Time Of Flight Mass Spectrometry

Question 1

What does each letter stand for
V
I
A
I
D
D
?

Answer 1

Vacuum
Ionisation
Acceleration
Ion drift
Detection
Data analysis

Question 2

Why is there a vacuum?

Answer 2

To prevent ions produced from colliding with air molecules

Question 3

What happens in ionisation?

Answer 3

Sample is dissolved in a volatile solvent

And is forced through a fine hollow needle connected to the positive terminal of a high voltage supply

Tiny positive charged droplets are produced

Solvent evaporates and droplets get smaller until many contain a single positively charged ion.

Question 4

What happens at the step of acceleration ?

Answer 4

Positive ions are attracted to a negatively charged plate which accelerates it.

Light ions/ more highly charged ions achieve a higher speed.

Question 5

What happens in the ion drift?

Answer 5

Ions pass through a hole in the negative plate forming a positive beam and travel along the flight tube.

Question 6

What happens at the detection phase ?

Answer 6

Lighter ions will arrive at the detector quicker than heavier ions with the same charge.

Flight time is recorded.

Positive ions pick up an electron from the detector, causing a current to flow.

Question 7

What happens in data analysis ?

Answer 7

Signal from detector is passed to a computer which generates a mass spectrum.

Question 8

What is the acronym for TOF?

Answer 8

VIA IDD

Via Imogen’s Dark Days