The present invention relates generally to analytical instrumentation and more particularly to a low pressure electrospray ionization system and process for effective transmission of ions between coupled ion stages with low ion losses. An electrospray ionization (ESI) source is characterized by a first vacuum chamber enclosing both an ESI transmitter and a feed line for a supply gas, the first vacuum chamber having an exit orifice positioned at an entrance to a first ion guide enclosed in a second vacuum chamber, wherein a sample comprising electrospray ions is transmitted from the ESI transmitter to the ion guide through the exit orifice. Systems and methods are described which provide up to complete transmission of ions between coupled stages with low effective ion losses. An "interfaceless" electrospray ionization system is further described that operates an electrospray at a reduced pressure such that standard electrospray sample solutions can be directly sprayed into an electrodynamic ion funnel which provides ion focusing and transmission of ions into a mass analyzer. Furthermore, chambers maintained at different pressures can allow for more optimal operating conditions for an electrospray emitter and an ion guide.