mass+spectroscopy

One of the more widely used instruments in organic compound structure identification is mass spectrometry. As the name implies, it identifies molecules (or parts of molecules) by their mass-to-charge ratio.

As a molecule leaves a chromatographic device such as a gas chromatograph, it is fed into a mass spectrometer. The molecule is then blasted apart in one of a number of ways. These parts are then ionically charged and are susceptible to magnetic and electric fields. The mass spectrometer can "filter" the ions using these fields, and determine the mass-to-charge ratio. This translates into an atomic mass unit, which tells the user a bit about the parts of the molecule.

Try an online demo of a single sector MS, and one of a dual sector MS.



As mentioned above, there are a few different ways of [|fragmenting or ionizing] a molecule. Common ones include:
 * electrospray ionization
 * MALDI (matrix-assisted laser desorption/ionization)
 * ICP (inductively coupled plasma)

Once the ions are created, they are filtered by magnetic and/or electric fields (called mass analyzers) in a number of ways. Here are a few common types of mass analyzers:
 * TOF (time-of-flight)
 * quadrupole (magnetic)
 * FT-ICR (Fourier transform-ion cyclotron resonance)

The molecule is then detected at the end of its path by a device that senses changes in electric charge or production of current by the passing ion.

A very useful result from using a mass spectrometer is the __molecular mass__ of a compound. Also, fragments of known mass can lead to identification of functional groups or connectivity within the molecule.

Here are some nice videos on how some types of mass spectroscopy work.

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Here are some example outputs from a mass spectrometer: