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WO2008018811A1 - Tête analytique servant à détecter des micro-impuretés de substances dans des gaz - Google Patents

Tête analytique servant à détecter des micro-impuretés de substances dans des gaz Download PDF

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Publication number
WO2008018811A1
WO2008018811A1 PCT/RU2006/000417 RU2006000417W WO2008018811A1 WO 2008018811 A1 WO2008018811 A1 WO 2008018811A1 RU 2006000417 W RU2006000417 W RU 2006000417W WO 2008018811 A1 WO2008018811 A1 WO 2008018811A1
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WO
WIPO (PCT)
Prior art keywords
electrode
drift
input
ionization
ion
Prior art date
Application number
PCT/RU2006/000417
Other languages
English (en)
Russian (ru)
Inventor
Yuri Petrovich Gorbachev
Vladimir Vladimirovich Ionov
Yuri Nikolaevich Kolomiec
Dmitri Aleksandrovich Moskalev
Original Assignee
Yuri Petrovich Gorbachev
Vladimir Vladimirovich Ionov
Yuri Nikolaevich Kolomiec
Dmitri Aleksandrovich Moskalev
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Yuri Petrovich Gorbachev, Vladimir Vladimirovich Ionov, Yuri Nikolaevich Kolomiec, Dmitri Aleksandrovich Moskalev filed Critical Yuri Petrovich Gorbachev
Priority to PCT/RU2006/000417 priority Critical patent/WO2008018811A1/fr
Publication of WO2008018811A1 publication Critical patent/WO2008018811A1/fr

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/622Ion mobility spectrometry

Definitions

  • Analytical head for detecting trace substances in gases
  • the invention relates to the field of gas analysis and can be used to determine microimpurities of substances in gases in solving environmental monitoring problems, detecting accidental emissions of toxic substances in production, controlling the atmosphere of a work area in enterprises associated with harmful working conditions, and searching for hidden explosive and narcotic substances during operational activities by special services or customs inspection at control passages.
  • the invention can also be used in gas chromatography as a sensitive detector with controlled selectivity.
  • the SPIP is a selective ionization detector whose operation is based on the dependence of the increment of the ion mobility coefficient on the voltage electric field strength [1].
  • the SPIP consists of a sequentially placed sample input chamber, an ionization chamber with an ionization source introduced into it, an ion separation device made in the form of an extended drift gap between two electrodes, and an ion collection system containing a collector electrode connected to a highly sensitive input of an electrometric amplifier .
  • the electrodes of the drift gap is the sum of a constant (U 1 ) and periodic asymmetric in polarity (U 2 (t)) high voltage electrical voltage. After ionization of impurities, the mixture of ions is fed into the drift gap by a continuous stream.
  • devices based on SPIP have significant advantages in selectivity, compared, for example, with traditional ion mobility spectrometers (SIP).
  • SIP ion mobility spectrometers
  • a drift gap of cylindrical geometry is used in SPIP, a focusing effect occurs [1], which consists in the localization of ions mainly near the average radius of the channel of the drift gap.
  • the ions are moved away from the walls of the drift gap, which leads to the practical absence of diffusion losses; I provides high sensitivity analysis.
  • portable SPIP devices intended for the analysis of amines, halogen-containing substances, nitro compounds, and explosives having a high affinity for an electron or proton use a nickel or tritium radioactive ⁇ -source that does not consume energy, has a small weight and dimensions creates a stable ionization current.
  • the recent tightening of the requirements for the operation of devices with radioactive sources necessitates the replacement of the radioactive ⁇ -source with an alternative.
  • the most suitable alternative source having small consumption and dimensions and creating a large ionization current with a high concentration of reactant ions, is a corona discharge ionization source.
  • a corona discharge ionization source [2] which is used mainly for the ion mobility spectrometer. It contains one or two corona electrodes inserted inside the target electrode made in the form of a cylinder. The corona electrodes contain a point electrode remote at the end, located perpendicularly or along the axis of the target electrode. Between the corona electrodes and the target electrode, a constant, pulsating, or both constant and pulsating potential difference of different magnitude and sign is applied to create a corona discharge. The reactants created in the ion source are introduced into the reaction chamber, where the analyzed impurity enters with the air stream.
  • Impurity ions formed in the reaction chamber due to ion-molecular collisions are introduced into the drift tube of the spectrometer using a gate lattice, where they are separated in the electric field by mobility. Then, the ions passing through the drift tube are recorded by the collector in the form of a sequence of peaks called the drift spectrum.
  • this corona ionization source for SPIP in the light of the solution of the problem is not effective. This is due to the large losses of ions that occur when they are introduced from the reaction chamber into the drift inter SPIP current. Indeed, when the reaction chamber is connected with the corona source to the drift gap of the SPIP, the appearance of local field disturbances in the ionic aperture of their junction is inevitable. When ions are transported by air flow or electric fields through such an aperture, they are scattered by field disturbances, as a result of which a significant part of the ions recombines on the walls of the drift gap and, accordingly, is lost for analysis.
  • an ion mobility spectrometer operating on the basis of ion mobility increment spectrometry (SPIT). It consists of a housing having an input for connecting to the external environment and an output, an ion separation device located inside the housing and made in the form of a drift gap formed by opposing electrodes connected to sources of constant compensating and variable asymmetric voltages, and an ionization source located near the drift gap and connected to the input for sample ionization, an ion aperture made as a passage between the ionization source and the drift gap tkom, a third electrode adjacent to the ion aperture and ion collection system located behind the electrode gap drift.
  • a corona discharge is considered as one of the ionization sources.
  • the corona electrode is mounted at the end of the third electrode, to which a potential sufficient to create a corona discharge is supplied.
  • the device operates as follows. The mixture of impurities under analysis is sucked through the inlet through the inlet from the external atmosphere and enters the ionization source, in which a high concentration of reactant ions is created using the corona discharge. Due to ion-molecular collisions, impurities are ionized and introduced through the ionic aperture into the drift gap using an electric field formed by the potential of the third electrode.
  • the ion mixture is transported along the drift gap electrodes by cleaned air to the ion collection system with simultaneous separation into components due to their movement across the gas flow under the action of a periodic strong asymmetric polar polarity electric field. Passing the drift gap ions are recorded by the ion collection system.
  • This device does not meet the requirements of the task due to the low sensitivity of the device caused by significant loss of ions when they enter the drift gap through the ionic aperture.
  • the aperture in the drift gap is usually small in size to exclude the influence of the ionization source on the separation process.
  • the small size of the aperture significantly limits the volume of the ionization region from which impurity ions with a certain mobility with a given configuration of electric fields and air flow profile can enter the drift gap through the aperture.
  • the remaining ions recombine on the wall of the drift gap or are carried away by the sampling stream and are excluded from the separation and, accordingly, registration process.
  • the edges of the aperture cause distortion of the electric field in the adjacent space, which leads to an even greater increase in ion loss and, accordingly, a decrease in the sensitivity of the device.
  • An object of the present invention is to increase the detection sensitivity of trace substances in a gas.
  • the specified task in the analytical head for detecting microimpurities of substances in gases including a flow channel containing sequentially located ionization chamber, consisting of an inlet pipe through which the analyzed gas and an ionization source introduced into it, an ion separation device for mobility, made in the form of a drift gap formed by coaxially located central potential and external grounded electrodes connected to sources of constant compensating and asymmetric alternating voltages and an ion collection system, characterized in that the ionization source is made in the form of a corona electrode, and the ionization chamber is combined with the inlet part of the drift gap and is formed by an inlet nozzle, a corona electrode inserted into the nozzle and the central electrode, while the corona electrode is mounted on the input end of the Central electrode along its axis and is electrically connected to it, or inserted into the input pipe through its wall and insulator at an angle to the inner surface of the inlet pipe.
  • the specified execution of the analytical head allows you to eliminate the loss of ions during their transportation from the ionization chamber to the drift gap and thereby significantly increase its sensitivity.
  • the combination in the analytical head of the ionization chamber with the entrance of the drift gap which eliminates the loss of ions during their transportation from the ionization chamber to the drift gap and thereby increase its sensitivity, has no analogues among the known devices operating on the basis of SPIP, and, therefore, meets the criterion "Inventive Level".
  • Figure l presents the analytical head with a corona electrode inserted into the inlet pipe through its wall and insulator.
  • Figure 2 presents the ionization chamber of the analytical head with a corona electrode mounted on the input end of the Central electrode.
  • the analytical head (see Fig. 1) includes: 1 - an ionization chamber containing an inlet pipe 2, a corona electrode of an ionization source 3 and an initial section of the central electrode 5, 4 - a drift gap formed between the central electrode 5 and the outer electrode b, 7 and 8 - sources of respectively constant compensating and variable asymmetrically voltages, 9 - ion collection system.
  • the analytical head works as follows.
  • the analyzed gas with the help of a pump (not shown in the figure) enters through the inlet pipe 2 into the ionization chamber, where the impurities contained in the gas are ionized using the corona discharge ionization source. Further, the impurity ions are carried along with the analyzed gas into the drift gap 4, during movement along which the ions are separated into components due to their drift across the gas flow under the action of a superposition of constant compensating (V 1 ) and periodic high-voltage (V 2 (asymmetric in polarity) t)) stresses. After the drift gap, the extracted ions enter the ion collection system 9, where they are captured by the collector electrode using the electric field acting in it.
  • V 1 constant compensating
  • V 2 periodic high-voltage
  • the proposed analytical head with a corona discharge ionization source has a high sensitivity for the analysis of microimpurities, which is ensured by extremely low ion losses in the ionization chamber.
  • the surface of the initial section of the central electrode is added to the ionization chamber as the target surface, in addition to the inner surface of the inlet pipe.
  • the corona discharge occurs in the volume limited by the surfaces of the corona electrode, the inlet nozzle, and the central electrode, where periodic electric fields of the drift gap central electrode are added to the fields of the corona electrode.
  • the location of the corona electrode on a holder isolated from the central electrode (Fig. 1) and its connection to an independent voltage source allows you to change the amplitude of the ac separation voltage without violating the operation mode of the corona electrode.
  • Such a head acquires the property of universality and can be used to solve problems where it is necessary to register a set of substances.
  • drift gap 40 mm long diameter of the central electrode 5 mm
  • diameter of the external electrode 9.4 mm The central electrode of the drift gap was supplied with an alternating voltage asymmetric in polarity with an amplitude of 3–5 kB and a frequency of 170 kHz.
  • the flow of the analyzed gas was ZOOml / min.
  • the corona electrode of the ionization chamber was a steel needle with a tip diameter of 0.15 mm. 2 versions of ionization chambers were manufactured.
  • the corona electrode was introduced through the wall of the inlet pipe to a depth of 3 mm and at a distance of 3 mm from the input end of the central electrode. In this case, a constant negative voltage of 2000 V was applied to the needle.
  • diluted 2,4,6-THT and TEN explosive pairs were supplied as an input sample, while the amplitude of the alternating voltage asymmetric in polarity was 4.5 kB and 3.5 kB, respectively.
  • Diluted 2,4,6-THT pairs were supplied to the head of the second option, and the amplitude of the alternating voltage asymmetric in polarity was 4.5 kB.
  • the detection threshold for 2,4,6-THT and TEN vapors for the head of the first variant was 1.4 ⁇ lO ⁇ 13 g / cm 3 and 0.8xl0 "13 g / cm 3, respectively, and the detection threshold for 2,4,6-THT vapor for the second variant heads - 1.3x10 " g / cm.

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

Abstract

La présente invention concerne une tête analytique servant à détecter des micro-impuretés de substances dans des gaz et comportant un canal d'écoulement comprenant, disposés en série, une chambre d'ionisation composée d'un tube d'admission par lequel un gaz pouvant être analysé est introduit et d'une source d'ionisation introduite dans ledit tube, un dispositif servant à séparer les ions en fonction de leur mobilité et se présentant sous la forme d'un espace de dérive formé par des électrodes à potentiel central et à la masse externe disposées coaxialement et connectées à des sources de tension asymétrique alternative et compensatoire continue, et un système collecteur d'ions. Selon cette invention, la source d'ionisation se présente sous la forme d'une électrode de décharge; la chambre d'ionisation est combinée à la partie d'admission de l'espace de dérive et est formée par le tube d'admission, l'électrode de décharge introduite dans ledit tube et l'électrode centrale; l'électrode de décharge est disposée sur une extrémité d'admission de l'électrode centrale le long de son axe et est soit électriquement connectée à celle-ci, soit introduite dans le tube d'admission à travers sa paroi et un isolateur selon un angle formé avec la surface interne du tube d'admission. Cette invention permet d'accroître la sensibilité de détection de micro-impuretés de substances dans un gaz.
PCT/RU2006/000417 2006-08-08 2006-08-08 Tête analytique servant à détecter des micro-impuretés de substances dans des gaz WO2008018811A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/RU2006/000417 WO2008018811A1 (fr) 2006-08-08 2006-08-08 Tête analytique servant à détecter des micro-impuretés de substances dans des gaz

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5684300A (en) * 1991-12-03 1997-11-04 Taylor; Stephen John Corona discharge ionization source
SU1412447A1 (ru) * 1986-11-03 1998-06-20 И.А. Буряков Дрейф-спектрометр для обнаружения микропримесей веществ в газах
RU2265832C1 (ru) * 2004-09-01 2005-12-10 Горбачев Юрий Петрович Аналитическая головка для обнаружения микропримесей веществ в газах
RU2004126270A (ru) * 2004-09-01 2006-02-27 Юрий Петрович Горбачев (RU) Источник ионизации коронного разряда для устройств обнаружения микропримесей веществ в газах

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU1412447A1 (ru) * 1986-11-03 1998-06-20 И.А. Буряков Дрейф-спектрометр для обнаружения микропримесей веществ в газах
US5684300A (en) * 1991-12-03 1997-11-04 Taylor; Stephen John Corona discharge ionization source
RU2265832C1 (ru) * 2004-09-01 2005-12-10 Горбачев Юрий Петрович Аналитическая головка для обнаружения микропримесей веществ в газах
RU2004126270A (ru) * 2004-09-01 2006-02-27 Юрий Петрович Горбачев (RU) Источник ионизации коронного разряда для устройств обнаружения микропримесей веществ в газах

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