In some embodiments, as shown in FIGS. 1, 2, and 3A, for example, the ESI device 20 can electrospray ion current 20s from at least one emitter 20e of the ESI device 20 into the inlet device 15, then through the inlet device 15 directly into a mass analyzer chamber 12 at high pressure. The inlet device 15 can be closely spaced apart from or abutting contact with the emitter 20e, while the emitter 20e discharges, e.g., electrosprays, the sample into a spatial region external to the vacuum chamber 12 at ambient (e.g., atmospheric) pressure then into the inlet tube 15. The electrospray 20s can be into ambient (i.e., atmospheric) pressure, then into the inlet aperture 15a which is at ambient pressure, then into the vacuum chamber 12 with the mass analyzer 30. The mass analyzer chamber 12 can be in fluid communication with a vacuum pump 70 via a valve 71. The external end 15e of the inlet device 15 is at atmospheric pressure, facing the ESI emitter 20e, while the mass analyzer vacuum chamber 12 is at a high pressure. The internal end 15i of the inlet device 15 is held inside the mass analyzer chamber 12. The inlet device 15 can be sealably attached to a wall 12w of the mass analyzer vacuum chamber 12 via a connector 18 such as a vacuum fitting, e.g., an Ultra-Torr? fitting from Swagelok, Inc., Solon, Ohio.
