mass defect

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mass defect

Chemistry
The difference in the mass of a polyatomic molecule and the sum of the masses of its constituent particles—i.e., electrons, protons and neutrons. The mass defect occurs because matter is converted into energy (as per Einstein’s E = mc2), which is the energy that binds the nucleus together and overcomes the mutual repulsion between protons.

Instrumentation
In mass spectrometry, mass defect refers to the positive or negative difference between an ion’s exact mass and the nearest integer.
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References in periodicals archive ?
, "Detection and Characterization of Metabolites in Biological Matrices Using Mass Defect Filtering of Liquid Chromatography/High Resolution Mass Spectrometry Data," Drug Metab.
, "Using Multiple Mass Defect Filters and Higher Energy Collisional Dissociation on an LTQ Orbitrap XL for Fast, Sensitive and Accurate Metabolite ID," Application Note: 417 (Thermo Fisher Scientific, 2008), www.thermo.com/appnotes.
Table I: Exact mass and mass defect of some common elements (Source: IUPAC).