Principle of mass spectrometry:

In mass spectrometry, the analyte in the vapour phase is bombarded with a beam of high energy which knock off an electron from it to form a positively charged radical or molecular ion, M    . The radical ions so obtained undergo fragmentation yielding smaller fragments. The radical ion and the fragments obtained from the molecule are then separated according to their m/z values using magnetic field analysers or double focussing mass analysers. These are then detected by a suitable transducer or analyser and an output is generated after suitable processing.

Most of the spectral techniques generally involve absorption, emission or scattering of radiation from different regions of electromagnetic spectrum; NMR had an additional requirement of keeping the sample in a homogenous magnetic field. On the other hand in mass spectrometry the molecule is ionised using a suitable method and fragmented; the fragments being then analysed