Reading Peaks in a Mass Spectrum

A mass spectrum shows the charged fragments in an analyte as peaks plotted by mass-to-charge ratio, or m/z. The x-axis gives the mass of each charged fragment divided by the number of charges it carries. The y-axis shows the relative abundance of each charged species based on the signal intensity recorded at the detector.

The mass spectrum of a molecule is a bar-graph plot of the relative abundance of its component fragments against their mass-to-charge ratio.

For example, consider the mass spectrum of methane. The electron beam incident on the methane molecule knocks off an electron to generate a methane radical cation. The mass signal at a mass-to-charge...