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Advanced Mass Spectrometry. F LORIDA I NTERNATIONAL U NIVERSITY . Piero R. Gardinali /Yong Cai/ Bruce McCord. Revised on August 23, 2009. First Steps. Introduction to mass spectrometry Definition of common terms A generic mass spectrometer Formation of ions The mass spectrum

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F lorida i nternational u niversity

Advanced Mass Spectrometry

FLORIDA INTERNATIONAL UNIVERSITY

Piero R. Gardinali/Yong Cai/ Bruce McCord

Revised on August 23, 2009


First steps

First Steps

  • Introduction to mass spectrometry

  • Definition of common terms

  • A generic mass spectrometer

  • Formation of ions

  • The mass spectrum

  • Why doing mass spectrometry?


Survey

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!


F lorida i nternational u niversity

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).


F lorida i nternational u niversity

1968

1988

Fenn developed ESI in 1988; Concept was proposed by Dole in 1968. Fenn received Nobel Prize in 2002

1918

Anode rays

Goldstein

1886

Electron m/z

Thomson

1897(Nobel Prize in 1906)

Magnetic deflection

Positive Ions

Wein

1898

Unit of charge

Millikan & Fletcher

1909

First parabola

Spectrograph

Thomson

1912

Metastable ions

Thomson

1913

1966

1953

1969

1952

1946

1980

1940

Nier

U-235

1956

Exact Mass

Benyon

1974

1978

1981

1987

1956

1919

Develop first MS with velocity focusing, Nobel Prize in 1922


Progress in experimental methods and improvements in solution sensitivity mass range and accuracy

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

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

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.


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Still spectroscopy?


F lorida i nternational u niversity

What is a mass spectrometer?

Illustration of the basic components of a mass spectrometry system.

Ionization

Source

Mass

Analzyer

Detector

selected

ions

Data

System

Inlet

all ions


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The mass spectrum

%Relative Abundance 

1265.0000321

843.00

421.0

360

m/z 


F lorida i nternational u niversity

What do I get from the instrument?

Mass spectrum of methanol by EI,

presented as a graph and a table


More definitions

More definitions

  • Base peak

    The 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

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

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

Differences between Masses

C20H42C100H202

Nominal: (20 x 12) + (42 x1) = 282 u(100x12) + (202x1) = 1402u

Monoisotopic: (20 x12) + (42 x 1.007825) = 282.33(100x12) + (202x1.007825) = 1403.5807

Average: (20 x 12.011) + (42 x 1.00794) = 282.5535(100x12.011)+(202x1.00794) = 1404.7039


F lorida i nternational u niversity

HOW DO I CREATE AN ION?

M + e- M.+ + 2e-


F lorida i nternational u niversity

HOW DO I CREATE AN ION?

M + e- M.+ + 2e-


F lorida i nternational u niversity

HOW DO I CREATE AN ION?

M + e- M.+ + 2e-

An then what?


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Radical cation

HOW DO I CREATE AN ION?

M + e- M.+ + 2e-


F lorida i nternational u niversity

  • 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


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