Chemistry Unit 1 AS level : Mass spectrometry

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Created by: Lamees Hussein
Created on: 23-11-13 11:10

What is a Mass Spectrometer

The mass spectrometer is the most useful instrument for the accurate determination of relative atomic masses

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What are atoms converted into before commencing in the process?

Atoms are converted into posstive ions.

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What is the very first process that happens if the sample is not in a gaseous state?

If the sample is not in a gaseous state or a volatile liquid, it is vapourised first by heating.

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What happens during ionisation?

A beam of electrons are shot from an electron gun, whcih knocks out electrons from the atoms or molecules of the sample so that they from possitive ions.

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What happens after vaporisation and ionsation?

Acceleration: This is when the possitive electrons are attracted towards negatvely charged plates and are accelerated to a high speed. The speed they reach depends on their mass. The lighter the ion, the faster they go

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What happens after acceleration?

Deflection: The beam ions that did not make it to the negative plates, then moves into magetic field at right angles to its direction of travel. The magnetic field deflects the beam of ions into an arc of a circle.

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What happens after deflection?

Detection: The magnetic field is gradually increased so that ions of increasing mass enter the detector.Ions strike the detector, lose their charge and create a current proportional to the abundance of each ion.

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What is formed at the very end of the process?

Mass spectrum, which is normally presented as a graph of relative abundance against mass to charge ratio. The relative abundance can be calculated from this.

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