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IB Chemistry - Mass Spectrometer
Transcript of IB Chemistry - Mass Spectrometer
Where and why is it used? How do you use it?
A mass spectrometer measures the mass/charge ratio of particles Well, why is this important? This is important because without it, we would have never discovered isotopes
Isotopes were discovered because when a mass spectrometer gives different mass/charge ratios for the same element, the only possible reason is that they have different masses (because normally the charges are the same). A different mass for the same element can only mean it has more neutrons, because the protons must remain the same. The particles are first vaporised because they cant go through the mass spec. as a liquid.
Then they are ionized, to become positivly charged because uncharged particles will not be deflected by the magnet.
Next they are accelerated so they have the same kinetic energy.
Then they will go through the magnetic field where they will be defelected. The lighter particles are deflected more and the heavier ones are deflected less.
Lastly, they hit the dector plate so the deflection can be measured and recorded.
The entire thing is a vaccume so the ions are not colliding with air particles. (http://www.chemguide.co.uk/analysis/masspec/masspec.GIF) More about each part Ionisation The particles become ionized because inside this section of the mass spectrometer they are bombarded by electons, given off by an electrically heated coil.
Acceleration This happens becuase the ionisation chamber is very positivly charged, and now the ions are too, so they repel. Then they pass through three slits, which gradually reduce in charge. They get pushed through these, and onto the next area. Deflection This is where the ions are deflected by the magnetic field. The mass, and the charge of the ions determines how much they are deflected. This deterimines the mass/charge ratio. Most of the ions will have a +1 charge, but some may have a +2, by getting a second electron knocked off in the ionization chamber. Detection When the ions hit the metal plate they gain an electron from the plate. This space of electron that moved is filled by others, and this movement of current is detected by the plate, and recorded.
1. Identification of unknown compounds
2. Determining the isotopic composition of elements in a compound
3. Determining the structure of a compound by observing its fragmentation
4. Measuring the amount of a compound in a sample using carefully designed methods
5. Studying the fundamentals of gas phase in ion chemistry
6. Determining other physical, chemical or biological properties or compounds.
Many clinical chemists, pharmisutical companies, as well as other people who study in fields of chemistry, physics, and biochemistry use mass spectrometers. First you must, put the particles through the machine.
Then you must retrive the data This chart is what is recorded in a mass spectrometer, it is the mass/charge ratio of H20 (water). The charge for these should be 1, so as you can see the mass of 18 ( the most abundent one ) is accurate because the mass of H20, if using the most common isotopes is 18. H20 + 1e => H20 (+1 charge) + 2e This is a simple calculation for the process of H20 going through the mass spectrometer. So how much does a mass spectrometer cost? Roughly $60,000
Works Cited Clark, Jim. "The Mass Spectrometer." Chemguide: helping you understand chemistry.
10 Sept. 2011 <http://www.chemguide.co.uk/analysis/masspec/howitworks.html>. "Mass Spectrometers." LabX - New and Used Laboratory Equipment For Sale. 10 Sept. 2011 <http://www.labx.com/v2/newad.cfm?catID=12&gclid=CMeaxuiOlqsCFY8DQAodKTP3wA>. "PNNL: NCRR Proteomics Resource - Tutorial for Interpreting General Mass Spectra."
PNNL: NCRR Proteomics Resource for Integrative Biology. July 2011. 10 Sept. 2011
<http://ncrr.pnnl.gov/training/tutorials/mass_spec_tutorial.stm>. Sunstrand, Hamilton "Mass Spectrometer and its Uses." EzineArticles Submission. 22 August. 2008
10 Sept. 2011 <http://ezinearticles.com/?Mass-Spectrometer-and-Its-Uses&id=1432440>. "Waters: MS - Mass Spectrometry." Waters: Home. Waters. 10 Sept. 2011