Method for determination of quantitative content of components in mixture

FIELD: physics, measurement.

SUBSTANCE: invention is related to methods for investigation of quantitative-qualitative composition of different mixtures. In method investigated mixture is excited by laser radiation, afterwards spectrum of its Raman scattering is registered. When quantitative content of components is determined, basic value Ij of Raman scattering strip intensity is selected, which corresponds to j component of mixture, where j=1…N, and N is total number of mixture components, afterwards ratio of Raman scattering strips intensities is defined for every investigated component of mixture and specified basic value Ik/Ij, where k=1…N, k≠j. Afterwards ratio of every component concentration is calculated to concentration of basic j component, and then partial concentration pl is calculated for every component.

EFFECT: provision of partial concentrations of mixture components with specified extent of accuracy and possibility to control mixture samples directly in reservoirs installed at arbitrary distance from metering equipment both in zone of sight line and outside, using simple equipment.

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The invention relates to methods of research quantitative and qualitative composition of the different mixtures, in particular alcohol, and can be used, for example, in the food industry, in particular, for quality control of alcoholic beverages and ethyl alcohol as raw materials for their manufacture.

The prior art method of measuring the concentration of alcohol in the solution by registering and measuring the absorption of the test solution radiation at specific wavelengths (see EN 2207564, IPC G01N 33/14, publ. 27.06.2003). The main disadvantages of this method are high sensitivity to the presence in the solution of sugar, as well as limiting the accuracy of determination of alcohol sensitivity recording equipment, namely the ratio signal/noise.

There is also known a method of determining the concentration of components in the mixture, is selected as the closest analogue in which excite the test solution by laser radiation is known and a certain power at a given wavelength (mainly in the infrared range), and then determine the concentration of each component of the line intensity of Raman scattering (CU) of this component (see US 5481113, IPC G01N 21/47, publ. 02.01.1996). The main disadvantages of this method are the need-ware is a high stability power excitation radiation, the limitation on the range of used wavelengths, and the need for mandatory pre-calibration measurements to construct curves of the intensity of the bands of CU concentration of this component, and in the same geometry of the excitation and reception, in which measurements are carried out for the studied (controlled) solution.

The technical result of the present invention is the composition of the mixture by measuring the partial concentrations of its components with the provision of these measurements directly in the containers without opening them, and sampling) with selectable wavelength excitation without strict limitations on the power of the exciting laser radiation at the location of the tanks at any distance from the measuring apparatus as in line-of-sight and beyond, with the final results in real time, the determination of the partial concentrations of the components with a given accuracy without conducting prior calibration measurements, and the measurement of the partial concentrations of the components, for example, in water-alcohol solutions - concentration of ethyl alcohol in the finished wine-vodka products, i.e. fortress, impurities other alcohols (methanol and others) in finished goods and raw materials, residual the odes in ethanol as raw material for wine and vodka.

This goal is achieved by the method of quantification of components in a mixture, in which excite the analyzed mixture by laser radiation, register its range of Raman scattering, and then establish the quantitative content of the components in a mixture based on the intensities of the bands of Raman scattering of these components, according to the invention when determining the quantitative content of components choose the basic value of Ijthe intensity of the Raman bands corresponding to the j-th component of the mixture, where j=1...N, and N is the total number of mixture components, and then determine the ratio of the intensities of the bands of Raman scattering of each of the investigated components of the mixture to the specified base value of Ik/Ijwhere K=1...N, k≠j, calculate the ratio of the concentration C* of each component to the concentration of the specified base of the j-th component of Cj

where σkj- the ratio of the cross sections of the bands of Raman scattering of the k-th and j-th components; µlj- the ratio of the molecular masses of these components, and then calculate the partial concentration of the pneach component of the expression

where n=1...N.

As a baseline intensity values can vybiral is registered by the intensity of Raman bands of the dominant component, in particular, the intensity of the Raman bands of water or ethanol.

The main difference of the proposed method known from the prior art counterparts is the fact that to determine the quantitative composition of the mixture components set the partial concentration of each component based on the ratio of the intensity of the Raman bands corresponding component to the base (reference) intensity. Due to the fact that analyses are not themselves intensity, and their relationship, in the claimed invention essentially removed known from the prior art severe restrictions on the power and wavelength of the exciting laser radiation, which significantly improves the manufacturability of the way and expands the scope of its application. In addition, due to the linear dependence of the intensity of the bands of Raman scattering substances from the power of the exciting radiation in the proposed method also provides the possibility of varying the accuracy of the quantification of components depending on the specific tasks by adjusting (increasing or decreasing) the power of the exciting laser radiation. Moreover, close to the area of the indicatrix CU allows you to register secondary radiation (CR) at any angle to the direction of propagation in bujdoso laser beam, in particular at an angle of 180°, i.e. in the backward direction. All this in turn allows the use of the claimed method for the rapid assessment of the qualitative and quantitative composition of the mixture (in particular, raw materials for the manufacture of spirits, or the spirits), even inside closed containers (in particular, for alcoholic beverages in sealed containers), allowing determination of the composition with a sufficient degree of accuracy using simple equipment.

The invention is illustrated hereinafter in more detail on specific, non-limiting amount of the claims of example with reference to the drawing, which shows a diagram of the installation for carrying out the proposed method.

The device for implementing the method includes a laser light source 1, which can be used, for example, a diode laser with wavelength, allowing the penetration of the excitation radiation through the walls of the standard vessel (glass or plastic)containing the analyzed mixture (solution), in particular with a wavelength selectable preferably, but not necessarily, in the range 400...550 nm.

Further shown in the drawing, the device for implementing the method may include the delivery excitation radiation to the sample 2 (for example, the rotary C is rcal m 1and m2to redirect emanating from the source 1 of radiation transmitting fiber optic cable 2A - if the contact sensing), the tool receiving secondary radiation 3 (for example, lens 3A, the focusing of the secondary radiation on the entrance slit of polychromator 3b lens or telescope in the case of non-contact remote sensing or transmitting fiber optic cable 2B - in case of contact sensing)associated with the tool 3 admission spectrum analyzer 4 (for example, a polychromator with a CCD line or multiple photodiodes configured to specific wavelengths corresponding to the wavelengths of CU measured components of the fluid), opto-electronic Converter (for example, CCD line or photodiode configured to specific wavelengths) 5 and the computing device 6 (PC).

To implement the method shown in the drawing device source 1 excitation radiation and the receiver (the analyzer 4, the inverter 5 and the computing device 6) is connected to the power supply. Radiation through the tool 2 delivery falls into the container (7a - when non-contact sensing or 7b - contact sensing), which excites the secondary radiation (radiation CU) from the components of the mixture (solution). Further secondary radiation through the tool receiving 3 (the lens 3A and the slit 3b and the and through fiber optic cable 2B) falls on a spectrum analyzer 4.

In the context of the inventive method, the following special cases of the implementation of the research mix:

(a) a non-contact remote sensing volume, which is located in line of sight; in this case, the laser beam is directed into the container with the sample 7a (and the need for turning the mirrors m1and m2in this case, actually disappears), and radiation CU reception optics (in particular, the lens 3A) is collected and focused onto the input slit 3b spectrum analyzer 4 (polychromator).

(b) contact remote sensing; in this case, the source 1 and the spectrum analyzer 4 (polychromator) attaches a Y-shaped fiber optic transceiver cable 2A-2B, consisting of a Central transmitting fiber and 6-8 receiving optical fibers surrounding it. Alternatively can be used two cable transmitting and receiving, which in General is less convenient, but in some special applications it may be appropriate. In General cases, the cable (or cables) are summed with their ends close to the container 7b-controlled fluid. The object may be outside the visible area of the device, as the cable allows bending in all planes.

Further optoelectronic Converter 5 converts the registered signal light into an electrical proportional to the light intensity, and transmits the data to the computing device 6, which is the determination of the partial concentrations of the components of the mixture.

It should be borne in mind that in the General case of an arbitrary ratio of the concentrations will be determined by dividing the intensity at each other and calculating the ratio according to the formula:

where- measured the intensity ratio of the bands KR 1-th and 2-th component of the mixture;

β - coefficient of correlation between this ratio and the ratio of concentrations With1/S2;

σ21- the ratio of the cross sections of CU strips Raman scattering of the 1st and 2nd components;

µ12- the ratio of the molecular masses of the first and second components;

α - instrumental factor that depends on the difference of the transmittance of the walls of the vessel containing the solution at wavelengths of CU components.

Possible errors associated with the variance of the rate of transmission in the vessel walls in most cases, can be neglected, since, as shown by experimental studies of the dispersion curves of the typical types of packaging, the choice of wavelength excitation always possible to provide the contact strips of the KYRGYZ Republic in the area in which differences of indicators transmittance can be neglected.

In addition, when using the inventive method for the study of alcohol-containing solutions should be borne in mind, that strip CU water and alcohols are close, so in most cases the variance of the rate of transmission is not affected. In some cases (in particular, if you want to study with a very high degree of accuracy) for the information of faults can be provided to the computing device 6, implementing the recovery algorithm of the partial concentrations of the components of the solution according to the intensities of the bands of CU, a special database containing a set of dispersion curves of the rate of transmission for typical classes of vessels (such information may be obtained from reference books).

The values of the parameters σ1and σ2, µ1and µ2can be obtained from the literature (see, for example, N.P. Romanov, Shuklin B.C.-section of the Raman scattering of liquid water. Optics and spectroscopy, 1975), which allows to calculate the coupling coefficient β. In the extreme case, if you get the data from the reference literature is not possible, the coupling coefficient β between the measured valuedetermined by the value of1/S2can be determined in a calibration measurement for each pair of components.

Thus, the relative intensities of the bands of Raman scattering of two mixture components and taking into account said the th above in relation to material dispersion index transmittance α by the formula (1) may be recovered against concentrations for each pair of components. In order to continue to receive the values of the partial concentrations for each of the components of the mixture (solution), you must select a base (reference) the intensity of the band KR, which will be calculated relative intensities of the bands of CU for each of the remaining components of the mixture and, accordingly, the relative concentrations of other components. As such the reference intensity may in different cases to get the intensity of the band KR dominant component, in particular the intensity of the band CU water (when determining the concentration of components in aqueous solutions, including alcohol), or the intensity of the band KR ethanol (for example, when studying the quality of the material for the production of alcoholic beverages), etc.

After selecting the reference intensity and determine the relative concentrations of each component (relative to the concentration of the j-th basic reference component) to calculate the partial concentration of the pneach of the components in the mixture (solution) you can use the expression

where n=1...N, N is the total number of mixture components.

Thus it is possible to provide a quantitative determination of the content of the components of the mixture (solution) with a given degree of accuracy. In this case the claimed method can be successfully used by the AK to control fixed (separate) samples (preferred contact method), and for sequential control of multiple samples, for example, sealed in a container samples moving through the pipeline.

In conclusion, it should again be noted that the above embodiment, of the invention are presented only for a better understanding of its nature and cannot be considered as limiting the volume of claims is fully defined only by the attached claims.

1. The method of quantification of components in a mixture, in which sequentially excite the analyzed mixture of laser radiation with the subsequent establishment of the quantitative content of at least one component based on the intensity of his band Raman scattering, characterized in that after excitation of a mixture of laser radiation record the Raman spectrum of its components, and when determining the quantitative content of components choose the basic value of Ijthe intensity of the Raman bands corresponding to the j-th component of the mixture, where j=1...N, and N is the total number of mixture components, and then determine the ratio of the intensities of the bands of Raman scattering of each of the investigated components of the mixture to the specified base value of Ik/Ijwhere k=1...N, k≠j, calculate the ratio of the concentration Withk j
,
where σkj- the ratio of the cross sections of the bands of Raman scattering of the k-th and j-th components; µkj- the ratio of the molecular masses of these components, and then calculate the partial concentration of the pneach component of the expression
where n=1...N.

2. The method according to claim 1, characterized in that as the baseline intensity values chosen by the registered value of the intensity of the bands of Raman scattering is the dominant component.

3. The method according to claim 1 or 2, characterized in that in the presence of the studied mixture of water as a basic intensity values choose the intensity of the corresponding Raman bands.

4. The method according to claim 1 or 2, characterized in that in the presence of the studied mixture of ethanol as the base intensity values choose the intensity of the Raman bands.



 

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