Mass Spectrometry (Different Analysers)

Question 1

Mass Analysers (HR-MS)

Answer 1

High resolution mass spectrometer. Double/Triple focusing with additional sectors and enables the accurate measurement of masses and allows determination of molecular formulae

Question 2

Mass Analysers (Quadrupoles)

Answer 2

Ions of different mass sequentially scanned through analyser (filter) by varying RF potentials of rods

Question 3

Mass Analysers (ToF-MS)

Answer 3

All ions accelerated to same energy, high velocities for lighter ions. Pulse of ions pass through drift tube where light ions traverse more rapidly.

Flight time is recorded

Question 4

Mass Analysers (RToF-MS)

Answer 4

Reflectron uses rings/grids to act as a mirror. Mirror compensates for the spread in KE of ions as they enter the drift tube.

Improves resolution of instrument.

Question 5

Mass Analysers (ToF Advantages)

Answer 5

• Multiplex Advantage (all ion masses recorded per pulse)
• Mechanically Simple
• Easily miniaturised
• Pulsed operation (suits pulsed sources such as lasers)

Disadvantage:
- Needs ion storage/traps to hold ions