Mass Spectrometry Courtesy www.lab-initio.com Purpose of Mass Spectrometry
Mass Spectrometry Courtesy www.lab-initio.com Purpose of Mass Spectrometry Produces Produces spectra spectra of of masses masses from from the the molecules molecules in in aa sample sample of of material, material, and and fragments fragments of of the the molecules. molecules. Used Used to to determine
determine the the elemental elemental composition composition of of aa sample sample the the masses masses of of particles particles and and of of molecules molecules potential potential chemical chemical structures structures of of molecules molecules by by analyzing analyzing the the fragments fragments the
the identity identity of of unknown unknown compounds compounds by by determining determining mass mass and and matching matching to to known known spectra spectra the the isotopic isotopic composition composition of of elements elements in in aa molecule molecule Stages The ionizer converts
some of the sample into ions. Mass analyzers separate the ions according to their mass-to-charge ratio. The detector records either the charge induced or the current produced when an ion passes by or hits a surface Mass Spectrometry Methods Ionization method Typical Analytes Sample Introduction Mass Range Electron Impact (EI)
Relatively small volatile GC or liquid/solid probe to 1,000 Daltons Chemical Ionization (CI) Relatively small volatile GC or liquid/solid probe to 1,000 Daltons
Electrospray (ESI) Peptides Proteins nonvolatile Liquid Chromatography or syringe to 200,000 Daltons Sample mixed in viscous matrix to 6,000 Daltons Sample mixed in solid matrix
to 500,000 Daltons Fast Atom Bombardment (FAB) Matrix Assisted Laser Desorption (MALDI) Carbohydrates Organometallics Peptides nonvolatile Peptides Proteins Nucleotides http://www.chem.arizona.edu/massspec/intro_html/intro.html Mass Spectrum of CO2 Molecular ion peak [CO2]+ = 44 Fragment Peaks [C]+ = 12 [O]+ = 16
[CO]+ = 28 Mass Spectrum of Bromine, Br2 Bromine has two isotopes: 50.69% 79 Br and 49.31% Molecular Ion Peaks [79Br81Br]+ [79Br79Br]+ Fragments 79 Br+ 81 Br+ [81Br81Br]+ 81 Br
Practice: Methyl Bromide, CH3Br Answers: Methyl Bromide, CH3Br [CH381Br]+ [CH81Br]+ and [CH379Br]+ [CH281Br]+ [CH3]+ [C81Br]+ and [CH279Br]+ [CH79Br]+ [81Br]+ [79Br]+ [C79Br]+ Practice: Methylene Chloride (CH2Cl2) Chlorine is 75.77% 35 Cl and 24.23% 37 Cl
Practice: Vinyl Chloride (CH2CHCl) Chlorine is 75.77% 35 Cl and 24.23% 37 Cl Spectra of Larger Molecules Spectra of large molecules have many fragments, and the interpretation of their spectra is beyond the scope of this course. Codeine, C18H21NO3 Toluene ( C7H8) Fragmentation **Note that the molecular ion peak is NOT the dominant peak in the spectrum Mass Spectrometry in Forensics Mass
Mass spectrometry spectrometry is is used used to to confirm confirm the the identify identify of of unknowns, unknowns, such such as as illegal illegal drugs drugs Unknowns Unknowns are are often often not not pure, pure, and and must must be be separated separated from
from aa mixture mixture Gas Gas chromatography chromatography is is used used to to separate separate the the components components of of the the mixture mixture Mass Mass spectrometry spectrometry fingerprints fingerprints the the components, components, so so that that they they can
can be be matched matched to to existing existing known known spectra spectra Mixture Gas Chromatograph Mass Spectrometer
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