PHAR 307 - Lecture 10: Introduction to basic concepts in mass spectrometry

mass to charge ratio of an ion (m/z)

mass of ion/number of electrical charges, dimensionless number

mass spectrometry

determines molecular masses of different molecules within a mixture, identifies unknown structures and quantifies relative abundance

mass spec measures in

gas phase, analytes need to be charged

mass and electromagnetic fields

smaller molecules will deflect more than larger molecules with the same charge

calculating average mass

sum of (relative abundance of isotope * atomic mass)

positive charges are made by

removal of electron, addition of proton, or positively charged ion

negative charge is made by

addition of electron or negatively charged ion

removal of electron makes

positive radical ion = molecular ion [M]+

hard ionization

molecules break apart into multiple daughter ions, molecule fragments

soft ionization

less energy used to ionize sample, minimal fragmentation, spectra contains most abundant molecule

base peak

most stable ion resulting from ionization process

peak with highest m/z ratio

often the molecular ion or directly related species

fragment ions

mass is lower than molecular mass, gives information about functional groups

M+H

molecular weight of compound after gaining proton