Mass spectrometry corona discharge

D. I. Carroll, I. Dzidic, R. N. Stillwell, K. D. Haegele and E. C. Homing, Atmospheric pressure ionization mass spectrometry. Corona discharge ion source for use in a liquid chromatograph mass spectrometer computer analytical system, Anal. Chem., 47, 2369 2373 (1975). 

Horning EC. Atmospheric pressure ionization mass spectrometry. Corona discharge ion source for use in liquid chromatograph-mass spectrometer-computer analytical system. Anal Chem 1975 47 2369-73. 

Thomson, B.A. (1989) Atmospheric Pressure Ionization and Liquid Chromatogra-phy/Mass Spectrometry - Together at Last. J. Am. Soc. Mass Spectrom. 9 187-193. Carroll, D.I., Dzidic, I., Stillwell, R.N., Haegele, K.D., Horning, E.C. (1975) Atmospheric Pressure Ionization Mass Spectrometry. Corona Discharge Ion Source for Lfse in A Liquid Chromatograph-Mass Spectrometer-Computer Analytical System. Anal. Chem. 47 2369-2373. 

Caroll, D. L Dzidic, L Haegele, K. D. Stillwell, R. N. Homing, E. C., Atmospheric Pressure Ionization Mass Spectrometry Corona-Discharge Ion Source for Use in Liquid Chromatography-Mass Spectrometry Computer Analytical System. Anal. Chem. 1975, 47, 2369-2373. 

Particularly in mass spectrometry, where discharges are used to enhance or produce ions from sample materials, mostly coronas, plasmas, and arcs are used. The gas pressure is normally atmospheric, and the electrodes are arranged to give nonuniform electric fields. Usually, coronas and plasmas are struck between electrodes that are not of similar shapes, complicating any description of the discharge because the resulting electric-field gradients are not uniform between the electrodes. 

The positive column is a region in which atoms, electrons, and ions are all present together in similar numbers, and it is referred to as a plasma. Again, as with the corona discharge, in mass spectrometry, plasmas are usually operated in gases at or near atmospheric pressure. 

The various stages of this process depend critically on the type of gas, its pressure, and the configuration of the electrodes. (Their distance apart and their shapes control the size and shape of the applied electric field.) By controlling the various parameters, the discharge can be made to operate as a corona, a plasma, or an arc at atmospheric pressure. All three discharges can be used as ion sources in mass spectrometry. 

All three types of discharge involve the formation of ions as part of the process. For various reasons, most of the ions are positive. The ions can be examined by mass spectrometry. If small amounts of a sample substance are introduced into a corona or plasma or arc, ions are formed by the electrons present in the discharge or by collision with ions of the discharge gas. 

Thus, either the emitted light or the ions formed can be used to examine samples. For example, the mass spectrometric ionization technique of atmospheric-pressure chemical ionization (APCI) utilizes a corona discharge to enhance the number of ions formed. Carbon arc discharges have been used to generate ions of otherwise analytically intractable inorganic substances, with the ions being examined by mass spectrometry. 

Cl is an efficient, and relatively mild, method of ionization which takes place at a relatively high pressure, when compared to other methods of ionization used in mass spectrometry. The kinetics of the ion-molecule reactions involved would suggest that ultimate sensitivity should be obtained when ionization takes place at atmospheric pressure. It is not possible, however, to use the conventional source of electrons, a heated metallic filament, to effect the initial ionization of a reagent gas at such pressures, and an alternative, such as Ni, a emitter, or a corona discharge, must be employed. The corona discharge is used in commercially available APCI systems as it gives greater sensitivity and is less hazardous than the alternative. 

Wilkes, J.G. Freeman, J.P. Heinze, T.M. Lay, J.O., Jr. Vestal, M.L. AC Corona-Discharge Aerosol-Neutralization Device Adapted to Liquid Chromatogra-phy/Particle Beam/Mass Spectrometry. Rapid Common. Mass Spectrom. 1995, 9, 138-142. 

G.A. Eiceman, J.H. Kremer, A.P. Snyder and J.K. TofFeri, Quantitative assessment of a corona discharge ion source in atmospheric pressure ionization-mass spectrometry for ambient air monitoring. International Journal of Environmental Analayrical Chemistry 33 (1988) 161—183. 

A.J. BeU and S.K. Ross, Reverse flow continuous corona discharge ionization. International Journal of Mass Spectrometry 218(2) (2002) LI—L6, also found in part at International Journal for Ion Mobility Spectrometry 5(3) (2002) 95—99. 

Figure 22-19 (a) Atmospheric pressure chemical ionization interface between a liquid chromatography column and a mass spectrometer. A fine aerosol Is produced by the nebulizing gas flow and the heater. The electric discharge from the corona needle creates gaseous ions from the analyte. [Adapted from E. C. Huang, T. Wachs, J. J. Conboy, and J. D. Henion, Atmospheric Pressure Ionization Mass Spectrometry," Anal. Chem. 1990,62,713A ] (b) Atmospheric pressure chemical ionization probe. [Courtesy Shimadzu Scientific Instruments, Columbia, MD.J... 

L. M. Smith, Corona Discharge in Charge Reduction Electrospray Mass Spectrometry, Anal. Chem. 2000, 72, 5158. 

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