Mass spectrometry single-stage

The main advantages of the ms/ms systems are related to the sensitivity and selectivity they provide. Two mass analyzers in tandem significantly enhance selectivity. Thus samples in very complex matrices can be characterized quickly with Htde or no sample clean-up. Direct introduction of samples such as coca leaves or urine into an ms or even a gc/lc/ms system requires a clean-up step that is not needed in tandem mass spectrometry (28,29). Adding the sensitivity of the electron multiplier to this type of selectivity makes ms/ms a powerhil analytical tool, indeed. It should be noted that introduction of very complex materials increases the frequency of ion source cleaning compared to single-stage instmments where sample clean-up is done first. 

The MS-MS equivalent of this technique is known as selected-decomposition monitoring (SDM) or selected-reaction monitoring (SRM), in which the fragmentation of a selected precursor ion to a selected product ion is monitored. This is carried out by setting each of the stages of mass spectrometry to transmit a single ion, i.e. the precursor ion by MSi and the product ion by MS3 (see Figure 3.8 above). 

Two-Dimensional Gel Electrophoresis As shown in Figure 3-22, two-dimensional gel electrophoresis allows the separation and display of up to 1,000 different proteins on a single gel. Mass spectrometry (see Box 3-2) can then be used to partially sequence individual protein spots and assign each to a gene. The appearance and nonappearance (or disappearance) of particular protein spots in samples from different tissues, from similar tissues at different stages of development, or from tissues treated in ways that simulate a variety of biological conditions can help define cellular function. 

Finnigan MAT are one of the major suppliers of this equipment. They supply equipment for single stage quadruple mass spectrometry, mass spectrometry-mass spectrometry, high mass high resolution mass spectrometry, ion trap detection, and gas chromatography-mass spectrometry. 

Along the gradient of the breakthrough curve, the lithium samples were isotopically assayed by mass spectrometry. The single stage enrichment factor was determined as follows (24) ... 

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