A Molecular Mass Spectra

The starling point fora mass speciromeirie analysis is the formation of gaseous analyte ions, and the. scope and the utility of a mass speciromeirie method is dictated by the ionization process, riie appearii nee of mass spectra for. i given molecular species sironglv depends on Ihe method used for ion formation. Table 2D-1 lists many of the ion sources that have been emploved in 

Basic Type Name and Acronym Ionizing Ageni 

Cias phase F.leclron impact ( () Energetic electrons 

Desorp(ion Field desorption (FD) High-potential electrode 

Gas-phase sources are generally restricted to the ionization of thermally stable compounds that have boiling points less than about 300 C. In must cases, this requirement limits gascuus sources to compounds with molecular masses less than roughly 10 Da. Desorption sources, which do not require volatilization of aii-aly le molecules, are applicable to analytes having molecular masses as large as 10 Da, 

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