RU2555507C1 - Analyser of composition of expired air - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: invention relates to analysis instrument building, and in particular to equipment allowing to diagnose certain types of human diseases by analysis of composition of the expired air. An analyser of composition of the expired air includes a continuous laser with wave length of 532 nm, a tight cell provided with two laser radiation inlet/outlet openings and with one scattered light outlet opening from its centre, a lens, a holographic filter, a high-aperture polychromator providing simultaneous recording of a spectrum in the range of 532-690 nm, as well as a control unit and a personal computer. Additionally, the cell is provided with a heating element connected to the control unit. Besides, a gas inlet of the cell is connected to an in-series located replaceable neck, a valve, an intermediate elastic chamber and an electric valve, and its gas outlet is connected to a small-size pump.

EFFECT: improving accurate determination of component composition of the expired air.

2 cl, 1 dwg

Description

The invention relates to the field of analytical instrumentation, in particular to equipment that allows you to diagnose certain types of human diseases by analyzing the composition of the exhaled air.

Currently, the method of non-invasive diagnosis of human diseases is being rapidly developed by analyzing the component composition of the exhaled air. It is known that exhaled air (BB) contains, in addition to the main atmospheric components (nitrogen, oxygen, carbon dioxide, water vapor), more than 100 other types of molecules with different concentrations. These fairly light gaseous compounds, which are formed in extremely small quantities in the body, are present in explosives in the form of traces (concentration of about 10 ^-6 %) and are signs or so-called markers of ongoing biochemical processes. Currently, a rather large amount of data is presented in the literature, indicating the possibility of using these gaseous markers in biomedical diagnostics. In this regard, to carry out such diagnostics, a universal device is required that can detect a large amount of gases with high accuracy.

A device for diagnosing human diseases by exhaled air [Device for diagnosing human diseases by exhaled air, patent for utility model RU 51849, 03/10/2006, A61B 5/00], consisting of N gas sensors. The main disadvantage of this device is a narrow set of detectable gas components, due to the fact that each sensor is designed to detect only one type of molecule. In this regard, the appearance of a component in exhaled air, for which there is no appropriate sensor, will be ignored.

The closest in principle to the patented device is a laser analyzer based on the method of Raman spectroscopy (Raman) of light [Natural gas composition analyzer, RU 126136, 03.20.2013, G01N 21/00]. This analyzer contains a cw laser with a wavelength of 532 nm, a focusing lens, a cuvette, a lens, a holographic filter, a fast polychromator that provides simultaneous registration of the spectrum in the range of 532-690 nm, as well as a control unit and a PC. The essence of his work is to register the Raman spectrum of the analyzed gas medium and determine its qualitative and quantitative composition from it. The main advantage of this analyzer is the ability to control all types of molecular components of the gaseous medium using a single laser with a fixed wavelength. At the same time, the main drawback of this approach (the use of Raman spectroscopy), in general, is the low intensity of the recorded Raman spectra. In this device, this drawback is solved by its focus on the analysis of natural gas, since natural gas enters the test laboratories under a pressure of 30-100 atm. Thus, due to the compression of the gaseous medium (since the intensity of the Raman signal linearly depends on the number of molecules per unit volume), a high level of intensity of useful scattered signals is ensured, which in turn provides the required accuracy of gas analysis. However, it is worth noting that this does not prevent this device from analyzing other gaseous media that are not at high pressure (for example, exhaled air), although with less accuracy.

The main disadvantage of this analyzer is the low accuracy of determining the component composition of explosives, due to the following factors:

- low intensity of the recorded Raman spectra of explosives, since the analyzed explosives are at a pressure close to atmospheric, and therefore, the concentration of molecules per unit volume is small;

- the impossibility of ensuring the correct replacement of the analyzed gas medium, as a result of which the remains of the previous gas in the cuvette will affect the reliability of the gas analysis;

- the precipitation of water vapor on the windows of the cuvette (due to the temperature difference between the explosive and the cuvette), which will slow down the alignment and, therefore, minimize the recorded signal.

The tasks to which the invention is directed are: increasing the intensity of the recorded Raman spectra of explosives, ensuring the correct replacement of the analyzed gas environment, and also providing conditions that impede the condensation process on the walls and windows of the cell.

EFFECT: increased accuracy of determining the component composition of exhaled air.

This result is achieved by the fact that in a system containing a continuous laser with a wavelength of 532 nm, an airtight cell equipped with two windows for input / output of laser radiation and one window for outputting scattered light from its center, a lens, a holographic filter, a high-speed polychromator, providing simultaneous registration of the spectrum in the range 532-690 nm, the control unit and the PC cuvette are additionally equipped with a heating element connected to the control unit, the gas inlet of the cuvette being paired with ovatelno replaceable mouthpiece valve, elastic intermediate chamber and a solenoid, and its gas outlet coupled to the small-sized pump.

In addition, the cuvette is additionally equipped with two spherical mirrors having a common center of curvature and located on the same optical axis in such a way that multiple passage of the laser beam is ensured through it. An additionally installed pair of spherical mirrors to ensure multi-pass of the laser beam through the cuvette provides an increase in the intensity of laser radiation inside the cuvette, thereby increasing the intensity of the recorded Raman spectra.

The system, consisting of a replaceable mouthpiece, a crane, an intermediate elastic chamber and an electrovalve for inlet of an explosive sample into a cuvette and a small-sized pump for its cleaning from extraneous gases, ensures the correct replacement of explosive samples in a cuvette.

It should be noted that in the known device and a number of others, the presence of water vapor in the analyzed explosive not only causes problems of their condensation, but also hinders the registration of other gas components, for example, in devices where absorption spectroscopy is used. To eliminate this, the explosive sample is drained, for example, by cooling the tubes supplying gas to a cuvette or other measuring devices with subsequent collection of water. Of course, this approach allows us to solve the problems, but in this case there is a change in the percentage of gas components that make up the explosive even before its analysis.

In turn, in the patented device, the drainage of the explosive sample is not necessary, since in the recorded spectrum of Raman scattering bands and scattering water vapor will not overlap the strips of other components and their concentration will also be determined along with other gas components. However, the condensation of water vapor on the windows of the cell due to a change in the refractive index of the light will lead to a weakening of the recorded Raman signal. In this regard, a heating element is additionally installed in the patented device, which provides a temperature of the cell walls close to 40 ° C, as a result of this, since the temperature of the explosive will not exceed this value, the condensation process entailing negative consequences will be eliminated.

Figure 1 shows a block diagram of the proposed system.

The analyzer contains a removable mouthpiece 1, a crane 2, an elastic chamber 3, an electrovalve 4, a cuvette 5, a heating element 6, a small-sized pump 7, a solid-state laser 8 with a wavelength of 532 nm, operating in continuous mode, spherical mirrors 9.10, a collection lens scattered radiation 11, holographic filter 12, polychromator 13, CCD matrix 14, control unit 15 and PC 16.

The proposed analyzer exhaled air works as follows.

When the device is turned on, the heating element 6 provides a temperature of the walls of the cell close to 40 ° C. When the valve 4 is closed, the small-sized pump 7 removes the remains of the gaseous medium from the cell 5 and creates a reduced pressure there. Then, through the interchangeable mouthpiece 1 with the open valve 2, the patient lets in exhaled air into the elastic chamber 3 increasing in volume, after which the valve 2 closes, fixing the incoming gas medium inside. After that, at the signal of the control unit 15, the electrovalve 4 opens and due to the pressure difference in the chamber 3 and the cell 5, the cell is filled with the gaseous medium to be analyzed. Next, the Raman spectrum recorded in the cell of the explosive sample is recorded. The exciting radiation from the laser 8 using mirrors 9 and 10 repeatedly passes inside the gas cell 5, where it is scattered on the molecules of the gas present. The scattered radiation is collected by the lens 11 and sent to the input of the fast polychromator 13, while passing through a holographic filter 12, whose role is to weaken the intensity of elastic light scattering at the frequency of the exciting radiation (the so-called Rayleigh scattering). Polychromator 13 decomposes the light that has got into it into a spectrum, which is then recorded by the CCD by matrix 14. The latter transmits electrical signals to the control unit 15, from where they are sent to PC 16 for mathematical processing, calculation of component concentrations and visualization of the results.

As an elastic chamber, a sealed reservoir can be used, operating on the principle of a balloon, which easily increases in volume when the gas medium (air) enters inside it with a pressure slightly higher than atmospheric and returns to its original volume (decreases) when the gas medium (air) is released .

Claims (2)

1. An analyzer of the composition of exhaled air, containing a continuous laser with a wavelength of 532 nm, a sealed cuvette, equipped with two windows for input / output of laser radiation and one window for outputting scattered light from its center, a lens, a holographic filter, high-speed polychromator, providing simultaneous registration spectrum in the range 532-690 nm, a control unit and a PC, characterized in that the cuvette is additionally equipped with a heating element connected to the control unit, and the gas inlet of the cuvette is paired with sequentially with a replaceable mouthpiece, a crane, an intermediate elastic chamber and an electrovalve, and its gas outlet is interfaced with a small-sized pump. 2. The analyzer according to claim 1, characterized in that the cuvette is equipped with two spherical mirrors having a common center of curvature and located on the same optical axis so that multiple passage of the laser beam is ensured through it.