WHAT IT IS
Magnetic Sector Mass Spectrometry is a form of mass spectrometry that uses a magnetic field to separate ions based on their mass-to-charge ratio (m/z).
HOW IT WORKS
In a magnetic sector mass spectrometer, ions are generated in an ion source (via electron impact, thermal ionization, or plasma), and accelerated through an electric field into a curved magnetic field region. As ions enter the magnetic sector, the Lorentz force causes them to follow curved paths. The radius of curvature depends on their velocity and mass-to-charge ratio.
Heavier ions or ions with lower charge are deflected less, while lighter ions or higher-charge ions are deflected more. By adjusting the magnetic field or ion acceleration energy, ions of different m/z can be focused onto a detector, such as a Faraday cup or an electron multiplier.
In multicollector magnetic sector instruments, several detectors are aligned at fixed positions to simultaneously measure multiple isotopes, improving precision and speed for isotope ratio analysis.
ADVANTAGES
High Mass Resolution: Capable of resolving ions with very small mass differences, essential for distinguishing isobaric species and analyzing complex mixtures.
Precise Isotope Ratio Measurements: Widely used in applications such as radiogenic isotope geochemistry and nuclear forensics due to excellent stability and reproducibility.
Stable Long-Term Performance: Magnetic fields and ion optics provide consistent results over extended runs, important for low-signal or high-precision applications.
Compatibility with Various Ion Sources: Can be used with gas, solid, and plasma ion sources for a wide range of sample types.
Multi-Detector Capability: Allows simultaneous collection of multiple ion signals, reducing noise and improving accuracy in isotope ratio measurements.
CHALLENGES AND LIMITATIONS
Size and Complexity: Typically larger and heavier than quadrupole or TOF instruments, requiring more space and infrastructure.
High Cost: The precision components and powerful magnets make these instruments expensive to build and maintain.
Slower Scanning Speed: Because mass selection relies on physical magnetic deflection, scanning across a wide m/z range is slower than in other analyzer types.
Magnetic Drift and Hysteresis: Magnetic field strength can vary over time, requiring frequent calibration or stabilization systems.