Mass Spectrometry

Mass Spectrometry

A technique used to determine the molar mass and formula of a compound by ionizing it and detecting the masses of the resulting ions.

Molecular Ion (M+•)

The ion that remains intact after ionization, representing the original molecule's mass.

Electron Impact (EI)

A method of ionizing molecules where a sample is bombarded with high-energy electrons, causing an electron to be ejected.

Base Peak

The tallest peak in a mass spectrum, representing the most abundant ion detected.

Isotope

Atoms of the same element that differ in the number of neutrons, resulting in different masses.

Relative Abundance

The percentage of a particular isotope's occurrence compared to other isotopes of the same element.

Fragmentation

The process where molecular ions break into smaller pieces or fragments during mass spectrometry.

(M+2)+• Peak

A peak in the mass spectrum that represents molecules containing isotopes like 13C or 37Cl, which appear at a mass two units higher than the molecular ion.

(M+1)+• Peak

A peak that results from the presence of isotopes, appearing at a mass one unit higher than the molecular ion.

Bromine Isotopes

79Br (51% abundance) and 81Br (49% abundance); lead to a 1:1 ratio of (M)+• and (M+2)+• peaks in mass spectrometry.

Chlorine Isotopes

35Cl (76% abundance) and 37Cl (24% abundance); they lead to a 3:1 ratio of (M)+• to (M+2)+• peaks in mass spectrometry.