Plasmaspray interfaces

Aerosols can be produced as a spray of droplets by various means. A good example of a nebulizer is the common household hair spray, which produces fine droplets of a solution of hair lacquer by using a gas to blow the lacquer solution through a fine nozzle so that it emerges as a spray of small droplets. In use, the droplets strike the hair and settle, and the solvent evaporates to leave behind the nonvolatile lacquer. For mass spectrometry, a spray of a solution of analyte can be produced similarly or by a wide variety of other methods, many of which are discussed here. Chapters 8 ( Electrospray Ionization ) and 11 ( Thermospray and Plasmaspray Interfaces ) also contain details of droplet evaporation and formation of ions that are relevant to the discussion in this chapter. Aerosols are also produced by laser ablation for more information on this topic, see Chapters 17 and 18. 

Application of HPLC-MS to the analysis of a black tea liquor was studied in a paper by Bailey 39 a great deal of useful information could be obtained without sample pretreatment. A tea liquor was applied to a wide-pore HPLC column connected to a mass spectrometer by a VG Plasmaspray interface. Pseudo-molecular ions were obtained from the flavanols, flavanol gallates, chlorogenic acids, 4-coumarylquinic acids, and caffeine, but the flavanol glycosides were extensively fragmented by the interface. Fragments were obtained from unresolved polymer that supported its previous designation as a flavanol polymer. 

A modification/enhancement of the TSP is the plasmaspray interface for discharge ionization which has also been commercialized. A TSP system can be operated in three different modes (a) filament-off mode, i.e., TSP ionization mode, (b) the filament-on mode, and (c) the discharge ionization mode. 

The nebulization and evaporation processes used for the particle-beam interface have closely similar parallels with atmospheric-pressure ionization (API), thermospray (TS), plasmaspray (PS), and electrospray (ES) combined inlet/ionization systems (see Chapters 8, 9, and 11). In all of these systems, a stream of liquid, usually but not necessarily from an HPLC column, is first nebulized... 

Dynamic FAB is an interface between a liquid chromatograph and a mass spectrometer and is, at the same time, an ion source. As an inlet/ion source, this technique fulfils a similar function to plasmaspray and electrospray, both of which are combined inlet/ion sources. 

LC can be combined with all kinds of mass spectrometers, but for practical reasons only quadrapolar, magnetic/electric-sector, and TOP instruments are in wide use. A variety of interfaces are used, including thermospray, plasmaspray, electrospray, dynamic fast-atom bombardment (FAB), particle beam, and moving belt. 

A group of techniques employing differential selection of solute ions relies on nebulisation and ionisation of the eluent, with some discrimination of ion selection in favour of the solute. Main representatives are APCI [544] and thermospray [545]. In a thermospray interface a supersonic jet of vapour and small droplets is generated out of a heated vaporiser tube. Controlled, partial vaporisation of the HPLC solvent occurs before it enters the ion source. Ionisation of nonvolatile analytes takes place by means of solvent-mediated Cl reactions and ion evaporation processes. Most thermospray sources are fitted with a discharge electrode. When this is used, the technique is called plasmaspray (PSP) or discharge-assisted thermospray. In practice, many... 

Detector MS, VG Trio 2 with a thermospray-plasmaspray LC interface, capillary probe tip at 300°... 

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