Particle Beam Interface PBI

Several other interface designs were introduced over this period, including continuous flow fast atom bombardment (CFFAB)" and the particle beam interface (PBI)," but it was not until the introduction of the API source that LC/MS applications really came to the forefront for quantitative analysis. Early work by Muck and Henion proved the utility of an atmospheric pressure interface using a tandem quadrupole mass spectrometer. 

In a particle-beam interface (PBI), the column effluent is nebulized, either pneumatically or by TSP nebulization, into a near atmospheric-pressure desolvation chamber, which is connected to a momentum separator, where the high molecular-mass analytes are preferentially transferred to the MS ion source, while the low molecular-mass solvent molecules are efficiently pumped away. The analyte molecules are transferred in small particles to a conventional EI/CI ion source, where they disintegrate in evaporative collisions by hitting a heated target, e.g., the ion source wall. The released molecules are ionized by El or conventional CL... 

A particle beam interface (PBI) better serves the purpose of LC-EI-MS [55-57]. The PBI removes the solvent by nebulization into an evacuated desolvation chamber from where the evolving microscopic sample particles are transferred into an El ion source via a jet separator (Fig. 5.14). Designs different from PBI have also been developed [57]. The PBI is comparatively robust and attained popularity in particular for low- to medium-polarity analytes, but has some drawbacks such as poor sensitivity especially with water-rich mobile phases, moderate linearity with polar compounds, and low tolerance for heat-sensitive compounds [58,59]. The most recent addition to LC-EI interfaces, also the simplest and most elegant solution, makes use of the very low liquid flow rates of nano-LC equipment [60,61]. The flow from a 30 pm i.d. fused silica capillary column is passed... 

In subsequent years (1988), the MAGIC system was commerciahzed, first by Hewlett-Packard (nowadays Agilent Technologies), and subsequently by other instrument manufacturers. Four commercial versions of the system have been available (1) the particle-beam interface, featuring an adjustable concentric pneumatic nebulizer, (2) the thermabeam interface with a combined pneumatic-TSP nebulizer, (3) the universal interface, in which TSP nebulization and an additional gas diffusion membrane is applied, and (4) the capillary-EI interface, which resulted from systematic modifications to existing PBI systems by Cappiello [83]. The first system was most widely used, and is discussed in more detail below. For some years, PBI was widely used for environmental analysis, especially in the US. 

MS is undoubtedly the solution of the near future for LC detection. Improvements made to interfacing devices together with a continuous and sensible diminution of instrumentation costs promote MS as a universal/selective tunable detection system. Atmospheric pressrue electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) are the most robust and popular devices for interfacing MS to LC systems. In Table 9, LC-MS data for some pesticides are given. Although ESI and APCI are more often used, other LC-MS interfaces produce reliable results in pesticide applications thermospray (TSI), particle beam (PBI) and matrix-assisted postsource decay laser desorption/ionization (CID-PSD-MALDI). 

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