Mass spectrum

A mass spectrum is an intensity versus m/z (mass-to-charge ratio) plot that represents a chemical analysis. The mass spectrum of a sample is a pattern representing the distribution of ions by mass (more correctly: mass-to-charge ratio) in a sample. It is a histogram usually made using an instrument called a mass spectrometer. Not all mass spectra of a given substance are the same. It can depend on the operating conditions of the instrument. For example, some mass spectrometers break the analyte molecules into many pieces; others observe the intact molecular masses with little fragmentation. A mass spectrum can represent many different types of information based on the type of mass spectrometer and the specific experiment; however, all plots of intensity vs. mass-to-charge are called "mass spectra".

Common fragmentation processes for organic molecules are the McLafferty rearrangement and alpha cleavage.

In the past, chemists with PhD degrees were needed to interpret mass spectra. Today, computer programs read the data and identify the compounds in a sample.

References

Other websites
 Interactive tutorial on mass spectra  National High Magnetic Field Laboratory
 Weighing Atoms: A layperson's introduction to mass spectrometry  National High Magnetic Field Laboratory
 What's in an Oil Drop: A layperson's introduction to Fourier Transform Ion Cyclotron Resonance   National High Magnetic Field Laboratory
 Quantities, Units and Symbols in Physical Chemistry (IUPAC green book)
 An introductory video on Mass Spectrometry The Royal Society of Chemistry

Category:Spectroscopy
Category:Mass spectrometry