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Document set current to 30 July 2026
Defined term · Analytical chemistry

Monoisotopic mass

The mass calculated using the most abundant isotope of each element. Requires high resolving power to determine for a peptide of several kilodaltons, and is not interchangeable with average mass.

Document identifier
CEI-GT-143
Series
Defined term
Version
1.0
Published
30 Jul 2026
Last reviewed
30 Jul 2026
Certainty
Not rated

§1Monoisotopic mass

§1.2Category

Analytical chemistry — Terms describing the determination of identity, purity, content and quality.

§1.3Related terms

  • Mass spectrometry — Determination of mass-to-charge ratio, used to confirm identity. For a peptide, deconvolution of the multiply charged envelope should return an average mass within a…
  • Average mass — The mass calculated using isotope-averaged atomic weights, and the value returned by deconvolution of an electrospray charge envelope at moderate resolution.
Compound Evidence Institute · CEI-GT-143 · https://compoundevidence.com/glossary/monoisotopic-mass/ · retrieved 30 July 2026
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