Multiple liquid flow electrospray interface

An apparatus for performing electrospray ionization of a liquid sample matrix, comprising:

• an input port for introduction of the liquid sample matrix;
• a central conduit coupled to the input port and having an output port providing an output liquid flow;
• a flow mixing structure disposed inside the central conduit in the flow path of the liquid sample matrix and prior to the outport port of the conduit;
• a first side channel coupled to the central conduit proximate of said flow mixing structure for introducing another fluid through said mixing structure into said central conduit;
• and
• a first valve coupled to the first side channel for controlling the flow of fluid through the side channel;
• and
• an electrospray ionization needle coupled to the output port of the central conduit,
• a second side channel having a volume isolated from the central conduit and the first side channel and coupled to the first side channel;
• and
• a second valve coupled to the second side channel for controlling the flow of fluid through the second side channel.