MODEL RELEASED. Mass Spectrometry. Female technician loading a sample into a mass spectrometer to analyse its chemical composition. A mass spectrometer works by deflecting a beam of charged atoms (ions) in a vacuum by passing it through an electric or magnetic field. Each element has a different charge to mass ratio and so will be deflected by a different amount. This spectrum" of ions can be detected electrically and analysed. The technique can be used to detect very low concentrations of chemicals."