Mass spectrometer electrospray ionization

A method of providing ions to a mass spectrometer having an interface member with an orifice through which ions are received for analysis, comprising:

• (a) providing a fluid at a capillary tip of an electrospray ionization source;
• (b) alternately providing:
• a first electric field between the tip and the interface member so as to direct an ion beam from the tip toward and through the orifice;
• and a second electric field which decreases beam divergence from at least part way toward the interface member wherein the first and second fields are provided at a time such that the second field is provided when ions emitted from the tip during provision of the first field are intermediate the tip and interface member.

A method of providing ions to a mass spectrometer having an interface member with an orifice through which ions are received for analysis, comprising:

• (a) providing a fluid at a capillary tip of an electrospray ionization source and applying a potential difference between the tip and the interface member so as to direct an ion beam from the tip toward and through the orifice;
• (b) alternately applying to an auxiliary electrode:
• a field enhancing potential which increases the electric field gradient from the capillary tip at least part way toward the interface member;
• and a focussing potential so as to decrease beam divergence from at least part way toward the interface member wherein the field enhancing and focussing potentials are applied at a time such that the focussing potential is applied when ions emitted from the tip during application of the field enhancing potential are intermediate the tip and interface member.

A mass spectrometer comprising:

• (a) an interface member with an orifice;
• (b) an analyzer section to receive ions which have passed through the orifice and detect them as a function of mass and charge;
• (c) an electrospray ionization source having a capillary with a channel and a tip, such that a fluid can be delivered to the tip through the channel;
• and
• (d) an electrode set and power supply connected to the set so as to alternately provide
• a first electric field between the tip and the interface member so as to direct an ion beam from the tip toward and through the orifice;
• and
• a second electric field which decreases beam divergence from at least part way toward the interface member wherein the power supply provides the first and second fields at a time such that the second field is provided when ions emitted from the tip during provision of the first field are intermediate the tip and interface member.

A mass spectrometer comprising:

• (a) an interface member with an orifice;
• (b) an analyzer section to receive ions which have passed through the orifice and detect them as a function of mass and charge;
• and
• (c) an electrospray ionization source having:
• (i) a capillary having a channel and a tip, such that when fluid is delivered to the tip through the channel and a potential applied between the tip and the interface member, an ion beam is directed from the tip toward the orifice;
• and
• (ii) an auxiliary electrode mounted with respect to the capillary tip, to which a focussing potential can be applied so as to decrease beam divergence from at least part way toward the interface member wherein said auxiliary electrode has a conical shape.