Question

Give 3 examples of ionization methods that find use in molecular mass spectrometry; compare and contrast with respect to ease of use, hard vs soft ionization, application and cost

Answer 1

One of the hard technique used in Mass spectrometry is electron impact ionization (EI). This mostly finds application in GC-MS. The hard nature of the technique is responsible for the weak or absence of molecular ion peak in the mass spectrum. But the extensive fragmentation is useful when combined to other techniques to elucidate the structure of unknown molecules.

The fast atom bombardment (FAB) and electron spray ionization (ESI) are the soft techniques of ionization. These techniques are specially useful in the analysis of thermally and mechanically unstable compounds, which can not be analysed by EI. ESI is one of the widely used technique in mass spectrometry especially in LC-MS.