How often must the mass spectrometer be calibrated?
Very infrequently. Once a ‘mass calibration model’ has been established empirically, this is stable for many weeks at a time. Also, it is common in the MS-200 to convert the mass spectrum to a ‘stick plot’, in which the height of a peak represents the peak area. In such ‘stick plots’ the peak is positioned at the ‘nominal’ mass rather than the absolute mass; thus a peak due to C2H 3Cl3 (absolute mass 131.930) will appear at 132. Minor shifts of the mass peak position are thus irrelevant in stick plots.
