Sep 14, 2023
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The other day I got to use this TIMS (Thermal Ionization Mass Spectrometer ) and it is so old! The computer program doesn't use a mouse, just keyboard entries and can't connect to the Internet. My prof said he picked it up from WashU one weekend and brought it home.
Can u explain me the peaks in mass spectrum?
Thank you for the awesome question!
Mass Spectrum Peaks 101
What exactly are they?
D:Ā Mass Spectrometry is an analytic technique that utilizes the degree of deflection of charged particles by a magnetic field to find the relative masses of molecular ions and fragments. [x]
So what does that mean?
Each peak in the mass spectrum represents fragments thatĀ ābreakā off into ions when a compound is charged. There are key peaks to look out for in a mass spectrum thatāll help you determine the molecular weight of a compound and its substituents.
Base Peak: the peak that has the highest intensity (100%) and is most abundant ion in the compound.Molecular Ion Peak (M): most likely the peak that indicates the weight of the compound.
Important Information -
Halogens: in some cases, youāll see peaks at M+1, M+2, etcā¦ These peaks will help you determine the ratio and amount of halogens that are present. For iodine, aĀ ālarger than normalā peak will be present at 127 m/z. Though, watch out for fluorine because it goes unnoticed in a mass spectrum. Instead, youāll have a molecular ion peak of -18 (ish) weight due to the fluorine being replaced with a carbocation.Ā
Nitrogen: itās simple to guess if thereās a nitrogen or not. The molecular ion peak will have an odd value.Ā
Trends: after looking at hundreds of mass spectrums, youāll start to notice similar peaks.
Tips -
I first look at the parent peak and molecular ion peak and subtract their difference. If you get a value of 15 m/z then you definitely have a methyl group in the compound. If you get 18 m/z then you have some type of alcohol group that left as water.Ā
Label each fragment peak as a guess to what it could be. You wonāt exactly get the whole compound from just looking at an MS, but it gives you a good start!
Watch out for those halogens!!!
Practice Problems - [x] [x] [x] [x] [x]
Hope this helps! xx
Metabolomics plays an important role in medicine production, diagnostics, biologics optimization and so many. You cannot carry out thisā¦
Health Ranger used āforensic acousticā analysis to determine there was a second shooter in Vegas on night of slaughter
Health Ranger used āforensic acousticā analysis to determine there was a second shooter in Vegas on night ofĀ slaughter
(General News)Ā Natural NewsĀ founder/editor Mike Adams,Ā the Health Ranger, used scientific methods to determine that there were two shooters, not just one ā 64-year-old Stephen Paddock ā who attacked some 22,000 people at a country music event in Las Vegas Oct. 1, killing 58 and wounding more than 500.
The technique he used is one that he often uses when conducting other research and testing atā¦
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Our TOF (time-of-flight mass spectrometer) is finally working, after 3 months of repairs. The instrument gods have smiled down upon us this day.
any tips on how to interpreting mass spec, ir, and nmr graphs?
Try to remember key functional group stretching frequencies for both IR and NMR. For IR, these are ketones, aldehydes, alcohols, carboxylic acids, and triple carbon bonds. For NMR, both H and C, there will be different stretching frequencies for whether the carbon is primary, secondary, tertiary, or quaternary (bonded to 1, 2, 3, or 4 other carbons respectively), as well as if thereās any oxygens or benzene rings present. For mass spec, you have to find the highest signal (as in furthest along the x-axis). Smaller signals from fragmentation can indicate which functional groups you have. One key trip-up that CHEM2001 likes to give is a symmetrical molecule. According to both C ad H NMR, you only have 4 carbons, but according to mass spec, you have 8, with an oxygen separating them (an ether). I got this in the structure determination in-class test. You just have to practice as much as possible and go through some worked solutions if youāre still having trouble.