Method and apparatus for improved electrospray emitter lifetime

1. A method for cleaning an electrospray emitter of a mass spectrometer, comprising:

(a) changing 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 by lowering a magnitude of a voltage applied between a counter electrode and the electrospray emitter, |V|;

(b) causing a cleaning solvent to flow through the 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) causing the droplet to dislodge from the electrospray emitter exterior.

2. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 1 , further comprising:

repeating the step (b) of causing the cleaning solvent to flow through the electrospray emitter and the step (c) of causing droplet dislodgment one or more additional times.

3. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 2 , wherein the step (b) of causing the cleaning solvent to flow through the electrospray emitter and the step (c) of causing droplet dislodgment are repeated for a duration of time corresponding to a pre-determined cleaning time period.

4. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 1 , wherein the step (c) of causing the droplet to dislodge from the electrospray emitter exterior comprises impacting the droplet with a pulse of gas.

5. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 4 , wherein the gas pulse is supplied from a nebulizing gas orifice of the electrospray emitter.

6. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 1 , wherein the step (b) of causing the cleaning solvent to flow through the electrospray emitter comprises causing a chromatographic mobile phase to flow through a chromatographic column to a coupling union and through the coupling union to the electrospray emitter, wherein the electrospray emitter, coupling union and chromatographic column are all housed within a removeable cartridge.

7. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 1 , wherein the step (b) of causing the cleaning solvent to flow through the electrospray emitter comprises introducing the cleaning solvent into an auxiliary inlet of a coupling union that fluidically couples the electrospray emitter to a chromatographic column, wherein the electrospray emitter, coupling union and chromatographic column are all housed within a removeable cartridge.

8. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 1 , wherein the steps (a) through (c) are performed automatically upon the occurrence of a pre-determined number of injections of a sample or samples into the electrospray emitter subsequent to a prior cleaning of the electrospray emitter.

9. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 1 , wherein the cleaning solvent comprises a first cleaning solvent, the method further comprising:

(d) causing a second cleaning solvent, comprising a composition different than a composition of the first cleaning solvent, to flow through the electrospray emitter at least until another droplet forms on the exterior surface of the electrospray emitter while operating the electrospray emitter in the dripping mode of operation; and

(e) causing the other droplet to dislodge from the electrospray emitter exterior.

10. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 9 , wherein the steps (a) through (e) are performed automatically upon the occurrence of a pre-determined number of injections of a sample or samples into the electrospray emitter subsequent to a prior cleaning of the electrospray emitter.

11. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 9 , wherein the step (d) of causing the second cleaning solvent to flow through the electrospray emitter comprises introducing the second cleaning solvent into an auxiliary inlet of a coupling union that fluidically couples the electrospray emitter to a chromatographic column, wherein the electrospray emitter, coupling union and chromatographic column are all housed within a removeable cartridge.

12. A method for cleaning a first electrospray emitter of a mass spectrometer, comprising:

(a) changing a mode of operation of the first electrospray emitter from a stable jet mode of operation to a dripping mode or a pulsating mode of operation by lowering a magnitude of a voltage applied between a counter electrode and the first electrospray emitter, |V 1 |;

(b) moving the first electrospray emitter from a first position from which electrospray ions are delivered to an inlet of a mass spectrometer to a second position;

(c) moving a second electrospray emitter to the first position;

(d) causing a cleaning solvent to flow through the first electrospray emitter at least until a droplet of the cleaning solvent forms on an exterior surface of the first electrospray emitter while operating the electrospray emitter in the dripping mode of operation; and

(e) causing the droplet to dislodge from the electrospray emitter exterior.

13. A method for cleaning a first electrospray emitter of a mass spectrometer as recited in claim 12 , further comprising:

(f) applying a voltage, V 2 , between the counter electrode and the second electrospray emitter that has a magnitude, |V 2 |, that causes the second electrospray emitter to operate according to a stable jet mode of operation;

(g) causing a sample-containing liquid to flow through the second electrospray emitter simultaneously with the execution of the step (d) of causing the cleaning solvent to flow through the first electrospray emitter and the step (e) of droplet dislodgment.

14. A method as recited in claim 13 , wherein the first electrospray emitter and the second electrospray emitter are housed within a same cartridge.

15. A method as recited in claim 14 , wherein the first electrospray emitter is fluidically coupled to a first chromatographic column and the second electrospray emitter is fluidically coupled to a second chromatographic column and the first and second chromatographic columns are both housed within the same cartridge that houses the first and second electrospray emitters.

16. A method for cleaning an electrospray emitter of a mass spectrometer as recited in claim 12 , wherein the steps (a) through (e) are performed automatically upon the occurrence of a pre-determined number of injections of a sample or samples into the first electrospray emitter subsequent to a prior cleaning of the first electrospray emitter.

17. A sample introduction system for a mass spectrometer comprising:

(i) a source of sample;

(ii) a chromatographic column comprising a column inlet that is fluidically coupled to the source of sample and a column outlet;

(iii) and electrospray emitter comprising an emitter inlet that is fluidically coupled to the column outlet;

(iv) a source of cleaning solvent that is fluidically coupled to the emitter inlet;

(v) a voltage supply electrically coupled to the electrospray emitter and 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 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 at least a portion of the cleaning solvent to flow from the source of cleaning solvent to and through the 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.

18. A sample introduction system for a mass spectrometer as recited in claim 17 , further comprising:

(vii) a source of gas,

wherein the computer-readable instructions that are operable to cause the droplet to dislodge from the electrospray emitter exterior are operable to cause the dislodgement by causing the source of gas to apply a pulse of gas to the droplet.

19. A sample introduction system for a mass spectrometer as recited in claim 17 , wherein the chromatographic column and the electrospray emitter are housed within a same cartridge.

20. A sample introduction system for a mass spectrometer as recited in claim 17 , wherein the computer-readable instructions are further operable to automatically execute the steps (a) through (c) upon the occurrence of a pre-determined number of injections of a sample or samples into the electrospray emitter subsequent to a prior cleaning of the electrospray emitter.

21. A sample introduction system for a mass spectrometer as recited in claim 17 , wherein the computer-readable instructions are further operable to:

(d) cause a cessation of the flow of cleaning solvent to and through the electrospray emitter;

(e) cause a flow of liquid sample to flow from the source of sample to the column inlet; and

(f) increase the applied value of |V|, wherein the increase of |V| causes a change of a mode of operation of the electrospray emitter from the dripping mode of operation to the stable jet mode of operation.