Limitations of Molecular MS

The major limitation to the use of MS is that compounds must be volatile or must be able to be put into the gas phase without decomposing. A variety of ionization sources have been developed to handle materials that are volatile, semivolatile, nonvolatile, or thermally labile, as described in Chapters 9 and 13. For compounds that are not volatile, chemical derivatization to a more volatile form can be performed to make them suitable for MS or GC-MS, as described in Chapter 12. Carboxylic acids can be converted to the corresponding volatile methyl esters, for example trimeth-ylsilane is another common derivatizing agent used to make volatile ether derivatives. 

Certain isomers cannot be distinguished by MS alone. Some isomers, such as the PCBs and PBDE isomers discussed in Section 10.3.5, may be able to be separated by chromatography prior to determination by MS. 

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