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Mass Spectrometer

A mass spectrometer is an analytical instrument used to measure the exact molecular mass of a sample by breaking the initial molecule into smaller, charged fragments. This could be used either to identify an unknown compound or validate the product of a synthetic process, by calculating the molecule's mass to charge ratio. The three fundamental parts of a mass spectrometer are the ionization source, the mass analyzer, and the detector.

  • Ionization Source: Once the sample has been loaded into the instrument, it is turned into a gas and charged with electric and magnetic fields: this is called Electrospray Ionization (ESI). An alternative is the MALDI technique, where the reagent is crystallized and then ionized by using a laser.
  • Mass analyzer: The ions are separated by magnetic and electric fields, based on their mass over charge ratio. Light and charged fragments will be accelerated by the fields and go through the analyzer faster.
  • Detector: The accelerated fragments hit the detector and their mass over charge values are stored and converted into a spectrum. The height of the peaks represents the relative abundance of the various components.

Representation of a Mass Spectrometer divided in four parts depicted as squares. First, the sample, which consists of a solution of different compounds, is ionized using different techniques when enters the ion source of the spectrometer, following a black arrow that is pointing to it. The ions are separated based on their mass over charge ratio before entering the mass analyser, which is displayed as a square to the right of the ion source. The sample goes from the mass analyser to another square called detector following a black arrow. The mass separated ions are converted into measurable signal and are ready to be detected by the detector, the last part of the spectrometer.

Figure 1. Mass Spectrometer Scheme