OCR AS Chemistry F331: Mass Spectrometry

HideShow resource information
  • Created by: LucySPG
  • Created on: 22-08-13 17:37
Preview of OCR AS Chemistry F331: Mass Spectrometry

First 124 words of the document:

Mass Spectrometry
Mass spectrometry is used to measure the atomic or molecular mass of different particles in a
sample.
The analysis takes place using a mass spectrometer.
Uses:
Mass spectrometry can be used to identify the mass and relative abundance of different
isotopes in an element such as the two isotopes of Chlorine, Chlorine-37 and Chlorine-35
The mass spectrometer can also be used to investigate the structure of molecular
compounds
Time-of- Flight Mass Spectrometer
Conditions for mass spectrometer:
- Low pressure so that sample particles do not collide with other particles
- Must be a gas
- Sample molecules must be charged so that they are positively charged ions

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

How a mass spectrometer works
Inlet valve Sample is introduced via a sample inlet
Most liquids vaporise at the low pressure in the machine but solids need to
be heated on special probes
The sample is turned into a gas
Ionisation area A heated filament produces high-energy electrons.
These electrons bombard any atoms or molecules in the sample and knock
electrons out.
Cations are formed. Charged ions are easier to manipulate than neutral
molecules.…read more

Page 3

Preview of page 3

Here's a taster:

Using Mass Spectra to Calculate Relative Atomic Mass and Relative Isotopic
Abundance
The mass spectrum of Boron
X-axis: shows the mass: charge ratio (m/z)
of each ion detected
Y-axis: intensity (%)
How to calculate the relative atomic mass
1. For each peak, read the % relative isotopic abundance from the y-axis and the relative
isotopic mass from the x-axis.
Multiply them together to get the total mass for each isotope.
2. Add up these totals
3.…read more

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »