Why Does the Rightmost Mass Spectrum Peak Reflect a Molecule’s Relative Molecular Mass, Irrespective of Its Intensity?
Mass spectrometry (MS) is a technique employed to determine the mass, structure, and composition of molecules. In a mass spectrum, the horizontal axis represents the mass-to-charge ratio (m/z), while the vertical axis represents signal intensity. Each peak corresponds to a specific ion or molecular fragment, with the peak intensity reflecting its relative abundance.
The rightmost peak in a mass spectrum is generally identified as the molecular ion peak (M⁺), which corresponds to the intact ion of the molecule under investigation. The m/z value of this molecular ion peak represents the relative molecular mass of the entire molecule because, during ionization, the entire molecule typically forms a high-mass ion.
Peak intensity, however, does not convey information about molecular mass; instead, it indicates the relative abundance of a given ion or fragment. Factors such as ionization efficiency, fragmentation, and experimental conditions influence the peak intensity, and these factors are independent of the molecular mass.
Thus, the rightmost peak in a mass spectrum represents the molecular ion peak, and its m/z value corresponds to the molecule’s relative molecular mass, while the peak intensity solely reflects the relative abundance of that ion or fragment.
MtoZ Biolabs, an integrated chromatography and mass spectrometry (MS) services provider.
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