CN116223414A - Method for estimating ultraviolet-visible absorption spectrum by utilizing three-dimensional fluorescence spectrum Rayleigh scattering signal - Google Patents
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- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 6
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Abstract
The invention provides a method for estimating ultraviolet-visible absorption spectrum by utilizing a three-dimensional fluorescence spectrum Rayleigh scattering signal, which comprises the steps of respectively collecting three-dimensional fluorescence spectrums of a blank control sample and a sample to be detected, intercepting and obtaining Rayleigh scattering spectrums of the blank control sample and the sample to be detected, and estimating the ultraviolet-visible absorption spectrum of the sample to be detected by utilizing the collected scattering spectrums. The method effectively utilizes Rayleigh scattering information in the commonly ignored three-dimensional fluorescence spectrum, and the estimated ultraviolet-visible absorption spectrum can be used for internal filtering effect correction or other spectroscopy analysis of the three-dimensional fluorescence spectrum, thereby providing an effective way for simplifying the structure and reducing the cost of the three-dimensional fluorescence spectrometer.
Description
Technical Field
The invention belongs to the field of analytical chemistry, and particularly relates to a method for estimating an ultraviolet-visible absorption spectrum by utilizing a three-dimensional fluorescence spectrum Rayleigh scattering signal.
Background
Three-dimensional fluorescence spectrum characterization techniques are used in large numbers for the analysis of various complex fluorescent solubilities with their accuracy, sensitivity, information richness and good reproducibility. However, prior to its actual exit from the laboratory, the technique of three-dimensional fluorescence spectrum acquisition still has many obstacles to be overcome. Among the most troublesome of these is the additional ultraviolet-visible absorption spectrum measurement, which can be used for the internal filtering effect correction of three-dimensional fluorescence spectra. Thus, the simultaneous use of an ultraviolet-visible spectrophotometer or the construction of dual light sources or dual detectors in a three-dimensional fluorescence spectrometer has so far become a prerequisite for obtaining accurate three-dimensional fluorescence spectra.
In the above-mentioned cases, the additional acquisition of the uv-vis absorption spectrum in the three-dimensional fluorescence spectrum measurement using the conventional method makes the optical path design in the spectrometer more complicated, the user cannot purchase more portable devices at lower cost, and the practical application of the three-dimensional fluorescence spectrum characterization technology in industry and environment is forced to be in a tie. Therefore, a method for extracting the ultraviolet-visible absorption spectrum from the three-dimensional fluorescence spectrum data is urgently needed to be established, and the three-dimensional fluorescence spectrum data can be acquired once and then can be self-corrected by an algorithm to obtain an accurate map.
Disclosure of Invention
Based on the problems existing in the prior art, the invention provides a method for estimating an ultraviolet-visible absorption spectrum by utilizing a three-dimensional fluorescence spectrum Rayleigh scattering signal, so that Rayleigh scattering information in a commonly ignored three-dimensional fluorescence spectrum is effectively utilized, and the estimated ultraviolet-visible absorption spectrum can be used for internal filtering effect correction or other spectroscopy analysis of the three-dimensional fluorescence spectrum, thereby providing an effective way for simplifying the structure and reducing the cost of a three-dimensional fluorescence spectrometer.
The invention adopts the following technical scheme for realizing the purpose:
a method for estimating an ultraviolet-visible absorption spectrum by using a three-dimensional fluorescence spectrum rayleigh scattering signal, which is characterized by comprising the following steps:
1) Preparing a sample solution to be detected and a blank control solution with the same scattering property as the sample solution to be detected;
2) Respectively collecting three-dimensional fluorescence spectrums of a sample solution to be detected and a blank control solution in the ultraviolet-visible wavelength range, and respectively extracting Rayleigh scattering spectrums of the sample solution to be detected and the blank control solution;
3) According to Rayleigh scattering spectra of a sample solution to be detected and a blank control solution, calculating an absorption value of the sample to be detected at each wavelength according to a formula (1), and obtaining an original ultraviolet-visible absorption spectrum of the sample to be detected:
wherein: lambda is the wavelength, A (lambda) is the absorption value of the sample to be measured at the wavelength lambda, S blank (lambda) represents Rayleigh scattering value of the blank solution at wavelength lambda, S sample (lambda) represents the Rayleigh scattering value of the sample solution to be measured at the wavelength lambda;
4) And carrying out smoothing treatment and/or baseline correction on the original ultraviolet-visible absorption spectrum obtained by calculation to obtain a final ultraviolet-visible absorption spectrum of the sample to be detected.
Further, the blank control solution contains the rest substances except the sample to be tested in the sample solution to be tested. Such as: if the sample solution to be measured is an aqueous solution only containing A, and when A is taken as the sample to be measured, the blank control solution is water. If the sample solution to be measured is an aqueous solution containing A and B, and A is taken as the sample to be measured, the blank control solution is an aqueous solution containing B (without A). Wherein A and B can be various substances.
Further, the specific method of the step 2) is as follows:
collecting three-dimensional fluorescence spectrums of a sample solution to be measured, and taking a maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position of each fluorescence emission spectrum as a Rayleigh scattering value S of the sample solution to be measured at the wavelength lambda sample (lambda); with lambda as abscissa and S sample (lambda) is the ordinate, namely the Rayleigh scattering spectrum of the sample solution to be detected is obtained;
collecting three-dimensional fluorescence spectrum of the blank control liquid, taking the maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position as the Rayleigh scattering value S of the blank control liquid at the wavelength lambda blank (lambda); with lambda as abscissa and S sample And (lambda) is the ordinate, namely the Rayleigh scattering spectrum of the blank control solution is obtained.
Further, three-dimensional fluorescence spectra of the sample solution to be detected and the blank control solution are respectively collected into a plurality of groups, outliers in a plurality of groups of maximum values near the position of the excitation wavelength lambda are removed, and then an average value is obtained to be used as Rayleigh scattering values at the wavelength lambda.
Further, the maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position is a maximum value in the range of the distance lambda being more than 1nm and less than 40nm, with the excitation wavelength lambda corresponding to the fluorescence emission spectrum as the center.
Compared with the prior art, the invention has the beneficial effects that:
according to the method for estimating the ultraviolet-visible absorption spectrum by utilizing the Rayleigh scattering signal of the three-dimensional fluorescence spectrum, the three-dimensional fluorescence spectrums of the blank control and the sample to be detected are respectively acquired, the Rayleigh scattering spectrums of the blank control and the sample to be detected are obtained by intercepting the three-dimensional fluorescence spectrums, and then the acquired scattering spectrums are utilized to estimate the ultraviolet-visible absorption spectrum. The method effectively utilizes Rayleigh scattering information in the frequently ignored three-dimensional fluorescence spectrum, and the estimated ultraviolet-visible absorption spectrum can be used for internal filtering effect correction or other spectroscopy analysis of the three-dimensional fluorescence spectrum, so that an effective way is provided for developing the three-dimensional fluorescence spectrometer with a simpler structure and lower cost, and the potential application range of the three-dimensional fluorescence spectrometer in actual industrial and living scenes is widened.
Drawings
FIG. 1 is a schematic flow chart of estimating an ultraviolet-visible absorption spectrum by utilizing a three-dimensional fluorescence spectrum Rayleigh scattering signal;
FIG. 2 shows the Rayleigh scattering spectra of the potassium dichromate solution and the blank solution in example 1 of the present invention.
FIG. 3 is a graph showing the comparison of the measured UV-visible absorption spectra of each solution prepared in example 1 of the present invention with the UV-visible absorption spectra estimated according to the method of the present invention.
FIG. 4 is a graph showing the comparison of the measured UV-visible absorption spectra of solutions of different turbidity prepared in example 2 of the present invention with the UV-visible absorption spectra estimated according to the method of the present invention.
Detailed Description
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further the features and advantages of the invention and are not limiting of the patent claims of the invention.
All noun expressions and abbreviations of the invention belong to the conventional noun expressions and abbreviations in the field of the art, and each noun expression and abbreviation is clear and definite in the relevant application field, and the person skilled in the art can understand clearly, accurately and uniquely according to the noun expressions and abbreviations.
As shown in fig. 1, the present invention provides a method for estimating an ultraviolet-visible absorption spectrum using a three-dimensional fluorescence spectrum rayleigh scattering signal, comprising the steps of:
1) Preparing a sample solution to be detected and a blank control solution with the same scattering property as the sample solution to be detected;
2) Respectively collecting three-dimensional fluorescence spectrums of a sample solution to be detected and a blank control solution in the ultraviolet-visible wavelength range, and respectively extracting Rayleigh scattering spectrums of the sample solution to be detected and the blank control solution;
3) According to Rayleigh scattering spectra of a sample solution to be detected and a blank control solution, calculating an absorption value of the sample to be detected at each wavelength according to a formula (1), and obtaining an original ultraviolet-visible absorption spectrum of the sample to be detected:
wherein: lambda is the wavelength, A (lambda) is the absorption value of the sample to be measured at the wavelength lambda, S blank (lambda) represents Rayleigh scattering value of the blank solution at wavelength lambda, S sample (lambda) represents the Rayleigh scattering value of the sample solution to be measured at the wavelength lambda;
4) And carrying out smoothing treatment and baseline correction on the calculated original ultraviolet-visible absorption spectrum to obtain a final ultraviolet-visible absorption spectrum of the sample to be detected.
In the invention, the blank control liquid with the same scattering property as the sample solution to be tested is a liquid containing the rest substances except the sample to be tested in the sample solution to be tested.
In the present invention, the process of collecting three-dimensional fluorescence spectrum includes: parameters such as integration time, detector resolution, gain and the like of the three-dimensional fluorescence spectrometer are firstly adjusted to enable the relative intensity of the test spectrum to be as large as possible but not to be overexposed. And then sampling the same sample and the corresponding blank for a plurality of times.
In the invention, the step 2) "respectively collects three-dimensional fluorescence spectra of the sample solution to be measured and the blank control solution in the ultraviolet-visible wavelength range, and respectively extracts Rayleigh scattering spectra thereof" comprises the following steps:
collecting three-dimensional fluorescence spectrums of a sample solution to be measured, and taking a maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position of each fluorescence emission spectrum as a Rayleigh scattering value S of the sample solution to be measured at the wavelength lambda sample (lambda); with lambda as abscissa and S sample (lambda) is the ordinate, namely the Rayleigh scattering spectrum of the sample solution to be detected is obtained;
collecting three-dimensional fluorescence spectrum of the blank control liquid, taking the maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position as the Rayleigh scattering value S of the blank control liquid at the wavelength lambda blank (lambda); with lambda as abscissa and S sample And (lambda) is the ordinate, namely the Rayleigh scattering spectrum of the blank control solution is obtained.
In the invention, three-dimensional fluorescence spectrums of a sample solution to be detected and a blank control solution are respectively collected into a plurality of groups, outliers in a plurality of groups of maximum values near the position of an excitation wavelength lambda are removed, and then an average value is obtained to be used as Rayleigh scattering values at the wavelength lambda. The outlier removal method includes, but is not limited to, absolute median deviation method, standard deviation method, percentile method and the like.
In the invention, the maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position is a maximum value in the range of the distance lambda of more than 1nm and less than 40nm, which is centered on the excitation wavelength lambda corresponding to the fluorescence emission spectrum.
The invention finally carries out smoothing treatment and baseline correction on the original ultraviolet-visible absorption spectrum obtained by calculation to obtain a final absorption spectrum. The smoothing process can adopt a sliding average method or a Savitzky-Golay filtering method and the like, and is mainly used for removing more obvious noise in a high-spectrum resolution mode. The baseline correction can be simply integrated translation, the translation can be obtained from measurement values under the known non-absorption wavelength, and the baseline correction can also be estimated by adopting a supervised machine learning method. The baseline correction can also be performed by establishing a baseline trend line by adopting a polynomial fitting method or a wavelet transformation method and the like for deduction correction.
For further explanation of the present invention, a method for estimating an ultraviolet-visible absorption spectrum using a three-dimensional fluorescence spectrum rayleigh scattering signal is provided in the following detailed description with reference to examples, but it should be understood that these examples are implemented on the premise of the technical scheme of the present invention, and detailed implementation and specific operation procedures are given only for further explanation of the features and advantages of the present invention, and not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Example 1 estimation of ultraviolet-visible absorption spectra of solutes from three-dimensional fluorescence spectra of true solutions
In this example, three substances, potassium dichromate, sodium 1, 2-naphthoquinone-4-sulfonate and humic acid, were selected in order to verify the effectiveness of the method in a true solution system.
First, a sample is configured and data is collected. Three sample substances were prepared to be high according to the maximum absorbance (maximum absorbance A max Approximately 2), medium (maximum absorbance A max About 1), low (maximum absorbance A max Approximately 0.5), insoluble impurities are removed by a microfiltration membrane, and then bubbles are removed by ultrasonic treatment. Three-dimensional fluorescence spectra of nine solution samples are respectively collected, and three-dimensional fluorescence spectra of pure water are collected as blank control.
Second, the data is processed and an initial estimate is obtained. Searching a maximum value in a 15nm range by taking excitation wavelength corresponding to each fluorescence emission spectrum of the three-dimensional fluorescence spectrum as a center, and taking the maximum value as a Rayleigh scattering value at the excitation wavelength corresponding to the emission spectrum; and taking the wavelength as an abscissa and the Rayleigh scattering value as an ordinate, so as to obtain the Rayleigh scattering spectrum of each sample solution to be detected and the blank control solution. Taking potassium dichromate as an example, the Rayleigh scattering spectra of the test solution and the blank control extracted from the three-dimensional fluorescence spectrum are shown in FIG. 2. An initial estimate of the uv-vis absorption spectrum of each true solution sample is made according to equation (1) using the acquired scatter spectrum.
Finally, a deviation is obtained according to the absorption value of the initial absorption spectrum of each substance at the lowest absorption (or the wavelength without absorption is determined), and the ultraviolet-visible absorption spectrum under the initial estimation is corrected by subtracting the deviation, so that the final estimation of the ultraviolet-visible absorption spectrum of different substances under different concentrations by the method is obtained. As shown in the second line of the graph of fig. 3, the uv-vis absorption spectrum estimated by the method is very similar to the real absorption spectrum (measured by the uv-vis spectrophotometer) corresponding to the first line of fig. 3, so that the effectiveness of the method in a true solution system is verified.
Example 2 estimation of the ultraviolet-visible absorption Spectrum from the three-dimensional fluorescence Spectrum of turbid liquid
In the embodiment, potassium permanganate which is absorbed in near ultraviolet and visible regions is selected as a solute, and turbidity of a turbid liquid system is regulated and controlled by adding a turbid liquid containing high polymers (polystyrene plastic particles) and inorganic silica particles, so that the effectiveness of the method on the turbid liquid system is verified.
First, a sample is configured and data is collected. By controlling the proportion of the solution and the turbid liquid, mixed solutions of the potassium permanganate solution with the same concentration under five index gradient turbidity values of 0.59, 1.36, 5.25, 24.66 and 121.73NTU are respectively prepared. In addition, a blank control solution of the above five turbidity types was prepared by diluting the turbid mother solution. Five samples and their corresponding blank three-dimensional fluorescence spectra were collected.
Second, the data is processed and an initial estimate is obtained. Searching a maximum value in a 20nm range by taking excitation wavelength corresponding to each fluorescence emission spectrum of the three-dimensional fluorescence spectrum as a center, and taking the maximum value as a Rayleigh scattering value at the excitation wavelength corresponding to the emission spectrum; and taking the wavelength as an abscissa and the Rayleigh scattering value as an ordinate, so as to obtain the Rayleigh scattering spectrum of each sample solution to be detected and the blank control solution. An initial estimate of the uv-vis absorption spectrum of each sample is made according to equation (1) using the acquired scatter spectrum.
Finally, the embodiment establishes an unsupervised correction method to further perform translational correction on the initial estimated absorption spectrum generated by the formula (1). The amount of translation used for correction is given by:
a T ×S+b T x C (S) (2); wherein each element is a column vector, S is an initial estimated ultraviolet-visible absorption spectrum, C (S) represents calculating a plurality of statistics for S, and vectors a and b represent projection weights of S and C (S), respectively. In this example, five statistics of maximum, minimum, average, median and standard deviation of the absorption spectrum vector S are taken to form C (S). The element values of the vectors a and b are obtained by the estimated/real ultraviolet visible absorption spectrum data of more than 20 compounds through the training of the alternating least square method.
Aiming at the initial ultraviolet-visible absorption spectrum obtained by the formula (1) in the embodiment, the translation correction coefficient is obtained by using the formula (2) and the initial spectrum is corrected, so that the final estimation of the method on the absorbance of the turbid potassium permanganate system can be obtained. As shown in FIG. 3, the correlation degree between the ultraviolet-visible absorption spectrum of the potassium permanganate estimated by the method and the real spectrum (measured by an ultraviolet-visible spectrophotometer) is steadily increased along with the increase of turbidity, which proves that the method has better applicability to the ultraviolet-visible absorption spectrum estimation of a turbid liquid system.
The above description is illustrative of the invention and is not intended to be limiting, but is to be construed as being included within the spirit and scope of the invention.
Claims (5)
1. A method for estimating an ultraviolet-visible absorption spectrum using a three-dimensional fluorescence spectrum rayleigh scattering signal, comprising the steps of:
1) Preparing a sample solution to be detected and a blank control solution with the same scattering property as the sample solution to be detected;
2) Respectively collecting three-dimensional fluorescence spectrums of a sample solution to be detected and a blank control solution in the ultraviolet-visible wavelength range, and respectively extracting Rayleigh scattering spectrums of the sample solution to be detected and the blank control solution;
3) According to Rayleigh scattering spectra of a sample solution to be detected and a blank control solution, calculating an absorption value of the sample to be detected at each wavelength according to a formula (1), and obtaining an original ultraviolet-visible absorption spectrum of the sample to be detected:
wherein: lambda is the wavelength, A (lambda) is the absorption value of the sample to be measured at the wavelength lambda, S blank (lambda) represents Rayleigh scattering value of the blank solution at wavelength lambda, S sample (lambda) represents the Rayleigh scattering value of the sample solution to be measured at the wavelength lambda;
4) And carrying out smoothing treatment and/or baseline correction on the original ultraviolet-visible absorption spectrum obtained by calculation to obtain a final ultraviolet-visible absorption spectrum of the sample to be detected.
2. The method according to claim 1, characterized in that: the blank control solution contains the rest substances except the sample to be detected in the sample solution to be detected.
3. The method according to claim 1, wherein the specific method of step 2) is:
collecting three-dimensional fluorescence spectrums of a sample solution to be measured, and taking a maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position of each fluorescence emission spectrum as a Rayleigh scattering value S of the sample solution to be measured at the wavelength lambda sample (lambda); with lambda as abscissa and S sample (lambda) is the ordinate, namely the Rayleigh scattering spectrum of the sample solution to be detected is obtained;
collecting three-dimensional fluorescence spectrum of the blank control liquid, taking the maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position as the Rayleigh scattering value S of the blank control liquid at the wavelength lambda blank (lambda); with lambda as abscissa and S sample (lambda) is the ordinate, namely Rayleigh scattered light of the blank control solution is obtainedA spectrum.
4. A method according to claim 3, characterized in that: and respectively collecting a plurality of groups of three-dimensional fluorescence spectrums of the sample solution to be tested and the blank control solution, removing outliers in a plurality of groups of maximum values near the excitation wavelength lambda, and taking an average value as a Rayleigh scattering value at the wavelength lambda.
5. A method according to claim 3, characterized in that: the maximum value of each fluorescence emission spectrum near the excitation wavelength lambda position is the maximum value in the range of the distance lambda being more than 1nm and less than 40nm, which takes the excitation wavelength lambda corresponding to the fluorescence emission spectrum as the center.
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