The Mass Spectrometer Detector

 

Basically, mass spectrometry involves first, the production of ions from the sample and these ions can be molecular ions, ion fragments or ion complexes, depending on the ionization process that is used. Second, the ions are then accelerated in a vacuum and, by applying a range of different magnetic and electrical techniques, the ions can be separated into their individual masses and each mass group sensed and identified. The sample is first vaporized in a vacuum, usually by heat, and the molecules in the vapour can then be ionized by one of a number of different processes, The charged ions then pass though an accelerator and into a mass discriminator. Mass discrimination can also be achieved in a number of different ways either by electric and/or magnetic deflection or by time of flight measurements. Finally, the separated ions pass into the ion sensor to be measured and their intensity recorded. The whole system is maintained under high vacuum. There are a number of interfaces that have been developed to couple a capillary electrophoresis instrument to a mass spectrometer; some of them are commercially available. The tandem system has been shown to exhibit sensitivities at the fentamole level for peptides protein digests and proteins.

 

Figure 18 shows a typical commercially available capillary electrophoresis instrument.

 

 

 

 

Figure 18. A Modern Electrophoresis Instrument