RU2337349C1 - Method of determining air biological contamination and device to this effect - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: method incorporates fluorimetry of focused volume of air sample with the fluorescence excited, the aforesaid air sample focused volume is formed by a virtual impactor in the air sample major flow separated from optical elements and spectral fluorimeter furnished with a minor air flow without aerosol particles. The device made up of a radiation source and spectral fluorimeter furnished with the fluorescence spectral decomposition optical element incorporates a virtual impactor to generate, at its output, a coaxial major and a minor flow, enveloping the former, the impactor major flow input representing an air sampler and the impactor minor flow input communicating with air medium via a zero-drag filter designed to clear air of aerosol particles. The virtual impactor outlet is connected to the vacuum system.

EFFECT: higher reliability and simpler air contamination estimation procedure.

4 cl, 7 dwg, 3 tbl

Description

The invention relates to analytical instrumentation and can be used in the design of instruments for determining air pollution by various fluorescent aerosol components (microorganisms, their metabolic products, toxins, etc.).

A known method of determining biological air pollution by laser sensing of the atmosphere with ultraviolet radiation and recording the background characteristics of the atmosphere, the intensity of the signals of the luminescence of the aerosol of toxic substances (OM) in the spectral region 300-440 nm and the intensity of the backscattering signals at the wavelength of the probe radiation, the ratio of which the presence or absence of interfering aerosols on the route (RU 2155954, G01N 21/64, 2000).

This method is difficult to operate and has low noise immunity.

There is also a method for determining biological air pollution, involving the selection and fractionation of a sample according to the size of aerosol particles suspended in it using a step impactor, followed by excitation of fluorescence using x-ray radiation and X-ray fluorescence analysis of the total internal reflection of the fractions (DE 3813329, G01N 15/02, G01N 1/22, G01N 15/00, 1989).

This method is dangerous and low sensitivity.

The specified group of methods includes determination of biological air pollution, which involves the selection and fractionation of a sample by the size of aerosol particles suspended in it using a suction impactor, followed by sorption of aerosol particles on a material with selective sorption activity, excitation of fluorescence of immobilized particles using ultraviolet radiation (UV). registration of the integral characteristic of fluorescence using a video camera and analysis of the fluorescence intensity taking into account shapes and size distributions of immobilized particles (JP 11337469, G06M 11/00, G01N 1/02, G01N 15/00, G01N 15/06, G01N 21/64, G01N 33/483, 1999).

When analyzing the concentration of microorganisms in the air, a sample is bubbled through a selective nutrient medium to concentrate live microbial cells, followed by a chemiluminescence reaction in a reaction chamber equipped with a quartz window coupled to a photomultiplier, which determines the chemiluminescence intensity (RU 2263896, G01N 21/62, 2005).

However, these methods are not universal, since they are based on a quantitative analysis of aerosol particles with a known morphology or chemiluminescence ability.

Closest to the claimed one is a method for determining biological air pollution, which provides for fluorimetry of the focused volume of the pumped air sample when excitation of the fluorescence of the aerosol particles contained in it is carried out using UV radiation with a frequency of 266 nm from a Q-switched laser. In this method, the laser is launched when an aerosol particle is detected in the focused sample volume by a two-beam synchronous detector, the channels of which are installed orthogonally and have different frequency characteristics (US 6947134, G01J 3/30, 2005).

However, the prototype method is difficult to configure and hardware design, and its technical implementation is uneconomical due to the extremely low efficiency of the used UV source. In addition, this method is difficult to implement when monitoring samples with a high concentration of aerosol particles due to clogging of the optical elements of the UVI source and fluorimeter, which leads to a decrease in the measurement sensitivity as the method is used, i.e. to reduce the reliability of operation.

Solved technical problem is to simplify the method and increase the reliability of its operation.

The solution to this technical problem lies in the fact that in the method for determining biological air pollution, which provides for fluorimetry of the focused volume of the pumped air sample when excitation of the fluorescence of the aerosol particles contained in it using UVI, the following change is made: the focused volume is formed using a virtual impactor in the major sample stream air separated from the optical elements of the UVI source and spectrofluorimeter by a minor air stream not containing aerosol astits.

The causal relationship of the changes made with the technical result achieved is as follows. The initial conflicting technical system contains the following conflicting pairs: 1) an air sample stream containing aerosol particles and optical elements of a UV source; 2) an air sample stream containing aerosol particles and optical elements of a spectrofluorimeter. The presence in the air sample of aerosol particles is necessary for their analysis and at the same time harmful due to their adhesion to the optical elements of the system. To resolve the conflict, the following standard was used to solve inventive problems: with a conflicting pair of substances, a third substance should be placed between them, which is usually a modification of one of them (Altshuller G.S. Creativity as an exact science. - Petrozavodsk: Scandinavia, 2004. ) In this case, the “gasket” is made of a stream of air that does not contain aerosol particles.

Figure 1 shows a diagram of a fundamental solution to a technical problem; figure 2 presents the scheme for obtaining the spectral characteristics of fluorescence using a spherical holographic lattice; figure 3 is a General diagram of a device for determining biological air pollution; figure 4 shows a diagram of a variant of the device with a diffraction element made in the form of a concave holographic grating; Figures 5-7 and Table 1-3 show the aerosol fluorescence spectra for Examples 1-3.

The principal technical solution is illustrated by the scheme of figure 1. As can be seen from the diagram, the sampled air is fed to the major input of the virtual impactor 1. Air that does not contain aerosol particles is connected to the minor input of the virtual impactor 1, which can be done, in particular, by passing atmospheric air through the aerosol filter 2. To implement this method, the virtual impactor 1 is configured to form at the major exit stream a sampled aerosol sample of air enclosed coaxially inside the minor stream of purified air exiting from the minor outlet fitting of this impactor. Thus, the stream of aerosol particles, on which the optical elements of the UV 3 source and spectrofluorimeter 4 are focused, is located in the air protective case of the air stream that does not contain aerosol particles. In the diagram of FIG. 1, the structure of a UVI source 3 and a spectrofluorimeter 4 is disclosed. UVI source 3 consists of a series-connected power supply unit 5, a UVI emitter 6 and an optical focusing element 7. As a part of the spectrofluorimeter 4, a lens 8 focused on a major air flow is highlighted, formed at the output of the virtual impactor 1, and an optoelectronic converter 9, which serves to obtain an electrical information signal about the level of fluorescence of the aerosol particles of the sample caused by UV radiation.

To implement the proposed method, a virtual impactor can be used, made on the basis of the Flora-100 impactor (TU 64-098-33-95), as well as the inventions SU 1468179, G01N 15/02, 1995; US 6698592, B07B 7/04, 2004, etc.

The known device for determining biological air pollution contains a virtual impactor equipped with a separator for separating aerosol suspension into fractions according to particle size, a filter collector for collecting fractions, analytical chambers installed at the collector outputs and connected to an infrared (IR) radiation unit and a scanning IR spectrophotometer (US 4942297, G01N 15/02, 15/06, 21/55, 1990).

Its disadvantage is the design complexity and low reliability of the analysis of aerosol particles of unknown nature, especially masked by liquid.

A device for determining biological air pollution is also known, comprising a virtual impactor configured to take and focus an air sample, connected to an optical particle counter by the light scattered by them in the visible region of the spectrum (WO 90/10858, G01N 15/14, 1990).

However, this device does not allow a qualitative analysis of aerosol pollution.

The development trend of devices for determining biological air pollution is to equip them with an impactor, to the outlet of which a sparging unit for the pumped sample in a selective nutrient medium, a sorption column and an analytical chamber equipped with a chemiluminescence or fluorescence sensor (US 6435043, G01N 15/10, 2002; RU 2263896, G01N 21/62, 2005; JP 11337469, G06M 11/00, G01N 1/02, G01N 15/00, G01N 15/06, G01N 21/64, G01N 33/483, G06M 11/00, G01N 1 / 02, 1999).

However, these devices are inconvenient in operation due to the cyclic analysis scheme they implemented, as well as the need to replace the selective nutrient medium or sorbent and flush the corresponding elements in each measurement cycle.

Closest to the claimed one is a device for determining biological air pollution, consisting of an impactor for pumping and focusing an air sample containing aerosol impurities, a UV-source laser with a modulated Q factor, aimed at a focused volume of an air sample, the control input of which is connected to the output of a two-beam synchronous detector, whose channels are installed orthogonally and have different frequency characteristics for detecting an aerosol particle in a focused the sample volume, and a spectrofluorimeter equipped with an optical element for the spectral decomposition of fluorescence of aerosol particles in a focused sample volume (US 6947134, G01J 3/30, 2005).

However, the prototype device is complex, uneconomical due to the extremely low efficiency of the used UV source, has low reliability of control of samples with a high concentration of aerosol particles due to clogging of the optical elements of the UV source and the fluorimeter. In addition, it is unacceptable for the technical implementation of the proposed method.

The technical task of the device is the ability to implement the proposed method, as well as simplifying the design of the prototype.

The solution to this problem lies in the fact that the device for implementing the method described in claim 1, consisting of an impactor for pumping and focusing an air sample containing aerosol impurities, an ultraviolet radiation source aimed at a focused volume of an air sample and a spectrofluorimeter equipped with an optical element spectral decomposition of fluorescence of aerosol particles in a focused sample volume, the following changes are made:

1) the impactor is made virtual with the possibility of forming at the output of the coaxial major and surrounding minor air flows;

2) the major input of the impactor is a sampling element of the analyzed air sample;

3) the minor input of the impactor is connected to the air through a filter of zero resistance for cleaning from aerosol particles;

4) the output line of the virtual impactor is connected to the vacuum system, which is simpler and more economical than installing compressors on its input lines.

It is advisable to perform the device in the embodiment with a correlation analyzer connected to the output of the spectrofluorimeter to compare the obtained spectral characteristics with the spectral characteristics of fluorescence of known aerosol air pollution.

It is also advisable to perform an element of spectral decomposition of fluorescence of aerosol particles in the form of a spherical (concave) lattice, the curvature of which is made from the calculation of focusing of the spectral fluorescence bands of aerosol particles of the sample along the Rowland arc. An analogue of this additional technical solution is US Pat. No. 4,254,325, G01J 3/20, 3/18, 3/12, 1981, which describes a scanning-type spectrograph-monochromator containing a UV or X-ray source connected in series with a vacuum chamber in which an optical slit for the passage of light, a threaded diffraction grating, and an optoelectronic converter. In this case, the threaded diffraction grating and the optoelectronic converter are mounted with the possibility of moving around the Rowland circle. The proposed technical solution in this part differs from this analogue in that

1) there is no vacuum chamber and an optical gap (there is no need for evacuation due to the possibility of working in the visible region of the spectrum);

2) the element of spectral decomposition of the fluorescence of aerosol particles contains a substrate, on the working surface of which a spherical (concave) diffraction grating is holographically formed with a numerical aperture in the range of 0.7-1.1, which provides a sharp increase in its aperture required under conditions of low radiation energies analyzed aerosol particles (here the lower limit of the numerical aperture value is indicated for reasons of ensuring the minimum sensitivity of the device, and the upper limit is limited by technological the possibilities of forming a holographic diffraction grating);

3) the axis of the major air flow at the output of the impactor, the diffraction grating and the photodetector are located in the Rowland circle for optical focusing of the diffraction grating and the photodetector to the major air flow at the output of the impactor.

To focus the optical elements in the proposed device, the radius of the working surface of a spherical diffraction grating should be 2 times the radius of the Rowland circle. The most appropriate implementation of the diffraction grating with a radius of 7 to 10 cm with a radius of the Rowland circle from 3.5 to 5 cm, while in the well-known technical solution involving the implementation of this element spherical, the radius of the working surface of the sphere was 5.2 m (RU 2105273, G01J 3/00, 1998), which does not provide the aperture necessary for the functioning of the device for the intended purpose. The holographic performance of the diffraction grating on a spherical surface makes it possible to increase the width of the studied fluorescence spectrum to at least 300 nm due to the number of grating strokes of 2000 lines / mm or more, while using the rifled method on a concave surface, this line density can hardly be reached. This increases the information content and accuracy of analyzes in the range of the visible region of the spectrum.

The spherical diffraction grating for the proposed device variant can be made according to the invention RU 1588084, G01J 3/18, 1999 using inorganic photoresist based on chalcogenide glass as a photosensitive material.

The principle of operation of such an element is illustrated in figure 2. The center of the major flow of the air sample, a holographically made spherical diffraction grating 10, formed on the substrate of the fluorescence spectral decomposition element 11 of the aerosol particles of the sample and the photodetector 12 of the optoelectronic transducer 9 are located in the Rowland circle, which provides optical focusing of the diffraction grating 10 and the photodetector 12 of the optoelectronic Converter 9 to a major air flow at the output of the impactor. As the photodetector 12, you can use the photomultiplier tube or the sensor of the camera. Rays of autofluorescence or fluorescence excited by UVI are reflected from the diffraction grating 10 at different angles, incident on the photodetector 12 in the spectrum range from λ ₁ to λ _n , from which the information on the fluorescence intensity spectrum is taken from the multi-channel output. The angles α, β, and γ indicated in the diagram characterize, respectively, the location of the fluorescence focus (major flow), the initial and final positions of the line of the photodetector 12 in a Roland circle relative to the symmetry plane of the diffraction grating 10. The values of these installation angles are determined from the calculation of the maximum possible use of the aperture photodetector 12. Thus, for a Roland circle with a radius of 3.5 cm and a length of the line of photodetector 12 equal to 5 cm, the values of the indicated angles are: α = 16 °, β = 23 °, and γ = 47 °, which ensures decomposition of the fluorescence spectrum estsentsii a band width of λ ₁ = 300 and λ ₂ = 650 nm.

In this embodiment, the focusing of the spectral bands and obtaining the fluorescence spectrum is carried out using one structural element, which leads to a simplification of the spectrofluorimeter assembly.

A variant of the device according to claim 2 of the formula (FIG. 3) comprises a virtual impactor 1 (see FIG. 1) for pumping and focusing a sample of air containing aerosol impurities, a UV radiation source 3 directed to the focused volume of the air sample, and a spectrofluorimeter 4 equipped with sequentially connected by an optical element 11 of the spectral decomposition of fluorescence of aerosol particles in a focused sample volume, a photodetector 12 and an optoelectronic converter 9, the output of which is connected to the information processing and visualization unit 13, computer-based. The virtual impactor 1 is configured to form at the output of the coaxial major and minor air flows surrounding it (pos. 14 and 15, respectively). The major inlet of the impactor 1 is a tubular intake element 16 of the analyzed air sample. The minor input of the impactor 1 is made coaxially outside the major in the form of a cylindrical filter 17 (filter option 2 of FIG. 1) of zero resistance, which is connected to the air and serves to clean the minor stream from aerosol particles. Between the filter 17 and the tubular element 16, a tubular diaphragm 18 is located coaxially with openings 19 made in its walls for the passage of filtered air from the outlet of the filter 17 into the diffuser chamber formed between the elements 16 and 18 to form a minor stream 15. The diameter of the holes 19 is a tuning parameter, set based on ensuring the required ratio of major and minor air flows at the output of impactor 1. The hollow end of the diaphragm 19 is hermetically connected to the quartz tube 20, the free end which is connected to the vacuum pump 21 through a filter 22, which serves to protect the vacuum pump 21 and the environment from the emission of aerosol particles. The implementation of the tube 20 of quartz allows you to place outside the source 3 of the UVI and spectrofluorimeter 4, the optical inputs of which are focused on the major flow 14. In the embodiment of figure 3, the source 3 of the UVI includes serially connected power supply 5, a semiconductor emitter 6 UVI and an optical focusing element 7 made in the form of a lens. The ends of the cylindrical filter 17 are closed by covers 23, pressed using sealing gaskets 24. The covers 23 and the filter 17 form a housing for accommodating the main structural elements of the impactor 1. At the same time, the holes 23 are made for the tight installation of the elements 16, 18 and 20.

In the technical implementation of the device, hepofilters, for example, types FS-1C and FS-1K, can be used as filters 17 and 22.

The vacuum pump 21 draws in atmospheric air through a tubular intake element 16 (major inlet) and through a filter 17 of zero resistance (minor inlet). The major flow at the outlet of element 16 forms the core of the jet, pressurized externally by a minor stream of air containing no aerosols, which, after cleaning on the filter 17, enters through the aperture 19 of the diaphragm 18 into the minor exit of impactor 1. When passing through the quartz tube 20, the focus of the major flow is determined fluorescence of aerosol particles as described above and explained in FIG.

In the embodiment of FIG. 4, the device further comprises a centrifugal filter 25 for coarse air cleaning of large aerosol particles (cyclone) installed at the sampling site. The output pipe of the filter 25 is connected to the major input 16 of the impactor 1. The element 11 of the spectral decomposition of the fluorescence of aerosol particles contains a substrate on the working surface of which a diffraction spherical grating 10 with a numerical aperture in the range of 0.7-1.1 is holographically formed. The axis of the major air flow at the output of the impactor 1, the diffraction grating 10 and the photodetector 12 are located in a Rowland circle for optical focusing of the diffraction grating 10 and the photodetector 12 to the major air flow at the output of the impactor 1.

This embodiment of the device further comprises a correlation analyzer 26 connected to the output of the spectrofluorimeter, for comparing the obtained spectral characteristics with the spectral characteristics of fluorescence of known aerosol pollution of the air. As a correlation analyzer 26, any correlation analyzer can be used to calculate the correlation ratio of the analyzed and basic functions of fluorescence intensity versus wavelength in a specified range of the fluorescence spectrum. It can be performed on the basis of a computer. It is also possible to perform a correlation analyzer according to (RU 2171499, G06T 5/00, 5/40, G06K 9/00, 9/62, 9/68, 9/70, 2001).

The operation of this embodiment of the device is described above and is explained in Fig.2.

The proposed technical solutions are illustrated by the following examples.

EXAMPLE 1. Samples of air contaminated with various aerosols are analyzed using the device of figure 4 with the following values of the design parameters: the value of the numerical aperture is 1.1; the radius of the Rowland circle is 3.5 cm; the radius of the holographic diffraction grating is 7.0 cm; UVI LED emitter wavelength - 395 nm; UV emitter power - 10 mW; the width of the spectrum of the received fluorescence is 400-700 nm; the total flow rate of air pumped through the impactor is 5.5 l / min with a ratio of major and minor flows of 1: 1; analysis duration - 10 s (from this time, from 90,000 to 1 million fluorescence spectra are examined).

An aerosol containing ^10-3 mol / L riboflavin is used as a reference sample. Test samples of polluted air contain aerosols of ovalbumin (10 ^-5 mol / L), fluorescein (10 ^-3 mol / L) and rhodamine (10 ^-3 mol / L).

The average values of the measurement results are given in table 1 and are presented in the graphs of figure 5. As can be seen from the table and graphs, the spectral characteristics of each of the samples have extremes at the following frequencies: riboflavin - 570 nm; ovalbumin - 450 nm; fluorescein - 530 nm and rhodamine - 650 nm. Using the correlation analyzer 26, the following values of the correlation relations of the corresponding functions were established in comparison with the spectral function of riboflavin fluorescence: ovalbumin - 0.52; fluorescein 0.79; rhodamine - 0.09.

EXAMPLE 2. Samples of air contaminated with riboflavin mixed with rhodamine in various concentrations are analyzed as in example 1.

Test samples of polluted air contain aerosols of riboflavin (10 ^-5 mol / l) with the addition of ovalbumin in volume fractions of 1: 1 (sample No. 1) and 1: 2 (sample No. 2).

The results are shown in table 2 and in the graphs of Fig.6. As can be seen from the table and graphs, the spectral characteristics of each of the samples have extremes at the following frequencies: riboflavin - 570 nm; sample No. 1 - 580 nm; and sample No. 2 - 590 nm with the following maximum relative values of the fluorescence intensity I - 300, 260 and 225 rel. units The values of the correlation relations in comparison with the spectral function of the fluorescence of riboflavin: sample No. 1 - 0.93; sample No. 2 - 0.97. High correlation ratios here indicate the possibility of identifying the desired component (riboflavin) in a mixture of aerosols.

EXAMPLE 3. Samples of air contaminated with riboflavin are analyzed as in example 1 at various values of the numerical aperture of the diffraction grating in the range from 0.6 to 1.1.

The results are shown in table 3 and in the graphs of Fig. 8. As can be seen from the table and graphs, as the value of the numerical aperture decreases under the influence of noise, the spectral characteristics are smoothed, and therefore reliable recognition of the fluorescence spectra is ensured when the numerical aperture is from 0.7 or higher. In particular, when the value of the numerical aperture is 0.6, the values of the output signal of the received fluorescence are reduced by 2-4 times compared with the version of the device having the value of the numerical aperture of 1.1, which results in a distortion of the results of the analysis of the correlation relations of the fluorescence spectra of the analyzed sample with a reference sample at low numerical apertures.

Thus, the use of the proposed method can improve its reliability by preventing the sticking of aerosol particles on the optical elements of the device that implements this method, as well as simplify and miniaturize the hardware design of the method.

Table 1
Spectral characteristics of fluorescence of aerosol particles in the reference and analyzed samples for example 1 (in relative units) λ, nm Standard (riboflavin) Sample No. 1 (rhodamine) Sample No. 2 (ovalbumin) Sample No. 3 (fluorescein) 400 thirty 10 one hundred fifty 440 fifty twenty 300 fifty 480 60 70 200 one hundred 520 180 one hundred one hundred 320 560 300 150 fifty 250 600 250 200 fifty 130 640 80 300 fifty fifty 680 fifty 150 fifty fifty K = 0.09 K = 0.52 K = 0.79

table 2
Spectral characteristics of fluorescence of aerosol particles in the reference and analyzed samples for example 2 (in relative units) λ, nm Standard (riboflavin) Sample No. 1 (riboflavin / ovalbumin, 1: 1 volume, fraction) Sample No. 2 (riboflavin / ovalbumin, 1: 2 volume, fraction) 400 thirty 55 fifty 440 fifty fifty 55 480 60 62 65 520 180 160 140 560 300 263 225 600 250 230 225 640 80 120 150 680 fifty 60 90 K = 0.93 K = 0.87

Table 3
Spectral fluorescence characteristics of riboflavin aerosol particles (in relative units) at various values of the numerical aperture of the diffraction grating λ, nm Numerical aperture 0.6 0.7 0.9 1,1 400 80 70 60 thirty 440 90 70 60 40 480 110 90 80 75 520 170 180 160 180 560 170 210 270 300 600 160 180 220 250 640 120 one hundred one hundred 80 680 one hundred one hundred 70 45

Claims (4)

1. The method of determining biological air pollution, providing for fluorimetry of the focused volume of the pumped air sample when excitation of the fluorescence of aerosol particles contained in the sample using ultraviolet radiation, characterized in that the focused volume is formed using a virtual impactor in the major stream of the air sample, separated from the optical elements of a source of ultraviolet radiation, and a spectrofluorimeter with a minor stream of air that does not contain aerosol particles. 2. A device for implementing the method described in claim 1, consisting of an impactor for pumping and focusing an air sample containing aerosol impurities, an ultraviolet radiation source directed to a focused volume of an air sample, and a spectrofluorimeter equipped with an optical element for the spectral decomposition of fluorescence of aerosol particles into focused sample volume and photodetector, characterized in that the impactor is made virtual with the possibility of forming coaxial major output of minor air flows that enclose it, while the major input of the impactor is an intake element of the analyzed air sample, the minor input of the impactor is connected to the air through a zero-resistance filter for cleaning from aerosol particles, and the output line of the virtual impactor is connected to the vacuum system. 3. The device according to claim 2, characterized in that the spectral decomposition element of the fluorescence of aerosol particles contains a substrate, on the working surface of which a spherical diffraction grating is holographically formed with a numerical aperture in the range of 0.7-1.1, with the axis of the major air flow the output of the impactor, the diffraction grating and the photodetector are located in a Rowland circle for optical focusing of the diffraction grating and the photodetector to the major air flow at the output of the impactor. 4. The device according to claim 2 or 3, characterized in that it is additionally equipped with a correlation analyzer connected to the output of the spectrofluorimeter to compare the obtained spectral characteristics with the spectral fluorescence characteristics of known aerosol air pollution.

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