z ratio are allowed to pass at any given time from here the ions enter the mass detector electron multiplier and are recorded by the controlling computer which knows which m z is exiting the mass analyzer at that instant when operated in full scan mode the quadrupole continuously and repeatedly ramps the monitored m z ratio from a preset lower limit to a preset upper limit and will detect all ions within that m z range over a set period of time a typical mass scan range will cover 35 500 m z four times per second at the conclusion of each individual scan the intensities of all m z ratios within that scan are summed giving a total ion current the total ion current tic chromatogram is a summation of all the m z intensities for each individual mass spectrum y axis plotted as a function of time x axis alternatively the data obtained by gc ms can be displayed in three dimensions like a cube to make use of the fact that repetitive scan gc ms data are really a three dimensional matrix of data x time y total ion current and z m z further one can choose to plot a single m z signal vs time this extracted ion chromatogram eic allows the mass spectrometer to be used as a selective detector the py gc ms of asphaltene.