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7.3.1 Total Ion Chromatogram

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.

John S. Riley, DSB Scientific Consulting