Improved techniques are provided for forming ionized molecules from electrosprayed droplets for analysis by a mass spectrometer. A high voltage is applied to a capillary tube for spraying droplets at substantially atmospheric pressure or above, and the electrosprayed droplets contain sample solute of interest and solvent. The electrosprayed droplets are passed into an ion generating chamber which is maintained at a pressure in the range of from 0.1 Torr to 10 Torr. The walls of the ion generating chamber are controllably heated to a temperature which will desolvate the droplets and produce ionized molecules of interest for analysis by the mass spectrometer. The electrospray technique does not rely upon a countercurrent heated gas flow, and provides a particularly simple and inexpensive means to couple electrospray ionization to either quadrupole or magnetic mass analyzers.

Electrospray method for mass spectrometry

A method of changing the energy of charged particles contained in a gas comprises allowing the gas to flow into a region of reduced pressure through a tube like member so that viscous forces exerted on the charged particles by the flowing gas molecules determine the kinetic energy of the charged particles. A potential gradient is maintained along the length of the tube so that the potential energy of the charged particles is changed as they pass through the tube. At the end of the tube a free jet expansion occurs so that the kinetic energy of the charged particles is no longer determined by the flowing gas, so that they can be accelerated to any desired kinetic energy by means of another potential gradient. The invention can be used to interface any high pressure ion source to a magnetic sector mass spectrometer, or to permit the operation of an electrospray ion source with an earthed inlet capillary with either a quadrupole or a magnetic sector mass spectrometer.

Process and apparatus for changing the energy of charged particles contained in a gaseous medium

An electrospray ion source for a mass spectrometer capable of generating ions from samples dissolved in a solution comprises a capillary tube (30) through which the said solution is pumped into a first chamber maintained substantially at atmospheric pressure and in which an inert gas, preferably heated, is flowing in a direction counter to the flow of the solution, and a small orifice (4) in the end wall (1) of the chamber opposite to and aligned with the capillary. A high potential difference is applied between the capillary tube (30) and the end wall (1) so thatthe solution is electrosprayed into the chamber and ions characteristic of the sample are formed. These ions are desolvated to a controllable extent by the inert gas, which is usually heated to improve the efficiency of the process and increase the maximum permissible flow rate of solution. The ions so formed pass through the small orifice (4) into a second chamber maintained at a reduced pressure, and into a mass spectrometer (29). Alternatively an additional pressure reduction stage can be included, so that the ions pass into a third chamber maintained at a still lower pressure in which the mass spectrometer (29) is situated through a hole (23) in skimmer (24). The ion source is particularly effective for the production of unfragmented and unsolvated ions from thermally unstable or involatile samples, and may be used as a liquid chromatograph - mass spectrometer interface.

Method and apparatus for the mass spectrometric analysis of solutions

A ion mobility spectrometer system with improved specificity. The ion mobility spectrometer (10) has a reaction chamber (12) and a drift chamber (14), an ionization source (32) disposed in the reaction chamber (12), an injection grid (24) separating said reaction and drift chambers (12, 14), a collector electrode (22) disposed in the drift chamber (14) and a sample input (16) injecting the sample and carrier into the reaction chamber. A source (70) injects acetone and/or carbon tetrachloride as reagents into the carrier gas prior to entering the sample input (16). The acetone reactant forms a dimer ion in the positive ion spectrum which impedes the clustering of water and provides a narrow fixed peak in the ion spectrum which serves as a reference point in the ion spectrum for the algorithm used in the electronic control unit generating an output characteristic of the sample. The carbon tetrachloride reactant forms a (H2O)nCl- ion which provides a reference in the negative ion spectrum for the algorithm used in the electronic control unit. The acetone and carbon tetrachloride reactants both rendering the ion mobility spectrometer (10) more specific for detection and identification.

Ion mobility spectrometer system with improved specificity

A method and apparatus are disclosed wherein a plurality of electric fields and of orthogonal spray configurations of vaporized analyte are so combined as to enhance the efficiency of analyte detection and mass analysis The invention provides reduced noise and increased signal sensitivity in both API electrospray and APCI operating modes

Orthogonal ion sampling for APCI mass spectrometry

Apparatus for analyzing sample gas consisting of a trace gas contained in a carrier gas. The sample gas is carried through a cylindrical duct; ions from the trace gas are formed, and are subjected to a transverse electric field which concentrates the flux of desired ions into an axial stream located away from the duct walls. The electric field may be produced by a combination of the duct walls and a central axial needle electrode in the duct, or by conical focussing screens or by cylindrical lens elements. The concentrated flux of ions passes through spaced interface and orifice plates containing a gas curtain between them and then passes into a vacuum chamber containing a mass spectrometer or other detector. The curtain gas, which blocks flow of carrier gas into the vacuum chamber, is cryo pumpable (e.g. CO2). The vacuum chamber contains surfaces cooled so as to cause deposit of the curtain gas thereon, thereby maintaining a vacuum. The cryo pumpable curtain gas arrangement may also be used to transfer other species or materials, such as materials arranged in a continuous strip, between two gaseous media, one at lower pressure than the other, without transfer of one such medium into the other.

Apparatus for analyzing trace components

Apparatus for analyzing trace components contained in a sample gas. The sample gas is directed into a reaction chamber and ionized. The resultant trace ions are drifted by an electric field, out of the sample gas, through an inert gas curtain and then through an orifice into a vacuum chamber where they are focused and analyzed. The curtain gas flow may be greater than the flow through the orifice, in which case the gas curtain acts as an ion window which is transparent to ions but blocks sample gas flow into the vacuum chamber. Alternatively, the curtain gas flow may be controlled to admit a desired flow of sample gas through the curtain into the vacuum chamber, in which case the gas curtain acts as a window for ions and as an infinitely variable orifice for the sample gas. Preferably the curtain gas is cryopumpable and is cryopumped by cooling the interior surface of the vaccum chamber.

Method and apparatus for analyzing trace components using a gas curtain

A method and apparatus for focussing and declustering trace ions travelling from a gas through an orifice into a vacuum chamber and to a mass analyzer in the vacuum chamber. Advantage is taken of the free jet expansion of the gas into the vacuum chamber by applying an electric focussing field in a specific region of the free jet. The region is selected sufficiently close to the orifice that the gas density limits the kinetic energy spread which the ions can acquire under the applied field, typically to 2 ev or less, while the early focussing increases the available ion signal. Declustering can be collision induced in the region by providing a field in the region sufficient to impart an internal energy of between 0.1 and 1.5 ev to ions in the region. The kinetic energy which the ions can acquire under the applied field is still limited by the density of the gas in the free jet, so that the kinetic energy spread which the ions can acquire is still limited. Preferably the focussing and declustering fields are produced by a single conical tapered lens element located at distance Xl from the orifice, where ##EQU1## and D is the orifice diameter, for atmospheric pressure and room temperature source conditions. The electric field between the lens element and the mass spectrometer is then controlled to limit the energy spread imparted to the ions in their travel from the lens elements to the mass spectrometer.

Method and apparatus for focussing and declustering trace ions

A multiple stage cryogenic vacuum pump is disclosed for transferring matter or species between a gas and a vacuum chamber. The vacuum chamber has an orifice through which the matter or species moves and through which some of the gas leaks into the chamber. The chamber also has an interior surface which is spaced from the path of movement of the matter or species and encircles such path, and an internal divider extending to a position adjacent the interior surface and dividing the chamber into a first region adjacent the orifice and a second region downstream from the first region, with the interior surface extending in both regions. The surface is cooled by a single refrigerating device to below the condensation temperature of the gas, to produce a pressure below atmospheric in the first region and a lower pressure in the second region. The divider contains an aperture through which the matter or species travels and may itself be cooled to precool gas contacting it. The matter or species may be ions or may be a strip of material to be treated. In the latter case the gas which is cryopumped can be warmed and flowed countercurrent to the strip to precondition the strip prior to its entry into the vacuum chamber.

Multiple stage cryogenic pump and method of pumping

A method of analyzing a trace gas, in which the trace gas is transported in a carrier gas stream into a reaction chamber where the trace gas is ionized. The carrier gas includes or is a reagent gas which is ionized in the reaction chamber and the ions of which in turn form trace gas ions. The carrier gas, which is cryopumpable, is then injected with the trace gas ions into a vacuum chamber, the walls of which are cooled to cryopump the reagent gas and thus strip it away from the trace gas ions. The trace gas ions are focussed into an analyzer and analyzed.

Janette A. Buckley

Papers

Apparatus for analyzing trace components

Method and apparatus for analyzing trace components using a gas curtain

Method and apparatus for focussing and declustering trace ions

Multiple stage cryogenic pump and method of pumping

Method and apparatus for analyzing trace components using a cryopumpable reagent gas