Method and apparatus for improved electrospray emitter lifetime

A sample introduction system for a mass spectrometer comprising:

• (i) one or more sample sources;
• (ii) at least one chromatographic column, each said chromatographic column comprising a column outlet and a column inlet that is fluidically coupled to the at least one of the one or more sample sources;
• (iii) a first and a second electrospray emitter, each electrospray emitter comprising an emitter inlet that is fluidically coupled to at least one column outlet;
• (iv) a source of cleaning solvent that is fluidically coupled to each emitter inlet;
• (v) a voltage supply electrically coupled to the first and second electrospray emitters and to a counter electrode;
• and
• (vi) a computer or electronic controller comprising computer-readable instructions that are operable to:
• (a) cause the voltage supply to lower a magnitude of a voltage applied between the counter electrode and the first electrospray emitter, |V|, wherein the lowering of |V| causes a change of a mode of operation of the electrospray emitter from a stable jet mode of operation to a dripping mode or a pulsating mode of operation;
• (b) cause the first electrospray emitter to move from a first emitter position from which electrospray ions are delivered to an inlet of a mass spectrometer to a second emitter position and, simultaneously, cause the second electrospray emitter to move from a third emitter position to a fourth emitter position;
• (b) cause at least a portion of the cleaning solvent to flow from the source of cleaning solvent to and through the first electrospray emitter at least until a droplet of the cleaning solvent forms on an exterior surface of the electrospray emitter while operating the electrospray emitter in the dripping mode of operation;
• and
• (c) cause the droplet to dislodge from the electrospray emitter exterior.