Ion sources for improved ionization
Improved apparatuses and methods are provided for ionizing samples and analyzing the samples with mass spectrometry.
1. An ion source comprising:
a housing that defines a chamber;
a capillary having a receiving end and a delivery end, wherein a liquid sample can be received from outside of the chamber through the receiving end and sprayed into droplets out of the delivery end in the chamber; and
a conduit surrounding the capillary for transmitting a heated gas, the conduit being connected to a nozzle to release the heated gas into the chamber, wherein the nozzle comprises at least one electrode to which a potential can be applied, which contributes to the generation of an electrical field at the delivery end of the capillary.
2. The ion source of claim 1 , further comprising an inlet that transfers ions to a mass spectrometer or ion mobility separating device, wherein said inlet is at a potential relative to the capillary that creates an electric field at the delivery end of the capillary for charging at least some of said droplets, wherein the potential of the nozzle is set to adjust said electrical field to enhance or to suppress said charging of the droplets.
3. The ion source of claim 2 , wherein the inlet is substantially orthogonal to the capillary.
4. The ion source of claim 1 , wherein the potential of the nozzle is tunable.
5. The ion source of claim 1 , wherein the capillary is grounded.
6. The ion source of claim 1 , configured to have the capillary and the nozzle at the same potential.
7. The ion source of claim 1 , further comprising a tube surrounding the capillary for transmitting a nebulizing gas to a location near the delivery end of the capillary to nebulize the sample.
8. The ion source of claim 7 , wherein the heated gas and the nebulizing gas are both released into the chamber in a flow parallel to the capillary.
9. The ion source of claim 7 , wherein the heated gas and the nebulizing gas are both released into the chamber in a flow concentric with the capillary.
10. The ion source of claim 1 , further comprising a shielding layer that acts as a heat sink.
11. The ion source of claim 10 , wherein the shielding layer comprises a thermal conductor having a surface that is chemically inert and/or has low emissivity.
12. The ion source of claim 1 , further comprising an insulator layer between the capillary and the conduit, the insulator layer being heat-insulating and electric-insulating.
13. The ion source of claim 1 , wherein the delivery end of the capillary is 6 mm or less away from the nearest part of the nozzle.
14. The ion source of claim 1 , wherein the delivery end of the capillary is 4 mm or less away from the nearest part of the nozzle.
15. The ion source of claim 1 , wherein the nozzle comprises an inner nozzle element and an outer nozzle element, both the inner and outer nozzle elements surrounding the capillary, wherein the inner and outer nozzle elements are configured to operate at different potentials.
16. A mass spectrometer system comprising the ion source of claim 1 , the mass spectrometer system further comprising a mass analyzer and an ion detector.
17. The mass spectrometer system of claim 16 , comprising an ion mobility separating device, a mass analyzer and an ion detector.
18. A method for generating ions from a liquid sample comprising analytes and a solvent, comprising:
passing the sample through a capillary;
in a chamber, spraying the sample into droplets out of the capillary;
subjecting the droplets to an electrical field to electrically charge at least some of the droplets;
providing a flow of heated gas from a nozzle into the chamber to confine the flow of the droplets, the nozzle being connected to a conduit which surrounds the capillary, wherein the nozzle comprises at least one electrode to which a potential is applied, which contributes to the generation of said electrical field;
whereby the solvent evaporates from the charged droplets to result in formation of analyte ions.
19. The method of claim 18 , further comprising providing a nebulizing gas to nebulize the sample.
20. The method of claim 18 , further comprising providing a heat sink to dissipate heat away from the capillary.
21. The method of claim 18 , wherein the heated gas is released to a place that is 5 mm or less away from the end of the capillary where the sample is sprayed out.
22. The method of claim 18 , wherein ions are generated from less polar analytes that are traditionally not amenable to electrospray ionization.