HRMS (High-Resolution Mass Spectrometry)

High-resolution mass spectrometry measures mass-to-charge ratio with sufficient precision — typically to within a few parts per million — to distinguish...

High-resolution mass spectrometry measures mass-to-charge ratio with sufficient precision — typically to within a few parts per million — to distinguish between molecular formulae of very similar nominal mass, thereby allowing the exact molecular formula of a compound to be determined directly from its measured mass rather than merely inferred. This capability is of particular importance in medicinal chemistry structure confirmation, since two structurally distinct compounds can readily share an identical nominal (unit) mass while differing at the fourth or fifth decimal place in exact mass, a distinction only high-resolution instrumentation such as time-of-flight (TOF) or Orbitrap mass analysers can reliably resolve; HRMS data, reported alongside the calculated exact mass for the proposed molecular formula and the observed mass accuracy in parts per million, is now considered a standard requirement for reporting a novel synthesised compound in the medicinal chemistry literature.