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Quadrupole Mass Spectrometry

المؤلف:  Max M. Houck، Jay A. Siegel

المصدر:  Fundamentals of Forensic Science

الجزء والصفحة:  P115-116

2026-07-01

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Quadrupole Mass Spectrometry

The quadrupole mass spectrometer has a set of four rods arranged in the corners of a square. Diagonally opposite rods have positive charges and the others, negative. As ions pass between the rods, the strength of the fields created by the rods are altered. This allows only certain mass/charge ratio ions to get through. Continual changing of the voltages across the rods permits all ions within a given range to be analyzed.

FIGURE 5.15 Diagram of a matrix-assisted laser desorption ionization (MALDI) mass spectrometer. A laser beam is focused on the sample chamber. The sample is embedded in a matrix that absorbs the energy from the laser and then transmits some of it to the sample. The sample ionizes and then is sent to the detector through a time-of-flight tube that separates the ions by their weight. One advantage of MALDI is that very little fragmentation of the ions takes place and molecular ions are very prominent.