RU2341789C2 - Method and device of multi-sensor detecting main priority pollutants of atmospheric air - Google Patents

Abstract

FIELD: ecology.

SUBSTANCE: device of multi-sensor quantitative detecting of main priority inorganic pollutants in atmospheric air: ammonium, sulfur dioxide and hydrogen sulfide includes multi-sensor system on superficial acoustic wave, consisting of three double lines of detention. Each detention line in double detention line represents sensor element, which is made on separate quartz crystal and is placed in separate measuring cell, sensitive coatings in form of functional polymer films being applied on all six sensor elements in space between counter-pin transformers of detention line. Sensitive coatings are by two identical in chemical structure and thickness, and differ from each other in each pair of sensor elements.

EFFECT: ensures method and device for express control (detecting) of main priority pollutants in atmospheric air at level of their dangerous for people's vital functions and (or) highly explosive and inflammable concentrations, including their (ammonium, sulfur dioxide, hydrogen sulfide) detecting at background of normal air composition and output of data about their quantitative content in atmospheric air units of concentration in mg/m^3.

2 cl, 6 dwg

Description

The present invention relates to the field of measurement technology, in particular to gas-analytical sensors - chemical sensors forming a multisensor system designed for simultaneous monitoring, i.e. detection and quantification of inorganic gases (vapors) in the air, which are the main priority pollutants of atmospheric air (OPZAV): ammonia, sulfur dioxide and hydrogen sulfide.

Ammonia, sulfur dioxide and hydrogen sulfide are among the six main priority pollutants of atmospheric air (OPZAV), its surface layer, which also includes dust, carbon monoxide and nitrogen dioxide, which are monitored everywhere and around the clock on the globe [RD 52.04.186 -89. Guidelines for the control of air pollution // State Hydromet of the USSR. M .: 1991. S.92-100]. In addition, ammonia is by far the most common refrigerant, being a source of increased fire and explosion hazard in chemical and other types of production [ПБ-09-220-98. Rules for the design and safe operation of ammonia and refrigeration units. C.21]. Most of the largest technological accidents of recent years are associated with ammonia. The tasks of controlling sulfur-containing compounds are associated with the extraction, processing and use of natural resources: coal, oil and gas. Hydrogen sulfide is an explosive and very toxic gas [Shirokov I. This smell is known to all // Grazhd. protection. - 1995. No. 8. S.47-48]. Sulfur dioxide ranks first in terms of tonnage emitted into the atmosphere among all pollutants [Sulfur oxides and suspended particles. WHO. Series "Hygienic criteria for the state of the environment." Issue 8. Geneva. 1982. 131 p.].

All methods and means of control of OPZAV can be divided into traditional chemical analytical methods and instrumental. Until now, the systematic monitoring of the HAZ in the surface layer is carried out by Roshydromet services using traditional chemical-analytical methods, including manual sampling of air samples in absorbers and their subsequent analysis in a chemical laboratory [RD 52.04.186-89. Guidelines for the control of air pollution // State Hydromet of the USSR. M .: 1991. 693 p.]. Such an analysis is time-consuming, non-express and does not lend itself to automation. For systematic and automated control of atmospheric air quality (automatic monitoring) stationary and mobile posts and stations based on cars are used, which are equipped with expensive chromatograph-mass spectrometers or a set of gas analyzers specialized for each pollutant [Rozinov G.L. Automatic analyzers and measuring systems for monitoring atmospheric pollution // Devices and Control Systems. 1994. No. 9. C.1-9]. In Russia, the third level of control of atmospheric air based on mobile stations is almost completely absent. such a station costs several million dollars [Popov A.A. // Devices and control systems. 1994. No. 9. S.15-17], and according to experts of Roshydromet, Russia's demand for such stations amounts to several thousand. In addition, it is worth noting the growing role of in-situ air analysis related to terrorist threats. This problem cannot be solved on the basis of either chemical-analytical methods or traditional instrumental physical-chemical methods, i.e. on the old element base of gas analytical instrumentation.

Recently, more and more complex gas-analytical problems of air control are being solved with the help of devices based on solid-state sensors - multisensors (multisensor systems) made using microelectronics technologies. For example, instruments for the control of explosives, narcotic substances and toxic substances are proposed, which are based on multisensor systems, the so-called “electronic noses”, sometimes combined with ultra-high-speed high-performance gas chromatography [EJStaples, S.Wiswanathan Ultrahigh-speed chromatography and virtual chemical sensors for detecting explosives and chemical warfare agents // IEEE Sensors journal, V.5, No. 4, august 2005]. On Columbia series spacecraft, technology using a multi-sensor electronic nose type system has been successfully used to control the vapors of organic and inorganic compounds in the atmosphere [Ryan MA et al. Monitoring Space Shuttle air for selected contaminants using an electronic nose // Proceedings of 28 ^th international conference on environmental systems, Danvers MA, July 12-16, 1998]. The use of such multisensor systems as an alternative to traditional gas analytical methods has the following advantages: lack of preliminary sample preparation, very short time of a single analysis (analysis of one sample), which gives a decisive advantage in the performance of analyzes per unit time, portability, low power consumption and material consumption, as well as the manufacture of the multisensor itself the system and the main structural components of the device using microelectronics technology, which gives another decisive advantage - rel respect to cheapness. A high degree of automation of analysis using this device does not require a highly qualified operator; there is the possibility of execution in a remote wireless version [Benes E., Groschl. M., Seifert F., Pohl A. Comparison between BAW and SAW sensor principles // 1997 IEEE International frequency control symposium P.5-20].

A patent search showed that the vast majority of devices of this type are designed to control the vapors of organic compounds in atmospheric air. In accordance with a known method [US patent No. 4895017, CL. G01N 031/06, publ. 01/23/90] to control, detect and quantify the vapors of organic compounds in air, a multisensor system is used, consisting mainly of several sensors (chemical sensors) on surface acoustic waves (SAW) in the construction of a double delay line with a frequency of 158 MHz, performed (each sensor) on a separate quartz crystal and having sensitive coatings based on "fluoropoliols", i.e. polyalcohols in whose molecules the hydrogen atoms are partially replaced by fluorine atoms [Ballantine D.S., Rose S.L., Grate J.W., Wohltjen H. Correlation of surface acoustic wave device coating responses with solubility properties and chemical structure using pattern recognition // Anal. Chem. 1986, V. 53, No. 14. P.3058-3066]. The method of molecular recognition of vapors of organic compounds in air in this patent and article is based on weak intermolecular interactions between molecules of adsorbate gases and polymer sorbents such as Van der Waals and hydrogen bonds, which are nonspecific intermolecular interactions that are the only cause of physical sorption. Both sensor elements - delay lines are made on the same quartz crystal and the analyzed air sample is supplied simultaneously to both SAW-sensor elements included in the double delay line, forming a chemical sensor - sensor. In each sensor, one of the sensor elements has a sensitive polymer coating, and the second - comparative - does not have such a coating. The multisensor system includes several double delay lines, which are connected to a high-frequency amplifier using a multiplexer, forming an oscillator with it. The measurement procedure is as follows: the analyzed air sample is simultaneously supplied to all chemical sensors - SAW sensors (double delay lines) included in the multisensor system. The method for extracting analytical signals is as follows: the analytical signals of the sensors that make up the data array are analyzed using a complex mathematical algorithm that includes predicting the expected equilibrium concentrations using a function called the Kalman filter and determining the concentration of chemicals from these predicted values.

The known method and device [US patent No. 4895017, CL. G01N 031/06, publ. 01/23/90] provide quick detection of vapors of organic compounds within a few minutes, indicating which particular compound or class of organic compounds is present in air, followed by the issuance of a range of vapor concentrations of a particular compound present in atmospheric air. This patent is the closest to the proposed invention for its intended purpose and technical essence, therefore, it is selected as a prototype.

The disadvantages of the known method and device are the following: 1) the inability of materials of sensitive coatings of surfactants of chemical sensors (sensors), which are used as films of partially fluorinated polyols, to enter into specific interactions with gas molecules of adsorbates stronger than interactions such as Van der Waals and hydrogen bonds, causing physical sorption, which completely excludes the possibility of chemisorption of vapor molecules of inorganic main priority atmospheric pollutants air, such as ammonia, sulfur dioxide and hydrogen sulfide. The chemical fragments that make up the polymer chains partially (several molar percent) contain hydroxyl groups and do not contain chemical groups capable of entering into specific interaction with molecules of OPZAV adsorbate gases. As a result, these surfactant sensors (sensors) are not able to detect inorganic pollutant molecules in the air with high selectivity and sensitivity. 2) The absolute technical impossibility of supplying airflows of different chemical composition to two SAW sensor elements included in the SAW sensor (double delay line), due to the fact that both delay lines (both sensor elements) are made on the same quartz crystal. 3) The impossibility of accurate molecular recognition, identification of pollutants in the analyzed air sample, associated with the imperfection of a complex mathematical algorithm that gives only the probabilistic nature of the solution to the identification problem.

The purpose of the invention is to develop a method and device for the rapid control (detection) of the main priority pollutants in the air at the level of their life-threatening people and (or) explosive and flammable concentrations, including their (ammonia, sulfur dioxide, hydrogen sulfide) detection on the background normal air composition and the issuance of data on their quantitative content in atmospheric air in units of concentration in mg / m ³ .

The problems solved by the invention are: 1) to provide simultaneous molecular recognition of all three OPZAV against the background of normal air composition, which is achieved by using thin films of functional polymers of various chemical structures as sensitive coatings of SAW sensors, as a result of which sensitive materials acquire the ability to enter into specific interaction with gas molecules - the main priority pollutants: ammonia, sulfur dioxide and hydrogen sulfide, providing their chemisorption by sensitive coatings of sensors in the presence of molecules forming air and other molecules that are unable to enter into specific interactions; 2) to provide the possibility of simultaneously supplying the flow of analyzed air with the same speed, but different in chemical composition: containing OPZAV and not containing OPZAV, on both sensor elements that are part of the surfactant chemical sensors forming a multisensor system; 3) to provide a more accurate and reliable identification of the HAZ in the atmospheric air sample in comparison with the probabilistic algorithm used in the prototype.

The stated goal and objectives are solved: the task of ensuring chemisorption of OPZAV molecules against the background of normal air composition is solved by the fact that instead of sensitive coatings of SAW sensors based on fluoropolyols, films of functional polymers based on polydimethylsiloxanes (PDMS), polyalkyl methacrylates (PAMA) or alkyl methacrylate copolymers are used in the known method (PAMA) with styrene sulfonate (SS) with ion-bound cations of organic dyes of two classes: triphenylmethane series (fuchsin, crystalline violet, brilliant green (BZ), etc.) and the acridine series [9- (p-dialkylaminostyryl) -10-alkylacridinium] of various degrees of modification (SM) from 0.02 to 0.30; [Soborover E.I., Tverskoy V.A., Tokarev S.V. Optical chemical sensor of sulfur dioxide based on films of functional polymers for air control of the working area. Copolymers of Acrylonitrile and Alkyl Methacrylates with Brilliant Green Styrene Sulfonate // J. Anal. chemistry. 2005.V.60. Number 3. S.307-315; Soborover E.I., Tverskoy V.A., Tokarev S.V. Optical chemical sensor of sulfur dioxide based on films of functional polymers for air control of the working area. Copolymers of polydimethylsiloxanes with an ion-bound diamond green cation // J. Anal. chemistry. 2005.V.60. No. 5. S.507-513.] (Figure 1).

The task of ensuring the possibility of simultaneously supplying the flow of analyzed air at the same speed and of different chemical composition, containing OPZAV and not containing OPZAV, to both sensor elements that are part of the SAW sensors (chemical sensors) forming a multisensor system, is solved by the fact that in the well-known instead of SAW sensors (chemical sensors), in which both sensor elements (both delay lines) are located on the same quartz crystal, SAW sensors are used in which each sensor element (one the delay line) is made on a separate quartz crystal, which is located in a separate measuring cell, which makes it possible to supply to each sensor element streams of the analyzed air containing OPZAV or not containing "clean air" (Figure 2).

The task of providing a more accurate and reliable identification of SAR in an atmospheric air sample is solved by the fact that in the known method in which sensitive coatings are applied to one of two sensor elements included in a differential SAW sensor (chemical sensor), and the second sensor element without sensitive coating It is used as a comparative one. On both sensor elements included in SAW sensors, identical in chemical structure and film thickness of the functional polymer, one of the above, are applied. Moreover, in all SAW sensors (in all three pairs of sensor elements) functional polymers with different chemical structures are used, but identical in each pair of sensor elements included in each of the three SAW sensors (Figure 2).

In addition, in accordance with the invention, in contrast to the known method, the supply of the analyzed air sample is divided into two stages. At the first stage, the flows of the analyzed air are fed to all six sensor elements with preliminary removal of the OPZAV from them; in the second stage, following the first, the flow of analyzed air continues to be supplied to the three sensor elements with preliminary removal of the RAM, and the flows of the analyzed air containing the RAM are fed to the other three sensor elements (Figure 3).

In addition, in contrast to the known method in accordance with the invention, analytical signals from three SAW sensors (chemical sensors) due to the chemisorption of OPZAV molecules by polymer films are obtained by pairwise subtraction of the sensor response values (in Hz) obtained at the first stage of the analysis air samples (measurements), from the values of the sensor responses (in Hz) obtained at the second stage of the inlet of the analyzed air sample (measurements).

In accordance with the invention, each SAW sensor element is located in a separate measuring cell; all measuring cells are connected by gas switching according to FIG. 3.

In accordance with the invention, functional polymers based on polydimethylsiloxane (PDMS), polyalkyl methacrylates (PAMA) and copolymers of PAMA with styrene sulfonate (CC) with ion-bound cations of triphenylmethane dyes (fuchsin, crystalline violet, brilliant green) (sensitive green) are proposed as sensitive materials for chemical sensors. and dyes of the acridine series [9- (p-dialkylaminostyryl) -10-alkylacridinium (Acr)] of various degrees of modification of the polymer chain (Figure 1).

In accordance with the invention, in the space between the interdigital transducers (IDT) of all six SAW delay lines, which are sensor elements, thin films of the order of 0.1 μm are applied, films of functional polymers, and in each pair of sensor elements included in one SAW chemical sensor - SAW sensor; identical in chemical structure and film thickness to one of the functional polymers are applied. In all three SAW sensors, functional polymers that are different in chemical structure and / or thickness are used.

In accordance with the invention, the procedure for analyzing an air sample and isolating an analytical signal is as follows (Figure 3):

1) Pumping of the analyzed air through the multisensor system in mode I (Roman) for 10 minutes, during which the absorbers (7, 8, 9) completely remove from the gas stream supplied to all six sensor elements of the multisensor system nitrogen dioxide (absorber 9 ), sulfur and ammonia and hydrogen sulfide (absorbers 7, 8); Based on the measurements of difference frequencies in three measuring channels from three double delay lines, using the methods of mathematical statistics, the levels of frequency noise in all three measuring channels (on all three SAW sensors) are determined (in this mode, clean air is supplied to all six sensor elements):

[(F ¹ ₁ ± ΔF ¹ ₁ ]); (F ¹ ₂ ± ΔF ¹ ₂ ); (F ¹ ₃ ± ΔF ¹ ₃ )] (subscripts correspond to the number of the measuring channel; superscripts correspond to the inlet mode of the atmospheric air sample); 2) Pumping the analyzed air sample through the multisensor system for 10 minutes in mode II (Roman), in which the air stream passed through the absorbers (7, 9) and does not contain any RAM is supplied to the sensor elements 1, 3, 5, and to the sensor elements 2,4,6, a stream of air is supplied that has passed only through an absorber of nitrogen oxides (9) and containing a feed. Difference signals from three double delay lines (three SAW sensors) along three measuring channels: [(F ¹¹ ₁ ± ΔF ¹¹ ₁ ); (F ¹¹ ₂ ± ΔF ¹¹ ₂ ); (F ¹¹ ₃ ± ΔF ¹¹ ₃ )] are recorded and processed according to the following algorithm: 1) Comparison of signals measured in modes I and II (Roman) in pairs from each pair of sensor elements with identical coatings: excess of the signal level in the II mode over the level measured in the I-th mode (exceeding the average statistical noise level) in at least one measuring channel signals the presence of a RAM in the analyzed air sample;

ΔF ₁ = (F ¹¹ ₁ ± ΔF ¹¹ ₁ ) - (F ¹ ₁ ± ΔF ¹ ₁ )

ΔF ₂ = (F ¹¹ ₂ ± ΔF ¹¹ ₂ ) - (F ¹ ₂ ± ΔF ¹ ₂ )

ΔF ₃ = (F ¹¹ ₃ ± ΔF ¹¹ ₃ ) - (F ¹ ₃ ± ΔF ¹ ₃ )

If ΔF ₁ > ΔF ¹ ₁ → There is a RAM in the sample;

If ΔF ₂ > ΔF ¹ ₂ → There is RAM in the sample;

If ΔF ₃ > ΔF ¹ ₃ → There is RAM in the sample;

If at the same time ΔF ₁ <ΔF ¹ ₁ ΔF ₂ <ΔF ¹ ₂ ΔF ₃ <ΔF ¹ ₃ → there is no RAM in the sample.

2) If OPZAV is in the sample, then a system of three equations with three unknowns is solved, which includes the difference signals according to claim 1) and three concentrations of OPZAV, with the output of the concentrations of three OPZAV in units of mg / m ³ .

ΔF ₁ = ΔF ₁ , _NH3 + ΔF _{1, SO2} + ΔF _{1, H2S} ; ΔF ₁ = k _{1, NH3} C _NH3 + k _{1, SO2} С _SO2 + k _{1, H2S} С _H2S

ΔF ₂ = ΔF _{2, NH3} + ΔF _{2, SO2} + ΔF _{2, H2S} ; ΔF ₂ = k _{2, NH3} C _NH3 + k _{2, SO2} С _SO2 + k _{2, H2S} С _H2S

ΔF ₃ = ΔF _{3, NH3} + ΔF _{3, SO2} + ΔF _{3, H2S} ; ΔF ₃ = k _{3, NH3} C _NH3 + k _{3, SO2} С _SO2 + k _{3, H2S} С _H2S,

where ΔF _{1, NH3} , ΔF _{1, SO2} , ΔF _{1, H2S} are the contributions made to the response of the 1st differential SAW sensor due to the chemisorption of ammonia, sulfur dioxide and hydrogen sulfide; ΔF _{2, NH3} , ΔF _{2, SO2} , ΔF _{2, H2S} - contributions made to the response of the 2nd differential SAW sensor due to the chemisorption of ammonia, sulfur dioxide and hydrogen sulfide; ΔF _{3, NH3} , ΔF _{3, SO2} , ΔF _{3, H2S} - contributions made to the response of the 3rd differential SAW sensor due to chemisorption of ammonia, sulfur dioxide and hydrogen sulfide; k _{1, NH3} , k _{1, SO2} , k _{1, H2S} - sensitivity coefficients of the 1st differential SAW sensor with respect to ammonia, sulfur dioxide and hydrogen sulfide; k _{2, NH3} , k _{2, SO2} , k _{2, H2S} - sensitivity coefficients of the 2nd differential SAW sensor with respect to ammonia, sulfur dioxide and hydrogen sulfide; k _{3, NH3} , k _{3, SO2} , k _{3, H2S} - sensitivity coefficients of the 3rd differential SAW sensor with respect to ammonia, sulfur dioxide and hydrogen sulfide; C _NH3 , C _SO2 , C _H2S are the desired concentrations of ammonia, sulfur dioxide and hydrogen sulfide in the stream of the analyzed air sample. In accordance with the invention, the multisensor system is preliminarily calibrated, which consists in the following: according to claim 2), the measurement procedures are supplied to the multisensor system in mode II (Roman) sequentially artificially prepared air samples containing one of three OPZAV with concentrations located at intervals of a few mg / m ³ up to hundreds of mg / m ³ (e.g., five concentrations) for the construction of calibration curves of sensors SAW sensors and calculating coefficients chu ity of each double line Hold for each of the three OPZAV (total 9):

[k _{1, NH 3} , k _{1, SO 2} ; k _{1, H2S} , k _{2, NH3} , k _{2, SO2} , k _{2, H2S,} k _{3, NH3} , k _{3, SO2} , k _{3, H2S} ].

The following are specific examples of experimentally obtained calibration graphs of one of the SAW sensors for all three RAM, from which the sensitivity coefficients of the differential SAW sensor for all three RAM were calculated, which are the tangent values of the slope of the calibration graphs and which are necessary for the implementation of the invention (Fig. 4, 5, 6).

Brief Description of the Drawings

Figure 1. The chemical formulas of functional polymers are: copolymers of siloxanes, copolymers of alkyl methacrylates, copolymers of alkyl methacrylates with styrosulfonate.

Figure 2. Differential SAW-chemical sensor, consisting of two SAW-sensor elements in the design of the delay line (1, 2), each of which is included in the feedback circuit of RF amplifiers (3, 4); differential (differential) SAW frequency from a diode-ring mixer (5) is read by a standard frequency meter.

Figure 3. SAW sensor elements 1, 2, 3, 4, 5, 6, forming pairwise (1, 2) (3, 4) (5, 6) three differential SAW sensor sensors, the signals from which form three measuring channels. Moreover, elements 1, 3, 5 are comparative, and elements 2, 4, 6 are analytical.

Figure 4. Example 1. Calibration graph of a differential SAW sensor with a sensitive coating based on PDMS on ammonia

(k _{1, NH3} = 91.5 ± 8.5).

Figure 5. Example 2. Calibration graph of a differential SAW sensor with a sensitive coating based on PDMS on sulfur dioxide

(k _{1, SO2} = 70.0 ± 6.5).

6. Example 3. Calibration graph of a differential SAW sensor with a sensitive coating based on PDMS on hydrogen sulfide

(k _{2, H2S} = 38 ± 16).

Claims (2)

1. A method of multisensory quantitative detection of the main priority inorganic pollutants in atmospheric air: ammonia, sulfur dioxide and hydrogen sulfide, characterized in that films of functional polymers with ion-bound cations of organic dyes are used as sensitive coatings of sensors (chemical sensors) that make up the multisensor system capable of entering into a specific interaction with the molecules of the main priority pollutants: ammonia, sulfur dioxide and hydrogen sulfide orods, while in all three pairs of sensor elements, functional polymers with different chemical structures are used, the measurements are carried out in two stages: at the first stage, all six sensor elements are supplied with flows of the analyzed air that are identical in speed and chemical composition with preliminary removal from them gases: ammonia, sulfur dioxide and hydrogen sulfide (clean air), at the second stage, flows of clean air are supplied to three sensor elements, and flows of the analyzed air are fed to three other sensor elements spirit without removing the listed gases, then the analytical signals of three sensors (sensors) are extracted, which consists in pairwise subtracting the signals received at the first stage of measurements from the signals received at the second stage of measurements, then they solve a system of three equations, which include the magnitude of the difference signals, relative to three unknowns, which are the concentrations of the three main priority pollutants in the atmospheric air sample: ammonia, sulfur dioxide and hydrogen sulfide ode. 2. The device for implementing the method according to claim 1, comprising a multisensor system on a surface acoustic wave, consisting of three double delay lines forming three sensors — chemical sensors, each delay line in the double delay line is a sensor element, which is made on a separate chip quartz and is located in a separate measuring cell, while sensitive coatings in the form of films of functional polymers are applied or located on all six sensor elements in the space between the meetings but with pin-type converters of the delay line, and these sensitive coatings are pairwise identical in chemical structure and thickness and differ from each other in each of the pairs of sensor elements.

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