1. Mass Spectrometry

2. List the 5 Main steps in Mass spectrometry ?
Starter Activity.
List the 5 Main steps in Mass spectrometry ?
What happens at each of these steps ?

3. Mass Spectrometry
Vaporisation, Ionisation, Acceleration, Deflection and detection

4. Mass Spectrometry
In module 1 – we used mass spectrometry to determine
The relative abundances of different isotopes of a sample of an element and hence deduce the relative atomic masses of the elements.
Identify the peak with the largest mass/charge ratio and use this to determine the identity of the molecule.

5. C2H5OH (g)  [C2H5OH]+• (g) + e-
Mass Spectrometry
When an ethanol (molecule) sample is introduced in to the mass spectrometer it behaves in the same way as an element. In that the sample is ionised – and electrons are ‘fired’ at it to knock electrons from the sample.
Ethanol has the formula C2H5OH
C2H5OH (g)  [C2H5OH]+• (g) + e-

6. C2H5OH (g)  [C2H5OH]+• (g) + e-
Mass Spectrometry
C2H5OH (g)  [C2H5OH]+• (g) + e-
At the ionisation stage
An electron will be ‘knocked’ off the molecule - forming the molecular ion.
When an electron is removed an single unpaired electron remains...
The ion has a positive charge
This ion is known as the molecular radical ion
M+• molecular ion– accelerated in the mass spectrometer, deflected and then detected.

8. [C2H5OH]+• (g) Mass Spectrometry
Are the heaviest ions that can be produced by a sample of ethanol and thus will produce a peak on the mass spectrum - known as the molecular ion peak.
The m/z value of the peak is the molecular mass.
Thus the mass of ethanol is 46.

9. Why so many peaks.
Many of the ions then break further – some of the bonds are broken upon ionisation and thus we have smaller ions of smaller molecular mass. Only fragments with a positive charge will be detected.
IONISATION
MOLECULAR ION
FRAGMENTION
RE-ARRANGEMENT

10. Ethanol. To analyse the Ethanol we need: 9 people to be Ethanol
1 person to ionise the Ethanol
1 person to be the detector
The students are to role play as the Ethanol goes through the MS and is broken up into fragments. Students who are the detector write down the m/z ratio of each fragment. They repeat this process in order to get a list of different fragment m/z ratios and compare to the mass spectra on slide 12.

11. Fragmentation of Ethanol
Molecular mass
CH3+ 15
CH3CH2+ 29
CH2+ 14
OH+ 17
CH2OH+ 31

12. CH2OH+ This is the most stable fragment formed (base peak)
CH3CH2OH+
CH3CH2+
CH3+
CH2+
OH+

13. High Resolution mass spectrometer
A problem arises when using conventional mass spectrometry. The molecular mass of propane is 44 The molecular mass of Ethanal is also 44. How are we able to distinguish between these two molecules given that the molecular ion formed in the conventional mass spectrometer will form peaks at 44m/z.

14. High Resolution mass spectrometer
This can be resolved by using a high resolution mass spectrometer – which works in the same way as a conventional mass spectrometer – however it is more accurate. Mr of Propane = Mr of Ethanal =
Element
Mass 1H
1.0
14N
14.0
16O
16.0
12C
12.0
Element
Mass 1H
1.0078
14N
16O
12C
Peaks formed on spectrum.

15. Into 3 groups please.

16. Give a fragmentation list for the following :
Neon
Chlorine
Hexane
3-Phenyl-2-propenal (C9H8O)
2-Butenoic acid (C4H6O2)

17. Homework. To create a list of fragments from the analysis of morphine.
Extension : How does it differ to Codeine ?