APCI ion source with asymmetrical spray

Patent metadata

Field	Value
Publication number	US-11189477-B2
Application number	US-201816639411-A
Country	US
Kind code	B2
Filing date	Aug 10, 2018
Priority date	Aug 17, 2017
Publication date	Nov 30, 2021
Grant date	Nov 30, 2021

Abstract

Systems and methods for atmospheric pressure chemical ionization are provided herein. In various aspects, the APCI apparatus, systems, and methods can provide an asymmetric sample spray into a vaporization chamber asymmetrically (e.g., off axis from the longitudinal axis of the vaporization chamber) so as to increase the interaction of the molecules in the sample spray with the vaporization chamber's sidewalls (and expose more of the molecules to the heat generated thereby), which can thereby result in improved consistency and/or efficiency of ion formation, and/or increased sensitivity relative to conventional APCI techniques.

First claim

The invention claimed is:

1. An atmospheric pressure chemical ionization
source for a mass spectrometer, comprising:
a heated vaporization tube defining a lumen extending from a vaporization tube inlet end to a vaporization tube outlet end along a central longitudinal axis, the vaporization tube outlet end configured to be disposed within an ion source housing in fluid communication with a sampling orifice of the mass spectrometer;
a sampling probe comprising a liquid conduit extending from a liquid conduit inlet end configured to receive a liquid sample comprising solvent molecules and sample molecules to a liquid conduit outlet end disposed within the lumen of the heated vaporization tube between the vaporization tube inlet end and the vaporization tube outlet end, said sampling probe further comprising a gas conduit at least partially surrounding the liquid conduit for providing a nebulizing gas about the liquid sample discharged from the liquid conduit outlet end,
the sampling probe further comprising a dimple formed on an inner sidewall of the gas conduit that at least partially surrounds the liquid conduit to deflect the liquid conduit such that the liquid discharged from the liquid conduit is directed along at a sidewall of the heated vaporization tube, wherein the liquid conduit outlet end is configured to discharge the liquid sample into a sample spray exhibiting a central axis that is not coaxial with the central longitudinal axis of the lumen, wherein the heated vaporization tube is configured to vaporize at least a portion of said solvent molecules and sample molecules as the sample spray traverses the lumen toward the vaporization tube outlet end,
a gas source coupled to said heated vaporization tube for introducing an entrainment flow of gas between an outer surface of the sampling probe and an inner wall of the heated vaporization tube into the vaporization tube so as to promote asymmetric flow of the sample spray within the heated vaporization tube and to inhibit back streaming of the sample spray; and
a charge source disposed adjacent to the vaporization tube outlet end configured to apply an electric charge to the vaporized solvent molecules and sample molecules as said vaporized solvent molecules and sample molecules exit from the vaporization tube outlet end into the ion source housing so as to ionize the sample molecules within the ion source housing.

2. The device of claim 1 , further comprising a gas source configured to provide a gas flow about the sampling probe to direct the liquid sample discharged from the sampling probe toward the inner sidewall of the heated vaporization tube.

3. The device of claim 1 , wherein the central axis of the sample spray intersects the heated vaporization tube.

4. The device of claim 1 , wherein at least the liquid conduit outlet end extends along a longitudinal axis that intersects the heated vaporization tube.

5. The device of claim 1 , wherein the vaporization tube is configured to be heated to a temperature in a range of about 100° C. to about 750° C.

6. The device of claim 1 , wherein the charge source comprises a corona discharge needle.

7. The device of claim 1 , wherein the heated vaporization tube and the sampling probe are configured such that the vaporized solvent molecules and sample molecules preferentially exit the heated vaporization tube from a side of the lumen's central longitudinal axis.

8. The device of claim 7 , wherein the charge source comprises a discharge needle that is disposed adjacent to the vaporization tube outlet end on said side from which said vaporized solvent molecules and sample molecules preferentially exit.

9. A method of ionizing sample molecules within a liquid sample, comprising:
providing a heated vaporization tube defining a lumen extending from a vaporization tube inlet end to a vaporization tube outlet end along a central longitudinal axis, the vaporization tube outlet end configured to be disposed within an ion source housing in fluid communication with a sampling orifice of a mass spectrometer,
providing a sampling probe comprising a liquid conduit extending from a liquid conduit inlet end configured to receive a liquid sample comprising solvent molecules and sample molecules to a liquid conduit outlet end disposed within the lumen of the heated vaporization tube between the vaporization tube inlet end and the vaporization tube outlet end, said sampling probe further comprising a gas conduit at least partially surrounding the liquid conduit for providing a nebulizing gas about the liquid sample discharged from the liquid conduit outlet end, wherein a dimple formed on an inner sidewall of the gas conduit that at least partially surrounds the liquid conduit deflects the liquid conduit such that the liquid discharged from the liquid conduit is directed along at a sidewall of the heated vaporization tube,
discharging the liquid sample from the liquid conduit outlet end into the lumen of the heated vaporization tube, wherein the lumen of the heated vaporization tube extends along a central longitudinal axis, wherein the liquid sample is discharged as a sample spray exhibiting a central axis that is not coaxial with the central longitudinal axis of the lumen;
vaporizing at least a portion of solvent molecules and sample molecules within the liquid sample as the sample spray traverses the lumen toward the vaporization tube outlet end;
introducing an entrainment flow of gas into the vaporization tube so as to promote asymmetric flow of the sample spray within the heated vaporization tube and to inhibit back streaming of the sample;
applying an electrical charge to at least one of the vaporized solvent molecules and sample molecules as they exit the vaporization tube outlet end into an ionization chamber such that the sample molecules are ionized within the ionization chamber;
transmitting the ionized sample molecules from the ionization chamber into the sampling orifice of the mass spectrometer; and
performing mass spectrometric analysis of the ionized sample molecules.

10. The method of claim 9 , wherein the ionization chamber is maintained at substantially atmospheric pressure.

11. The method of claim 9 , wherein the gas flow is configured to maintain the liquid sample discharged from the sampling probe toward the inner wall of the heated vaporization tube on the side of the central longitudinal axis on which the sample spray is offset.

12. The method of claim 9 , wherein the central axis of the sample spray as the sample spray exits the sampling probe intersects the heated vaporization tube.

13. The method of claim 9 , further comprising maintaining the heated vaporization tube at a temperature in a range of about 100° C. to about 750° C.

14. The method of claim 9 , wherein the vaporized solvent molecules and sample molecules preferentially exit the heated vaporization tube from one side of the lumen's central longitudinal axis.

15. The method of claim 14 , wherein the electrical charge is applied by a charge source disposed adjacent to the vaporization tube outlet end on said side from which said vaporized solvent molecules and sample molecules preferentially exit from the heated vaporization tube.

16. The atmospheric pressure chemical ionization source of claim 1 , wherein said liquid conduit is configured to discharge the liquid sample along an axis that is substantially perpendicular to said central longitudinal axis of the heated vaporization tube.

17. The atmospheric pressure chemical ionization source of claim 1 , wherein said liquid conduit is configured to discharge the

Assignees

• Dh Technologies Dev Pte Ltd

Inventors

• Covey Thomas R
• Kovarik Peter

Classifications

• H01J49/049

  with means for applying heat to desorb the sample; Evaporation · CPC title

• H01J49/045

  with means for using a nebulising gas, i.e. pneumatically assisted · CPC title

• H01J49/0404

  Capillaries used for transferring samples or ions (electrospray nozzles H01J49/167) · CPC title

• H01J49/165 Primary

  Electrospray ionisation · CPC title

• H01J49/145 Primary

  using chemical ionisation · CPC title