Mass spectral techniques field desorption

An electron impact mass spectrum of calcium leuco-vorin has not been obtained because the compound is not sufficiently volatile. It would be difficult to isolate the free acid without first dehydrating the compound. Due to its ionic nature, calcium leucovorin will not dissolve in common silylating reagents. Field desorption, another mass spectral technique, generally lends itself more to compounds like leucovorin. Indeed, this technique has been applied successfully to methotrexate and other folic acid analogs.1 ... 

In principle it should be possible to determine M and M , by mass spectrometry, since the technique directly provides the information needed— oligomer molecular weights (AQ and relative abundances (or number of molecules, Field desorption was the first mass spectral method to be used to directly determine molecular weight averages of synthetic polymers (1980). ... 

Field desorption (FD) and fast atom bombardment (FAB) mass spectrometry provides mass spectral information about compotmds that are not very volatile but these two techniques are not used often in polymer science since they have several disadvantages. Electrospray ionization (ESI) mass spectrometry can also be used to obtain the above information about polymers, but ESI spectra are generally complicated due to differences in charge state distributions. Static secondary ion mass spectrometry (static SIMS) is a surface-sensitive MS technique, which is suitable for studying the interfaces of polymers with respect to chemical structure and molecular weight as well as end groups and surface contaminants. Laser desorption... 

To compensate for the energy spread, the first stage of the two-stage acceleration field can be activated shortly after ion production or ejection from the sample. This event typically occurs in the nanosecond to low microsecond range. The method is known as time-lag focusing or delayed extraction technique. In TOF-MS equipped with matrix-assisted laser desorption/ionization (MALDI) ion source, delayed extraction may improve the mass resolving power by a factor of two- to fivefold [9, 10]. Mass resolving power defines the sharpness of spectral features, which is explained in Chapter 5. 

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