Environmental Technologies Group, Inc.

The Bendix Corporation

Allied Corporation

Technispan LLC

Alliedsignal Inc.

Glenn E Spangler

Donald N Campbell

Robert C Davis, Jr

Julio A Reategui

Kishore N Vora

John P Carrico, Jr

John P Carrico

Eugene F Fafaul

Joseph E Roehl

Joseph L Mangum

Alvin Dorman

Gautam B Patel

Stanley Seeb

John F Wroten, Jr

John N Cox

Charles E Martin

A discharge ionization source, for use for example with an ion mobility spectrometer or atmospheric pressure ionization mass spectrometry. The source uses two or more electrodes for ionization and control, and solid state circuitry for operation. Inductive coupling of the discharge gap to the electronics is not necessary. The source can be operated as a continuous dc discharge, or as a pulsed discharge. The two-electrode configuration provides an anode and cathode with an optional adjustable gap. One of the electrodes can be hollow to enhance ionization efficiency (e.g., hollow cathode) and/or to accept effluent from a gas or liquid (including electrophoresis) chromatographic column. The three-electrode configuration adds a third or control electrode to additionally stabilize the discharge. The third electrode may be biased at the potential of the anode through a ballast resistor, and be located near the cathode. When used in this manner, the third electrode pre-ionizes the gas in the wider discharge gap, and initiates the discharge with a lower breakdown potential. The third electrode may also be used to switch the mode of operation of the discharge source from a gas phase ionizer to an electrospray ionizer. The discharge is pulsed and/or initiated by applying a potential (dc or pulsed) to the cathode. A transistor switch capacitively coupled to a negative diode clipping circuit may be used to double the potential applied across the discharge gap. The average power dissipation is less than a watt.

Discharge ionization source

An apparatus and method to separate and store ions by exploiting mobility characteristics of the ions. A sample is introduced into a trap volume and ionized. The ions are separated according to their mobility characteristics by applying an electric field to the trap volume. The ions thus migrate to equilibrium positions in the trap volume due to a difference in mobilities and to changes in the electric field. The ions may be sequentially scanned from the trap by changing the electric field. The identity of ions within the trap may then be determined.

Ion mobility storage trap and method

An improved photoionization ion mobility spectrometer is disclosed which utilizes a flashlamp as the source for ionization. A gas sample is introduced via a carrier gas into a ionization chamber which is part of the spectrometer cell. Ionizable molecules contained in the injected gas sample are ionized by the ultraviolet light emitted from the flashlamp. The ionized molecules are attracted by an electrostatic drift field into a drift chamber and travel therethrough against the flow of a drift gas counter-current thereto until they are captured by a collector located in the drift chamber opposite to the ionization chamber. A dopant with an effective ionization potential lower than the photon energy of the emitted light can be introduced into the ionization chamber to further improve the sensitivity and specificity.

Photoionization ion mobility spectrometer

A system for and a method of increasing the sensitivity of organic vapor detection in ion mobility spectrometer by as much as three (3) orders of magnitude. Vapors are collected from the gas to be analyzed by controlled adsorption and are subsequently thermally released as an enriched concentration into the reactor volume of an ion mobility spectrometer. The herein disclosed system of preconcentrator and ion mobility spectrometer is easier to maintain and is more portable than other instruments of comparable sensitivity and the reliable operation is simpler. In one experiment, the computed enrichment factor of 3,500 for the preconcentrator lowered the limit of detection from 10 ppt for the ion mobility spectrometor alone down to 0.003 ppt for the embodiment of this invention. The sensitivity, compactness, ease of operation and ruggedness make the invention a suitable choice as a sensitive, efficient, and rapid detector of narcotics, toxic and explosive materials. Such detectors find applications at airports, surface transportation terminals, facility inspection points and security stations.

Preconcentrator for ion mobility spectrometer

An ion mobility spectrometer, ionization detector and mass spectrometer is described having a reaction region, and a region for introducing a sample gas, liquid or solid samples into the reaction region and an electrolyte in the reaction region of an alkali salt heated to a predetermined temperature, such as room temperature to 1000.degree. C., to provide a chemical reaction between the alkali atoms, cations or complement anions with the sample to provide product ions. The invention provides a non-radioactive ionization source for ionization of a broad class of compounds.

Selective ionization of gas constituents using electrolytic reactions

An ion mobility spectrometer is described for detecting sample gas in a carrier gas incorporating a block of ceramic material having a passageway wherein the passageway contains an ionization source, a resistive material on the walls of the passageway prior to and after a shutter grid to form a reaction region and drift region respectively, an aperture grid and a collector. A radioactive or non-radioactive ionization source may be inserted into one end of the passageway while the aperture grid and collector may be inserted into the other end and rigidly positioned with respect to the block of ceramic material. The invention simplifies the exchange of the ionization sources where it may be either radioactive or non-radioactive, and improves the assembling and sealing of the ion mobility spectrometer cell.

All ceramic ion mobility spectrometer cell

A method for operating an Ion Mobility Spectrometer in which an analyte sample is ionized in the spectrometer reaction chamber and the analyte ions are permitted to flow freely from the reaction chamber into the spectrometer drift chamber. The ion current output from the spectrometer ion current detector is observed during this time. The ion flow from the reaction chamber to the drift chamber is then momentarily interrupted and the time delay between the time of ion flow interruption and the appearance of a decrease in the ion current detector output is observed. Different substances are characterized by different delays. The concentrations of the different substances may be determined by measuring the change in detected ion current after the ion flow interruption.

Method and apparatus for enhanced ion spectra generation and detection

A thermionic emitter for providing positive ions has been described incorporating a mixture of beta-alumina and inert material such as charcoal positioned on a filament for heating the mixture. Alternately the invention may incorporate beta-alumina with inert material such as nickle deposited in selected areas. The invention overcomes the problem of generating positive ions with low power consumption.

Thermionic ionization source

An ion mobility spectrometer, ionization detector and mass spectrometer is described having a reaction region, and means for introducing a sample gas, liquid or solid samples into the reaction region and an electrolyte in the reaction region of an alkali salt heated to a predetermined temperature, such as room temperature to 1000.degree. C., to provide a chemical reaction between the alkali atoms, cations or complement anions with the sample to provide product ions. The invention provides a non-radioactive ionization source and provides a means for ionization of a broad class of compounds.

An ion mobility spectrometer is described for detecting gas constituents in an ambient air incorporating a cylindrical tube containing a reaction region, a shutter assembly and a drift region therein, the cylindrical tube fits within a housing having a chamber or space between the cylindrical tube and the housing for heating drift gas prior to entry into the drift region. Further, the cylindrical tube may have interior annular ledges to facilitate positioning of the shutter assembly and an aperture grid. The invention overcomes the problem of controlling the temperature of the drift gas prior to entry into the drift region to enhance the uniformity of ion drift mobility times and the problem of a mechanical assembly which is difficult to dissemble.

Ion mobility spectrometer

An ion mobility spectrometer system with improved specificity. The ion mobility spectrometer has a reaction chamber and a drift chamber, an ionization source disposed in the reaction chamber, an injection grid separating said reaction and drift chambers, a collector electrode disposed in the drift chamber and a sample input injecting the sample and carrier into the reaction chamber. A source injects acetone and/or carbon tetrachloride as reagents into the carrier gas prior to entering the sample input. 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 (H.sub.2 O).sub.n Cl.sup.- 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 more specific for detection and identification.

Ion mobility spectrometer system with improved specificity

An ion mobility detector has dual drift regions respectively on either side of a centrally located reaction region and respectively separated therefrom by dual shutter grids. Each drift region terminates in a Faraday cup. An ion accelerating electrical field gradient is provided between the Faraday cups so that negative ions are drawn into one drift region and positively charged ions are drawn into the other drift region.

Apparatus for simultaneous detection of positive and negative ions in

An ion mobility detector in which selectivity and sensitivity is enhanced by converting through surface interactions sample gas or vapor to a form more readily ionized or by converting through surface interactions interferent gas or vapor to a form less readily ionized. To accomplish the conversion, samples may be passed through a catalytically reactive filter prior to injection into the detector reaction region; exposed to a reactive coating placed on the surface of a permeable membrane prior to diffusion therethrough into the reaction region or exposed to a reactive coating placed on the interior walls of the reaction region.

Chemical conversion for ion mobility detectors using surface interactions

A membrane interface is provided over the sample inlet port of an ion mobility detector. Sample, included as a vapor component in a gas stream impinging the exterior surface of the membrane, penetrates the membrane and is carried into the ion mobility detector by means of a carrier gas which scrubs the interior surface of the membrane.

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Lutherville, MD, United States of America

Glenn E Spangler