sector field mass spectrometer

Sector field mass spectrometers separate ions based on their mass-to-charge ratio using static magnetic fields, often supplemented by static electric fields, which direct the ions onto a circular path, the deflection of which is used to determine the ion mass. Different sectors of magnetic and electric fields are combined with each other and the Lorentz force law is used to calculate the mass.

In the first step, the ions are accelerated in an electric field, which ensures that all ions have a similar kinetic energy.

In sectors with magnetic fields, ions with a higher m/z ratio (heavier ions or those with a lower charge) are deflected with less effect. Ions with a lower m/z ratio (lighter ions or those with a higher charge), on the other hand, are deflected to a greater extent.

In sectors with electric fields, the Lorentz force acting on the ions depends solely on the charge and the strength of the electric field. Such sectors are primarily used to further focus and separate the ions. The electric field can be used to adjust the energy distribution of the ions and to improve the resolution.

Double focussing devices, which focus ions with slightly different velocities on one point in the detector and simultaneously focus ions with a slightly inclined trajectory, offer the highest resolution.

The resolution capacity of sector field mass spectrometers reaches up to R = 100,000.

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