The gate electrode is optional. In some embodiments, the tube electrode 48t can have an independent DC voltage applied to it. The ion funnel 48f can have a combination of RF and DC potentials applied. When the mass spectrometer 10 includes the tube electrode 48t, the tube itself can also function as the gate. When the mass spectrometer 10 includes an ion funnel 48f, ions can be gated in several ways (i.e., turning off DC potentials, switching one DC potential and the like).
FIGS. 4A-4D also illustrate that, in some embodiments, the mass spectrometer 10 can have a single chamber 12 holding both the mass analyzer 30 and the detector 40 at a common high pressure. Thus, mass analysis and detection are performed at a single, common high pressure background, e.g., at or >50 mTorr, more typically at or greater than 100 mTorr (such as between about 100 mTorr and 1 Torr, in particular embodiments), optionally with ambient air as the buffer gas. In some embodiments, a holding compartment 60 (FIG. 2) can be used to allow electrospray 20s and/or mass spectrometry to be carried out using an alternate buffer gas as noted above.
FIGS. 3A and 4A illustrate that, in some embodiments, the inlet device 15 in communication with the ESI device 20 can electro spray directly into the high pressure chamber 12 holding the mass analyzer 30.
