Drug compounds mass defect

One of the more powerful techniques is a new software tool called mass defect filtering.176 185-188 A mass defect can be defined as the difference between the exact mass and nominal mass of a compound.189 Typically, drug-like molecules (and their metabolites) will have mass defects that differ from those of endogenous matrix materials. While a mass spectrometer that has unit mass resolution cannot differentiate a test compound from an isobaric matrix compound, a high mass resolution MS may be able to differentiate many isobaric matrix compounds from test compounds. 

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