Filament resistance, small-volume

In thermal-ionization mass spectrometry (TIMS), samples consist of fg-ng quantities of chemically separated and purified analyte dissolved in a small volume (typically 1-10 pi). The solution is deposited on a refractory metal filament (e.g., high-purity W or Re), where it is evaporated to dryness. The filament is then heated to temperatures of 1,000-2,500°G in the ion source by resistive heating. If the ionization potential of the analyte is low compared to the work function of the filament, some of the analyte atoms will be ionized and emitted from the filament surface. TIMS ion sources commonly incorporate a second filament arranged... 

---