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Mass Spectrometry

The Basics...

Mass spectrometry is used to identify chemical compounds. For example, a forensic examiner may need to know if a drink was poisoned. To do this they would first use chromatography to separate the various compounds in the drink from one another and then use a mass spectrometer to identify each compound.

The mass spectrometer works by ionizing a compound (basically pelting it with electrons) which will break the compound into smaller parts. Then the machine sends these parts through a magnetic field to a detector which is used to determine the masses and charges of these smaller parts. A graph is created that shows these mass to charge ratios. The graph is then matched to a known graph or the graph can be used to reconstruct what the initial compound must have been.

The Details...

Mass Spectrometry Video - this YouTube video gives the principals of mass spectrometry. View it and then use the websites below to learn to interpret the output.

Mass Spectrometry Tutorial - This site has a nice introduction and examples and quizzes to test your interpretation. You don't need to know every mass spec on the site, but make sure you have a good idea on how the graphs are created and how to read one.

Pedagogica Mass Spec Tutorial - an excellent interactive to help understand what is happening inside the machine. (this tutorial is already installed on our classroom computers so don't click the link at school - instead, open the S-drive, go to the PedagogicaActivities folder and double-click on the file 'workspace.jar'. Then open the CCAtoms folder and open the Mass Spec tutorial)

Why is there that M+1 peak? - This helps explain why there is often a small peak one or two units above the total mass. (hint: isotopes)


If you understand the above, you should be good for the purposes of our class. The sites below are just resources for more information should you ever need it.

ASMS What is Mass Spectrometry - explains mass spectrometry and why you would use it. It also shows the characteristics of a mass spectrum graph.

Spectral Database for Organic Compounds - type in the compound and get a variety of spectral graphs.

Simulate MS for Elements - this is a pretty neat java interactive where you can type in an element and see it's simulated MS based on isotopes.

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