Solution absorbance spectrum measuring device and method

Abstract

The present invention belongs to the field of spectroscopy technology, and in particular, relates to a device and method for measuring the absorbance spectrum of a solution. The device includes a continuous spectrum white light source, a cuvette holder, a variable optical path assembled cuvette, a fiber optic spectrometer and a host computer. The variable optical path assembled cuvette is built with a solution to be tested, and the variable optical path assembled cuvette is arranged in the cuvette holder. The white light emitted by the continuous spectrum white light source passes through the solution to be tested and then enters the fiber optic spectrometer. The fiber optic spectrometer is connected to the host computer. The fiber optic spectrometer collects the spectrum of white light under the control of the host computer, and the host computer calculates the absorbance spectrum of the solution to be tested according to the spectrum. The present invention is suitable for trace, strong solvation effect and high transparency solutions, the device has low cost, and can achieve one-time absorbance spectrum measurement.

Description

Technical Field

[0001] The invention belongs to the technical field of spectroscopy, and in particular relates to a device and method for measuring a solution absorbance spectrum. Background Art

[0002] A variety of mature methods have been developed to measure the absorbance of solutions. The mainstream methods for measuring the spectral transmittance of solutions include spectrophotometry and fiber optic spectrometer measurement. Regardless of which measurement method is used, in order to obtain the best accuracy, it is necessary to introduce a reference sample and calibrate the transmittance of the measurement results; or measure samples of different concentrations or optical pathlengths and solve the absorbance of the solution based on the Beer-Lambert law.

[0003] When using a spectrophotometer or spectrometer to measure the absorbance spectrum of a sample, the reference sample is generally an empty sample cell or a sample cell with the same solvent, both of which will introduce certain errors. If the measured liquid is a pure liquid, it cannot be calibrated by the same solvent sample cell itself, so it is necessary to use an empty sample cell for calibration, the interior of which will be affected by the reflection and scattering of the interface between the air and the cell wall, thereby reducing the accuracy. Therefore, the national standard GB / T 7962.9-2010 adopts the method of using the refractive index to calculate the reflectivity and then remove it. The Chinese invention patent named "Method for measuring the spectral transmittance of liquids" (publication number CN104880426A, publication date September 2, 2015) uses a refractometer to measure the refractive index of the liquid and the cell wall, calculates the interface reflectivity, and corrects the transmittance error.

[0004] Since the reflectivity is affected by coating, surface micromorphology, etc., the paper "Solvent-conjugation-induced ultrafast dynamics of enhanced reverse saturable absorption in lead phthalocyanine derivatives solutions" published in the journal "Physica Scripta" in 2022 pointed out that solvents of different concentrations may produce different degrees of solvation effect with solute molecules, resulting in different absorption cross-section spectra of samples at different concentrations, that is, they no longer conform to the exponential relationship given by the Beer-Lambert law. Therefore, the commonly used colorimetric analysis method (obtaining the absorbance of the solution by establishing a concentration gradient calculation) is not suitable for the absorbance spectrum of such solvation effect solutions.

[0005] In view of this situation, in order to more accurately calculate the spectral absorbance of the solution, especially the solution with strong solvation effect and the solvent with high transparency, i.e. the absorbance spectrum, a more reliable solution is to use variable optical path difference, not to change the concentration of the solution itself, and use multiple sets of data to calculate the accurate absorbance spectrum, i.e. the different optical path measurement method. At present, many companies such as Avantes and Leysen have adopted variable optical path immersion transmission probe to realize this solution. The solution can be briefly described as follows: the light is transmitted to the top of the probe through the optical fiber bundle (6 pieces) composed of "6+1" Y-type optical limit, and is reflected by the reflection window composed of white diffuse reflection material through a set optical path, and then returns to the central optical fiber (1 piece) in the probe to transmit back to the spectrometer. In this solution, multiple optical components such as optical fiber, two sapphire windows and white diffuse reflection material are required, and the stability and full spectrum transmission / reflection performance of these optical components are extremely high, and the cost is relatively high. In particular, the immersion device also requires the wall material to withstand corrosion from various organic substances including acid / alkali. According to the national standard GB / T 6682-2008, the samples of the reference cell and the sample cell are the same, but the optical path lengths of the cuvettes of the sample cell and the reference cell are different, and the ratio of the transmittance of the long optical path absorption cell to the short optical path absorption cell is the transmittance of the difference between the long and short optical path lengths of the solution. The principle of this measurement method is to add the solution to be tested to a cuvette of different optical path lengths, use a blank cuvette of the same optical path length as a reference, and measure the absorbance or transmittance of the liquid to be tested in the sample cell, ultimately eliminating the effect of the container wall to improve the measurement accuracy. However, this method is affected by the subtle differences in the properties of the cuvette walls, and there is still room for improvement in test accuracy.

[0006] Taking this into consideration, Ye Rongchun and others from Guangdong Ocean University designed an electrically displaceable piston device in the paper "Measurement of Absorption Coefficient of High-Transmittance Liquids" published in the journal "Journal of Guangdong Ocean University" to change the optical path by changing the position of the piston. Since the wall of the device is not replaced, the authors claim that this method has higher measurement accuracy than the method described in GB / T 6682-2008. However, the device involves a relatively complex optical system and is not suitable for large-scale promotion.

[0007] In the existing technology, spectrophotometry cannot control the influence of interface reflection; the method of calculating reflection by removing the refractive index will introduce indirect errors; the colorimetric analysis method cannot measure the changes of solutions whose absorption cross sections change with concentration and pure liquids; the different optical path measurement method is most suitable for measuring the absorbance spectrum of such solutions. In order to ensure accuracy, the existing different optical path measurement methods mostly use various complex devices and simple reference methods, which not only have high requirements for the cleaning and maintenance of the devices, but also lack appropriate statistical methods to reduce measurement errors. Summary of the invention

[0008] In view of this, the invention aims to provide a solution absorbance spectrum measurement device and method to solve the problem that the existing solution cannot measure the absorbance spectrum of high-transmittance liquid and solution with solvation effect for a long time, stably and accurately. The present invention designs a low-cost, high-precision solution absorbance spectrum measurement device and method for high-transmittance solvation effect solution, which is suitable for trace, strong solvation effect and high-transparency solution. The device of the present invention has low cost and can realize one-time absorbance spectrum measurement.

[0009] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0010] A solution absorbance spectrum measuring device comprises a continuous spectrum white light source, a cuvette holder, a variable optical path assembled cuvette, a fiber optic spectrometer and a host computer, wherein:

[0011] The variable optical pathlength assembled cuvette is built with a solution to be tested, and the variable optical pathlength assembled cuvette is arranged in a cuvette holder. The white light emitted by a continuous spectrum white light source passes through the solution to be tested and is incident on a fiber optic spectrometer. The fiber optic spectrometer is connected to a host computer. The fiber optic spectrometer collects the spectrum of the white light under the control of the host computer, and the host computer calculates the absorbance spectrum of the solution to be tested based on the spectrum.

[0012] Furthermore, the variable optical path assembled cuvette includes two fused quartz sheets and a silica gel component, and the two fused quartz sheets are arranged on both sides of the silica gel component to prevent the solution to be tested placed in the silica gel component from flowing out.

[0013] Furthermore, the silica gel component includes at least one silica gel block, and a liquid tank is provided at the center of the silica gel block, and the liquid tank is used to place the solution to be tested.

[0014] Furthermore, the hardness of the silica gel block is greater than 70HA, the thickness of the silica gel block is 1 mm, and the transmittance of the fused quartz sheet in the wavelength range of 400 nm-1100 nm is greater than 90%.

[0015] Furthermore, the host computer includes a computer.

[0016] A method for measuring a solution absorbance spectrum is implemented using a solution absorbance spectrum measuring device, and specifically comprises the following steps:

[0017] S1: Build a solution absorbance spectrum measurement device;

[0018] S2: assembling n cuvettes with different optical path lengths in sequence, placing the n cuvettes with different optical path lengths in the cuvette holder in order from the smallest to the largest optical path length, and using a fiber optic spectrometer to collect the white light spectra passing through the n cuvettes with different optical path lengths;

[0019] S3: Based on the n white light spectra collected by the fiber optic spectrometer, the transmittance spectra of the white light passing through n cuvettes with different optical path lengths are calculated in sequence;

[0020] S4: based on the transmittance spectra of white light passing through n cuvettes with different optical path lengths calculated in step S3, eliminating pathological data;

[0021] S5: Perform linear programming analysis on the optical path array and transmittance spectrum array after eliminating the pathological data to obtain the final wall transmittance and absorbance spectrum of the solution to be tested.

[0022] Furthermore, before performing step S1, the continuous spectrum white light source is preheated, and the optical fiber spectrometer is controlled by the host computer so that the optical fiber spectrometer collects the initial spectrum of white light emitted by the continuous spectrum white light source.

[0023] Furthermore, in step S3, the calculation formula of the transmittance spectrum of white light passing through n different optical pathlength cuvettes is:

[0024] T n =S n / S0;

[0025] Among them, T n is the transmittance spectrum of white light passing through the nmm pathlength cuvette, S n is the spectrum of white light passing through the nmm pathlength cuvette, and S0 is the initial spectrum of white light emitted by the continuous spectrum white light source.

[0026] Furthermore, step S4 specifically includes the following steps:

[0027] S41: Based on the transmittance spectra of white light passing through n different optical pathlength cuvettes calculated in step S3, an optical pathlength array and a transmittance spectrum array are constructed:

[0028] ;

[0029] ;

[0030] in, is the optical path array, is the 1mm optical path corresponding to the 1mm optical path cuvette, is the 2mm optical path corresponding to the 2mm optical path cuvette, is the 3mm optical path corresponding to the 3mm optical path cuvette, is the nmm optical path length corresponding to the nmm optical path length cuvette, is the transmittance spectrum array, is the transmittance spectrum of white light passing through a 1mm pathlength cuvette, is the transmittance spectrum of white light passing through a 2mm pathlength cuvette, is the transmittance spectrum of white light passing through a 3mm pathlength cuvette;

[0031] S42: Based on the polyfit function, linear programming analysis is performed on the optical path array and transmittance spectrum array to obtain the absorption coefficient:

[0032] ;

[0033] in, α is the absorption coefficient, It is an intermediate parameter obtained through linear programming analysis and has no physical meaning;

[0034] S43: Calculate the standard deviation of the actual transmittance spectrum and the theoretical transmittance spectrum of white light passing through the nmm pathlength cuvette by the following formula:

[0035] ;

[0036] ;

[0037] ;

[0038] in, is the wall transmittance, is the standard deviation, is the standard deviation function, is the theoretical transmittance spectrum of white light passing through the nmm pathlength cuvette, is the wall transmittance;

[0039] S44: Calculate the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of white light passing through the imm pathlength cuvette by the following formula: :

[0040] ;

[0041] in, is the theoretical transmittance spectrum of white light passing through the imm pathlength cuvette, is the actual transmittance spectrum of white light passing through the imm pathlength cuvette;

[0042] S45: If >2 , then As pathological data, the data related to the pathological data are removed from the optical path array and the transmittance spectrum array respectively, and step S5 is executed. Otherwise, replace , repeat step S44 until the calculation of the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of the white light passing through all the cuvettes with different optical path lengths is completed.

[0043] Furthermore, in step S5, a linear programming analysis is performed on the optical path array and the transmittance spectrum array after the pathological data are removed based on the polyfit function, and the final wall transmittance and the absorbance spectrum of the solution to be tested are obtained according to the linear programming analysis results:

[0044] ;

[0045] ;

[0046] ;

[0047] in, is the absorption coefficient after removing the ill-conditioned data, After eliminating the pathological data, the intermediate parameters obtained through linear programming analysis have no physical meaning. is the optical path array after removing the pathological data, is the transmittance spectrum array after removing the pathological data, is the final absorbance spectrum of the solution to be tested, is the final wall transmittance.

[0048] Compared with the prior art, the invention can achieve the following beneficial effects:

[0049] (1) The solution absorbance spectrum measurement device created by the present invention adopts a variable optical path assembly cuvette composed of a fused quartz sheet and a silica gel component, which not only reduces the measurement cost, but also ensures the accuracy of the absorbance spectrum measurement. The device has the advantages of high transmittance in the near-ultraviolet-visible-near-infrared full spectrum, and the device proposed by the present invention has the characteristics of disposable use, allowing the measurement of trace samples, and being resistant to acid, alkali and organic solvent corrosion.

[0050] (2) The present invention creates the solution absorbance spectrum measurement method, which adopts the design of transmittance of multiple optical paths, uses linear programming methods combined with statistical means to eliminate pathological data, reduce the statistical error of absorbance spectrum measurement, and obtain the absorbance of the solution to be tested and the total wall transmittance. In subsequent experiments, when the same wall is used, the absorbance spectrum of the solution to be tested can even be directly calculated through a single measurement, and there is no need to change the optical path multiple times, and the accuracy of the measurement can be guaranteed. The present invention solves the problem of decreased accuracy caused by the difference in optical properties (such as reflectivity, absorbance and scattering rate) between the reference container and the sample container when measuring the absorbance spectrum, and at the same time avoids the situation where the change in the light absorption cross section of the solvation effect solution caused by changing the solution concentration causes inaccurate measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0052] Figure 1 A schematic diagram of the structure of a solution absorbance spectrum measuring device according to an embodiment of the present invention;

[0053] Figure 2 This is a front view of the silica gel block described in the embodiment of the present invention;

[0054] Figure 3 A cross-sectional view of a silica gel block according to an embodiment of the present invention;

[0055] Figure 4 A top view of the silica gel block described in the embodiment of the present invention;

[0056] Figure 5 A three-dimensional schematic diagram of a silica gel block according to an embodiment of the present invention;

[0057] Figure 6 A front view of the fused quartz plate described in the embodiment of the present invention;

[0058] Figure 7 A three-dimensional schematic diagram of a fused quartz plate according to an embodiment of the present invention;

[0059] Figure 8 A schematic diagram of a method for measuring a solution absorbance spectrum according to an embodiment of the present invention;

[0060] Fig. 9 This is a graph showing the transmittance spectrum measurement results of the cadmium selenide quantum dot-toluene solution described in the embodiment of the present invention;

[0061] Fig.10 The absorption coefficient distribution diagram of the embodiment of the present invention is as a function of wavelength;

[0062] Fig.11 The transmittance distribution diagram of the vessel wall as a function of wavelength described in the embodiment of the present invention is created.

[0063] Description of reference numerals:

[0064] 1. Continuous spectrum white light source; 2. Cuvette holder; 3. Variable optical path assembled cuvette; 4. Fiber optic spectrometer; 5. Host computer; 31. Silica gel block; 32. Liquid tank; 33. Fused quartz sheet. DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0066] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0067] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0068] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0069] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0070] like Figure 1As shown, the solution absorbance spectrum measuring device includes a continuous spectrum white light source 1, a cuvette holder 2, a variable optical path assembled cuvette 3, an optical fiber spectrometer 4 and a host computer 5. The continuous spectrum white light source 1 generates a deuterium-halogen white light source of 200nm-1200nm, provides a stable (error is less than 0.1%) continuous spectrum white light of 200nm-1200nm, is coupled into the cuvette holder 2 through a first optical fiber, a variable optical path assembled cuvette 3 is placed in the cuvette holder 2, and a solution to be tested is built in the variable optical path assembled cuvette 3, and the white light passing through the solution to be tested is coupled into the second optical fiber and transmitted to the optical fiber spectrometer 4, and the optical fiber spectrometer 4 is connected to a computer to obtain data and perform data processing.

[0071] The cuvette holder 2 is formed by splicing two front and rear collimating lenses and a metal cuvette slot, and the collimating lens is included in the standard cuvette holder 2 .

[0072] The variable optical path assembly cuvette 3 is composed of two fused quartz sheets 33 and a silica gel component. The two fused quartz sheets 33 are arranged on both sides of the silica gel component to prevent the test solution placed in the silica gel component from flowing out. The silica gel component includes at least one silica gel block 31. The length and width of the silica gel block 31 are the same as those of the fused quartz sheet 33. A liquid tank 32 is arranged in the center of the silica gel block 31. The liquid tank 32 is used to place the test solution. The shapes of each component are as follows: Figure 2-Figure 7 As shown: As an example, the length of the silica gel block 31 is 45 mm, the width is 10.2 mm, the two ends of the liquid tank 32 are semicircles, the middle is a cuboid, the radius of the semicircles at both ends is 6 mm, the length of the cuboid is 18 mm, the width is 6 mm, the length of the fused quartz sheet 33 is 45 mm, the width is 10.2 mm, and the thickness is 1 mm. The size of the silica gel block 31 and the fused quartz sheet 33 is not limited, and different sizes of the silica gel block 31 and the fused quartz sheet 33 can be customized for different specifications of the cuvette holder 2.

[0073] The hardness of the silica gel block 31 is required to be above 70HA (Shore hardness, unit degree, divided into type A and type D, silica gel hardness is generally measured using type A, called HA) to prevent excessive deformation of the variable optical path assembly cuvette 3. The fused quartz sheet 33 is required to have a transmittance of more than 90% in the wavelength range of 400nm-1100nm. The fused quartz sheet 33, the silica gel assembly, and the fused quartz sheet 33 are pressed together in a "sandwich" structure, and the airtightness is maintained by the liquid surface tension and atmospheric pressure, and can be disassembled and cleaned at any time.

[0074] When making a variable optical path length assembly cuvette 3, the optical path length of the cuvette is set by setting the number of silica gel blocks 31 in the silica gel assembly. For example, when making a 1mm optical path length cuvette, only one silica gel block 31 is placed in the silica gel assembly, and the thickness of the silica gel block 31 is 1mm. When making a 2mm optical path length cuvette, two silica gel blocks 31 are placed in the silica gel assembly, and the two silica gel blocks 31 are placed overlappingly. The 2mm liquid tank 32 formed by the two overlapping silica gel blocks 31 is used to place the solution to be tested, so that the white light passes through the 2mm optical path length where the solution to be tested is located. The nmm optical path length in the nmm optical path length cuvette refers to the distance that the white light passes through the liquid to be tested. The plane where the liquid tank of the variable optical path length assembly cuvette 3 is located is placed vertically to the horizontal plane where the cuvette holder 2 is located. Taking the white light passing through the 1mm optical path length cuvette as an example, the white light passes through one fused quartz sheet 33, the 1mm thick liquid to be tested and the other fused quartz sheet 33 in turn, and then is transmitted to the optical fiber spectrometer 4 through the second optical fiber.

[0075] After the present invention has made 1mm optical path cuvette, 2mm optical path cuvette and 3mm optical path cuvette, it is left to stand for 24 hours, and the liquid inside the silica gel component still does not leak, because silica gel has very low surface energy, and itself has high hydrophobicity and conformability to smooth surfaces. In addition, the main component of the cured silica gel is hydrated silicon dioxide, which has high corrosion resistance and stability, and is commonly used as a sealing material for various organic / inorganic reagent bottles. Therefore, as a vessel wall, it can ensure that the variable optical path assembled cuvette 3 has good air tightness and stability. The main component of the fused quartz sheet 33 is silicon dioxide, which also has high corrosion resistance and stability. Under the action of internal liquid tension and atmospheric pressure, no clamp is required, and the assembled cuvette has a certain sealing ability. When changing the optical path, only one side of the fused quartz sheet 33 needs to be removed, wiped clean, and assembled with a new hard silica gel block 31 with a liquid tank, and then the solution to be tested is poured in, and the other side of the fused quartz sheet 33 is sealed to complete the change of the optical path. Since the fused quartz plate 33 used to replace the optical path is the same, the influence of the wall on the absorbance can be eliminated.

[0076] After obtaining the transmittance spectrum of the solution to be tested under different optical path lengths, linear programming analysis is used to eliminate pathological data and calculate the absorbance of the solution and the absorbance of the wall. The obtained absorbance can be directly used in subsequent experiments. When the same device is used, the absorbance spectrum of the solution to be tested can be directly calculated, and there is no need to change the optical path many times. Since the cost of assembling the various materials of the variable optical path assembly cuvette 3 is very low, the silica gel side wall and the fused quartz sheet 33 wall are easy to clean or can be used once, avoiding sample contamination due to multiple incomplete cleaning. Compared with the existing electric displacement piston device and the variable optical path immersion transmission probe device, in the same experiment, the fused quartz sheet 33 removed when changing the optical path has no cleaning dead corners, and can be easily cleaned on the surface by ultrasound or manual methods, so it has higher anti-pollution performance.

[0077] The material of the variable optical path assembled cuvette 3 of the present invention has excellent characteristics such as stability, low cost, easy cleaning and maintenance, etc. The variable optical path assembled cuvette 3 is used as a sample container, which has the potential for convenient, low cost and large-scale industrial production.

[0078] like Figure 8 As shown, a solution absorbance spectrum measurement method provided by the present invention is implemented using a solution absorbance spectrum measurement device, and specifically includes the following steps:

[0079] S1: Build a solution absorbance spectrum measurement device;

[0080] Before performing step S1 , the continuous spectrum white light source 1 is preheated, and the upper computer 5 is used to control the optical fiber spectrometer 4 so that the optical fiber spectrometer 4 collects the initial spectrum of white light emitted by the continuous spectrum white light source 1 .

[0081] S2: assembling n cuvettes with different optical path lengths in sequence, placing the n cuvettes with different optical path lengths in the cuvette holder 2 in order from the smallest to the largest optical path length, and using the optical fiber spectrometer 4 to correspondingly collect white light spectra passing through the n cuvettes with different optical path lengths;

[0082] In step S2, the front and rear fused quartz sheets used to assemble n cuvettes with different optical path lengths are identical, and silicone blocks of different thicknesses (equal to the optical path length) are spliced ​​in the middle.

[0083] S3: Based on the n white light spectra collected by the optical fiber spectrometer 4, the transmittance spectra of the white light passing through n different optical path cuvettes are calculated in sequence by the following formula:

[0084] T n =S n / S0;

[0085] Among them, T n is the transmittance spectrum of white light passing through the nmm pathlength cuvette, S nis the spectrum of white light passing through the nmm pathlength cuvette, S0 is the initial spectrum of white light emitted by the continuous spectrum white light source 1;

[0086] S4: based on the transmittance spectra of white light passing through n cuvettes with different optical path lengths calculated in step S3, eliminating pathological data;

[0087] Step S4 specifically includes the following steps:

[0088] S41: Based on the transmittance spectra of white light passing through n different optical pathlength cuvettes calculated in step S3, an optical pathlength array and a transmittance spectrum array are constructed:

[0089] ;

[0090] ;

[0091] in, is the optical path array, is the 1mm optical path corresponding to the 1mm optical path cuvette, is the 2mm optical path corresponding to the 2mm optical path cuvette, is the 3mm optical path corresponding to the 3mm optical path cuvette, is the nmm optical path length corresponding to the nmm optical path length cuvette, is the transmittance spectrum array, is the transmittance spectrum of white light passing through a 1mm pathlength cuvette, is the transmittance spectrum of white light passing through a 2mm pathlength cuvette, is the transmittance spectrum of white light passing through a 3mm pathlength cuvette;

[0092] S42: Based on the polyfit (polynomial fitting) function, linear programming analysis is performed on the optical path array and transmittance spectrum array to obtain the absorption coefficient:

[0093] ;

[0094] in, α is the absorption coefficient, It is an intermediate parameter obtained through linear programming analysis and has no physical meaning. Proportional to the absorbance of the wall;

[0095] Through the linear function y=αx+β , perform fitting, i.e. linear programming analysis. The fitting method used is polynomial fitting, and the function used is recorded as polyfit function (linear programming formula). The order of the linear function is 1, so the solution of parameters α and β is given by the above formula.

[0096] S43: Calculate the standard deviation of the actual transmittance spectrum and the theoretical transmittance spectrum of white light passing through the nmm pathlength cuvette by the following formula:

[0097] ;

[0098] ;

[0099] ;

[0100] in, is the wall transmittance, is the standard deviation, is the standard deviation function, is the theoretical transmittance spectrum of white light passing through the nmm pathlength cuvette, is the wall transmittance;

[0101] S44: Calculate the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of white light passing through the imm pathlength cuvette by the following formula: :

[0102] ;

[0103] in, is the theoretical transmittance spectrum of white light passing through the imm pathlength cuvette, is the actual transmittance spectrum of white light passing through the imm pathlength cuvette;

[0104] S45: If >2 , then As pathological data, the data related to the pathological data are removed from the optical path array and the transmittance spectrum array respectively, and step S5 is executed. Otherwise, replace , repeat step S44 until the calculation of the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of the white light passing through all the cuvettes with different optical path lengths is completed.

[0105] In step S45, in order to remove the pathological data, the corresponding label of the data to be judged is m , the transmission spectrum of the data to be judged is , calculate the difference between the theoretical transmittance and the actual transmittance of the data to be judged

[0106] ;

[0107] If satisfied

[0108] ;

[0109] Then the transmittance spectrum of the data to be judged is pathological data.

[0110] S5: Perform linear programming analysis on the optical path array and transmittance spectrum array after eliminating the pathological data to obtain the final wall transmittance and absorbance spectrum of the solution to be tested.

[0111] In step S5, a linear programming analysis is performed on the optical path array and the transmittance spectrum array after the pathological data are removed based on the polyfit function, and the final wall transmittance and the absorbance spectrum of the solution to be tested are obtained according to the linear programming analysis results:

[0112] ;

[0113] ;

[0114] ;

[0115] in, is the absorption coefficient after removing the ill-conditioned data, After eliminating the pathological data, the intermediate parameters obtained through linear programming analysis have no physical meaning. is the optical path array after removing the pathological data, is the transmittance spectrum array after removing the pathological data, is the final absorbance spectrum of the solution to be tested, is the final wall transmittance.

[0116] Assume that the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of white light passing through all different optical pathlength cuvettes is calculated in sequence, and only This pathological data:

[0117] ;

[0118] ;

[0119] After eliminating all pathological data, the remaining data must not be less than 3 groups. If the remaining data is less than 3 groups, the corresponding optical path difference experiment needs to be supplemented.

[0120] Linear programming analysis is performed using the data after removing all pathological data to recalculate α and β to obtain the final absorbance of a single wavelength. Wall transmittance Repeat the same steps for all wavelengths to obtain the corresponding absorbance spectrum. and wall transmittance spectrum .

[0121] In step S2, taking the assembly of a 1mm optical path cuvette as an example, the specific steps are as follows: take a 1mm thick silica gel block 31 with a liquid groove 32 and align and stack it with a fused quartz sheet 33, and press it to expel the interface air; use a burette to drip about 160μL of solution into the liquid groove 32 of the silica gel block 31; gently align one side of another fused quartz sheet 33 with the silica gel block 31, slowly tilt it until it fits with the upper surface of the silica gel block 31, and press it again to expel the interface air. If there is leakage after assembly, use clean paper to gently absorb it, and be careful not to touch the optical surface. At this time, the 1mm optical path cuvette has a certain degree of airtightness. If it is not strong enough, you can also use plastic wrap to tie the upper and lower ends of the cuvette.

[0122] Place different optical path cuvettes in the cuvette holder 2 in sequence, and cover the cuvette holder 2 with a lid. After the test is completed, disassemble the 1mm optical path cuvette. The specific steps of disassembly are as follows: first, place the 1mm optical path cuvette horizontally on the table of the fume hood, gently lift up the fused quartz sheet 33 on the top and clamp it, and immerse the fused quartz sheet 33 in a cleaning solution such as distilled water, ethanol, acetone, etc. according to the mutual solubility of the solution and the solvent, and shake or ultrasonicate for 2 minutes until its optical surface is clean, and then dry the cleaning solution residue. Discard the remaining solution and silica gel sheet, and clean another fused quartz sheet 33 according to the above steps; repeat the above steps of assembling the cuvette to assemble the 3mm optical path cuvette. Repeat the white light spectrum test, transmittance spectrum calculation, and disassembly steps multiple times to change the optical path and perform transmittance test; for example, obtain the sample transmittance spectrum T1 of 1mm optical path, the sample transmittance spectrum T2 of 3mm optical path, and the sample transmittance spectrum T3 of 5mm optical path; enter the data processing step to solve the absorbance spectra A1, A2, A3 and the wall transmittance spectrum T cuv (referring to the reference transmittance under the influence of absorption and scattering of two quartz plates). Among them, the wall transmittance T cuv It can be used for subsequent experiments. The specific steps are as follows: assemble according to the above steps for assembling the cuvette n mm optical path cuvette, the two fused quartz plates 33 used are the same as in the previous experiment. Measure the transmittance spectrum T of the solution to be tested n , then the corresponding absorbance spectrum A n =T n / T cuv ; The corresponding absorption coefficient spectrum α n =-ln(A n ) / n , unit: mm -1 .

[0123] The data processing steps involved in the present invention mainly include two parts: pathological data elimination and linear programming analysis. The elimination of pathological data refers to the situation that the transmittance of some wavelengths is less than 0 or greater than 1, or the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of a single corresponding optical path is greater than twice the standard deviation of the theoretical transmittance spectrum fitted by other data. Specific factors may include: a certain band of continuous spectrum white light is contaminated by foreign matter such as dust in the optical path and undergoes a sudden change; some insoluble particles in the solution to be tested happen to be in the optical path in a certain test, etc. Pathological data with transmittance less than 0 or greater than 1 should be eliminated before calculation. If the experiment cannot be repeated to obtain reliable data due to the low signal-to-noise ratio, the data of the wavelength should be deleted or interpolated; for the situation that the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of a single corresponding optical path is greater than twice the standard deviation of the theoretical transmittance spectrum fitted by other data, it should be eliminated during the linear programming analysis process.

[0124] Solve the absorbance spectrum based on Beer-Lambert's law:

[0125] ;

[0126] in, For the light path.

[0127] If the influence of the optical properties of the wall (such as reflectivity, absorbance, and scattering rate) is taken into account, the actual transmittance can be expressed as

[0128]

[0129] Taking the logarithm of both sides, we have

[0130]

[0131] This formula has the form of a linear equation, so it can be reversed to solve for T cuv In order to obtain the absorbance spectrum, it is necessary to calculate each specific wavelength λ separately.

[0132] like Fig. 9 As shown, the transmittance spectra of CdSe quantum dots-toluene solution at different optical path lengths are compared. As the optical path length increases, the transmittance gradually decreases.

[0133] The calculated absorbance spectrum is as follows Fig.10 As shown, from a physical point of view, the absorption coefficient spectrum Relative to the absorbance spectrum More essentially (intrinsic, this parameter is not easily affected by parameters other than the system (material properties) and represents some intrinsic properties of the material), the absorbance spectrum can be calculated from the absorption coefficient spectrum, that is, . Fig.10The lower right corner is due to the fact that the transmittance spectrum of white light has pathological data with a transmittance greater than 1. After using the above-mentioned elimination method, it is found that the pathological data here is caused by the corresponding wavelength light source signal being too weak. Therefore, the corresponding experiment cannot be supplemented, resulting in the loss of corresponding data.

[0134] Fig.11 The transmittance of the two fused quartz slices is affected by the wall, including factors such as interface reflection and the absorption rate of the wall itself. It can be seen that the total transmittance of the two fused quartz slices is close to 87%. Since the two fused quartz slices are from the same batch and have the same specifications, it can be inferred that the wall transmittance of a single fused quartz slice is >90% (square root of the total transmittance).

[0135] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0136] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A solution absorbance spectrum measuring device, characterized in that: It includes a continuous spectrum white light source, a cuvette holder, a variable optical path assembly cuvette, a fiber optic spectrometer and a host computer, wherein: The variable optical pathlength assembled cuvette is built with a solution to be tested, and the variable optical pathlength assembled cuvette is arranged in the cuvette holder. The white light emitted by the continuous spectrum white light source passes through the solution to be tested and then enters the fiber optic spectrometer. The fiber optic spectrometer is connected to the host computer. The fiber optic spectrometer collects the spectrum of the white light under the control of the host computer, and the host computer calculates the absorbance spectrum of the solution to be tested according to the spectrum. The variable optical path assembly cuvette comprises two fused quartz sheets and a silica gel component, wherein the two fused quartz sheets are arranged on both sides of the silica gel component to prevent the solution to be tested placed in the silica gel component from flowing out; The silica gel component comprises at least one silica gel block, a liquid tank is arranged at the center of the silica gel block, and the liquid tank is used to place the solution to be tested.

2. The solution absorbance spectrum measuring device according to claim 1, characterized in that: The hardness of the silica gel block is greater than 70HA, the thickness of the silica gel block is 1mm, and the transmittance of the fused quartz sheet in the wavelength range of 400nm-1100nm is higher than 90%.

3. The solution absorbance spectrum measuring device according to claim 1, characterized in that: The host computer includes a computer.

4. A method for measuring a solution absorbance spectrum, implemented using the solution absorbance spectrum measuring device according to claim 2 or 3, characterized in that: The specific steps include: S1: Build a solution absorbance spectrum measurement device; S2: assembling n cuvettes with different optical path lengths in sequence, placing the n cuvettes with different optical path lengths in the cuvette holder in order from the smallest to the largest optical path length, and using the fiber optic spectrometer to collect white light spectra passing through the n cuvettes with different optical path lengths; S3: based on the n white light spectra collected by the fiber optic spectrometer, sequentially calculating the transmittance spectra of white light passing through n cuvettes with different optical path lengths; S4: based on the transmittance spectra of white light passing through n cuvettes with different optical path lengths calculated in step S3, eliminating pathological data; S5: Perform linear programming analysis on the optical path array and transmittance spectrum array after eliminating the pathological data to obtain the final wall transmittance and absorbance spectrum of the solution to be tested.

5. The method for measuring the absorbance spectrum of a solution according to claim 4, characterized in that: Before performing step S1, the continuous spectrum white light source is preheated, and the fiber optic spectrometer is controlled by a host computer so that the fiber optic spectrometer collects an initial spectrum of white light emitted by the continuous spectrum white light source.

6. The method for measuring the absorbance spectrum of a solution according to claim 4, characterized in that: In step S3, the calculation formula of the transmittance spectrum of white light passing through n different optical path cuvettes is: T n =S n / S0; Among them, T n is the transmittance spectrum of white light passing through the nmm pathlength cuvette, S n is the spectrum of white light passing through the nmm optical pathlength cuvette, and S0 is the initial spectrum of white light emitted by the continuous spectrum white light source.

7. The method for measuring the absorbance spectrum of a solution according to claim 4, characterized in that: The step S4 specifically includes the following steps: S41: Based on the transmittance spectra of white light passing through n different optical pathlength cuvettes calculated in step S3, an optical pathlength array and a transmittance spectrum array are constructed: ； ； in, is the optical path array, is the 1mm optical path corresponding to the 1mm optical path cuvette, is the 2mm optical path corresponding to the 2mm optical path cuvette, is the 3mm optical path corresponding to the 3mm optical path cuvette, is the nmm optical path length corresponding to the nmm optical path length cuvette, is the transmittance spectrum array, is the transmittance spectrum of white light passing through a 1mm pathlength cuvette, is the transmittance spectrum of white light passing through a 2mm pathlength cuvette, is the transmittance spectrum of white light passing through a 3mm pathlength cuvette; S42: Based on the polyfit function, linear programming analysis is performed on the optical path array and transmittance spectrum array to obtain the absorption coefficient: ； in, α is the absorption coefficient, It is an intermediate parameter obtained through linear programming analysis and has no physical meaning; S43: Calculate the standard deviation of the actual transmittance spectrum and the theoretical transmittance spectrum of white light passing through the nmm pathlength cuvette by the following formula: ； ； ； in, is the wall transmittance, is the standard deviation, is the standard deviation function, is the theoretical transmittance spectrum of white light passing through the nmm pathlength cuvette, is the wall transmittance; S44: Calculate the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of white light passing through the imm pathlength cuvette by the following formula: : ； in, is the theoretical transmittance spectrum of white light passing through the imm pathlength cuvette, is the actual transmittance spectrum of white light passing through the imm pathlength cuvette; S45: If >2 , then As pathological data, the data related to the pathological data are removed from the optical path array and the transmittance spectrum array respectively, and step S5 is executed. Otherwise, replace , repeat step S44 until the calculation of the difference between the actual transmittance spectrum and the theoretical transmittance spectrum of the white light passing through all the cuvettes with different optical path lengths is completed.

8. The method for measuring the absorbance spectrum of a solution according to claim 7, characterized in that: In step S5, a linear programming analysis is performed on the optical path array and the transmittance spectrum array after the pathological data are removed based on the polyfit function, and the final wall transmittance and the absorbance spectrum of the solution to be tested are obtained according to the linear programming analysis results: ； ； ； in, is the absorption coefficient after removing the ill-conditioned data, After eliminating the pathological data, the intermediate parameters obtained through linear programming analysis have no physical meaning. is the optical path array after removing the pathological data, is the transmittance spectrum array after removing the pathological data, is the final absorbance spectrum of the solution to be tested, is the final wall transmittance.

Images