Mass spectrometry

Mass spectrometry, year 12 A, level

1. Mass spectrometry Monday, 15 April 2013

2. Layout of mass spectrometer

3. Mass spectrometer

4. Mass spectrometer

5. Key peaks Molecular ion peak – also called the parent ion. If the compound is R-H the peak is due to the R-H + ion – this is the loss of just one electron. Has the highest m/z value. Base peak – this is the most abundant peak – often associated with the loss of just one CH 3 group – so has m/z value which is 15 less than the molecular ion peak.

6. Some key points Molecules break up easily at weak bonds. Positive ions of secondary and tertiary carbon atoms are more stable than those from primary ions. The presence of the C=O bond makes ions more stable. The M+1 peak is due to an atom of 13 C being present in the sample

7. Mass spectra of ethanol

8. Mass spectra of propanal and propanone

9. Questions