How can a mass defect be used to assign a molecules structur

How can a mass defect be used to assign a molecule\'s structure based on its mass spectrum?

Solution

Mass defect is defined as removal of each atom\'s mass from integer bounded mass. It is the difference in the mass of a composite atom/molecule and sum of the masses of its component parts (nominal mass).

This mass defect is used to determine the molecular structure. The absolute value of the mass defect of an ion reflects the ion elemental composition because each element has a unique mass defect.

The absolute mass defect of an ion represents the total of mass defect of all the atoms in molecule.

Relative mass defect (RMD) It is the ratio of (mass defect/measure monisotopic mass)x 10⁶where units are ppm.

RMD value will be increased as fragmentation of ion mass decreases. Mass defect filtering of complex mass spectrum data is used to selectively detect the compounds including drugs, metabolites and other complex compounds.