massaspectrometrie met hoge resolutie (HRMS)

Except for the ¹²C isotope, the masses of elemental nuclei are close to—but not precisely—whole numbers.

However, mass spectra typically show the particle mass rounded to the nearest whole number, which is called the nominal atomic or molecular mass.

This approximation makes it difficult to distinguish molecules with similar molecular masses that differ by only decimal points.

For example, cyclopentanone and cyclohexane have the same nominal molecular mass when rounded to the nearest whole number. Such molecules can be distinguished using high-resolution mass spectrometry.

HRMS uses narrow magnetic field stages to detect particle masses with an accuracy of 0.0001 unified atomic mass units. The mass determined by high-resolution mass spectrometry is known as the exact molecular mass.

The details of the exact molecular mass can be used to distinguish molecules with the same nominal molecular mass. This, in turn, helps identify the molecular formula of the sample.