Lab 2: Mass spectroscopy

Using mass spectrometry information about for instance pollutants in the surrounding atmosphere can be obtained.

http://kurslab.physics.kth.se/~berg/MassSpec1.jpg

A Quadrupole Mass Spectrometer (QMS) consists of gas inlets, vacuum pumps, and a detector unit, as shown above.

Task 1 Investigate how a QMS works by studying what parameters have to be used to let ions pass through the QMS, hittingand hit the lastend detector. Start with fluorine (F), m=19 amu. InVia the link below you can do the simulation by setting the angle to 90 degrees, the DC voltage to 40 V. Try different AC voltages to make the ions pass the instrument. Determine the AC voltage interval which will give you a mass resolution of 1 amu. Use Virtuella laborationer, Massspektroskopi, to perform a QMS simulation.

Task 2 qDetermine the constituents of a gaseous sample below. The intensities give the relative amounts of the atoms or molecules. The figure below shows the counter screen of a Mass spectrometer. One can choose different amplifying factors when recording the spectra, in this case 1X, 5X, and 50X (click to enlarge). ¶

http://kurslab.physics.kth.se/~berg/1x.jpg http://kurslab.physics.kth.se/~berg/5x.jpg http://kurslab.physics.kth.se/~berg/50x.jpg¶

Try to determine which atoms or molecules can be seen in the simple spectra and their intensity relations. Click the boxes and check how the signals change. Often one has to use several amplifications in order to get an intensity relation between the peaks.