Method and apparatus for improving electrospray ionization of solute species
AssigneeAnalytica of Branford, Inc.
InventorsCraig M. Whitehouse, John B. Fenn, Shida Shen, Cawthon Smith
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Abstract
The subject invention teaches the use of mechanical vibration to enhance the electrostatic dispersion of sample solutions into the small, highly charged droplets that can produce ions of solute species for mass spectrometric analysis. Such vibration turns out to be surprisingly effective at ultrasonic frequencies for solutions with flow rates, conductivities and surface tensions too high for stable dispersion by electrostatic forces alone as in conventional electrospray ionization. Several embodiments of the invention are described for purposes of illustration. Other possible embodiments will become apparent to those skilled in the art.
Claims112
A method for the production of ions from a liquid sample for analysis of said ions, comprising:
- providing a tubular conduit having an exit end, said tubular conduit having a channel of small diameter at said exit end, said exit end serving as the tip of said tubular conduit,
- passing said liquid sample through said tubular conduit;
- maintaining said conduit at an electrical potential at said exit end relative to a conductive surface at some distance from said exit end, said conducting surface serving as a counter electrode to said conduit,
- simultaneously subjecting said liquid sample to both an electrostatic field and mechanical vibration at the point of exit form said tubular conduit to form charged droplets of said liquid sample at said point of exit and to induce emission of ions from said charged droplets.
A method of analyzing liquid samples which comprises the production of charged droplets from said liquid sample, and the production of ions from said charged droplets, said method comprising the steps of:
- flowing a first liquid sample to be analyzed through a first tubular conduit with a small diameter at an exit end so that said first liquid sample emerges from said exit end of said first tubular conduit,
- flowing a second solution through the annulus between an inner bore of a second tubular conduit and the outer surface of said first tubular conduit, where said first tubular conduit extends through said inner bore of said second tubular conduit, with means to adjust the relative positions of the exit ends of said first and said second tubular conduits, said second solution exiting at the exit end of said second tubular conduit, wherein said second solution mixes with said first liquid sample,
- maintaining at said exit of said first and second tubular conduits a bath gas,
- supplying to either said first or second tubular conduit an electrical potential capable of maintaining said exit end of said second tubular conduit at a high potential with respect to some neighboring conductive surface so as to produce a strong electrostatic field at said exit end of said second tubular conduit such that an electric current flows from said second tubular conduit to said neighboring surface when said mixture of liquid sample and second solution is flowing through said second tubular conduit, said electrical current comprising charged droplets and molecular ions driven through said bath gas by said electrostatic field, said charged droplets having been produced by said electrostatic field from said mixture of said liquid sample and second solution as said mixture emerges from said exit end of said second tubular conduit, and said molecular ions having been produced from said charged droplets as they evaporate in said bath gas,
- providing a means for simultaneously mechanically vibrating said second tubular conduit's exit end at high frequency while it is at high potential relative to said neighboring surface, said mechanical vibration aiding in said charged droplet formation from said mixture as it emerges from said second tubular conduits exit end, and said mechanical vibration aiding in emission of ions from said charged droplets.
- passing said bath gas containing said evaporating charged droplets and molecular ions produced from said evaporating charged droplets into an analyzing means for analysis of said ions.
An apparatus for the production of ions from a liquid sample for analysis of said ions, comprising:
- a liquid sample,
- providing a tubular conduit having an exit end, said tubular conduit having a channel of small diameter at said exit end, said exit end serving as the tip of said tubular conduit,
- maintaining said conduit at an electrical potential at said exit end relative to a conductive surface at some distance from said exit end, said conducting surface serving as a counter electrode to said conduit,
- means for simultaneously subjecting said liquid sample to both an electrostatic field and mechanical vibration at the point of exit from said tubular conduit to form charged droplets of said liquid sample at said point of exit and induce the emission of ions from said charged droplets.
Dependencies are inferred from the claim text.