Mass spectrometry

[JFK90787]

Mass spectrometry wasn't mentioned once in my review (TPR) but I see at least one question on it on almost every other test, usually in the form of a graph or something, and I have no idea what the hell is going on. Does anyone know a concise guide online of what we need to know about Mass Spectrometry for MCAT purposes? I can find tons of MS info on google but it's all fairly dense and I don't think I'll need to know that much for this test

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[LostInStudy]

Try Chad's lectures here, he has a good way of putting things concisely. Other than that I would just suggest looking it up yourself in your TPR book. There's no way around memorizing a few of the main values.

Hope this helps,

-LIS

 

[JFK90787]

Where is the mass spec info there? I looked under the G chem thread and did ctrl+F mass spec with no results

Edit: I should clarify I'm looking for the type of mass spec that they include in the G chem section, not HNMR or IR/UV spec

 

[whiteshadodw]

Where is the mass spec info there? I looked under the G chem thread and did ctrl+F mass spec with no results

Edit: I should clarify I'm looking for the type of mass spec that they include in the G chem section, not HNMR or IR/UV spec

ok so check it. the idea behind mass spectrometry is that you want to separate molecules based on mass. ie, you have K-Cl, but you have K-Cl^17 and K-Cl^18. Do you see how these two have separate masses? You can separate these based on mass. Other applications include identifying amino acid sequence in a protein and identifying fats or other compounds. i'll briefly try to explain how they do it.

every spectrometer has an ionizer. the ionizer creates ions on proteins/fats/etc (pretty much anything). you can have proteins where just one atom gets ionized, or MULTIPLE atoms in the protein get ionized. old spectrometers utilize electric fields (i'm not sure about current ones, there are many mass spec methods/machines nowerdays but if you learn how the most basic ones work you'll understand mass spec). what happens when you pass a charged particle through an electric field or magnetic field (you should know this from studying physics, EM chapters specifically). the atoms are accelerated towards a certain direction, and because they have different mass they have different accelerations, right (same force though, same B field, F=ma). based on the time of flight (TOF) or distance travelled you can figure out the mass. and you can also figure out the charges they have which would also effect the force due to B field. you can use the mass to charge ration (m/z) to determine mass of compounds, composition of compounds etc. btw, i left out a bunch of stuff about how to determine the sequence of a peptide, but the link should be better.

http://www.chem.arizona.edu/facilities/msf/index.html

check the powerpoints on the bottom left under "biochemistry lab"