Mass spectrometry book questions

Question 1

1, Briefly describe how the time of flight spectrometer works.

Answer 1

Time-of-Flight (TOF) is a mass analyser that utilises an electric field to accelerate generated ions through the same electrical potential, and then measures the time each ion takes to reach the detector.

Question 2

3, how are ions created? Why are the two spectra so different?

Answer 2

Because mass spectrometry measures the mass of charged particles, only ions will be detected, and neutral molecules will not be seen. Ions are created by giving electrons to a molecule (producing a negatively charged ion) or taking electrons away from a molecule (producing a positively charged ion)

Question 3

Describe EI (Electron Impact)

Answer 3

Sample components collide with fast electrons emitted from a filament and are thereby ionized. At the same time molecules are broken down. This breakage of molecules in mass spectrometry is called fragmentation. Therefore, with the EI method, molecular and fragment ions are created

EI is hard ionization method, so there occurs many fragments, sometimes losing molecular ion.

Question 4

Soft ionization techniques

Answer 4

A variety of ionization techniques are used for mass spectrometry. Two soft ionization methods – matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI)

Question 5

What are positive and negative ionization techniques

Answer 5

To put it simply, positive ions are molecules that have lost one or more electrons whereas negative ions are actually oxygen atoms with extra-negatively-charged electrons.