Mass Spectra

Abstract

A mass spectrometer is a device for producing and weighing ions from a compound for which we wish to obtain molecular weight and structural information. All mass spectrometers use three basic steps: molecules M are taken into the gas phase; ions, such as the cations M^•+, MH⁺ or MNa⁺, are produced from them (unless the molecules are already charged); and the ions are separated according to their mass-to-charge ratios (m/ze). The value of z is normally one, and since e is a constant (the charge on one electron), m/z gives the mass of the ion. Some of the devices that are used to produce gas-phase ions put enough vibrational energy into the ions to cause them to fragment in various ways to produce new ions with smaller m/z ratios. Through this fragmentation, structural information can be obtained.