WO2014098630A1

WO2014098630A1 - Device for recognition of contaminations on the basis of a ceramic chamber for a faims or dms spectrometer

Info

Publication number: WO2014098630A1
Application number: PCT/PL2013/000152
Authority: WO
Inventors: Mirosław MAZIEJUK; Wiesław GALLEWICZ; Michał CEREMUGA; Jarosław ŁAWRENCZYK; Tomasz Marcin ADAMCZYK-KOREYWO
Original assignee: Wojskowy Instytut Chemii I Radiometrii
Priority date: 2012-12-18
Filing date: 2013-11-27
Publication date: 2014-06-26
Also published as: PL402111A1

Abstract

A device according to the invention is characterised by maximum reduction of disturbances caused by the current flowing through the supply conduits and efficient sealing of the chamber at its gas inlet and outlet, favourably influencing such parameters as temperature, pressure or degree of ionisation, making the device easy to assemble and disassemble. The essence of the device consists in the fact that it has a chamber (5) and control units, voltage generator (11) for chamber control and an amplifier (12) for the ionic current in one plane, and the gas inlet (7) and the gas outlet (8) of the chamber are located in the flat bottom surface of the chamber, while in the locations of these holes, the chamber is supported on supports (2, 3) having a gas feeding hole (9) and a gas discharge hole (10) to /from the chamber in their flat top surfaces, the holes being in contact with the gas inlet and the gas outlet in the chamber, respectively.

Description

Device for recognition of contaminations on the basis of a ceramic chamber for a FAIMS or DMS spectrometer

The invention relates to a device for recognition of contaminations on the basis of a ceramic chamber for a FAIMS or DMS spectrometer, intended for detection of chemical contamination.

Modern spectrometers enable detection and identification most organic substances considered highly toxic. Currently, for detection of highly toxic chemical substances (toxic warfare agents, toxic industrial substances), detectors based on IMS (Ion Mobility Spectrometry) technology are mostly used. Most often, they are classic spectrometers operating at about +50°C, characterised by good sensitivity but not too high resolution, leading in practical solutions to so-called "false" alarms. After detecting a chemical contamination, the signalling device generates a warning signal, i.e. turns on a sound or light signal or sends a signal to turn on devices defined by user, e.g. fan-powered filters or alarm systems. The number of "false" alarms should be as low as possible, as they discredit the contamination detection system and may cause unnecessary initiation of alarm procedures.

The chamber of an IMS detector is divided into two zones. The first zone is the area from the semipermeable membrane to the dosing mesh, in which ionisation is carried out using a β- or a-radioactive source. The second zone is a drift area - from the dosing mesh to the collecting electrode. To the mesh before the radioactive source, high voltage is applied (generally from 1.5 kV to 3 kV), while the metal rings have lower and lower potentials in sequence from the source to the collecting electrode. Thus, the field is shaped so as to move the ions along linear paths from the ionisation zone to the collecting electrode. The majority of gaseous substances have various mobilities; therefore, the time of passage of the ions through the drift area varies, allowing for their identification. A series of works is currently underway in order to improve properties of devices for contamination detection. One such solution consists in coupling a classic ion mobility spectrometer with a spectrometer with a transverse field of high strength and high frequency - FAIMS in a cascade system. The FAIMS (Field Asymmetric Ion Mobility Spectrometry) technique is based on a phenomenon of segregation of ions passing through the detector volume. A FAIMS detector is built from opposite ceramic plates, to which a high frequency high voltage is applied. Under the influence of an electric field generated in the detector volume, segregation on the collecting electrode occurs. The observed segregation of the ions present in the flowing gas results from their various mobilities in fields with lower and higher strengths. The mobility of ions depends on the mass and charge of a passing ion and on the velocity of the flowing gas. Under the influence of variable electric field applied to the electrodes, the capture of ions with mobilities which do not meet the conditions of stable flow through the detector occurs. Considering the dependence of mobility of ionic particles migrating through the sensitive volume of a spectrometer on the value of the compensated field, we are dealing with a particular ionic filter.

The design of a hybrid FAIMS-IMS system consists in application of a FAIMS spectrometer as the first stage, but without a collecting electrode. Its principle of operation is similar as in the case of an ion trap. After passing through an ionisation source, ions of the analysed gas enter the ionic trap in the form of two parallel rectangular plates. Between the plates, a high strength field (above 10 000 [V/m]) is applied. Owing to the effect of the dependence of the ions' mobility on the electric field, separation of ions may be obtained, because the electric field in the ionic trap may be shaped so that only the selected ions reach the collecting electrode.

FAIMS spectrometers are about ten times more sensitive; moreover, they enable separation of gaseous substances such as acetone, benzene and toluene, which, till now, have not been distinguished by classic IMS spectrometers, even those with high resolution. An important factor of the operation of FAIMS spectrometers, omitted in scientific papers or patent descriptions, consists in the stability of the temperature of the flowing gas. The temperature of the gas has a significant influence on the mobility of ions, hence on the positions of arising electric peaks originating from various gaseous substances.

An embodiment of such closed chambers in glass systems is known, enabling high purity of the chamber, but unfortunately not ensuring adequate temperature stability of the flowing gas.

Polish patent application No. P-394898 discloses the chamber of an ion mobility spectrometer, whose essence consists in the fact that heating resistors, the ioniser's electrodes, the detector's electrodes and collecting electrodes, as well as conducting contacts, are deposited onto ceramic plates in the form of layers of noble metals. The heating resistors are located on the external surface of ceramic plates in the form of a resistive layer made of ruthenium dioxide. On the internal surfaces of the upper and lower ceramic plate, the following elements are deposited in sequence, starting from the gas inlet up to the chamber: electrodes of the gas ioniser in the form of layers of radioactive nickel, HV electrodes and collecting electrodes in the form of gold layers. The conducting contacts are made of a palladium-silver layer. On the side edges of the ceramic plates, edge contacts made of silver layers are located.

The goal of the invention was to develop a design for a signalling device of chemical contamination on the basis of an IMS / DMS chamber, enabling the limitation of disturbances on components collecting ionic current, as well as resistant to all possible hazards that may occur in the case of devices installed in motor vehicles.

A device for recognition of contaminations, on the basis of a ceramic chamber for a FAIMS or DMS spectrometer, is characterised by the fact that it has a chamber and control units, voltage generator for the chamber control and an ionic current amplifier all in one plane, and the chamber inlet and outlet for the gas are located on the flat bottom surface of the chamber, with chamber supports located in the place of these holes and which have holes for feeding the gas to the chamber and carrying it away from the chamber in the top flat surfaces of the supports, which are in contact with the inlet and outlet of the chamber, respectively.

Installation of control units in the same plane with the chamber allows for bringing them maximally close, practically eliminating cables needed to connect these units with the chamber, leading to maximum reduction of disturbances caused by the current flowing through them. The second preferable effect consists in direct connection of the gas inlet and outlet with the corresponding holes in the supports. This reduces problems with proper sealing of the chamber.

Moreover, locating the ioniser unit in the inlet support, close below the chamber, reduces the path length for the gas flowing from the unit to the chamber, favourably influencing the stability of parameters of the gas, such as temperature, pressure or degree of ionisation. Furthermore, this makes the device easy to assemble and disassemble, because installation or deinstallation of the ceramic chamber requires only the screwing or unscrewing of several screws. Inconvenient sealing of the chamber is not required.

The device, according to the invention, is shown in the embodiment in the form of drawings. Fig. 1 shows its axial cross- section, Fig. 2 - a view from the top, Fig. 3 - a view of the ceramic chamber.

Two supports are fixed to the base JL : the inlet support 2 and the outlet support 3. On the supports, a mounting plate 4 is installed. A ceramic chamber 5 is fixed to the supports in a recess of the mounting plate. An ionisation unit 6 is located in the inlet support. The ceramic chamber is positioned in relation to the supports in a way ensuring contact of its inlet 7 and outlet 8 with holes in the supports, a feeding hole 9 and a discharge hole 10 carrying the gas away from the chamber. In the mounting plate and near the chamber, a control voltage generator 11, for the DMS chamber and an amplifier of the ionic current 12 are located. The analysed gas is fed to the device via the inlet 14 located in the inlet support and carried away from the device via the outlet 15 located in the outlet support.

Claims

Claim

A device for recognition of contaminations on the basis of a ceramic chamber for a FAIMS or DMS spectrometer, characterised in that it has a chamber (5) and control units, voltage generator (11) for chamber control and an amplifier (12) for the ionic current in one plane, and the gas inlet (7) and the gas outlet (8) of the chamber are located in the flat bottom surface of the chamber, while in the locations of these holes, the chamber is supported on supports (2, 3) having a gas feeding hole (9) and a gas discharge hole (10) to/ from the chamber in their flat top surfaces, the holes being in contact with the gas inlet and the gas outlet in the chamber, respectively.