Principle of meta-stable defocusing in mass spectrometry

Theory of metastable ion generation in mass spectral studies as well as principle for their defocusing technique have been discussed. Detailed discussion have been made to record the metastable ions in single focusing (sector type) instruments and expanded to double focussing Nier-Jhonshon geometry as well as that to reverse geometry instruments. Merits and demerits of both types of instruments for recording such spectra have been discussed. Further, some illustrative examples are cited when the technique was in the process of development, showing the applications of this technique in identifying a compound while present in a mixture without taking recourse to pre-separation.