Method and apparatus for electrospray ionization
OwnerJohn B Fenninventor
Life of this patent
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Abstract
Sample liquid is supplied to the ion source of an Electrospray Ionization Mass Spectrometer (ESIMS) by capillarity induced flow through a wick element comprising a permeable porous aggregate of fibers or particles of material that is wetted by the sample liquid. This method of liquid introduction eliminates the need for pumps of pressurized gas to drive the flow. It also makes possible the convenient extraction of a representative sample from a stream of liquid flowing at any rate, no matter how large.
Claims17
A method for characterizing solute species in a liquid solution which comprises the following essential steps:
- (a) immersing the entrance end of a wick element in said liquid solution, said liquid solution comprising at least one solute species in a vaporizable solvent, said wick element comprising a porous permeable aggregate of material that is wettable by said liquid solution so that capillarity causes said solution to migrate through said wick to the exit end opposite from the entrance end immersed in said liquid solution,
- (b) maintaining, as in conventional electrospray ionization, a potential difference between said wick and its surroundings that is large enough to produce at the exit end of said wick element an electric field sufficiently intense to disperse the arriving liquid into ambient bath gas as a fine spray of charged droplets, said ambient gas being maintained at a pressure sufficiently high to prevent formation of an electrical discharge in said gas by said electric field,
- (c) allowing solvent to evaporate from such charged droplets, thereby producing gaseous ions from at least some of said solute species,
- (d) characterizing said gaseous solute ions by measurement of at least one of their properties.
In the well established apparatus and procedures of Electrospray Ionization Mass Spectrometry (ESIMS), wherein sample solution is injected into a region of intense electric field through a small bore capillary tube, the improvement which comprises replacing said small bore capillary tube by a wick comprising an aggregate of porous permeable material wettable by the sample solution so that said sample solution migrates by capillarity through said wick from its entrance end immersed in said sample solution to its exit end in the region of intense electric field where the emerging sample solution is dispersed by said intense electric field into bath gas as a fine spray of charged droplets.
An apparatus for characterizing solute species in a solution comprising said solute species dissolved in a vaporizable solvent, said apparatus comprising as essential components:
- (a) a means for providing a region containing an intense electric field, (b) a means for supplying said solution of solute species in a vaporizable solvent from a primary source to said region containing said intense electric field so that said liquid is dispersed as a fine spray of charged droplets into an ambient bath gas, said means of supplying said solution to said high field region comprising a wick element through which said liquid migrates by capillarity from an entrance end immersed in said liquid, to an exit end in the high field region where said high field disperses the emerging liquid into said fine spray of charged droplets, said wick element comprising a porous permeable aggregate of material wettable by said solution,
- c) a means for providing a flow of dry bath gas into said high field region to facilitate evaporation of solvent from said charged droplets,
- (d) a means of characterizing the ions formed when solvent from said charged droplets of said solution of said solute species evaporates into said ambient bath gas.
In any of the varieties of apparatus that are widely used for practicing the well established technique of Electrospray Ionization Mass Spectrometry (ESIM) and in which the solution to be analyzed is injected into the high field region through a small bore capillary tube, the improvement by which said small bore capillary tube is replaced by a wick element comprising an aggregate of porous permeable material that is wettable by said solution and through which said solution migrates by capillarity from its entrance end immersed in said solution to its exit end from which said solution emerges into said high field region to become dispersed as a fine spray of highly charged droplets into a dry bath gas.
In the practice of Thin Layer Chromatography the improvement by which during development of the chromatogram the end of the chromatographic strip, remote from the end immersed in mobile phase solvent, is exposed to an intense electric field that disperses arriving mobile phase as a fine spray of charged droplets into ambient dry bath gas wherein solvent evaporation from said droplets produces gaseous ions of sample solute species that can be characterized by mass and mobility analyses to provide information on the identity of the solute species giving rise to said ions.
In the practice of Thin Layer Chromatography the improvement that provides information on the identity of a species in a particular zone on a thin layer chromatogram by execution of the following steps:
- (a) pressing an area in the midsection of a strip of paper or other porous permeable material wet with a suitable solvents against the section of chromatogram occupied by the zone containing the species to be identified,
- (b) immersing one end of said strip in a pool of said suitable solvent and inserting the other end of said strip into a bath gas in which a nearby electrode at high potential relative to said pool of suitable solvent produces an intense electric field at the end of said strip of paper or other porous permeable material that is immersed in said bath gas, said electric field dispersing as a fine spray of charged droplets into said gas the solution that arrives at the end of said paper strip due to capillarity induced migration through said strip, said droplets containing solute species from the zone of interest on said chromatogram dissolved in said solvent,
- (c) allowing evaporation of solvent into said bath gas from said charged droplets to produce gaseous ions of said solute species from said zone of interest on said chromatogram,
- (d) characterizing said gaseous ions by mass and/or mobility analysis, obtaining information on the identity of said solute species.
In the practice of paper chromatography the improvement that provides information on the identity of a species in a particular zone on a paper chromatogram by execution of the following steps:
- (a) pressing an area in the midsection of a strip of paper or other porous permeable material wet with a suitable solvent, against the section of chromatogram occupied by the zone containing the species to be identified,
- (b) immersing one end of said strip in a pool of said suitable solvent and inserting the other end of said strip into a bath gas in which a nearby electrode at high potential relative to said pool of suitable solvent produces an intense electric field at the end of said strip of paper or other porous permeable material that is immersed in said bath gas, said electric field dispersing as a fine spray of charged droplets into said gas the solution that arrives at the end of said paper strip due to capillarity induced migration through said strip, said droplets containing solute species from the zone of interest on said chromatogram dissolved in said solvent,
- c) allowing evaporation of solvent into said bath gas from said charged droplets to produce gaseous ions of said solute species from said zone of interest on said chromatogram,
- (d) characterizing said gaseous ions by mass and/or mobility analysis, thus obtaining information on the identity of said solute species.
Dependencies are inferred from the claim text.