Mass spectrometry

Question 1

Time of flight mass spectrometer is a device that enables what?

Answer 1

It enables substances to be analysed by determining the masses of ions formed

Question 2

Describe the 4 stages involved in analysing a sample?

Answer 2

1) Electron Spray Ionisation - sample is dissolved in a volatile solvent and injected through a fine hypodermic needle and subjected to a high voltage, forming a positively charged ion.
2) Acceleration - positively charged ions are accelerated towards a negatively charged electrode. This provides all ions with the same Kinetic Energy
3) Ion Drift - positively charged ions are electrostatically attracted to the negative charged cathode.
4) Ion detection and data analysis - ions of different masses are detected electronically and produce a small, varying electrical current that can be amplified and displayed on a computer. A mass spectrum is produced

Question 3

If there are 4 peaks in a spectrum how many isotopes are present?

Answer 3

4

Question 4

What is relative atomic mass (Ar)?

Answer 4

The average mass of an atom compared with 1/12th the mass of an atom of 12C. Which has the value of 12.0000 on this scale.

Question 5

What is relative molecular mass (Mr)?

Answer 5

The average mass of a molecule compared with 1/12th the mass of an atom of carbon-12. It is the sum of the relative atomic masses of the atoms in a molecule.