Hewlett-packard Company

Agilent Technologies, Inc.

Mahmoud F Abdel-Rahman

Carl A Myerholtz

William H Wilson

Robert P Rhodes

James W Baker

Andrew Martin Warchol

Roger L Firor

An electronic circuit and a method of generating an electrical discharge for an ionization detector system. The electronic circuit includes a transformer with a primary portion and a secondary portion. The circuit and method produce an electrical discharge across a set of electrodes. The discharge is stable over time and has relatively low peak currents associated therewith.

Enhancing the stability of electrical discharges

An ion mobility spectrometer is disclosed which includes a sample input port, an ion generator, an ionization chamber receiving and ionizing samples, an ion gate for causing the ionized samples to travel in a direction, and a drift region for receiving the directed ionized samples and for subjecting the ionized samples to an electric potential. The ionized samples then separate according to their electric charge and mass and are detected by a sensor having an output with linear, non-linear, and logarithmic characteristics. The ion mobility spectrometer further includes circuitry coupled to the sensor for linearizing the output such that the non-linear and logarithmic characteristics are linearized while preserving the linear characteristics. The circuitry operates to linearize the output by multiplying the output by a first function determined from a second function by extrapolating linear and logarithmic characteristics based on a logarithmic plot, dividing the output current by the extrapolation, adding 1, and raising the result to a power determined from a slope of the logarithmic characteristics to obtain a linearizing function. The result is one continuous linear plot in conformance with the fundamental gain of the IMS detector.

Ion mobility spectrometer having extended linear dynamic range

An ionization detector includes a unique combination of elements including a non-radioactive glow discharge source, a gas flow area designed to promote mixing of sample gas with a reagent gas, a GC column interface which directs air leaks away from the sample area, and a signal electrode designed to discriminate against ion collection. This embodiment includes a body defining a detector cavity and a sample flow area. A plurality of electrodes are disposed within the body including a glow discharge source having a first and second discharge electrode located near one end of the body, a guard electrode located longitudinally intermediate to the discharge electrode and the sample flow area, and a signal electrode disposed within a signal electrode cavity located near an end opposite to the guard electrode. A column interface depends from the body, in communication with the sample flow area. The column interface includes a reagent inlet and a purge outlet which extend laterally from a longitudinal portion of the column interface. A column from a GC extends through the longitudinal portion and is partially disposed within the sample flow area.

Miniaturized glow discharge electron capture detector

The present disclosure relates to a gas chromatograph having a plurality of layers or channels. The chromatograph typically comprises an inlet that receives a sample to be analyzed, a column disposed in each of the plurality of chromatograph layers, each column being in fluid communication with and downstream from the inlet and having a stationary phase coating its inner surfaces, and a detector in fluid communication with and downstream from at least one of the columns. In a preferred arrangement, the chromatograph includes a pre-column disposed in each of the chromatograph layers upstream of the columns, each pre-column being in fluid communication with the inlet and having a stationary phase coating its inner surfaces.

Multilayered gas chromatograph

A gas injector comprises (1) a carrier gas channel through which a carrier gas can enter the injector, (2) an output channel through which the carrier gas and a gaseous sample can be injected from the device to an analytical instrument, (3) a sample gas channel capable of holding the gaseous sample, and (4) a switch structure regulating the connections among the sample gas channel, the carrier gas channel and the output channel. The injector also comprises at least a purge channel through which the carrier gas can flow across part of the device, purging therein and preventing contaminants from reaching the output channel. The gas injector provides a low baseline noise and a high signal to noise ratio when applied to a sensitive analytical instrument.

Internally purged gas injector

An apparatus for and method of making a discharge ionization detector. The apparatus comprises a detector body, a detector cavity, located in the detector body and having a discharge electrode and an second discharge electrode, wherein an electric discharge runs between the second discharge electrode and the discharge electrode, and a signal electrode which attracts ionized molecules, an inlet interface, through which a discharge gas enters the detector, an analyte inlet, through which the analyte enters the detector cavity, and an outlet through which the analyte and discharge gas exit the detector body, wherein the apparatus is hermetically sealed. The apparatus is hermetically sealed by vacuum brazing the components to the detector body. The present invention can also have a detector volume as small as 10 micro-liters or less. The method comprises machining a body material to form a detector body, by forming a detector cavity, a column bore and a plurality of electrode bores, preparing the body surface for bonding, and bonding a plurality of electrodes, an inlet interface, a column interface and a vent interface to the detector body, whereby a hermetically sealed system is formed that has a detection zone volume of approximately 5-100 micro-liters.

Hermetically-sealed miniaturized discharge ionization detector

Energy efficiency of a thermal zone in an analytical instrument is improved by use of an oven housing module having an enclosure body defining an oven cavity, wherein the enclosure body exhibits a size and shape sufficient to receive a component to be subjected to temperature control within a thermal zone located in the oven cavity. A temperature control assembly includes a vent assembly communicating with ambient air, a fan, and a fast cooling flap, wherein the temperature of the thermal zone may be modulated by supplementing the oven cavity air with ambient air. The fast cooling flap may be operated for opening one side of the oven cavity to ambient conditions such that ambient air may be rapidly introduced to the oven cavity and the cavity air may be rapidly exhausted from the oven cavity for rapid cooling of the thermal zone. The oven cavity is very compact so as to allow only a marginal amount of cavity volume to be disposed about the temperature-controlled component, so as to permit efficient circulation of cavity air around the component for efficient temperature control of the component, and yet minimize the volume of the oven cavity, thus reducing the effective thermal mass of the enclosure body.

Oven housing module in an analytical instrument

A multichannel capillary column having an interior wall defining a single internal bore, wherein the interior wall defines a plurality of n channels and n ridges, wherein adjacent channels are partially separated by a respectively interposed ridge, and wherein a central, coaxial portion of the internal bore allows cross-channel fluid communication between all of the n channels.

Multichannel capillary column

Linearization of an ionization detector is obtained by processing the output signal derived from the ionization detector so as to compensate for the naturally-occurring logarithmic decay of the detector response at high sample concentrations. Linearization is accomplished according to a linearizing formula:

Ionization detector system having linearized output signal

Apparatus for purification of a discharge gas, wherein the discharge gas is selected from a group of noble gases, and most preferably is helium or argon. The purification of the discharge gas is achieved by attraction and removal of at least one ionized contaminant in the discharge gas, wherein the contaminant exhibits an ionization potential that is less than the excitation potential of the discharge gas. A discharge gas purification system may be constructed to include a discharge ionization detector that employs a discharge chamber and discharge source for effecting a discharge to provide photons and metastables for ionization of an analyte in an adjacent ionization chamber, wherein the discharge chamber includes a bleed flow for attracting and removing ionized contaminants present in the discharge chamber.

Discharge gas purification system

An ionization detector for detection of an analyte includes a source chamber having a source of ionizing particles and receiving a fluid stream of detector gas; an ionization chamber connected to the source chamber at an ionization chamber entrance therebetween so as to allow metastables and photons to be generated in the source chamber and to be transferred in the fluid stream to the ionization chamber; a signal electrode assembly located in the ionization chamber; and a signal measuring circuit for measuring ionized analyte molecules. The signal electrode assembly includes a spaced array of electrodes including a collector electrode, a first signal electrode, and a second signal electrode. The first signal electrode is situated immediately downstream from the ionization chamber entrance and substantially upstream of the collector electrode, so as to extend the detection zone to the vicinity of the ionization chamber entrance.

Extended detection zone in an ionization detector

Method and apparatus are disclosed for improved transfer of ionizing particles from a source chamber to a detection zone in an ionization chamber in an ionization detector. An ionization detector includes a source chamber, an inlet for introducing detector gas to the source chamber, a transitional structure including a flow guide that directs detector gas flow between the source chamber and the adjacent ionization chamber, an inlet for introducing sample gas containing an analyte into the ionization chamber, and an outlet port for exhausting the mixture of the sample gas and the detector gas. The aspect ratio of the flow guide causes the linear velocity of the detector gas stream to be highest at a throat in the flow guide and to decrease as the detector gas stream approaches a detection zone in the ionization chamber, thereby suppressing analyte diffusion from the ionization chamber through the flow guide. The aspect ratio of the flow guide also provides an unimpeded path for transit of photons from the source chamber to the detection zone in the ionization chamber.

Method and apparatus for suppression of analyte diffusion in an

Method and apparatus for purification of a discharge gas, wherein the discharge gas is selected from a group of noble gases, and most preferably is helium or argon. The purification of the discharge gas is achieved by attraction and removal of at least one ionized contaminant in the discharge gas, wherein the contaminant exhibits an ionization potential that is less than the excitation potential of the discharge gas. A discharge gas purification system may be constructed to include a discharge chamber, an inlet for supplying a pressurized flow of discharge gas into the discharge chamber, a discharge device for effecting a discharge in the discharge chamber to effect ionization of a contaminant in the discharge gas, and a bleed flow device located with respect to the discharge and to the discharge cathode for electrically attracting and removing a bleed flow of the discharge gas in the discharge chamber. A disproportionate amount of the ionized contaminants thus created are captured in the bleed flow. An outlet may be provided for directing an output flow of the discharge gas from the discharge chamber to provide purified flow of discharge gas.

Method and apparatus for purification of a discharge gas

An ionization detector having an upper ionization chamber, a lower ionization chamber, and a radioactive source located in the upper ionization chamber but shielded from the lower ionization chamber by a barrier. A substantially constant fluid stream of detector gas is supplied to the upper ionization chamber so as to fill the upper ionization. The radioactive particle emitter is disposed on the periphery of the interior of the upper ionization chamber so as to generate a constant supply of alpha particles into the internal volume defined by the upper ionization chamber. The interaction of the alpha particles and the detector gas generates metastables and photons as the alpha particles traverse a portion of the volume in the upper ionization chamber. The lower ionization chamber is coupled to the upper ionization chamber so as to receive the detector gas flow and the metastables. A sample fluid is directed into the lower ionization chamber, preferably by way of a carrier gas flow supplied from an outlet end of a capillary separation column, and the metastables present in the lower ionization chamber then ionize the analyte molecules. An outlet is provided in the base of the lower ionization chamber so as to vent the combined flows of the carrier gas, sample fluid, and the detector gas. In the preferred embodiment, the carrier gas and the detector gas are helium. The barrier is interposed in the path between the radioactive source and the lower ionization chamber so as to prevent entry of the radioactive particles into the lower ionization chamber where there may ensue some interaction of the radioactive particles with analyte molecules in the lower ionization chamber. As a result, the primary mechanism for ionization of the analyte molecules is substantially restricted to an interaction of the metastables with the analyte molecules.

Ionization detector

In a discharge ionization detector, a method and apparatus are disclosed for increasing the transfer of photons and metastables from a discharge chamber to a ionization chamber, while effecting ion discrimination of the ionic current with respect to a signal cathode, thereby reducing the effect of ionic current in the signal output. Preferred embodiments of the invention include a discharge source located in a discharge chamber, means for introducing discharge gas flow into the discharge chamber, a flow guide that directs discharge gas flow between the discharge chamber and an adjacent ionization chamber, and inlet port for introducing a flow of sample gas containing an analyte into the ionization chamber and an outlet port for exhausting the sample gas and the discharge gas. A plurality of apertures in the flow guide are situated proximate the discharge source so as to promote the rapid and efficient transfer of photons and metastables from the discharge source into the ionization chamber. A signal cathode and the ionization chamber are biased in a circuit with an electrometer so as to provide a detector output signal.

Growing community of inventors

West Grove, PA, United States of America

Mahmoud F Abdel-Rahman