TIC and RIC for mass

FIGURE 4.6 TIC fromGCMS analysis of headspace gases above a pharmaceutical product. 

In the majority of mass spectra examined in previous chapters, a molecular ion peak was present with an intensity that made it relatively easy to identify. In some cases, however, the molecular ion was either absent or of extremely low intensity the molecnlar ion was too nnstable to withstand the high energy imparted to it by the electron beam. The remainder of this chapter is devoted to descriptions of the varions methods that have been devised to produce molecular ions in lower-energy states. 

Atmospheric pressure chemical ionization (APCI) Matrix-assisted laser desorption ionization (MALDI) Direct analysis in real time (DART) 

It was stated in Chapter 2 that organic molecules in the vapor state are ionized when an amount of energy equal to the ionization potential is transferred from an electron beam to the molecules, as depicted in Equation 4.1  

The ionization potential I can be measured by mass spectrometry. The minimum electron energy at which the molecular ion is formed is determined by lowering the potential between the filament and electron trap in small steps until the molecular ion is no longer detected. 

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