RU2620198C1 - Piezo-desorber for gas analysis devices - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: piezo-desorber for gas analysis devices comprises a chamber with a lid, positioned inside the chamber piezoceramic plate soldered to the rack which is moulded in the dielectric holder, is fixed in it by dielectric stub and through which the electrical contact is made to the lower side of the piezoceramic plate, a flexible conductor, making a contact to the upper side of the plate. Piezo-desorber also includes a housing, which has the generator board inside, exciting oscillations of the piezoceramic plate, closing with the lid, piezo-desorber locking knot on the input of the gas analyzer, consisting of a flange, a union nut and sealing bushing, a dielectric contact rack with two contact units located on the body. At the same time the sorbent placed on the piezoceramic plate, simultaneously affected by the two factors - ultrasound and heating conditioned upon the heat release due to its mechanical and electrical losses.

EFFECT: increased desorption rate of the target substance from the sorbent.

1 dwg

Description

Technical field

The invention relates to the field of analytical instrumentation, in particular to gas analysis devices designed to detect microconcentrations of substances, and can be used in conjunction with detectors of explosive vapor in the air.

State of the art

An effective method of increasing the detection ability of gas analysis instruments is to pre-concentrate the target substance on any sorbent, followed by activated desorption of this substance and delivering it in a gas sample to the gas analysis device. The desorption rate determines the peak concentration of the target substance supplied to the gas analyzer. The higher the desorption rate, the greater the peak concentration of the target substance and the lower its detection threshold. As a gas analysis device, for example, an ion mobility spectrometer (drift spectrometer) can serve.

Most often, thermal or radiation heating is used as a factor activating desorption.

A device for controlling traces of explosives on documents - passports, tickets, etc. (patent RU 2293303, publ. 10.02.2007), based on the principle of thermal desorption. The device is permanently integrated into the inspection equipment, has a camera of a sufficiently large volume, into which controlled documents are placed, where they are blown. The disadvantage of this device is the low threshold sensitivity due to the large volume of the chamber and the low rate of thermal desorption due to the limitation of the heating temperature.

Known thermal desorber (patent WO 2014/045057, publ. 03/27/2014) containing a special rod with a removable swab to collect traces of the target substance and subsequent thermal desorption of the target substance from the tampon and feeding it into the gas analysis device. The device has a limitation in efficiency due to the low rate of thermal desorption, as well as the previous device.

A device is known (patent US 8569691, publ. 10.29.2013) for preconcentration of the target substance to increase the detection ability of the gas analysis device, which is a tube with a sorbent having an exit to the working chamber of the drift spectrometer, the output is blocked by an electromagnetic valve. The device operates in two modes. In the sorption mode, the test gas (air) is pumped through a tube with a closed valve with traces of the target substance, which is concentrated on the sorbent. In the desorption mode, the sorbent in the tube is thermally heated at a high speed and the sample with an increased concentration of the target substance enters through the open valve into the working chamber of the spectrometer. The effectiveness of the method, as above, is limited by the rate of increase in the temperature of the sorbent.

In patent US 7884320, publ. 02/08/2011, the design of the ion mobility spectrometer is proposed, including the target substance collector, which is a tube with a sorbent for the target substance, through which the test air is pumped. A distinctive feature of the device is that sorption is carried out at a low temperature, and thermal desorption during heating. Cooling and heating are carried out by switching the polarity of the voltage on the Peltier element used for cooling and heating. The use of Peltier elements increases both the efficiency of sorption due to cooling, and desorption due to rapid heating, which increases the efficiency of the dermodesorber. The disadvantage of this method is the high power consumption.

There is also a method of increasing the detection ability of ion mobility spectrometers, based on placing the test object in a sealed chamber with high pressure, followed by a sharp release of pressure, stimulating the desorption of the target substance from the surface of the test object (US patent 7204125, published on 04.17.2007). The disadvantage of this method is the bulkiness of the design, the complexity of the technical implementation and low efficiency.

Another physical factor, in addition to increasing temperature and lowering pressure, which can stimulate desorption, is the effect of ultrasound.

A known method (patent US 8153964, publ. 10.04.2012), which uses the action of ultrasound on the test fluid with a dissolved target substance (analyte). Ultrasonic exposure leads to increased formation of steam containing analyte, which is drawn through the capillary into the evacuated working chamber of the device (for example, a quadrupole mass spectrometer). A limitation of the method is its applicability only to liquid media.

A known method (patent US 8161797, publ. 24.04.2012) sampling hazardous chemicals (in particular explosive) with low volatility from hard to reach surfaces (for example, gaps in the tiled floor, the corners between the wall and the floor, etc.) using ultrasound. Ultrasonic vibrations are created by a generator based on piezoelectric ceramics and transmitted to a thin titanium rod (sonotron), which acts on the surface of the object under study, stimulating the desorption of the target substance from the surface, which is drawn into the gas analysis device by a stream of air. The device provides the desorption of the target substance from the surface, but does not provide pre-concentration.

The closest in technical solution is a stripper for ion mobility spectrometers (patent RU 2305282, published 05.08.2005), in which a paper towel or metal mesh with traces of the target substance adsorbed on it (explosives, drugs, etc.) pre-assembled during wiping the surfaces of suspicious objects, and then heated with an electric lamp for thermal desorption of the target substance and transfer it to the device entrance by blowing air flow. The effectiveness of the method implemented in this device is limited by the rate of thermostimulated desorption, determined by the heating rate of the wipes.

Disclosure of invention

An object of the present invention is to increase the detection ability of gas analysis instruments by preconcentrating the target substance on some sorbent, followed by the simultaneous effective effective piezoelectric and thermal desorption of this substance and its delivery in a gas sample to a gas analysis apparatus.

The difference of the present invention from the prototype presented in patent RU 2305282 is that traces of the target substance with low volatility are collected from the test surface on some sorbent, such as a tissue, and a tissue is placed in the chamber on the surface of the piezoelectric plate, which is used to generate ultrasonic vibrations. In the process of generating ultrasonic vibrations, the piezoceramic plate is rapidly heated due to heat generation due to mechanical and electrical losses in it. In this case, the heating of the napkin located on the surface of the piezoceramic plate occurs much faster than when heated by an electric lamp, as in the prototype. The simultaneous effect on the napkin of these two factors causes increased desorption of the target substance. The desorbed target substance is directed by a stream of air into the working chamber of a gas analysis device, for example, a drift spectrometer.

The positive effect is to increase the desorption rate of the target substance from the sorbent (wipes) under the influence of a combination of two factors, ultrasound and rapid heating, compared with desorption caused only by heating.

Brief Description of the Drawing

FIG. 1. The design of the piezoelectric stripper for gas analysis instruments: 1 - chamber; 2 - camera cover; 3 - piezoceramic plate; 4 - dielectric clip; 5 - a rack of a piezoelectric element; 6 - dielectric plug; 7 - the cover of the compartment of the generator, exciting oscillations of the piezoceramic plate; 8 - stripper body; 9 - a union nut; 10 - flange; 11 - a sealing sleeve; 12 - contact rack; 13 - contacts.

An embodiment of the invention

The piezoelectric stripper consists of a chamber 1 with a cover 2. Inside the chamber 1 there is a piezoceramic plate 3 soldered to a rack 5, through which electrical contact is made to the lower side of the piezoceramic plate. Contact to the upper side of the plate is made using a flexible conductor (not shown). The stand of the piezoelectric element 5 is pressed into the dielectric cage 4 and fixed in it using a dielectric plug 6. The entire piezoceramic assembly is attached to the bottom of the chamber 2 using screws (not shown). The camera assembly is attached to the body of the piezo-desorber 8, inside of which there is a generator board that excites the oscillations of the piezoelectric ceramic plate, which is closed by a cover 7. A fixing unit for the piezo-desorber is also attached to the body 8 at the inlet of the gas analyzer. This assembly consists of a flange 10, a union nut 9 and a sealing sleeve 11, which excludes sample dilution due to air intake from the outside of the gas analyzer. On the housing 8 is a dielectric contact rack 12 with two blocks of contacts 13.

Piezo desorber works as follows. Trace substances with low volatility in trace amounts are collected from the test surface on a sorbent. The sorbent is placed in the chamber 1 on the surface of the piezoceramic plate 3 used to generate ultrasonic vibrations. When generating ultrasonic vibrations, heat is generated due to mechanical and electrical losses in it, which leads to heating of the piezoceramic plate 3 and the sorbent located on it. The simultaneous effect on the sorbent of a combination of ultrasonic vibrations and high temperature causes increased desorption of the target substance. A stream of air sucked through a slit 14 in the housing of the chamber 1, the desorbed target substance is sent to the working chamber of a gas analyzer, for example, a drift spectrometer.

The positive effect is to increase the desorption rate of the target substance from the sorbent under the influence of a combination of two factors, ultrasound and rapid heating, compared with desorption caused only by heating.

Claims (1)

A piezoelectric stripper for gas analysis instruments, including a chamber with a lid located inside the chamber, a piezoceramic plate attached to a conductive stand, which is pressed into a dielectric holder, fixed in it with a dielectric plug and through which electrical contact is made to the lower side of the piezoceramic plate, a flexible conductor, making electrical contact to the upper side of the piezoceramic plate, the body of the piezoelectric stripper, the fixing unit of the piezoelectric stripper at the input Asti analyzer, characterized in that on the sorbent that is placed on the piezoceramic plate, have a simultaneous effect two factors - ultrasound and heating due to heat generation due to mechanical and electrical losses therein.

Images