If all the signal intensities (all mass peaks) for one scan are added
together, one obtains the total ion current. The total ion current
reduces the two dimensional mass spectral data to one signal: the
total ion signal collected during a given scan. Plotting the total
ion current against time (or scan number) gives the Total Ion Chromatogram
(TIC). When a data file is loaded into memory using the Data Analysis
module, the TIC is drawn to the screen. Note that the TIC resembles
any other chromatogram; it is detector signal vs. time. By displaying
data as a TIC, the mass spectrometer is used as a general detector;
there is no selectivity in the data.
Exercise: From the Data Analysis module, load the file EVALDEMO.D. By examination of the TIC, how many compounds were detected during this run.