Gas Phase Hard Ionisation Methods

The samples are usually introduced through a heated direct insertion probe or, for extremely volatile samples, through a gas chromatograph. El is the oldest and best characterised ionisation method and can be applied to all volatile and thermally stabile compounds. El mass spectra show a high reproducibility ( fingerprinting ) often used in combination with mass spectral hbraries [22]. Additionally, structural information can be obtained by the fragmentation pattern produced. 

Samples can be introduced into the ion source through a heated direct insertion probe or by a gas chromatograph. As a variation on Cl, the analyte can be placed on a filament and rapidly heated in the Cl plasma in the presence of reagent gas. This so-called desorption Cl reduces fragmentation and is applicable to samples that cannot be thermally desorbed without decomposition. 

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