced in a mass spectrometer?

  1+
• What is the purpose of the vacuum in a TOF mass spectrometer?

  To prevent ions from colliding with air molecules
• What is the role of the mass spectrometer in chemical analysis?

  To provide detailed information about samples
• How can the mass spectrum be used to determine the composition of a sample?

  By analyzing the peaks and their heights