CH9080
UNIVERSITY OF WARWICK
MASTER OF SCIENCE EXAMINATIONS: MARCH 2010
MASS SPECTROMETRY
Time allowed
2 hours
Read carefully the instructions on the answer book and make sure that the particulars required are entered
on each answer book.
Percentages in square brackets are intended, as a guide to the time candidates should spend in answering
the corresponding part of the question.
Answer ANY TWO QUESTIONS
Question 1
a.
What is the structure associated with this positive ion electron impact mass spectrum?
[30%]
1
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b.
What is the structure associated with this positive ion electron impact spectrum? Assign structures to
each peak whose mass is noted on the spectrum. Draw 'fishhook' diagrams for each structure to explain
its formation.
[70%]
Question 2
a. Draw a diagram of a MALDI-TOF mass spectrometer, label the appropriate parts and describe their
function. What is the difference between "linear" mode and "reflector" mode?
[30%]
b. In a linear mode MALDI-TOF experiment, calculate the time-of-flight of singly charged ions using the
following parameters: Ion source potential, 20 kV; drift tube grounded. Drift tube length: 1.5 meters.
Mass of the ion: 1348.6 Da.
[20%]
c. Draw a diagram of an electrospray quadrupole ion trap mass spectrometer. Explain how the ion trap
works, and explain how ions can be "scanned" out into a detector.
[30%]
d. In a quadrupole ion trap, using the equation below calculate the low mass cut off (LMCO) for the trap if
it is run at 500 Vrf amplitude, 850 kHz, a pole-to-pole (z - axis) minimum inner distance of 12 mm, and a
z/r aspect ratio of 1.1.
LMCO is given by qz  0.908 
8eV
m (r 2  2 z 2 )
[20%]
2
2
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Question 3
a. Given the sequence of the peptide (VFDKDGDGYISAAELR), assign all the peaks in the spectrum
which are labeled with a mass (if possible). This is a CID/CAD MS/MS spectrum of the 2+ ion, at m/z
878.5. Hint: this is the same sequence as in part b, so the results should be consistent.
[50%]
3
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b. Given the sequence of the peptide (VFDKDGDGYISAAELR), assign all the peaks in the spectrum
which are labeled with a mass (if possible). This is an ETD MS/MS spectrum of the 2+ ion, at m/z
878.5. Hint: this is the same sequence as in part a, so the results should be consistent
[50%]
END
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Useful tables:
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