Name: how mass spectrometers sort ions
Uploaded: 2024-04-04T10:51:33.000Z
Duration: 1 min 16 s
Channel: JoVE

The mass spectrometer ionizes molecules and produces a mass spectrum from the fragment distribution.
It performs three functions: ionization of molecules or atoms, separation of the ion fragments, and detection of ions.
In electron ionization, a common ionization method, a vaporized sample in the ionization chamber bombarded with a high-energy electron beam produces radical cations. The radical cation quickly fragments into neutral molecules, radicals, and cations.
The cations are then accelerated into an analyzing chamber by a series of negatively charged accelerator plates.
Many common analyzers apply a magnetic or electrical field to the analyzing chamber, which bends the trajectories of ions based on their mass and charge.
Only ions of particular m/z values have the exact trajectory to pass through the narrow slit placed in front of the ion detector for a given magnetic or electrical field.
By altering the field, the mass analyzer scans through a range of ion masses, with their abundances recorded in the mass spectrum.

massaspectrometer

Mass Spectrometers

Deze les beschrijft de instrumentatie van een massaspectrometer: een fysiek instrument om massaspectrometrie op analyt moleculen uit te voeren en de karakteristieke massaspectra vast te leggen. Dit wordt bereikt via drie hoofdfuncties:

<ol>
	<li>Omzetting van de analyt atomen/moleculen in de gasfase in een straal van positief of negatief geladen ionen door ionisatie.</li>
	<li>Scheiding van de geladen soorten op basis van hun massa-ladingsverhouding.</li>
	<li>Registratie van de relatieve abundantie van elk type ion.</li>
</ol>

In de ionisatiekamer van de massaspectrometer wordt de verdampte analyt in een vacuüm getroffen met hoogenergetische elektronen. De energie van het elektron is ongeveer 70 eV, voldoende om een ​​elektron van de analyt te strippen. Het resulterende moleculaire ion fragmenteert verder in geladen soorten en neutrale moleculen. De massaspectrometer registreert alleen de massa van geladen soorten, omdat de lading de controle van moleculen door een elektrisch of magnetisch veld mogelijk maakt.

Het moleculaire ion en zijn geladen fragmenten worden versneld door een reeks negatief geladen versnellerplaten die op de juiste manier in de detector in de analysekamer zijn geplaatst. Op het pad tussen de versnellerplaat en de detector wordt een magnetisch veld aangelegd, waardoor een curve in het pad van geladen soorten ontstaat. Bij een constant magnetisch veld hangt de kromtestraal af van de moleculaire massa van de geladen soort. Het plaatsen van een spleet vóór de detector zorgt ervoor dat alleen geladen soorten met een bepaald molecuulgewicht de detector bereiken.

Door het magnetische veld te variëren, kunnen de geladen soorten met alle molecuulgewichten bij de detector worden geregistreerd, voor elke soort met een uniek molecuulgewicht tegelijk. Door alle magnetische velden te scannen, geeft de massaspectrometer informatie over de relatieve abundantie van alle geladen soorten als het massaspectrum.

This lesson details the instrumentation of a mass spectrometer&#8212;a physical instrument to perform mass spectrometry on analyte molecules and record ...

Education

JoVE Core

Analytical Chemistry

Analytische chemie

Unit 1

Principles of Mass Spectrometry

Principes van massaspectrometrie

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

how mass spectrometers sort ions

A mass spectrometer sorts charged ions by their mass-to-charge ratio and records their relative abundance. It turns vaporized analyte molecules into ions, separates them, and then measures the signal from each type of ion.

The process begins in the ionization chamber. The analyte is in the gas phase inside a vacuum, and it is struck by high-energy electrons. The electrons have about 70 eV of energy, which is enough to remove an electron from the analyte and form a molecular ion.

After ionization, the molecular ion can break into charged fragments and neutral molecules. The instrument records only the charged species. Their charge allows them to be controlled by electric or magnetic fields.

Next, the molecular ion and its charged fragments are accelerated by a set of negatively charged accelerator plates. These plates move the ions toward the detector in the analyzing chamber. A magnetic field bends the path of the ions as they travel between the accelerator plate and the detector.

At a constant magnetic field, the radius of the curved path depends on the molecular mass of the charged species. A slit placed in front of the detector helps admit only ions with a particular molecular weight. By changing the magnetic field, ions of different molecular weights can reach the detector one at a time.

As the instrument scans through the magnetic fields, it records the relative abundance of the charged species. The result is a mass spectrum. This spectrum shows the ions detected across the range of molecular weights.

How Mass Spectrometers Sort Ions

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Mass spectrometry fragmentation patterns show how a molecular ion breaks apart after ionization. When a molecule loses an electron inside the mass spectrometer, its structure becomes unstable. The ion then fragments at bonds that often produce the most stable pieces. One common pattern is cleavage of a single bond in the molecular ion. This break forms a radical and a cation. The bond can split in more than one way, but the favored path is the one that gives the more stable carbocation rather...

mass spectrometers

A mass spectrometer sorts charged ions by their mass-to-charge ratio and records their relative abundance. It turns vaporized analyte molecules into ions, separates them, and then measures the signal from each type of ion. The process begins in the ionization chamber. The analyte is in the gas phase inside a vacuum, and it is struck by high-energy electrons. The electrons have about 70 eV of energy, which is enough to remove an electron from the analyte and form a molecular ion. After...

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Reading Peaks in a Mass Spectrum

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Mass Analyzers and Ion Separation

Mass analyzers separate ions by their mass-to-charge ratio, or m/z, in a mass spectrometer. After a sample is vaporized in the ionization chamber, it is hit with a high-energy electron beam. This creates a radical cation and also produces neutral molecules, radicals, and cations. Negatively charged accelerator plates then push the cations into the mass analyzer, where they are sent on to the detector. Several mass analyzer designs are commonly used. These include magnetic sector,...

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key terms and concepts

Learn how a mass spectrometer ionizes analytes, bends charged ions with a magnetic field, and records a mass spectrum for each molecular weight.

How Mass Spectrometers Sort Ions | JoVE K12

analytical chemistry

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How Mass Spectrometers Sort Ions

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