Ion source for mass spectrometer and method of producing analyte ion stream

Patent metadata

Field	Value
Publication number	US-9305761-B2
Application number	US-201414458311-A
Country	US
Kind code	B2
Filing date	Aug 13, 2014
Priority date	Aug 14, 2013
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

An ion source for a mass spectrometer and a method of ionizing a sample are disclosed. A droplet generator is configured to emit a stream of analyte droplets, which are ionized upon impact with a target, thus forming an ion stream. Preferably, the droplets have a diameter that is greater than a preset value to increase the kinetic energy of the droplets. Additionally, the droplet generator can be configured to create a gas flow that increases the kinetic energy of the droplets. In one embodiment, the target is positioned upstream of an inlet of a mass spectrometer so that the ion stream enters the inlet. In another preferred embodiment, the target is positioned downstream of the inlet so that the stream of droplets passes through the inlet of the mass spectrometer, and the inlet is provided with a pressure drop that increases the kinetic energy of the droplets.

First claim

The invention claimed is:

1. An ion source for producing an ion stream from a sample for a mass spectrometer, the ion source comprising:
a droplet generator including:
a first capillary tube having an exit; and
an actuator configured to expel a droplet from the first capillary tube through the exit in response to receiving an electrical signal; and

a target, wherein the ion source is configured to apply an electric potential to the target without forming a corona discharge, and wherein the droplet generator is configured so that droplets exiting the first capillary tube are caused to impact upon the target, thus forming the ion stream.

2. The ion source of claim 1 , wherein the droplet generator is configured to provide a gas flow that increases a kinetic energy of the droplets.

3. The ion source of claim 2 , wherein the droplet generator further includes a second capillary tube surrounding the first capillary tube, the second capillary tube configured to provide the gas flow that increases the kinetic energy of the droplets.

4. The ion source of claim 3 , wherein the second capillary tube is concentric with the first capillary tube and the exit of the first capillary tube is located within the second capillary tube.

5. The ion source of claim 1 , wherein the actuator includes a piezoelectric element, said ion source further comprising:
an electrical source configured to supply the electrical signal to the piezoelectric element, wherein the electrical signal includes electrical pulses at a preset frequency, thereby producing droplets at the preset frequency.

6. The ion source of claim 5 , wherein the preset frequency is between 100 Hz and 15 kHz.

7. The ion source of claim 1 , wherein the exit of the first capillary tube has a diameter that is greater than a preset value and the droplets have diameters substantially the same as the diameter of the first capillary tube.

8. The ion source of claim 7 , wherein the preset value is at least 30 μm.

9. The ion source of claim 1 , wherein the target is positioned upstream of an inlet of the mass spectrometer so that the ion stream enters the inlet of the mass spectrometer.

10. The ion source of claim 1 , wherein the target is positioned downstream of an inlet of the mass spectrometer so that the droplets enter the inlet of the mass spectrometer.

11. The ion source of claim 10 , wherein the inlet is provided with a pressure drop that increases a kinetic energy of the droplets.

12. An ion source for producing an ion stream from a sample for a mass spectrometer, the ion source comprising:
a droplet generator including:
a first capillary tube having an exit; and
an actuator configured to expel a droplet from the first capillary tube through the exit in response to receiving an electrical signal;

a target, wherein the droplet generator is configured so that droplets exiting the first capillary tube are caused to impact upon the target, thus forming the ion stream; and
a corona discharge pin positioned so that the droplets or the ion stream pass by the corona discharge pin.

13. A method of producing an analyte ion stream from a sample for a mass spectrometer, comprising:
receiving an electrical signal;
expelling, with an actuator of a droplet generator, droplets from an exit of a first capillary tube in response to receiving the electrical signal;
applying an electric potential to a target without forming a corona discharge; and
causing droplets exiting the first capillary tube to impact the target in order to form the ion stream.

14. The method of claim 13 , further comprising:
providing, with the droplet generator, a gas flow that increases a kinetic energy of the droplets.

15. The method of claim 14 , wherein providing the gas flow with the droplet generator includes providing the gas flow with a second capillary tube that surrounds the first capillary tube.

16. The method of claim 13 , wherein the actuator includes a piezoelectric element, said method further comprising:
supplying, with an electrical source, the electrical signal to the piezoelectric element, the electrical signal including pulses at a preset frequency; and
producing droplets at the preset frequency.

17. The method of claim 16 , wherein producing droplets at the preset frequency includes producing droplets at a frequency between 100 Hz and 15 kHz.

18. The method of claim 13 , wherein expelling the droplet with the actuator includes expelling a droplet having a diameter of at least 30 μm.

19. The method of claim 13 , further comprising:
positioning the target downstream of an inlet of a mass spectrometer so that the droplets enter the inlet; and
providing the inlet with a pressure drop that increases a kinetic energy of the droplets.

20. A method of producing an analyte ion stream from a sample for a mass spectrometer, comprising:
receiving an electrical signal;
expelling, with an actuator of a droplet generator, droplets from an exit of a first capillary tube in response to receiving the electrical signal;
causing droplets exiting the first capillary tube to impact a target in order to form the ion stream; and
positioning a corona discharge pin so that the droplets or the ion stream pass by the corona discharge pin.

21. The ion source of claim 1 , wherein the target is an impactor pin.

22. The method of claim 13 , wherein causing droplets exiting the first capillary tube to impact the target includes causing droplets exiting the first capillary tube to impact an impactor pin.

Assignees

• Waters Technologies Corp

Inventors

• Jarrell Joseph A

Classifications

• H01J49/16 Primary

  using surface ionisation, e.g. field-, thermionic- or photo-emission · CPC title

• H01J49/0454

  with means for vaporising using mechanical energy, e.g. by ultrasonic vibrations · CPC title