Moving-belt interface advantages

The advantages and disadvantages of this type of interface, particnlarly in comparison to the moving-belt interface which was available at the same time, are listed below. This was one of the first LC-MS interfaces to be made commercially available and, although used in a number of laboratories, its development was halted premamrely by the introduction of the thermospray interface (as we shall see later). 

Arguably the ultimate LC-MS interface would be one that provides El spectra, i.e. a spectrum from which structural information can be extracted by using famihar methodology, and this was one of the great advantages of the moving-belt interface. There is, however, an incompatibility between the types of compound separated by HPLC and the way in which electron ionization is achieved and therefore such an interface has restricted capability, as previously discussed with respect to the moving-belt interface (see Section 4.2 above). 

An evalnation of the applications of the moving-belt interface, which was the most widely nsed LC-MS interface based on analyte enrichment, demonstrates both the strength and the weakness of this approach. The advantage of complete analyte enrichment, i.e., solvent removal prior to MS introduction, is a free choice of ionization method. Thns, El mass spectra can be acquired. The disadvantage is that the analytes are transferred in solid state, i.e., on a solid support like the belt, requiring vaporization prior to the ionization. Therefore, the analytes should have sufficient vapour pressure and thermal stability. 

Seven different LC-MS interfaces are described in Chapter 4, with particular emphasis being placed on their advantages and disadvantages and the ways in which the interface overcomes (or fails to overcome) the incompatibilities of the two techniques. The earlier interfaces are included for historical reasons only as, for example, the moving-belt and direct-liquid-introduction interfaces, are not currently in routine use. The final chapter (Chapter 5) is devoted to a number of illustrative examples of the way in which LC-MS has been used to solve various analytical problems. 

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