High resolution mass spectrometry (HRMS) analysis in the laboratory

Firstly, high-resolution mass spectrometers (HRMS) with analysers capable of accessing the exact mass, such as the time-of-flight (TOF) mass spectrometer or Orbitrap, are used to quantify organic contaminants. The performance of the analysers is compared by their powers of resolution, which is defined as the ability to provide signals that can be distinguished for two peaks of similar masses.

The ability to distinguish between ions of different elemental composition with very close molecular masses is therefore determined by the resolving power. Therefore, high resolving powers are required to distinguish between peaks with very close masses. A mass spectrometer is considered to be high resolution if its RP resolving power is > 10,000 (FWHM at m/z 200). While the most efficient mass spectrometers are capable of reaching a resolving power of around 1,000 (FWHM at m/z 200), a TOF will be able to reach a resolving power of 60,000 (FWHM at m/z 200) and a device with an Orbitrap analyser can reach a resolving power of up to 600,000 (FWHM at m/z 200).

Thus, HRMS allows accurate measurement of molecular or single isotopic masses.