ANALYTICAL TECHNIQUES FOR TRACE ORGANIC-COMPOUNDS .4. TANDEM MASS-SPECTROMETRY FOR ORGANIC TRACE ANALYSIS - (TECHNICAL REPORT)

Tandem mass spectrometry is a very sensitive method for the identification of organic compounds in mixtures. The first mass spectrometer serves to ionize all components of the mixture and to select out a major ion, most often the molecular ion of the compound(s) of interest, which is then fragmented by injection into a region containing a neutral gas at intermediate pressure and the resulting fragment ions are then separated and mass analyzed in the second mass spectrometer. This approach makes quantitative analysis more specific and reliable by monitoring a specific fragment ion from the precursor ion of interest. It also allows qualitative analysis by interpretation of the fragment ion spectrum of a particular component independent of the presence of the others. Tandem mass spectrometers consist of either three quadrupoles, the second one serving as the collision region; two magnetic instruments; or a combination of both. Some of the measurements can be carried out with one double-focusing mass spectrometer but at the expense of resolution.