Selected Terms for Clarification

The author of this chapter takes the freedom to explain a few selected terms that— based on his teaching experience—are often not well understood and may even be misused. Although this is not an exhaustive list, clarification of these terms may help in reading the whole book more comprehensively by readers whose primary expertise is not in mass spectrometry. For a detailed guidance of terminology, we refer again to the book by Sparkman [1]. 

Although they are related, the measured accurate mass should be distinguished from the calculated exact mass, which is the mass determined by summing the exact isotope masses of the elements present in a particular ion. For example, the calculated exact mass of (acetone molecular ion) is 58.0419 Da, and 

Resolution of a mass spectrometer is related to the ability of a mass analyzer to separate two ions with different m/z ratios. The resolution is defined as / = M/AM, where M is a given mass and AM is the difference between the given mass and the neighboring mass peak with, for example, 10% peak height (see Fig. 28). 

The terms low resolution and high resolution are often misused meaning not accurate mass/survey and accurate mass measurements, respectively. High 

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