Shimadzu Corporation

Osaka University

Kei Shinada

Shigeyoshi Horiike

Takahiro Nishimoto

Katsuhisa Kitano

Masahiro Ueda

Shinji Nagamachi

Mitsuyoshi Yoshii

Tetsuo Ohashi

Yukio Oikawa

Satoshi Matsuoka

Satoshi Hamaguchi

A light source emits excitation light to discharge gas that flows through a dielectric tube. A ground electrode unit includes a first ground electrode and a second ground electrode arranged at a distance from each other in an axial direction of the dielectric tube. A high-voltage electrode is provided between the first ground electrode and the second ground electrode. A first distance between the first ground electrode and the high-voltage electrode is shorter than a second distance between the second ground electrode and the high-voltage electrode. A cover is provided on an outer wall of the dielectric tube at a position between the first ground electrode and the high-voltage electrode. The light source is arranged to emit excitation light such that an optical axis thereof is directed toward a position where the cover is not provided on the outer wall of the dielectric tube.

Dielectric barrier discharge ionization detector and gas chromatography analyzer

A discharge ionization detector includes: a gas passage () through which an electric-discharge gas is to be passed; a plasma generation electrode (-) configured to generate an electric discharge in the gas passage so as to generate plasma from the electric-discharge gas; a sample-gas introduction section () through which a sample gas is introduced into the gas passage; a collection electrode () configured to collect ions generated from a sample with the plasma; a bias electrode () located between the plasma generation electrode and the collection electrode, and configured to create an electric field for guiding the charged particles to the collection electrode; and a DC power unit () capable of independently controlling a voltage applied to the bias electrode and a voltage applied to the collection voltage. A peak-shape abnormality in a signal output can be suppressed by appropriately adjusting the voltages.

Discharge ionization detector

A BID includes: a discharger () including a dielectric pipe () and a pair of electrodes () attached on an outer wall of the dielectric pipe, the pair of electrodes () being arranged at a distance from each other in a direction along a central axis of the dielectric pipe (), the discharger () being arranged so that plasma generating gas is introduced from a first end of the dielectric pipe () and configured to generates dielectric barrier discharge inside the dielectric pipe () to generate plasma; a detection section () including a sample gas introduction section () and a collection electrode () for collecting ions, the detection section () being configured to ionize components in the sample gas using light emitted from the plasma generated in the discharger () and to detect the generated ions by collecting them using the collection electrode (); and a voltage supply (') for generating a potential difference between the pair of electrodes ().

Dielectric barrier discharge ionization detector

A dielectric barrier discharge ionization detector capable of achieving a high signal-to-noise ratio is provided. The detector includes: a discharging section for generating plasma from argon-containing gas by electric discharge; and a charge-collecting section for ionizing a component in a sample gas by an effect of the plasma and for detecting ion current formed by the ionized component. The discharging section includes a cylindrical dielectric tube having a high-voltage electrode connected to AC power source as well as upstream-side and downstream-side ground electrodes and formed on its outer circumferential wall. A semiconductor film is formed on the inner circumferential surface of the tube. The upstream-side and downstream-side ground electrodes are respectively made longer than the initiation distances for a creeping discharge between the high-voltage electrode and a tube-line tip member as well as between the high-voltage electrode and the charge-collecting section.

To suppress baseline current other than baseline current derived from the ionization of impurities, and to achieve the enhancement of the SN ratio of a detection signal and the improvement of the lower limit of detection, the inner diameter of a bias electrode for collecting an ion derived from a sample component is made smaller than the inner diameter of an insulating member separating the bias electrode and a collector electrode. Light emitted from plasma formed by dielectric barrier discharge is shielded by the bias electrode, so that the light is not cast directly on the surface of the insulating member. Therefore, the photoelectric effect caused by casting light of high energy does not occur on the surface of the insulating member, whereby a decrease in electric resistance of the surface can be prevented.

Provided is a method for separating a substance accommodated in a vessel-shaped structure comprising subjecting a vessel-shaped structure, which includes a vessel portion a, a vessel portion b, and a self-fusing material X connecting the both vessel portions, and which accommodates a substance selected from the group consisting of a liquid, a solid a gas, and a dispersion system, to the steps: (i) pulling the vessel portion a and the vessel, portion b away from each other to extend the self-fusing material X; (ii) fusing the extended self-fusing material X together between the vessel portion a and the vessel portion b to separate the accommodated substance; and (iii) cutting a fused part of the self-fusing material X to separate the vessel-shaped structureinto a separated structure.

Method for separating substance accommodated in vessel

A discharge ionization current detector of the present invention is used for a detector for a gas chromatograph and suitable for analyzing high-boiling components. A discharge ionization current detectoris mainly constituted by a plasma generating sectionand an ion collecting section. Regarding the ion collecting section, an ion collecting electrodeand a bias electrodeare arranged, and furthermore, an insulating member made of sapphire or aluminum oxide having a purity equal to or greater than 99.5% is arranged between the ion collecting electrodeand the bias electrode

Discharge ionization current detector

A dielectric barrier discharge ionization detector (BID) capable of achieving a high level of signal-to-noise ratio in a stable manner is provided. In a BID having a high-voltage electrode, upstream-side ground electrode and downstream-side ground electrode circumferentially formed on the outer circumferential surface of a cylindrical dielectric tube, a heater for heating the cylindrical dielectric tube or tube-line tip member attached to the upper end of the same tube is provided. Increasing the temperature of the cylindrical dielectric tube by this heater improves the stability of the electric discharge, whereby the amount of noise is reduced and a high level of signal-to-noise is achieved.

The dielectric barrier discharge ionization detector includes: a dielectric tube through which a plasma generation gas is passed; a high-voltage electrode formed on the outer wall of the dielectric tube; two ground electrodes and formed on the outer wall of the dielectric tube, with the high-voltage electrode in between; a voltage supplier for applying AC voltage between the high-voltage electrode and each ground electrode to generate electric discharge within the dielectric tube and thereby generate plasma from the plasma generation gas; and a charge-collecting section for detecting an ion current formed by ionized sample-component gas produced by the plasma. The distance between one ground electrode and the high-voltage electrode is longer than a discharge initiation distance between these two electrodes, while the distance between the other ground electrode and the high-voltage electrode is shorter than the discharge initiation distance between these two electrodes.

A dielectric barrier discharge ionization detector Includes: a dielectric tube; a high-voltage electrode connected to an AC power source and circumferentially formed on the outer wall of the dielectric tube; upstream-side and downstream-side ground electrodes and circumferentially formed above and below the high-voltage electrode; a discharging section for generating electric discharge to create plasma, from a gas containing argon; and a charge-collecting section for ionizing sample-gas components by the plasma and detecting an ion current formed by the ionized components. The detector also satisfies one or both of the following conditions: the upstream-side ground electrode is longer than a creeping discharge initiation distance between a tube-line tip member at the upper end of the dielectric tube and the high-voltage electrode; or the downstream-side ground electrode is longer than a creeping discharge initiation distance between the high-voltage electrode and the charge-collecting section.

A dielectric barrier discharge ionization detector includes: a discharging section for generating plasma from argon-containing gas by electric discharge, including a dielectric tube on the outer wall of which a high-voltage electrode connected to AC power source as well as upstream-side and downstream-side ground electrodes and are circumferentially formed; and a charge-collecting section for ionizing sample-gas components by the plasma and detecting ion current formed by ionized components. The dielectric tube is made of a material whose resistivity is 1.0&#xd7;10&#x3a9;cm or lower. Furthermore, the detector satisfies at least one of the following conditions: the upstream-side ground electrode is longer than a ground electrode length which allows creeping discharge between the high-voltage electrode and a tube-line tip member; or the downstream-side ground electrode is longer than a ground electrode length which allows creeping discharge between the high-voltage electrode and the charge-collecting section.

To widen the dynamic range of a dielectric barrier ionization detector (BID), an insertion length of a sample injection tubeinto a second gas passageis set so that a sample-gas ejection portis located on the downstream side of a dilution gas from the upper edge of a collector electrodeat which a DC electric field concentrates. By this setting, although the detection sensitivity is lower than in the case where the sample-gas ejection portis placed to maximize the detection sensitivity, the decrease in the detection sensitivity to high-concentration samples is reduced since absorption of light by the sample gas is alleviated. Consequently, the sample-concentration range with a linearly-changing sensitivity becomes wider than that of conventional BIDs. Although the detection sensitivity becomes lower than that of conventional BIDs, a detection sensitivity adequately higher than that of FIDs can be ensured.

Dielectric barrier discharge ionization detector and method for tuning the same

A low-OH-content quartz glass with an OH content equal to or lower than 5 ppm is used as a cylindrical tube () covering the surface of metallic plasma generation electrodes (and) for generating a low-frequency barrier discharge. It has been found that, in the low-frequency barrier discharge, hydrogen and oxygen originating from the OH contained in a dielectric material are released into plasma gas for a long period of time, constituting a primary cause of an increase in the baseline current. The use of a low-OH-content quartz glass dramatically lowers the baseline current and thereby improves the S/N ratio and the detection limit.

Provided is a discharge ionization current detector that is highly durable and yet can be produced at a low cost. An electrode structureconsisting of a dielectric-coated metal tube, with an insulator-coated metal wireincluded therein, is inserted from above into a first gas passage including a dielectric tube. The metal tubeis connected to the ground on the upstream side of the first gas passage. One end of the metal wireis extracted from the upstream side of the first gas passage to the outside and connected to a bias power source. An area which is not covered with the insulator is provided at the other end of the wire. This area is arranged in a second gas passage, which extends from the downstream end of the first gas passage. A metal electrode consisting of a flanged metal tubeis placed in the second gas passage and connected to an ion current detecting circuit. In the present configuration, the second gas passage, which should be heated to high temperatures, has fewer portions at which metallic parts are in contact with insulating members. This is advantageous for improving the durability of the device and reducing the used amount of expensive, highly heat-resistant sealing members and/or insulating members.

An adjusting method for a discharge ionization current detector of the present invention is provided for a discharge ionization current detector for a gas chromatograph, which improves the precision and reproducibility of measurements results of the detector. The discharge ionization current detector adjusts at least one of purity of introduced helium gas, a flow rate of the introduced helium gas, an amplitude of voltage of the low-frequency dielectric barrier discharge, and a frequency of the voltage of the low-frequency dielectric barrier discharge so that intensity of light having a wavelength of 640 nm reaches the maximum in a range of wavelengths of 250 to 700 nm with respect to light emitted by the helium plasma.

Growing community of inventors

Uji, Japan

Kei Shinada