Mass Spectrometry in the Chemistry of Natural Products

Abstract

Mass spectrometry (MS) is one of the very first spectral methods dating back to the beginning of this century (1913, J.J. Thomson, parabola spectrograph; 1918, A.J. Dempster, spectrometer, and 1919, F.W. Aston, spectrograph).1 It measures mass, one of the two basic properties of matter, as the mass-to-charge-ratio of ions, (m/z in atomic mass units, scale relative to 12C) while other spectral methods usually measure frequency, either absorbed or emitted. Thus, in a sense, the mass spectrometer is an extension of the balance, the principal tool of a chemical laboratory. Sensitivity of mass spectral measurements approaches single ion detection and the accuracy of mass determination may be in order of ppm. The quest for this precise information characterizes all three major phases of the application and development of mass spectrometry: detection of isotopes, “inorganic phase”, followed by extensive analysis of molecules of relatively low molecular weight, “organic phase”, and the most recent “biological phase” in which ionization and analysis of ions derived from a much wider variety of polar and large organic molecules becomes possible. Immense developments of instrumentation, increasing analytical applications, and an ever increasing range of compounds accessible to measurement do not change the heart of mass spectrometry and the simplicity of the fundamental information provided.