Time Of Flight Mass Spectrometry

Question 1

How to work out the mass of one atom?

Answer 1

(mass number/avogadros constant) /1000

Question 2

What are the stages of time of flight spectometry?

Answer 2

Ionisation, acceleration, ion drift, detection

Question 3

What is electron impact ionisation and what does it form?

Answer 3

Electron gun firing high energy electrons at vapour sample to knock off one electron from each atom to form positive ions. Forms X(g)->X(g)+ + e-

Question 4

What is electrospray ionisation and what does it form?

Answer 4

Dissolving sample in volatile solvent to inject into chamber through a fine hypodermic needle that is positively charged so that the particles gain a proton and become positively charged. The solvent then evaporates, forming X(g)+H(g)+ -> XH(g)+

Question 5

How are the ions accelerated through the tube and why?

Answer 5

Accelerated by an electric field so they all have the same kinetic energy.

Question 6

How are ions distinguishable by the detector?

Answer 6

The lighter ions will travel faster and reach the detector first which generates a movement of electrons and hence an electric current which is measured.

Question 7

What is the equation for kinetic energy?

Answer 7

0.5mv*2

Question 8

What are the equations for time?

Answer 8

d/v
d√m/2KE