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Technique:
Mass Spectrometry is a technique that identifies the chemical structure by breaking up the molecule into mass fragments. Then measuring the intensity of the mass to charge ratio (called the mass spectrum), and comparing the result to a database of known compounds. Commonly used to quantify and identify organic compounds. There are techniques for the analysis of inorganic substances.
Application:
Mass Spectrometry provides the definitive identification of materials by the unique mass spectrum of the compound.
Mass Spectroscopy is used at Armstrong in a variety of ways.
• Detection and characterization of Ignitable Liquids.
• Detection and identification of Environmental threats.
• Forensic Identification & Quantification of Drugs of Abuse.
The Science Behind:
A mass spectrometer operates using four main stages; producing ions from the sample, separating the ions of different masses, detecting the number of ions at each mass/charge ratio and finally recording the data. The most common ionization methods are electron ionization and chemical ionization. Different methods are necessary for different types of samples analysis. Separating the ions is done with an analyzer using electric and magnetic fields in a vacuum, based upon the ions mass-to-charge ratio. Detection is done with a variety of different mass analyzers, each having advantages and disadvantages for the type of analysis required. Data collection and comparison to existing databases is required to fully utilize this information. The NIST database is the national standard but each operator and manufacturer has additional databases.
The data from analysis is commonly presented in the form of a mass spectrum. An example is below:
Other References:
On-line formal textbook of Mass Spectrometry:
American Society for Mass Spectrometry
Wikipedia Definition of Mass Spectroscopy
Analyzer - The type of instrumentation used to do the fragmentation & separation.
The most common types are the quadrupole & ion trap analyzers.
Chemical Ionization - The production of charged mass fragments by collision with a charged molecule. Examples of which are NH3 or CH3OH.
Detector - The component used to measure the mass fragments, almost universally, is an electron multiplier.
Electron Ionization - The production of charged mass fragments by electron impact.
GC/MS - Gas Chromatography with Mass Spectrometer as the Detector.
Mass Fragments - The mass to charge ratio for portions of the molecule.
Mass Spectrum - is a graphical presentation of the measurement of the individual mass fragments and the amount present.
MS/MS - A Mass Spectrometer connected in series with another Mass Spectrometer. Generally a GC is still the initial instrument.
NIST - National Institute of Standards and Technology is a non-regulatory federal agency within the U.S. Commerce Department.
Chemical Ionization - The production of charged mass fragments by collision with a charged molecule. Examples of which are NH3 or CH3OH.
Detector - The component used to measure the mass fragments, almost universally, is an electron multiplier.
Electron Ionization - The production of charged mass fragments by electron impact.
GC/MS - Gas Chromatography with Mass Spectrometer as the Detector.
Mass Fragments - The mass to charge ratio for portions of the molecule.
Mass Spectrum - is a graphical presentation of the measurement of the individual mass fragments and the amount present.
MS/MS - A Mass Spectrometer connected in series with another Mass Spectrometer. Generally a GC is still the initial instrument.
NIST - National Institute of Standards and Technology is a non-regulatory federal agency within the U.S. Commerce Department.