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 identifica tion of organic compounds in mixtures. The first mass spectrometer ser ves 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, whic h is then fragmented by injection into a region containing a neutral g as at intermediate pressure and the resulting fragment ions are then s eparated and mass analyzed in the second mass spectrometer. This appro ach makes quantitative analysis more specific and reliable by monitori ng a specific fragment ion from the precursor ion of interest. It also allows qualitative analysis by interpretation of the fragment ion spe ctrum of a particular component independent of the presence of the oth ers. Tandem mass spectrometers consist of either three quadrupoles, th e second one serving as the collision region; two magnetic instruments ; or a combination of both. Some of the measurements can be carried ou t with one double-focusing mass spectrometer but at the expense of res olution.