Piezo-electric vibration on an in-source surface ionization structure to aid secondary droplet reduction

Patent metadata

Field	Value
Publication number	US-10020177-B2
Application number	US-201214438246-A
Country	US
Kind code	B2
Filing date	Oct 25, 2012
Priority date	Oct 25, 2012
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

An ion source is disclosed comprising a nebulizer and a target. The nebulizer is arranged and adapted to emit, in use, a stream of analyte droplets which are caused to impact upon the target and to ionize analyte to form a plurality of analyte ions. The target is vibrated by a piezo-electric vibration device to reduce the size of resultant secondary droplets.

First claim

The invention claimed is:

1. An ion source comprising:
one or more nebulisers and one or more targets; and
a vibration device arranged and adapted to cause said one or more targets to vibrate;
wherein said one or more nebulisers are arranged and adapted to emit, in use, a stream predominantly of droplets which are caused to impact upon said one or more targets and to ionise said droplets to form a plurality of ions
wherein said vibration device is arranged and adapted to vibrate said one or more targets at a frequency f selected from the group consisting of: (i) <1 kHz; (ii) 1-2 kHz; (iii) 2-3 kHz; (iv) 3-4 kHz; (v) 4-5 kHz; (vi) 5-6 kHz; (vii) 6-7 kHz; (viii) 7-8 kHz; (ix) 8-9 kHz; (x) 9-10 kHz; (xi) 10-11 kHz; (xii) 11-12 kHz; (xiii) 12-13 kHz; (xiv) 13-14 kHz; (xv) 14-15 kHz; (xvi) 15-16 kHz; (xvii) 16-17 kHz; (xviii) 17-18 kHz; and (xix) 18-19 kHz.

2. An ion source as claimed in claim 1 , wherein said vibration device is arranged and adapted to cause said one or more targets to vibrate in order to reduce the size of resultant secondary droplets through surface disruption.

3. An ion source as claimed in claim 1 , wherein said vibration device comprises a piezo-electric vibration source.

4. An ion source as claimed in claim 1 , wherein said droplets comprise analyte droplets and said plurality of ions comprise analyte ions.

5. An ion source as claimed in claim 1 , wherein said droplets comprise reagent droplets and said plurality of ions comprise reagent ions.

6. An ion source as claimed in claim 1 , wherein an analyte liquid is supplied to said one or more targets and is ionised to form a plurality of analyte ions or a reagent liquid is supplied to said one or more targets and is ionised to form reagent ions which transfer charge to neutral analyte atoms or molecules to form analyte ions or which enhance the formation of analyte ions; wherein:
said one or more targets comprise one or more apertures and wherein said analyte liquid or said reagent liquid is supplied directly to said one or more targets and emerges from said one or more apertures.

7. An ion source as claimed in claim 1 , wherein said one or more targets are coated with one or more liquid, solid or gelatinous analytes and wherein said one or more analytes are ionised to form a plurality of analyte ions.

8. An ion source as claimed in claim 1 , wherein said one or more targets are formed from one or more analytes and wherein said one or more analytes are ionised to form a plurality of analyte ions.

9. An ion source as claimed in claim 1 , wherein said ion source comprises an Atmospheric Pressure Ionisation (“API”) ion source.

10. An ion source as claimed in claim 1 , wherein said one or more nebulisers are arranged and adapted such that the majority of the mass or matter emitted by said one or more nebulisers is in the form of droplets not vapour; wherein:
at least 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% of the mass or matter emitted by said one or more nebulisers is in the form of droplets.

11. An ion source as claimed in claim 1 , wherein said one or more nebulisers are arranged and adapted to emit a stream of droplets wherein the Sauter mean diameter of said droplets is in a range: (i) <5 μm; (ii) 5-10 μm; (iii) 10-15 μm; (iv) 15-20 μm; (v) 20-25 μm; or (vi) >25 μm.

12. An ion source as claimed in claim 1 , wherein said stream of droplets emitted from said one or more nebulisers forms a stream of secondary droplets after impacting said one or more targets; wherein:
said stream of droplets or said stream of secondary droplets traverse a flow region with a Reynolds number (Re) in the range: (i) <2000; (ii) 2000-2500; (iii) 2500-3000; (iv) 3000-3500; (v) 3500-4000; or (vi) >4000.

13. An ion source as claimed in claim 1 , wherein at the point of said droplets impacting said one or more targets said droplets have one or more of the following:
a Weber number (We) selected from the group consisting of: (i) <50; (ii) 50-100; (iii) 100-150; (iv) 150-200; (v) 200-250; (vi) 250-300; (vii) 300-350; (viii) 350-400; (ix) 400-450; (x) 450-500; (xi) 500-550; (xii) 550-600; (xiii) 600-650; (xiv) 650-700; (xv) 700-750; (xvi) 750-800; (xvii) 800-850; (xviii) 850-900; (xix) 900-950; (xx) 950-1000; and (xxi) >1000; and
a Stokes number (S k ) in the range: (i) 1-5; (ii) 5-10; (iii) 10-15; (iv) 15-20; (v) 20-25; (vi) 25-30; (vii) 30-35; (viii) 35-40; (ix) 40-45; (x) 45-50; and (xi) >50.

14. An ion source as claimed in claim 1 , wherein the mean axial impact velocity of said droplets upon said one or more targets is selected from the group consisting of: (i) <20 m/s; (ii) 20-30 m/s; (iii) 30-40 m/s; (iv) 40-50 m/s; (v) 50-60 m/s; (vi) 60-70 m/s; (vii) 70-80 m/s; (viii) 80-90 m/s; (ix) 90-100 m/s; (x) 100-110 m/s; (xi) 110-120 m/s; (xii) 120-130 m/s; (xiii) 130-140 m/s; (xiv) 140-150 m/s; and (xv) >150 m/s; or
said one or more targets are arranged <20 mm, <19 mm, <18 mm, <17 mm, <16 mm, <15 mm, <14 mm, <13 mm, <12 mm, <11 mm, <10 mm, <9 mm, <8 mm, <7 mm, <6 mm, <5 mm, <4 mm, <3 mm or <2 mm from the exit of said one or more nebulisers.

15. An ion source as claimed in claim 1 , wherein said one or more nebulisers are arranged and adapted to nebulise one or more eluents emitted by one or more devices over a period of time; wherein:
said one or more devices comprise one or more liquid chromatography separation devices.

16. An ion source as claimed in claim 1 , wherein said one or more nebulisers comprise:
one or more rotating disc nebulisers; or a
first capillary tube having an exit which emits, in use, said stream of droplets.

17. An ion source as claimed in claim 16 , further comprising one or more heaters which are arranged and adapted to supply one or more heated streams of gas to the exit of said one or more nebulisers; wherein either:
(i) said one or more heaters surround said first capillary tube and are arranged and adapted to supply a heated stream of gas to the exit of said first capillary tube; or
(ii) said one or more heaters comprise one or more infra-red heaters; or
(iii) said one or more heaters comprise one or more combustion heaters.

18. An ion source as claimed in claim 1 , further comprising one or more heating devices arranged and adapted to directly or indirectly heat said one or more targets; wherein:
said one or more heating devices comprise one or more lasers arranged and adapted to emit one or more laser beams which impinge upon said one or more targets in order to heat said one or more targets.

19. An ion source as claimed in claim 1 , wherein in a mode of operation said one or more targets are maintained at:
a positive potential and wherein said droplets impacting upon said one or more targets form a plurality of positively charged ions; or
a negative potential and wherein said droplets impacting upon said one or more targets form a plurality of negatively charged ions.

20. An ion source as claimed in claim 1 , further comprising a device arranged and adapted to apply a sinusoidal or non-sinusoidal AC or RF voltage to said one or more targets.

21. An ion source as claimed in claim 1 , wherein said one or more targets are arranged or otherwise positioned so as to deflect said stream of droplets or said plurality of ions towards an ion inlet device of a mass spectrometer.

22. An ion source as claimed in claim 1 , wherein said one or more targets are positioned upstream of an ion inlet device of a mass spectrometer so that ions are deflected towards the direction of said ion inlet devi

Assignees

• Micromass Ltd

Inventors

• Bajic Stevan
• Douce David
• Jones Gordon

Classifications

• H01J49/16

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

• H01J49/0454 Primary

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

• H01J49/0445 Primary

  with means for introducing as a spray, a jet or an aerosol (electrospray ion sources H01J49/165) · CPC title

• H01J49/061

  Ion deflecting means, e.g. ion gates · CPC title

• H01J49/045 Primary

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