FLORIDA INTERNATIONAL UNIVERSITY Advanced Mass Spectrometry Piero R. Gardinali/Yong Cai/ Bruce McCord Revised on August 23, 2009
Feb 12, 2016
FLORIDA INTERNATIONAL UNIVERSITY
Advanced Mass Spectrometry
Piero R. Gardinali/Yong Cai/ Bruce McCord
Revised on August 23, 2009
First Steps
Introduction to mass spectrometryDefinition of common termsA generic mass spectrometerFormation of ionsThe mass spectrumWhy doing mass spectrometry?
Survey:
No previous knowledge of MS?Know basic operation but no theory?Comfortable user?I can do a manual tune!I took your MS class (did you pass?)
I will be helping with the class!
Mass spectrometry is a powerful analytical technique that is used to identify unknown compounds, to quantify known materials, and to determine the structural and chemical properties of molecules.
Detection of compounds can be accomplished with very minute quantities. (as little as 10 -12 grams).
Anode raysGoldstein
1886
Electron m/zThomson
1897 (Nobel Prize in 1906)
Magnetic deflectionPositive Ions
Wein1898
Unit of chargeMillikan & Fletcher
1909
First parabola Spectrograph
Thomson1912
Metastable ionsThomson
1913
1918
1919
1940Nier
U-235
1956
19531952
1946
1956Exact Mass
Benyon
1969
1978
1980
1981 1987
19681988
1974
1966
Develop first MS with velocity focusing,
Nobel Prize in 1922
Fenn developed ESI in 1988; Concept was proposed by Dole in 1968. Fenn received Nobel Prize in 2002
Progress in Experimental Methods and Improvements in Solution, Sensitivity, Mass
Range, and Accuracy • Resolution: m/Δm from 13 (Y1913) to 8,000,000
(Y1998)• Sensitivity: as low as 800 yoctomoles (~480
molecules)( measure peptide in solution)• Mass range: several tens of millions D (40.5 MD)• Accuracy: isotope measurement
Did you know that mass spectrometry is used to…
• Detect and identify illegal steroids in athletes • Monitor the breath of patients during surgery • Determine the composition of molecular species found in space • Determine whether honey is adulterated with corn syrup • Locate oil deposits by measuring petroleum precursors in rock • Monitor fermentation processes for the biotechnology industry • Detect dioxins in contaminated fish, water and soil • DNA Fingerprinting! • Establish the elemental composition of semiconductor materials • Speed the development of new drugs
Basic concepts
The basis of mass spectrometry (MS) is the production of ions that can be separated or filtered according to their mass to charge ratios (m/z) and detected. The resulting mass spectrum is a plot of the abundance of the produced ions as a function of the m/z ratio.
Still spectroscopy?
What is a mass spectrometer?
Illustration of the basic components of a mass spectrometry system.
IonizationSource
MassAnalzyer Detector
Inlet all ionsselected
ionsData
System
%R
elat
ive
Abu
ndan
ce
1265
.000
0321
843.
00
360
421.
0
m/z
The mass spectrum
What do I get from the instrument?
Mass spectrum of methanol by EI, presented as a graph and a table
More definitions
Base peakThe most intense peak of a mass spectrum is called base peak
• Usually mass spectra are normalized to the most intense peak by setting its intensity to 100 % relative intensity.
• This offers the advantage of being independent from absolute intensities which may extremely vary between measurements.!!!!!!
• Thus, normalization to the base peak makes comparison of spectra much easier.
More about ions and fragments
Molecular ion
The molecular ion is directly created from the corresponding neutral molecule by addition or removal of one electron
i.e. it still has the same molecular formula.
The molecular ion is usually labeled as M+. or M-., respectively.
Quasimolecular ions are different from molecular ions in that they are formed by addition or removal of some ionic particle.
Ways to define and calculate the mass of an atom, molecule or ion
• Average mass: calculated using the atomic weight, which is the weighted average of the atomic masses of the different isotopes of each element in the molecule.Often used in stoichiometric calculations.
• Nominal mass: calculated using the mass of the predominant isotopes of each element rounded to the nearest integer value that corresponds to the mass number.
• Monoisotopic mass: calculated using the extract mass of the most abundance isotope for each constituent element.Use monoisotopic mass if possible in MS
Differences between Masses
C20H42 C100H202
Nominal: (20 x 12) + (42 x1) = 282 u (100x12) + (202x1) = 1402uMonoisotopic: (20 x12) + (42 x 1.007825) = 282.33 (100x12) + (202x1.007825) = 1403.5807Average: (20 x 12.011) + (42 x 1.00794) = 282.5535 (100x12.011)+(202x1.00794) = 1404.7039
HOW DO I CREATE AN ION?
M + e- M.+ + 2e-
HOW DO I CREATE AN ION?
M + e- M.+ + 2e-
HOW DO I CREATE AN ION?
M + e- M.+ + 2e-
An then what?
HOW DO I CREATE AN ION?
M + e- M.+ + 2e-
Radical cation
•Ion free path ???
•Free mean path ???
K: Boltzmann constant, T: temperature (in K)p: pressure (in Pa): collision cross-section (in m2)
P in pascals
P in milli Torrs