Charged droplet spray probe
View Patent ↗An improved sample introduction probe is disclosed for the production of ions from liquid sample solutions in an electrospray ion source. Nebulization of a liquid sample emerging from the end of an inner flow tube is pneumatically assisted by gas flowing from the end of an outer gas flow tube essentially coaxial with the inner sample flow tube. The disclosed probe provides for adjustment of the relative axial positions of the ends of the liquid and gas flow tubes without degrading the precise concentricity between the inner and outer tubes. Additionally, the terminal portion of the outer gas flow tube may be fabricated either from a conductive or dielectric material, thereby allowing the pneumatic nebulization and electrospray processes to be optimized separately and independently. Hence, the disclosed invention provides a pneumatically-assisted electrospray probe with improved mechanical and operational stability, reliability, reproducibility, and ease of use compared to prior art probes.
1. A charged droplet sprayer apparatus comprising:
a) a sample delivery tube comprising en entrance end and an exit end, for transporting a liquid sample downstream from said entrance end to said exit end;
b) a guide tube through which said sample delivery tube extends, said guide tube allowing said sample delivery tube to move freely along the axis of said guide tube while essentially preventing displacement of said sample delivery tube in any direction orthogonal to said guide tube axis;
c) a conduit for gas flow, said conduit comprising the annular space between at least a portion of said sample delivery tube proximal to said exit end, and a gas flow tube surrounding and essentially coaxial with said portion, the exit opening of said gas flow tube being proximal to said exit end of said sample delivery tube;
d) means for flowing gas through said gas flow conduit;
e) means for forming an electric field at said exit end; and
f) means for adjusting the axial position of said sample delivery tube within said guide tube, wherein the relative axial positions of said exit end of said sample delivery tube and said exit opening of said gas flow tube is adjusted.
2. An apparatus according to claim 1 , whereby said sample introduction tube comprises an electrically conductive material, and said gas flow tube comprises a dielectric material.
3. An apparatus according to claim 1 , whereby said sample introduction tube comprises an electrically conductive material, and said gas flow tube comprises an electrically conductive material.
4. An apparatus according to claim 1 , whereby said sample introduction tube comprises a dielectric material, and said gas flow tube comprises an electrically conductive material.
5. An apparatus according to claim 1 , whereby said sample introduction tube comprises a dielectric material, and said gas flow tube comprises a dielectric material.
6. An apparatus according to claim 1 , whereby said gas flow tube comprises a dielectric material proximal to and including said exit opening, and comprises a conductive material elsewhere.
7. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said means for adjusting the relative axial positions of said exit end of said sample delivery tube and said exit end of said gas flow tube further comprises means for maintaining the relative angular orientation between said sample delivery tube and said gas flow tube essentially constant during said adjustment.
8. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said gas flow tube comprises a tapered outer surface profile with a low-angle taper, such that the cross-sectional outer dimension of said gas flow tube decreases in the downstream direction.
9. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said exit end of said sample delivery tube has a blunt face.
10. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said exit end of said sample delivery tube has a sharpened-edge face.
11. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said exit opening of said gas flow tube has a blunt face.
12. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said exit opening of said gas flow tube has a sharpened-edge face.
13. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said exit end of said sample delivery tube is located proximal to and upstream of said exit opening of said gas flow tube during operation.
14. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said exit end of said sample delivery tube is located proximal to and downstream of said exit opening of said gas flow tube during operation.
15. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said exit end of said sample delivery tube is located at essentially the same axial position as said exit opening of said gas flow tube during operation.
16. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said means for forming an electric field comprises maintaining said sample delivery tube and said gas flow tube at ground potential.
17. An apparatus according to claims 1 , 2 , 3 , 4 , 5 , or 6 , wherein said means for forming an electric field comprises high voltage applied said sample delivery tube and said gas flow tube.