A method for estimating UV-visible absorption spectra using Rayleigh scattering signals from three-dimensional fluorescence spectra

Abstract

This invention provides a method for estimating UV-visible absorption spectra using Rayleigh scattering signals from three-dimensional fluorescence spectra. The method first collects three-dimensional fluorescence spectra of a blank control and a test sample, extracts Rayleigh scattering spectra from these spectra, and then uses the collected scattering spectra to estimate the UV-visible absorption spectrum of the test sample. This method effectively utilizes the often-overlooked Rayleigh scattering information in three-dimensional fluorescence spectra. The estimated UV-visible absorption spectrum can be used to correct for inner filter effects in three-dimensional fluorescence spectra or for other spectral analyses, providing an effective approach to simplifying the structure and reducing the cost of three-dimensional fluorescence spectrometers.

Description

Technical Field

[0001] The invention belongs to the field of analytical chemistry, and in particular relates to a method for estimating ultraviolet-visible absorption spectrum by utilizing Rayleigh scattering signals of three-dimensional fluorescence spectrum. Background Art

[0002] Three-dimensional fluorescence spectroscopy, with its precision, sensitivity, information-richness, and excellent repeatability, is widely used in the analysis of various complex fluorescent solutions. However, before it can truly move beyond the laboratory and gain widespread application, the technology for acquiring three-dimensional fluorescence spectra still has many obstacles to overcome. Among these, one of the most difficult obstacles is the additional measurement of UV-visible absorption spectra, which can be used to correct for the inner filter effect of the three-dimensional fluorescence spectrum. Therefore, to date, either the simultaneous use of UV-visible spectrophotometers or the construction of dual light sources or dual detectors in three-dimensional fluorescence spectrometers have become prerequisites for obtaining accurate three-dimensional fluorescence spectra.

[0003] In these circumstances, conventional methods for acquiring UV-visible absorption spectra alongside 3D fluorescence spectroscopy measurements complicate spectrometer optical path design, hindering the cost-effectiveness of more portable equipment. Consequently, the practical application of 3D fluorescence spectroscopy in industrial and environmental applications has reached a critical stalemate. Therefore, there is an urgent need to develop a method for extracting UV-visible absorption spectra from 3D fluorescence spectral data. This method, which allows for self-calibration of the 3D fluorescence spectral data after a single acquisition, can generate accurate spectra using algorithms. Summary of the Invention

[0004] Based on the problems existing in the above-mentioned prior art, the present invention provides a method for estimating the ultraviolet-visible absorption spectrum using the Rayleigh scattering signal of the three-dimensional fluorescence spectrum. The method effectively utilizes the Rayleigh scattering information in the three-dimensional fluorescence spectrum that is often overlooked. The estimated ultraviolet-visible absorption spectrum can be used for inner filter effect correction or other spectral analysis of the three-dimensional fluorescence spectrum, providing an effective way to simplify the structure and reduce the cost of the three-dimensional fluorescence spectrometer.

[0005] To achieve the purpose, the present invention adopts the following technical solutions:

[0006] A method for estimating ultraviolet-visible absorption spectrum using Rayleigh scattering signals of three-dimensional fluorescence spectrum is characterized by comprising the following steps:

[0007] 1) preparing a sample solution to be tested and a blank control solution having the same scattering properties as the sample solution to be tested;

[0008] 2) collecting three-dimensional fluorescence spectra of the sample solution to be tested and the blank control solution in the ultraviolet to visible wavelength range, and extracting their Rayleigh scattering spectra respectively;

[0009] 3) Based on the Rayleigh scattering spectra of the sample solution to be tested and the blank control solution, the absorption value of the sample to be tested at each wavelength is calculated according to formula (1) to obtain the original UV-visible absorption spectrum of the sample to be tested:

[0010]

[0011] Where: λ is the wavelength, A(λ) is the absorbance of the sample to be tested at wavelength λ, S blank (λ) represents the Rayleigh scattering value of the blank control solution at wavelength λ, S sample (λ) represents the Rayleigh scattering value of the sample solution to be tested at wavelength λ;

[0012] 4) Smoothing and / or baseline correction are performed on the calculated original UV-visible absorption spectrum to obtain the final UV-visible absorption spectrum of the sample to be tested.

[0013] Furthermore, the blank control solution contains the remaining substances in the test sample solution excluding the test sample. For example, if the test sample solution is an aqueous solution containing only A, and A is the test sample, the blank control solution is water. If the test sample solution is an aqueous solution containing A and B, and A is the test sample, the blank control solution is an aqueous solution containing B (but not A). Both A and B can be multiple substances.

[0014] Furthermore, the specific method of step 2) is:

[0015] Collect the three-dimensional fluorescence spectrum of the sample solution to be tested, and take the maximum value of each fluorescence emission spectrum near its excitation wavelength λ as the Rayleigh scattering value S of the sample solution to be tested at wavelength λ. sample (λ); with λ as the horizontal coordinate and S sample (λ) is the ordinate, i.e., the Rayleigh scattering spectrum of the sample solution to be tested is obtained;

[0016] Collect the three-dimensional fluorescence spectrum of the blank control solution, and take the maximum value of each fluorescence emission spectrum near its excitation wavelength λ as the Rayleigh scattering value S of the blank control solution at wavelength λ. blank (λ); with λ as the horizontal coordinate and S sample (λ) is the vertical coordinate, that is, the Rayleigh scattering spectrum of the blank control solution is obtained.

[0017] Furthermore, multiple sets of three-dimensional fluorescence spectra of the sample solution to be tested and the blank control solution are collected respectively, and the outliers in the multiple sets of maximum values near the excitation wavelength λ are removed and the average value is taken as the Rayleigh scattering value at the wavelength λ.

[0018] Furthermore, the maximum value of each fluorescence emission spectrum near the excitation wavelength λ is centered at the excitation wavelength λ corresponding to the fluorescence emission spectrum, and the maximum value is found within a range greater than 1 nm and less than 40 nm from λ.

[0019] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0020] The present invention provides a method for estimating UV-visible absorption spectra using Rayleigh scattering signals from three-dimensional fluorescence spectra. The method first collects three-dimensional fluorescence spectra of a blank control and a test sample, extracts Rayleigh scattering spectra from these spectra, and then uses the collected scattering spectra to estimate the UV-visible absorption spectra. This method effectively utilizes the often-overlooked Rayleigh scattering information in three-dimensional fluorescence spectra. The estimated UV-visible absorption spectrum can be used to correct for inner filter effects in three-dimensional fluorescence spectra or perform other spectral analyses. This method provides an effective approach for developing simpler, lower-cost three-dimensional fluorescence spectrometers, broadening their potential applications in real-world industrial and everyday scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the process of estimating UV-visible absorption spectrum using Rayleigh scattering signal of three-dimensional fluorescence spectrum in the present invention;

[0022] Figure 2 The Rayleigh scattering spectra of the potassium dichromate solution and the blank control solution in Example 1 of the present invention are shown.

[0023] Figure 3 3 is a comparison chart of the measured UV-visible absorption spectra of each solution prepared in Example 1 of the present invention and the UV-visible absorption spectra estimated according to the method of the present invention.

[0024] Figure 4 This is a comparison diagram of the measured UV-visible absorption spectra of the solutions with different turbidities prepared in Example 2 of the present invention and the UV-visible absorption spectra estimated according to the method of the present invention. DETAILED DESCRIPTION

[0025] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent claims of the present invention.

[0026] All noun expressions and abbreviations in the present invention are conventional noun expressions and abbreviations in this field. Each noun expression and abbreviation is clear and unambiguous in its relevant application field. Those skilled in the art can clearly, accurately and uniquely understand them based on the noun expressions and abbreviations.

[0027] like Figure 1As shown, the present invention provides a method for estimating ultraviolet-visible absorption spectrum using Rayleigh scattering signals of three-dimensional fluorescence spectrum, which comprises the following steps:

[0028] 1) preparing a sample solution to be tested and a blank control solution having the same scattering properties as the sample solution to be tested;

[0029] 2) collecting three-dimensional fluorescence spectra of the sample solution to be tested and the blank control solution in the ultraviolet to visible wavelength range, and extracting their Rayleigh scattering spectra respectively;

[0030] 3) Based on the Rayleigh scattering spectra of the sample solution to be tested and the blank control solution, the absorption value of the sample to be tested at each wavelength is calculated according to formula (1) to obtain the original UV-visible absorption spectrum of the sample to be tested:

[0031]

[0032] Where: λ is the wavelength, A(λ) is the absorbance of the sample to be tested at wavelength λ, S blank (λ) represents the Rayleigh scattering value of the blank control solution at wavelength λ, S sample (λ) represents the Rayleigh scattering value of the sample solution to be tested at wavelength λ;

[0033] 4) The calculated original UV-visible absorption spectrum is smoothed and baseline corrected to obtain the final UV-visible absorption spectrum of the sample to be tested.

[0034] In the present invention, the blank control solution having the same scattering properties as the sample solution to be tested is a liquid containing the remaining substances in the sample solution to be tested except the sample to be tested.

[0035] In the present invention, the process of acquiring a three-dimensional fluorescence spectrum includes first adjusting parameters such as the integration time, detector resolution, and gain of the three-dimensional fluorescence spectrometer to maximize the relative intensity of the test spectrum without overexposure. Then, multiple sampling is performed on the same sample and its corresponding blank.

[0036] In the present invention, the process of step 2) "collecting three-dimensional fluorescence spectra of the sample solution to be tested and the blank control solution in the ultraviolet to visible wavelength range, and extracting their Rayleigh scattering spectra respectively" includes:

[0037] Collect the three-dimensional fluorescence spectrum of the sample solution to be tested, and take the maximum value of each fluorescence emission spectrum near its excitation wavelength λ as the Rayleigh scattering value S of the sample solution to be tested at wavelength λ. sample (λ); with λ as the horizontal coordinate and S sample (λ) is the ordinate, i.e., the Rayleigh scattering spectrum of the sample solution to be tested is obtained;

[0038] Collect the three-dimensional fluorescence spectrum of the blank control solution, and take the maximum value of each fluorescence emission spectrum near its excitation wavelength λ as the Rayleigh scattering value S of the blank control solution at wavelength λ. blank (λ); with λ as the horizontal coordinate and S sample (λ) is the vertical coordinate, that is, the Rayleigh scattering spectrum of the blank control solution is obtained.

[0039] In the present invention, multiple sets of three-dimensional fluorescence spectra are collected from the sample solution and the blank control solution. After removing outliers from the multiple maxima near the excitation wavelength λ, the average value is calculated as the Rayleigh scattering value at wavelength λ. Methods for removing outliers include, but are not limited to, the absolute median deviation method, the standard deviation method, and the percentile method.

[0040] In the present invention, the maximum value of each fluorescence emission spectrum near the excitation wavelength λ is centered at the excitation wavelength λ corresponding to the fluorescence emission spectrum, and the maximum value within the range of greater than 1 nm and less than 40 nm is sought.

[0041] Finally, the present invention smoothes and baseline corrects the calculated raw UV-visible absorption spectrum to obtain the final absorption spectrum. The smoothing process can use methods such as sliding average or Savitzky-Golay filtering, which is mainly used to remove more obvious noise in high spectral resolution mode. The baseline correction can use a simple overall translation, and the translation amount can be obtained from the measurement value at a wavelength with known no absorption, or it can be estimated using supervised machine learning methods. Baseline correction can also use methods such as polynomial fitting or wavelet transform to establish a baseline trend line for subtraction correction.

[0042] To further illustrate the present invention, a method for estimating an ultraviolet-visible absorption spectrum using a three-dimensional fluorescence spectrum Rayleigh scattering signal provided by the present invention is described in detail below in conjunction with examples. However, it should be understood that these examples are implemented based on the technical solution of the present invention. Detailed implementation methods and specific operating procedures are provided only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. The scope of protection of the present invention is not limited to the following examples.

[0043] Example 1: Estimating the UV-Vis absorption spectrum of a solute from its three-dimensional fluorescence spectrum

[0044] In this example, potassium dichromate, sodium 1,2-naphthoquinone-4-sulfonate and humic acid were selected to verify the effectiveness of this method in a true solution system.

[0045] First, configure the sample and collect data. Prepare three sample substances according to the maximum absorbance (maximum absorbance A max ≈2), medium (maximum absorbance Amax ≈1), low (maximum absorbance A max Solutions with three concentrations (100 μg / ml, 0.5 μg / ml) were prepared. Insoluble impurities were removed using a microfiltration membrane, and air bubbles were removed using ultrasonic treatment. Three-dimensional fluorescence spectra were collected for each of the nine solution samples, and a 3D fluorescence spectrum of pure water was collected as a blank control.

[0046] Secondly, process the data and get an initial estimate. Centered on the excitation wavelength corresponding to each fluorescence emission spectrum of the three-dimensional fluorescence spectrum, find the maximum value within 15nm as the Rayleigh scattering value at the excitation wavelength corresponding to the emission spectrum; use the wavelength as the horizontal coordinate and the Rayleigh scattering value as the vertical coordinate to obtain the Rayleigh scattering spectrum of each sample solution to be tested and the blank control solution. Taking potassium dichromate as an example, the Rayleigh scattering spectra of the sample solution to be tested and the blank control solution extracted from the three-dimensional fluorescence spectrum are as follows: Figure 2 The collected scattering spectrum is used to make an initial estimate of the UV-visible absorption spectrum of each true solution sample according to formula (1).

[0047] Finally, the deviation is obtained based on the absorption value of the initial absorption spectrum of each substance at the lowest absorption (or the wavelength where no absorption is determined), and the UV-visible absorption spectrum under the initial estimate is corrected by subtracting the deviation, thereby obtaining the final estimate of the UV-visible absorption spectrum of different substances at different concentrations by this method. Figure 3 The second row of pictures shows that the UV-visible absorption spectrum estimated by this method is consistent with Figure 3 The real absorption spectra corresponding to the first row (measured by UV-visible spectrophotometer) are very similar, so the effectiveness of this method in real solution systems is verified.

[0048] Example 2: Estimating the UV-Vis Absorption Spectrum of a Turbid Liquid from Its Three-Dimensional Fluorescence Spectrum

[0049] In this example, potassium permanganate, which absorbs in both the near-ultraviolet and visible regions, was selected as the solute. The turbidity of the system was regulated by adding a turbid solution containing a polymer (polystyrene plastic particles) and inorganic silica particles. The purpose was to verify the effectiveness of this method for turbid liquid systems.

[0050] First, sample preparation and data acquisition were performed. By manipulating the ratio of the solution to the turbidity solution, potassium permanganate solutions of the same concentration were prepared at five exponential gradient turbidities: 0.59, 1.36, 5.25, 24.66, and 121.73 NTU. Furthermore, blank control solutions at these five turbidity levels were prepared by diluting the turbidity solution stock solution. Three-dimensional fluorescence spectra were collected for the five samples and their corresponding blank controls.

[0051] Next, the data is processed to obtain an initial estimate. Centered on the excitation wavelength corresponding to each fluorescence emission spectrum in the three-dimensional fluorescence spectrum, the maximum value within a 20nm range is found as the Rayleigh scattering value at the excitation wavelength corresponding to that emission spectrum. The Rayleigh scattering spectrum of each sample solution and blank control solution is obtained, with the wavelength as the horizontal axis and the Rayleigh scattering value as the vertical axis. Using the collected scattering spectrum, an initial estimate of the UV-visible absorption spectrum of each sample is obtained according to Equation (1).

[0052] Finally, this embodiment establishes an unsupervised correction method to further perform translation correction on the initial estimated absorption spectrum generated by equation (1). The translation amount used for correction is given by the following equation:

[0053] a T ×S+b T ×C(S) (2); Where each element is a column vector, where S is the initial estimated UV-Vis absorption spectrum, C(S) represents the calculation of multiple statistics on S, and vectors a and b represent the projection weights of S and C(S), respectively. In this embodiment, five statistics, namely the maximum, minimum, mean, median, and standard deviation of the absorption spectrum vector S, are used to construct C(S). The element values of vectors a and b are obtained by training with the alternating least squares method using estimated / real UV-Vis absorption spectrum data for more than 20 compounds.

[0054] For the initial UV-visible absorption spectrum obtained by formula (1) in this embodiment, the translation correction coefficient is obtained by formula (2) and the initial spectrum is corrected to obtain the final estimate of the absorbance of the turbid potassium permanganate system by this method. Figure 3 As shown in the figure, the correlation between the UV-visible absorption spectrum of potassium permanganate estimated by this method and the real spectrum (measured by UV-visible spectrophotometer) steadily increases with the increase of turbidity, indicating that this method is also suitable for estimating the UV-visible absorption spectrum of turbid liquid systems.

[0055] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for estimating ultraviolet-visible absorption spectrum using Rayleigh scattering signals of three-dimensional fluorescence spectrum, characterized in that: The steps include: 1) preparing a sample solution to be tested and a blank control solution having the same scattering properties as the sample solution to be tested; 2) collecting three-dimensional fluorescence spectra of the sample solution to be tested and the blank control solution in the ultraviolet to visible wavelength range, and extracting their Rayleigh scattering spectra respectively; 3) Based on the Rayleigh scattering spectra of the sample solution to be tested and the blank control solution, the absorption value of the sample to be tested at each wavelength is calculated according to formula (1) to obtain the original UV-visible absorption spectrum of the sample to be tested: Where: λ is the wavelength, A(λ) is the absorbance of the sample to be tested at wavelength λ, S blank (λ) represents the Rayleigh scattering value of the blank control solution at wavelength λ, S sample (λ) represents the Rayleigh scattering value of the sample solution to be tested at wavelength λ; 4) Smoothing and / or baseline correction are performed on the calculated original UV-visible absorption spectrum to obtain the final UV-visible absorption spectrum of the sample to be tested.

2. The method according to claim 1, wherein: The blank control solution contains the remaining substances in the sample solution except the sample to be tested.

3. The method according to claim 1, characterized in that The specific method of step 2) is: Collect the three-dimensional fluorescence spectrum of the sample solution to be tested, and take the maximum value of each fluorescence emission spectrum near its excitation wavelength λ as the Rayleigh scattering value S of the sample solution to be tested at wavelength λ. sample (λ); with λ as the horizontal coordinate and S sample (λ) is the ordinate, i.e., the Rayleigh scattering spectrum of the sample solution to be tested is obtained; Collect the three-dimensional fluorescence spectrum of the blank control solution, and take the maximum value of each fluorescence emission spectrum near its excitation wavelength λ as the Rayleigh scattering value S of the blank control solution at wavelength λ. blank (λ); with λ as the horizontal coordinate and S sample (λ) is the vertical coordinate, that is, the Rayleigh scattering spectrum of the blank control solution is obtained.

4. The method according to claim 3, wherein: Multiple sets of three-dimensional fluorescence spectra of the sample solution to be tested and the blank control solution are collected respectively, and the outliers in the multiple sets of maximum values near the excitation wavelength λ are removed and the average value is taken as the Rayleigh scattering value at the wavelength λ.

5. The method according to claim 3, wherein: The maximum value of each fluorescence emission spectrum near the excitation wavelength λ is centered at the excitation wavelength λ corresponding to the fluorescence emission spectrum, and the maximum value within the range of greater than 1 nm and less than 40 nm is sought.

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