Mass spectrometry
Average molar masses

Mass spectrometry is an absolute method for determining the molar masses of molecules, but until now it has only been applied to small molecules. Recently, however, new techniques have emerged that provide sufficient resolution for higher molar masses, corresponding to macromolecules. Multiple electrospray ionization creates multiple charges on a macromolecule, greatly increasing the resolution limit of mass spectrometry. Single ionization, using a laser flash in the presence of a compound called matrix, enables time-of-flight measurement in a cavity of given geometry, with the travel time directly related to the molar...