Paul traps operation modes

The practicalities of Paul traps operated in MS" modes (n > 1) are quite complex, exemplified by the length of this section (much longer than that for e.g., time of flight analyzers), which was necessary to present even this abbreviated version of the underlying principles and their experimental realization. Many of the scan functions are fairly complex and the ease-of-use of Paul traps for such experiments relies heavily on computer control with... 

Like most successful clever ideas, the mass selective instability scan mode seems rather simple once someone had conceived it. However, it turned out (Stafford 1984) that full experimental reahzation of the potential of the method required another innovation, the exploitation of the collisional coohng/focusing effect of a low pressure of helium, discussed above. It was found (Stafford 1984) that the presence of helimn at a relatively high pressure of approximately 10 torr significantly enhanced the mass resolution, sensitivity and detection limit of a Paul ion trap operated as a mass spectrometer using the mass selective instability scan to obtain the mass spectrum. 

The basic theory of operation of quadrupole devices was enunciated almost 100 years before the quadrupole ion trap was invented by Paul and Steinwedel ( ]. The pioneering work of the inventors was recognized by the award of a 1989 Nobel Prize in Physics to Wolfgang Paul [2]. The quadrapole ion trap functions both as an ion store for gaseous ions and as a mass spectrometer. The mass-selective axial instability mode of ion trap operation developed by Stafford et al. [3] made possible the commercialization of the quadrupole ion trap. It should be recalled that the trapping parameter is given by... 

Figure 6.26 Comparison of scan cycles (and cycle times) used in operating a Paul ion trap in fuU scan MS mode, in full scan MS mode, and in MRM mode in which both precursor and fragment ions are isolated using selective injection techniques (but observation and detection of the fragment stiU requires a scan function).

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