What is a Double Focusing Mass Spectrometer?
Like all mass spectrometers, a double focusing mass spectrometer has an ion source, a mass analyzer, and a detector. In place of a quadrupole or ion trap mass analyzer, an electrostatic sector separates ions based on their kinetic energy (1/2mv2) and a large magnet separates ions based on their momentum (mv). Ions having many m/z ratios pass through an entrance slit into the mass analyzer while at any instant, only ions within a very narrow spread of m/z ratio are focused onto and pass through the exit slit to the detector. Hence, the ions have been “double focused” for both kinetic energy and momentum. Relatively few double focusing mass spectrometers are available compared to quadrupole and ion trap mass spectrometers due to their high cost (about $500,000 vs $100,000), their large size (an entire room vs a bench top), and their difficulty of use (since research flexibility is emphasized rather than specific production capabilities for which many variables are permanently set). Defin
