Field desorption emitter heating current

Ktimmler, D. Schulten, H.-R. Correlation Between Emitter Heating Current and Emitter Temperature in Field Desorption Mass Spectrometry. Org. Mass Spectrom. 1975,10, 813-816. 

In field desorption (FD), the sample is deposited onto the emitter, a high voltage is applied, and a current is passed through the emitter to heat up the filament. Mass spectra are acquired as the emitter current is gradually increased and the sample is evaporated from the emitter into the gas phase. Tlie analyte... 

Field (desorption) ionization (FDI) was first described by Beckey in 1969 [4]. In FDI, the sample solution is deposited on a lO-qm-diameter FDI emitter, which is activated to provide for whiskers or microneedles on the surface [5, 6]. The emitter is kept at a high potential (> 5 kV) in the high-vacuum ion source, mostly of a sector instmment (see Fig. 7.1). By passing through a current, slow heating of the emitter is achieved. As heating of the emitter continues, nonvolatile analytes can be desorbed and ionized by various mechanisms. High local electrical fields at the... 

Thermal ionization of preformed ions may be observed for organic and inorganic salts. In tiiis case tiie field lowers the desorption temperature, facilitates focusing, and enhances the ion current. The emitter is used as a "solid probe" to hold and heat the sample. Thermal ionization is most commonly observed for organic and inorganic salts it is hardly ever observed for polymers. 

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