In some embodiments, preferably at least when using low ESI flow rates, e.g., typically <1 μL/min, the at least one emitter 20e can be positioned axially with the inlet 15e. In other embodiments, the at least one emitter 20e can be above, below and/or to the side of the inlet 15e.
In the embodiment shown in FIG. 1, the internal end of the inlet device 15i can be in communication with, shown as held by, an electrode 28. The internal end of the inlet device 15i and the electrode 28 can be spaced apart from a gate electrode 38 and/or entry of the mass analyzer 30 by between about 1 mm to about 20 mm, more typically between about 1 mm and about 10 mm, such as about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm and about 10 mm. In some embodiments, the electrode 28 is an accelerating electrode for the ions.
