Combination ion source

Application of Combination Ion Source To Detect Environmentally Important Compounds... 

A new universal interface and combination ion source is described which allows choice of ionization modes among electron impact (El), chemical ionization (Cl), and Thermospray. Results obtained with this system on a Vestec Model 201 LC-MS are presented for some test compounds and some environmentally important compounds on the Appendix VIII list. The relative advantages of the different ionization modes for compound identification and quantitation are discussed and data are presented on the performance of the system. 

Hua, L., Wu, Q., Hou, K., Cui, H., Chen, R, Wang, W, Li, J., Li, H. (2011) Single Photon Ionization and Chemical Ionization Combined Ion Source Based on a Vacuum Ultraviolet Lamp for Orthogonal Acceleration Time-of-flight Mass Spectrometry. Anal. Chem. 83 5309-5316. 

A schematic view of the GC-SIOMS apparatus is shown in Figure 2. The design of the SI probe assembly is such that the Re ribbon filament (for instance, 6 X 0.75 X 0.025 mm) can be placed in the center of the conventional electron ionization (El) ion source chamber. This combined ion source allows an easily inter-... 

Torr must be maintained to achieve the desired Cl reactions. Depending on the construction of the instrument, either changing the ion volume, a change of the whole ion source, or only a software switch is necessary. Through the straightforward technical realization, in the case of combination ion sources, and through the use of ion trap mass spectrometers. Cl has become established in residue and environmental analysis, even for routine methods. 

Combination sources with mechanical devices for sealing the El to the Cl source have so far only proved successful with magnetic sector instruments. With quadrupole instruments combination ion sources (or ion volumes) are available. 

Thermal ionization of samples inside the Knudsen cell takes place at high temperatures and the Knudsen cell can itself be a source of thermal ions. The charge and quantity of escaping ions depend on the draw-out potential in front of the effusion hole. A combined ion source can operate in two modes, to register either neutral or charged particles escaping from the cell. 

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