RU2706420C1 - Combined device for gravimetric and chemical analysis of aerosols - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to mass analysis means, is intended for gravimetric and chemical analysis of aerosols for detection, identification and quantitative determination of chemical compounds in laboratory, production and field conditions and enables to determine distribution by size, counting and mass concentration of aerosol particles in gas and aerosol phases of air-dispersed media. Device based on mass spectrometer comprises corona electrode and counter electrode for charging aerosol particles in corona discharge between electrodes, program-controlled high-voltage pulse voltage source with corona discharge current stabilizer connected to corona-forming electrode, counter-electrode supply source and corona discharge current meter connected to counter electrode, which detects ion currents of packets of particles passing through the discharge gap at different speed and deposited on the counter electrode. Counter electrode is made mesh with 50–90 % transparency for particles in corona discharge, provides deposition and accumulation of aerosol particles on grid and is equipped with power supply providing heating to preset temperature and programmable thermal desorption and evaporation of aerosol particles deposited on the mesh for their preliminary separation and programmable thermal decomposition of the settled non-volatile and low-volatile substances to obtain their mass spectra. Counter electrode is conjugated with mass spectrometer by means of input device in form of selective membrane. Data control and data recording unit is connected to the high-voltage pulse supply source of the corona-forming electrode, the corona discharge current meter of the corona-forming electrode, the counter electrode supply source and the mass spectrometer ion detector.

EFFECT: high sensitivity of analysis by reducing detection thresholds of components of the aerosol phase owing to accumulation thereof on the counter electrode, high reliability of identifying substances by programmed thermal desorption and preliminary separation of components of the aerosol phase, as well as by obtaining mass spectra of volatile products obtained after thermal decomposition of non-volatile and low-volatility substances sorbed on deposited dust particles.

7 cl, 6 dwg

Description

The invention relates to means for detecting and identifying chemical compounds in the gaseous and aerosol phases using gravimetric and mass spectrometric analysis and can be applied in laboratory, industrial and field conditions.

The proposed combined device is designed to simultaneously determine the distribution of aerosol particles in the gas stream by size, their calculated and mass concentration, as well as the chemical composition of the gas and aerosol phases of the aerodispersed medium.

To conduct a chemical analysis of aerodispersed media containing impurities in the gas phase or in the form of aerosols with different dispersion, it is necessary to take a sample and enter it into the ion source of the mass spectrometer in the form of gas or vapor. Moreover, the sample should be representative of the chemicals contained both in the gas phase of the medium and in aerosol particles. With continuous monitoring of the aerodispersed medium, for example, in industrial premises and the control of technological processes, the selection and introduction of the analytes into the mass spectrometer must be continuous and stable.

Known devices that implement the electric induction principle of measuring the parameters of the aerodisperse system, the action of which is based on charging aerosol particles in the zone of a pulsed unipolar corona discharge and subsequent measurement of their total space charge by induction method / for example, SU 340942 "Method for measuring the concentration of the dispersed phase of an aerosol", 1972 ; SU 523333 "Device for continuous measurement of dustiness of gases", 1976; SU 525007 "Device for measuring the bulk density of electric charges in a gas", 1976; SU 602829 "Device for measuring the volumetric density of charges of particles in a gas", 1978; SU 1182557 "Method of" detecting a fire hazard ", 1985; RU 2459268" Electric induction fire detector ", 2011, etc.

The electro-induction principle of continuous control of aerosols has high sensitivity, speed and ease of use. Devices allow you to instantly record changes in the concentration of aerosol particles of any chemical composition and size in real time. If you have information about the particle size distribution, you can determine the calculated and mass concentration of aerosol particles.

In known devices, aerosol particles are charged in a charging chamber, a corona discharge between the corona electrode and the counter electrode is applied to charge the aerosol particles under the action of the potential difference applied between them. The geometry in which the corona discharge is formed may be different. The corona electrode can be made in the form of a single metal point (needle) or an ensemble of many points, a blade, wire or several wires, wire mesh, etc. The counter electrode can be a conductive plate, wire mesh, cylinder, etc. [1].

A device is known according to the patent of the Russian Federation RU 2459268 "Electro-induction fire detector", 2011, which is the basis of the production of the fire induction smoke detector IP 213-001, JSC "Research Institute" Radar MMS [2].

The device [2] includes an air flow inducer, a corona discharge charging chamber for charging aerosol particles, an induction electrode for measuring the total aerosol particle charge, a measuring amplifier, an information processing unit, a power supply unit, and a corona discharge current stabilization device.

The unipolar pulsed corona discharge in [2] is ignited between the tip of a needle located along the axis of the air flow and a cylindrical electrode through which air with an aerosol is pumped by a flow inducer. Further downstream, an induction electrode is installed in the form of a cylinder connected to the input of the measuring amplifier.

Aerosol particles in the charging chamber during a pulsed discharge receive a charge proportional to their size and concentration. Passing through the measuring chamber, they induce a charge on the measuring electrode, the magnitude of which depends on their volumetric electric charge.

A common drawback of such devices is that they cannot determine the chemical composition of the aerodispersed medium, which is extremely important in environmental studies, air control in industrial premises and in the control of technological processes.

Mass spectrometric and chromato-mass spectrometric methods are also known for determining the chemical composition of aerosols, in which aerosol particles are vaporized at the input of a sample input device into a mass spectrometer (MS) or into a gas chromatograph-mass spectrometer (GC-MS) complex, and information on the composition of aerosol particles is obtained from mass spectra by comparing them with spectra from a database. To determine the elemental composition of aerosol particles, secondary emission mass spectrometry or inductively coupled plasma ionization mass spectrometry is used. To obtain information on the chemical composition of aerosols, mass spectrometry with ionization at atmospheric pressure or with electron impact ionization is used. The most complete and reliable information on the chemical composition of aerosol particles is provided by the methods of gas chromatography-mass spectrometry (GC-MS) with preliminary separation of multicomponent gas mixtures into fractions in a gas chromatograph and subsequent mass spectrometric analysis of the isolated fractions [3].

A device for analyzing particle sizes and composition of aerosols is known, in which aerosol particle sizes, evaporation and mass spectrometric chemical analysis of particle vapors ("Aerosol Mass Spectrometer for Size and Composition Analysis of Submicron Particles") are determined [4]. A device for analyzing particle sizes and aerosol composition contains a sequentially evacuated aerosol sampling and preparation chamber, a particle size measuring chamber, and a particle detection chamber separated by apertures. A system of aerodynamic lenses is installed in the chamber for sampling and preparing the aerosol sample, sequentially focusing the particle flow into a narrow beam, which is introduced into the particle size measuring chamber (particle size analyzer), because the speed of particles depends on their mass / size, characterized by the size of the aerodynamic diameter. The beam of particles passes through a rotating shutter-modulator with two radial slots, each of which is paired with a detector in the form of an infrared photodiode. The detection of particles moving along a segment of a path of known length with a time resolution makes it possible to determine the speed of a particle by which its aerodynamic diameter is determined. The shutter-modulator duty cycle is determined by the passage of the aerosol from the last of the lenses installed in the sample collection and preparation chamber to the photodiode detector. The signal of a pair of photodiode detectors controlling the gap through which the particle beam passes determines the time-of-flight cycle of the particle and is used to synchronize the detection of particles with a time resolution. A gate-modulator operating at a fixed frequency of 150 Hz determines the temporal resolution of the period of flight of particles equal to about 7 ms. With increasing frequency, the temporal resolution increases (less than 7 ms) when measuring the aerodynamic diameter of the particle, which also provides information on the composition of the aerosol, up to individual particles.

The particles separated by the time of flight enter the particle detection chamber and fall on the surface of the evaporator heated from a minimum temperature of 280 degrees to 600 degrees. The evaporator is a resistively heated tube closed at the end, upon collision with which the volatile or unstable components in / on the particle instantly evaporate. The evaporator is integrated with an ion source - an electron impact ionizer installed at the input of a quadrupole mass spectrometer. The analysis of particles of different chemical composition is carried out at various fixed temperatures of the surface of the evaporator. Ions passing through the quadrupole are collected, amplified by an electron multiplier, and, falling on the ion collector (detector), are recorded. A computer-based control and data recording unit sets the settings for the mass spectrometer, synchronizes the shutter-modulator cycle and electronic amplifier signals, and real-time data collection and analysis.

A known device for analyzing particle sizes and aerosol composition, including an aerosol particle size analyzer, an aerosol particle evaporator, a mass spectrometer including an ion source, a mass analyzer and a mass spectrum detector connected to a data control and recording unit, is selected as the closest analog of the claimed invention.

A disadvantage of the known device is the complexity of the aerodynamic and vacuum systems of the device, which includes three sufficiently powerful turbomolecular vacuum pumps with the corresponding vacuum infrastructure (fore-vacuum pumps and vacuum valves, pressure sensors, vacuum control system, etc.).

The present invention is the creation of a compact combined device that provides information for simultaneously determining the distribution of aerosol particles in size, their counting and mass concentration, as well as the chemical composition of the gas and aerosol phases.

The problem is solved in that in a device for analyzing particle sizes and aerosol composition, including an aerosol particle size analyzer, an aerosol particle evaporator, a mass spectrometer including an ion source, a mass analyzer, an ion detector connected to a control unit and recording data, in accordance with by the invention, the aerosol particle size analyzer is made in the form of a corona electrode and a counter electrode for charging aerosol particles in the corona discharge between the corona electrode and the counter electrode, and is provided with a source thereof high-voltage power supply and a corona discharge current stabilizer connected to the corona electrode, as well as a counter electrode power source and a corona discharge current meter connected to the counter electrode, the counter electrode being an evaporator and designed to provide heating to a predetermined temperature and coupled to a device for introducing the sample into the ion source mass spectrometer, while the control unit and data recording is connected to a source of pulsed high-voltage power supply of the corona electrode, a corona electrode current meter of a corona electrode, a counter electrode power source and a mass spectrum detector.

In addition, the corona electrode is made in the form of a point electrode.

In addition, the corona electrode is made of mesh from a metal wire with a diameter of 0.01-0.1 mm

In addition, the counter electrode is made mesh with a transparency of 50-90% for aerosol flow.

In addition, the corona current stabilizer is installed according to the feedback scheme with the source of pulsed high-voltage power supply of the corona electrode.

In addition, the counter electrode power supply is equipped with a heating temperature sensor and a counter temperature stabilizer for heating the counter electrode.

In addition, the device for introducing the sample into the ion source of the mass spectrometer is made in the form of a selective membrane.

The technical result of the invention is to increase the speed, reliability and sensitivity of the analysis due to the exclusion of mechanical systems when modifying the particle beam of the analyzed gas in an inhomogeneous electric field of the corona discharge, giving the counter electrode a new function of the evaporator of the deposited particles, increasing the sensitivity and reliability of the analysis of the composition of the gas medium due to deposition and accumulation particles on the counter electrode, programmable thermal destruction of the deposited particles for preliminary separation dividing them into components, as well as programmable thermal desorption of particles deposited on the counter electrode to separate and determine the composition spectrum of the volatile and non-volatile components of the aerosol. The invention is illustrated in FIG. 1-6.

In FIG. 1 presents a diagram of the inventive device, the positions in which are indicated: 1 - corona electrode; 2 - counter electrode, 3 - insulators in which electrodes 1 and 2 are installed; 4 - a source of pulsed high-voltage power supply of the corona electrode with a corona discharge current stabilizer (the latter is not shown in Fig. 1); 5 - power supply counter electrode; 6 - corona discharge current meter; 7 - a device for introducing a sample into the ion source of a mass spectrometer; 8 - source of mass spectrometer ions; 9 - mass analyzer; 10 - ion detector; 11 - vacuum pumping system; 12 - control unit and data processing.

In FIG. 2 shows the design of the system “corona electrode-counter electrode” (with Fig. 1) when performing electrodes mesh, in which 1 is a corona electrode; 2 - counter electrode; 3 - insulators in which electrodes 1 and 2 are installed.

In FIG. Figure 3 shows the oscillograms of the aerosol space charge pulses recorded as the dependence of the corona discharge current on the change in the voltage in the pulse applied to the corona electrode for the cases of the absence of aerosol (a) and in the presence of aerosol in the discharge gap between the electrodes (b) ..

In FIG. Figure 4 shows the mass spectra of the analyzed air recorded by the ion detector in the form of the dependence of the ion detector current on the ratio of the mass to the particle charge m / z, in the absence (a) and presence (b) of aerosol particles in the air.

In FIG. Figure 5 shows the mass spectra of the analyzed air with an aerosol recorded by the ion detector in the form of the dependence of the ion detector current on the value of the mass / charge ratio of the particle m / z, measured with the corona discharge turned off (a) and (b) on

In FIG. Figure 6 shows the mass spectra of an aerosol containing dichloroethane and perfluorotributylamine recorded by the ion detector as the dependence of the detector current on the ratio of the mass to particle charge m / z with a change in the temperature of heating of the counter electrode.

The invention consists in the following. A pulsed high voltage voltage is applied to the corona electrode, igniting a corona discharge, the pulse duration and the duty cycle of the voltage pulses are selected depending on the nature and parameters of the aerosol particles. To measure the space charge of aerosol particles, a grid counter electrode is used, a program-controlled power source of the counter electrode creates a voltage on it, which leads to the deposition of oppositely charged particles from the corona discharge, their accumulation, and programmable resistive heating of the grid to a given temperature provides evaporation (thermal desorption and thermal destruction) particles deposited on it, the flow of which through a selective membrane enters the mass spectrometer to obtain a mass spectrum of the components of the flow hour eggs formed volatile and non-volatile components of the gas. The movement of particles in the corona discharge follows a change in the shape of the electric pulse supplied to the corona electrode, in accordance with the mobility of the ions. In the absence of an aerosol, the mobility of the ions of the main components of the air (nitrogen, oxygen, water vapor, hydrogen) is approximately the same, the ions reach the counter electrode approximately at the same time as a packet, while the peak of the pulse of the ion packet characterized by the current through the counter electrode is close to flat. The difference in the mobilities of the ions of the gas components is reflected in the shape (slope) of the leading and trailing edges of the pulse. Information on the size distribution of aerosol particles is obtained from the time-of-flight spectra of aerosol particles between the corona electrode and the counter electrode, and information on the chemical composition of the aerodispersed medium is obtained from the mass spectra by comparing them with the spectra of the mass spectrometer database.

The device is as follows (Fig. 1). The particle size analyzer includes a corona electrode (1) and a counter electrode (2) installed in insulators (3) (Fig. 2). The flow of the aerodispersed medium is created using the "electric wind" arising under the influence of a corona discharge in the discharge gas gap between the corona electrode (1) and the counter electrode (2) under the action of a high potential difference applied between them. A source of pulsed high voltage voltage (4) is connected to the corona electrode (1), which is connected by feedback to a corona discharge current stabilizer (not shown in Fig. 1), providing a voltage of pulsed corona discharge of about 7 kV. The programmed mode of operation of this circuit is set by the control and data processing unit (12). The counter electrode (2) is also under voltage supplied from the power source (5), which leads to electrostatic deposition of charged particles on it from the electro-gas-dynamic flow in the corona discharge and the flow of electric current, which is recorded by the corona current meter (6). The corona electrode (1) can be made pointed or grid with a small radius of curvature to create a highly inhomogeneous electric field near its surface, necessary for the effective excitation of a corona discharge in a gas medium, for example, in the form of a metal tip (needle) or a mesh of thin metal wire diameter 0.01-0.1 mm. The counter electrode (2) for capturing corona ions is made mesh, permeable, ensuring the transmission of aerosol particles, while its transparency for the aerosol flow is 50-90%. Information on the size distribution of aerosol particles is obtained by recording with a meter (6) a corona current strength adequate to the space charge of deposited aerosol particles. By varying the current of the corona discharge in time, the time spectrum of aerosol particles passing by the distance between the corona electrode (1) and the counter electrode (2) is established.

Applying voltage to the counter electrode (2) leads to its resistive heating, and at a certain value of the temperature of the counter electrode (2), thermal desorption of the layer of particles deposited on it begins, thermal destruction of volatile and unstable compounds in their composition and evaporation of particles from the counter electrode (2), which implements the function of an evaporator . Maintaining the required temperature of the heated counter electrode (2) is provided by a program-controlled heating temperature sensor and a heating temperature stabilizer (not shown in Fig. 1), included in the circuit of the counter electrode power source (5). The stream of particles that left the counter electrode-evaporator (2) is fed to the input of the particle input to the mass spectrometer (7), which is opposite to the evaporator. The particle input device (7) is made in the form of a selective membrane that poorly transmits water vapor, nitrogen and oxygen, but well transmits vapors of organic substances, which, passing through the selective membrane, enter the mass spectrometer and pass sequentially the ion source of the mass spectrometer (8) , in which they are ionized by electron impact, acquiring the corresponding energy eV, a mass analyzer (9), in which the separation of ions by size occurs, for example, the ratio of the mass of the ion to its charge, and the formation of ion packets. As a mass analyzer (9), for example, a quadrupole mass analyzer (“mass filter”) can be used. Next, the ion packets fall into the collector - ion detector (10), where they are converted into an ion current corresponding to the line of the mass spectrum. The mass spectrometer is equipped with a vacuum pumping system (11), which creates and maintains a high vacuum, and the ion detector (10) is connected to the control and data processing unit (12). Information on the chemical composition of the aerodispersed medium is obtained from the mass spectra by comparing them with the spectra of the mass spectrometer database.

The device operates as follows. A square-shaped pulsed high voltage with steep edges with an amplitude sufficient to ignite a corona discharge (of the order of 4-7 kV), positive or negative, approaches the corona electrode (1) from the power source (4) controlled by the control and data processing unit (12) polarity. In a corona discharge, during the action of a high voltage pulse, gas molecules are ionized and aerosol particles are charged. In this case, an impulse packet of charged ions and aerosol particles is created, moving towards the counter electrode (2) both under the influence of an electric field and under the influence of the electro-gas-dynamic flow of an “electric wind”. Due to the different mobility of the charged particles in the electric and gas-dynamic fields, the packet of particles spreads and particles of different sizes reach the counter electrode (2) at different time points in accordance with their time of flight of the discharge gap. Charged aerosol particles are deposited on the counter-electrode grid (2) under the action of the grid potential with the opposite sign with respect to the sign of the charged particles. The current of corona discharge ions and charged aerosol particles deposited onto the grid (2) is measured using a current meter (6). The value of the measured volumetric electric charge on the counter electrode grid (2) is proportional to the charge and the calculated concentration of aerosol particles. The duty cycle of the high voltage pulses and the length of the discharge gap are chosen to provide an informative form of the current pulse at the counter electrode (2), which allows one to judge the particle size distribution.

The power source (5) of the counter electrode grid heater (2), controlled by the control and data processing unit (12), provides its direct heating and stabilization of the set temperature (the sensor and temperature stabilizer are not shown in Fig. 1). On the counter electrode grid (2) heated to a temperature set by the control unit (12), the deposited aerosol particles evaporate. The flow of gas and vapor of the vaporized aerosol enters the input of the sample inlet device to the mass spectrometer (7). For the example of FIG. Figure 1 shows the sample inlet device (7) in the form of a selective membrane that poorly transmits water vapor, nitrogen and oxygen, but transmits organic vapor vapor well. Gas and aerosol particle pairs are ionized in the ion source (8), analyzed by the mass analyzer (9) by the ratio of the mass of the ions to their charge, and recorded by the ion detector (10) in the form of the ion current from the ion packet with the same mass-to-particle ratio, giving a line in the mass spectrum. The measured mass spectrum and the signals from the corona discharge current meter (6) are processed in the data processing unit (12), which provides information on the chemical composition of the gas and aerosol particles, as well as their calculated and mass concentration.

In FIG. Figure 2 shows, for example, the design of an aerosol particle analyzer with a mesh corona (1) and counter electrode (2), which are installed in insulators (3). The distance between the electrodes of the discharge gap is 30 mm. A pulsed corona discharge voltage of about 7 kV is maintained by feedback on the corona discharge current measured by a current stabilizer. The pulse width set by the control and data processing unit (12) is about 50%. The “electric wind” of the corona discharge provides a stable aerodispersion flow of approximately Q ~ 2 l / s at a corona discharge current of about 20 μA. Shown in FIG. 2, a device that is simple in design can be installed, for example, as an option, at the input of the membrane input of the sample in the Micropor portable portable mass spectrometer with a quadrupole mass analyzer (Scientific Instruments JSC, St. Petersburg).

When determining the composition of the aerodispersed flow, a high voltage is applied to the corona electrode (1) from the power source (4), and voltage is applied to the counter electrode (2) from the power source (5) according to the program set by the control and data processing unit (12), providing programmable resistive heating of the grid (2). As the temperature of the counter electrode grid (2) increases, the aerosol particles evaporate, and particles containing substances with high vapor pressure evaporate at lower temperatures. Thus, when the grid temperature changes, the substances contained in aerosol particles are separated (as in a gas chromatograph in GC-MS complexes), which facilitates the interpretation of measured mass spectra and increases the reliability and information content of complex gravimetric and chemical analysis. Programmable heating of the counter electrode grid (2) provides a controlled and reproducible process of separation of analytes.

The heated counter electrode grid (2) can provide detection and identification of hardly volatile or nonvolatile substances sorbed on dust particles, which are also charged in the corona discharge field and deposited on the grid. In the absence of heating, such substances cannot be detected. But when the grid is heated on its surface, thermal destruction of the deposited molecules of nonvolatile substances can occur. In this case, non-volatile molecules can decompose on the surface of the network with the formation of fragments having a higher vapor pressure, which can evaporate from the network and can be analyzed by a mass spectrometer. Thus, non-volatile substances can be detected and identified by the spectra of volatile products of their thermal degradation.

In a trend analysis and tracking changes in the concentration of aerosol substances over time of specific given substances, for example, when controlling production processes, the mass spectrometer is tuned to the characteristic lines of these substances, the intensities of which are measured at fixed temperatures of the counter electrode grid (2), which ensure effective evaporation of the given substances .

The comparative efficiency of using the inventive device is illustrated by the following examples, which are given in parallel in the respective FIGS. 3-5 for ease of perception and comparison.

In FIG. 3a) shows the shape of the current pulse (waveform) measured at the counter electrode (2) in the air stream in the absence of an aerosol. For research here, similarly to the prototype, a pulse packet of charged particles was formed by a slit shutter. In the absence of an aerosol, the mobility of ions of the main components of the air (nitrogen, oxygen, water vapor, hydrogen) is approximately the same, ions reach the counter electrode grid approximately simultaneously, and the peak of the current pulse of the ion packet measured at the counter electrode is close to flat. The difference in the mobilities of the ions of the air components is reflected only on the shape (slope) of the front (left) and trailing (right) fronts of the pulse.

In FIG. 3b) shows the shape of the current pulse measured at the counter electrode (2) in the air stream in the presence of aerosol particles. In this study, a simple aerosol particle generator with temperature sublimation was used to obtain aerosol. Comparison of FIG. 3a) and FIG. 3b) shows that, in the presence of an aerosol in air, the steepness of the leading and trailing edges of the pulse, which reflect the ion mobility of the main air components, is preserved, but the signal amplitude increases, and the peak of the pulse has a more complex shape, which reflects the presence of charged particles with different mobility. From the waveform of FIG. 3b) it can be seen that finely dispersed aerosol particles with greater mobility predominate in the flow, which leads to a maximum signal amplitude near the leading edge of the pulse. Software processing of the difference signal between pulses FIG. 3b) and FIG. 3a) makes it possible to isolate a part of the signal caused by the aerosol phase of the aerodispersed medium and to determine the spectrum of mobilities of aerosol particles, their calculated and mass concentration. Algorithms for calculating the electrical mobility of aerosol particles charged in a corona discharge are given, for example, in [5].

In FIG. 4 shows mass spectra in the range of mass numbers of 50-100 amu, measured in the absence (Fig. 4, a) and the presence (Fig. 4, b) of aerosol particles in the air. Mass spectra are reduced to a single scale of mass numbers and intensities. Mass spectra differ in the composition of the lines, their intensities, and the ratios of the intensities of the lines. The presence of aerosol in air leads to a change in the mass spectrum and to a significant increase in the line intensity, by more than an order of magnitude.

In FIG. Figure 5 shows the mass spectra of air with an aerosol measured with (a) off and (b) on the corona discharge. It is seen that the intensity of the lines of the mass spectrum when the corona discharge is turned on increases by about 30%. This means that the substances contained in the aerosol phase partially evaporate in the corona discharge plasma, which can, on the one hand, distort the data of gravimetric analysis of particle size distribution (calculated and mass concentration), and, on the other hand, increase the sensitivity of chemical mass spectrometric analysis.

Presumably, the distortion of the spectrum of the gravimetric composition of the aerosol is inherent in all devices with the charging of aerosol particles in the corona discharge field. However, with appropriate calibrations of the inventive device, containing both a gravimetric analyzer and a mass spectrometer, this effect can be taken into account.

In FIG. 6 shows in three-dimensional representation the mass spectra of aerosol particles deposited on the counter electrode (2) containing perfluorotributylamine (boiling point 178.7 ° C) and dichloroethane (boiling point 83.5 ° C), measured with increasing temperature of the counter electrode grid (2) from 20 ° C to 150 ° C. The analysis shows that as the temperature rises to 55 ° C, only dichloroethane lines to m / z = 100 (molecular weight of dichloroethane 98.96) are present in the mass spectrum, the intensity of which increases with increasing temperature to 50 ° C and then begins to decrease. With a further increase in temperature, dichloroethane completely evaporates from the counter electrode grid (2), dichloroethane lines disappear in the mass spectrum and perfluorotributylamine lines (molecular weight 671.1) appear, the intensity of which increases with increasing temperature.

The use of the inventive combined device allows you to individually investigate the gas and aerosol components of the aerodispersed medium, and also include in the process of mass spectrometric analysis of the substances contained in the aerosol particles, and thereby significantly increase the sensitivity of chemical analysis.

The proposed combined device in comparison with the prototype is compact and structurally simple, does not require additional to the standard mass spectrometric systems, flow drivers, pumping means, pressure and vacuum control. At the same time, the device is multifunctional and allows you to perform the following tasks:

- to provide a stable, controlled flow of the sample to the input of the sampling system in the mass spectrometer by using the "electric wind" of the corona discharge;

- determine the size distribution, the calculated and mass concentration of aerosol particles in the aerodispersed medium;

- to precipitate aerosol particles on the counter-electrode grid and to carry out the accumulation of substances contained in the aerosol phase to increase the sensitivity of the analysis (lower thresholds for the detection of specified substances);

- carry out thermoprogrammed desorption of substances deposited on the counter-electrode grid, i.e. preliminary separation of substances contained in aerosol particles to increase the reliability of identification of substances;

- carry out thermal decomposition of non-volatile and hardly volatile substances sorbed on dust particles and deposited on a counter-electrode, for the detection and identification of non-volatile substances from the spectra of volatile products of their thermal destruction;

- carry out chemical analysis of substances in the gas and aerosol phases of aerodispersed media to detect, identify and quantify controlled chemical compounds in laboratory, industrial and field conditions.

Literature:

1. New reference chemist and technologist. Processes and apparatuses of chemical technologies. SPb .: ANO NPO Professional, 2004, section 10.4.3.

2. RF patent RU 2459268 "Electro-induction fire detector", 2011

3. Lebedev A.T. Mass spectrometry for the analysis of environmental objects. Moscow: Technosphere, 2013 .-- 632 s, ISBN 978-5-94836-363-9, (Translated from English).

4. Jayne, John T .; Leard, Danna C .; Zhang, Xuefeng. "Development of an Aerosol Mass Spectrometer for Size and Composition Analysis of Submicron Particles." Aerosol Science and Technology. 33: 1-2, July-August 2000, p. 49-70.

5. Alekseenko A.V., Yakimov S.A. The use of electrohydrodynamic modeling for calculating the electrical mobility of aerosol particles charged in a corona discharge // Tomsk State University Journal. Novosib. gos.un-ta. Series: Physics. 2016.Vol. 11, No. 4. S. 5-16. ISSN 1818-7994. Bulletin of the ISU. Series: Physics. 2016. Volume 11, No. 4 © A.V. Alekseenko, S.A. Yakimov, 2016.

Claims (7)

1. A device for analyzing particle sizes and aerosol composition, including a series-installed evacuated aerosol particle size analyzer, an aerosol particle evaporator, a mass spectrometer including an ion source, a mass analyzer, an ion detector connected to a data recording and control unit, characterized in that the aerosol particle size analyzer is made in the form of a corona electrode and a counter electrode for charging aerosol particles in a corona discharge and is equipped with a source of high-voltage pulse voltage and a corona discharge current stabilizer connected to the corona electrode, as well as a counter electrode power source and a corona current meter connected to the counter electrode, the counter electrode being an evaporator and designed to heat up to a predetermined temperature and coupled to a device for introducing a sample into the ion source of the mass spectrometer while the control and data recording unit is connected by the outputs to the source of pulsed high-voltage power supply of the corona electrode, to the current meter of the corona corona discharge electrode, counter electrode and a power source ion detector of the mass spectrometer. 2. The device according to p. 1, characterized in that the corona electrode is made in the form of a pointed electrode. 3 The device according to p. 1, characterized in that the corona electrode is made mesh. 4. The device according to claim 1, characterized in that the counter electrode is made mesh with a transparency of about 50-90% with respect to the aerosol stream. 5. The device according to p. 1, characterized in that the corona current stabilizer is installed according to the feedback scheme with a source of pulsed high-voltage power supply of the corona electrode. 6. The device according to p. 1, characterized in that the power source of the counter electrode is equipped with a heating temperature sensor and a stabilizer of the heating temperature of the evaporator. 7. The device according to claim 1, characterized in that the device for introducing the sample into the ion source of the mass spectrometer is made in the form of a selective membrane.

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