Terahertz time-domain attenuated total reflection method-based solvent water content detection system and method

Abstract

The application discloses a terahertz time-domain attenuated total reflection method solvent water content detection system and method, relates to the online detection field of solvent water content by means of terahertz time-domain spectroscopy technology, and comprises a terahertz time-domain detection device for emitting a terahertz signal to an ATR sensor module, receiving a terahertz total reflection signal emitted from the ATR sensor module, and transmitting the terahertz total reflection signal to a data processing terminal; a first ATR sensor module for receiving a sample solvent to be detected and performing total reflection on the terahertz signal by means of the sample solvent to be detected; a second ATR sensor module for performing total reflection on the terahertz signal by means of a standard sample solvent; a sample solvent online liquid taking device for controlling the sample solvent to be detected to flow through the first ATR sensor module; and a data processing terminal for calculating the water content of the sample solvent to be detected according to the terahertz total reflection signal. The application can perform online nondestructive detection on the water content of a solvent.

Description

Technical Field

[0001] This invention relates to the field of online detection of solvent water content using terahertz time-domain spectroscopy, and particularly to a solvent water content detection system and method based on terahertz time-domain attenuated total reflectance method. Background Technology

[0002] With the development of modern fine chemical industries, higher demands are placed on the accurate detection and control of solvent water content. Researching online rapid detection methods for solvent water content and exploring the optical parameter characteristics and inversion laws of solvent water content under terahertz attenuated total internal reflection time-domain spectroscopy is of significant industrial application value for real-time detection and accurate measurement and control of solvent water content. Solvent water content detection methods have always been a hot research topic in the field of industrial testing both domestically and internationally. Summary of the Invention

[0003] The purpose of this invention is to provide a solvent water content detection system and method based on terahertz time-domain decay total internal reflection method. By detecting the correspondence between the sample solvent water content and its optical parameters at a preset concentration gradient, the solvent to be tested is sampled online using an online sample solvent sampling device, enabling online non-destructive detection of the solvent water content.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A solvent water content detection system based on terahertz time-domain attenuated total reflection method, the system comprising a terahertz time-domain detection device, an ATR sensor module, an online sample solvent sampling device, and a data processing terminal;

[0006] The terahertz time-domain detection device is connected to the ATR sensor module and the data processing terminal respectively; the terahertz time-domain detection device is used to transmit terahertz signals to the ATR sensor module and receive terahertz total internal reflection signals emitted from the ATR sensor module, and is also used to transmit the terahertz total internal reflection signals to the data processing terminal.

[0007] The ATR sensor module includes a first ATR sensor module and a second ATR sensor module;

[0008] The first ATR sensor module is connected to the online sample solvent sampling device; the first ATR sensor module is used to receive the sample solvent to be tested delivered by the online sample solvent sampling device, and to use the sample solvent to be tested to perform total reflection of the terahertz signal;

[0009] The second ATR sensor module is used to perform total internal reflection of the terahertz signal using a standard sample solvent;

[0010] The online sample solvent sampling device is used to control the flow of the sample solvent to be tested through the first ATR sensor module;

[0011] The data processing terminal is used to calculate the water content of the solvent in the sample to be tested based on the terahertz total reflection signal.

[0012] Optionally, the online sample solvent extraction device includes a peristaltic pump, an input pipeline, and an output pipeline;

[0013] The peristaltic pump is installed in the input pipeline or the output pipeline; the peristaltic pump is used to control the flow of the solvent of the sample to be tested through the first ATR sensor module;

[0014] One end of the input line is connected to the solvent of the sample to be tested; the other end of the input line is connected to the sample inlet of the first ATR sensor module; the solvent of the sample to be tested flows into the first ATR sensor module through the input line;

[0015] One end of the output pipeline is connected to the solvent of the sample to be tested; the other end of the output pipeline is connected to the sample outlet of the first ATR sensor module; the solvent of the sample to be tested flows out of the first ATR sensor module through the output pipeline;

[0016] Optionally, the ATR sensor module includes a sample chamber, a sample inlet, a sample outlet, a sample cavity, and a silicon prism;

[0017] The reflecting surface of the silicon prism is the bottom surface of the sample chamber;

[0018] The bottom surface of the sample chamber is in contact with the reflective surface of the silicon prism; the sample chamber is provided with a sample inlet and a sample outlet; the sample solvent flows into the sample chamber through the sample inlet; the sample solvent flows out of the sample chamber through the sample outlet;

[0019] The terahertz signal is incident on the incident surface of the silicon prism and reflected by the reflecting surface of the silicon prism to obtain the terahertz total internal reflection signal; the terahertz total internal reflection signal is emitted from the exit surface of the silicon prism.

[0020] Optionally, the optical parameters of the ATR sensor module satisfy:

[0021]

[0022] Where θ1 is the incident angle of the terahertz wave on the reflecting surface of the ATR sensor, n1 is the refractive index of the ATR sensor medium, and n2 is the maximum refractive index of the solvent of the sample to be detected.

[0023] Optionally, the apex angle of the silicon prism is 51.6°.

[0024] Optionally, the refractive index of the silicon prism is 3.42.

[0025] A method for detecting solvent water content based on terahertz time-domain attenuated total reflectance method, applied to the aforementioned terahertz time-domain attenuated total reflectance method solvent water content detection system, the method comprising:

[0026] A multiple linear regression model is used to obtain the water content of the sample solvent; the output of the multiple linear regression model is the water content of the sample solvent; the inputs of the multiple linear regression model are the change in the absorption coefficient of the sample solvent and the change in the refractive index of the sample solvent.

[0027] The third terahertz total reflection signal of the sample solvent to be tested is obtained to obtain the first terahertz time-domain sample signal.

[0028] The fourth terahertz total reflection signal, obtained by total reflection of the terahertz signal by the standard sample solvent, is used to obtain the second terahertz time-domain sample signal.

[0029] The transfer function of the first ATR sensor module is determined based on the terahertz time-domain reference signal and the first terahertz time-domain sample signal.

[0030] The transfer function of the second ATR sensor module is determined based on the terahertz time-domain reference signal and the second terahertz time-domain sample signal.

[0031] Based on the transfer function of the first ATR sensor module, the Fresnel equation is applied to obtain the total reflection coefficient and dielectric constant of the solvent of the sample to be detected;

[0032] Based on the transfer function of the second ATR sensor module, the Fresnel equation is applied to obtain the total reflection coefficient and dielectric constant of the standard sample solvent;

[0033] The refractive index and absorption coefficient of the solvent in the sample to be tested are determined based on the total reflection coefficient and dielectric constant of the solvent in the sample to be tested.

[0034] Based on the total reflection coefficient and dielectric constant of the standard sample solvent, determine the refractive index and absorption coefficient of the standard sample solvent;

[0035] The changes in refractive index and absorption coefficient are determined based on the refractive index and absorption coefficient of the solvent in the standard sample and the solvent in the sample to be tested.

[0036] Based on the changes in refractive index and absorption coefficient, the water content of the solvent in the standard sample is determined using the multiple linear regression model.

[0037] Optionally, the multiple linear regression model for obtaining the water content of the sample solvent specifically includes:

[0038] The first terahertz total internal reflection signal of the ATR sensor module in a solvent-free state is obtained to obtain the terahertz time-domain reference signal;

[0039] Second terahertz total reflection signals of terahertz signals were obtained by total reflection of terahertz signals by sample solvents of different concentrations, thus obtaining terahertz time-domain signals of sample solvents of different concentrations;

[0040] Based on the terahertz time-domain signals of the sample solvents at different concentrations and the terahertz time-domain reference signal, the transfer function of the ATR sensor module corresponding to the sample solvents at different concentrations is obtained;

[0041] Based on the transfer function of the ATR sensor module corresponding to the sample solvent of different concentrations, the total reflection coefficient and dielectric constant of the sample solvent of different concentrations are calculated by applying the Fresnel equation.

[0042] Based on the total reflection coefficient and dielectric constant of the solvent samples with different concentrations, determine the changes in refractive index and absorption coefficient.

[0043] Principal component analysis is performed on the changes in refractive index and absorption coefficient to determine the changes in refractive index and absorption coefficient with cumulative contributions exceeding a set threshold, thereby obtaining the final changes in refractive index and absorption coefficient.

[0044] Based on the changes in the final refractive index and the final absorption coefficient, the water content of the solvent at different concentrations in the samples is inverted using multiple linear regression, resulting in a multiple linear regression model.

[0045] Optionally, performing principal component analysis on the refractive index change and the absorption coefficient change to determine the refractive index change and absorption coefficient change whose cumulative contribution exceeds a set threshold, and obtaining the final refractive index change and the final absorption coefficient change, specifically includes:

[0046] Principal component analysis is performed on the change in refractive index and the change in absorption coefficient to determine the covariance matrix of the change in refractive index and the covariance matrix of the change in absorption coefficient.

[0047] Determine the refractive index eigenvalues ​​of the covariance matrix of the refractive index change and the absorption coefficient eigenvalues ​​of the covariance matrix of the absorption coefficient change;

[0048] Arrange the refractive index eigenvalues ​​from largest to smallest to obtain a refractive index eigenvalue matrix;

[0049] Arrange the absorption coefficient eigenvalues ​​from largest to smallest to obtain the absorption coefficient eigenvalue matrix;

[0050] Based on the refractive index eigenvalue matrix, the refractive index change corresponding to the eigenvalue with a cumulative contribution rate greater than a first set threshold is determined as the final refractive index change.

[0051] Based on the absorption coefficient eigenvalue matrix, the change in absorption coefficient corresponding to the eigenvalue with a cumulative contribution rate greater than the second set threshold is determined as the final change in absorption coefficient.

[0052] Optionally, the multiple linear regression model is:

[0053] B = β0 + β1Δα + β2Δn + ε;

[0054] Where B is the output of the multiple linear regression model, β0 is the linear regression constant, β1 is the linear regression coefficient of the change in absorption coefficient, β2 is the linear regression coefficient of the change in refractive index, and ε is a random variable.

[0055] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0056] This invention enables rapid detection of water content in various solvents by selecting ATR sensor modules with different parameters; it also allows for online detection of water content in volatile solvents without affecting solvent composition through an online sample solvent extraction device; furthermore, by combining dual ATR sensor modules with the detection optical path of a terahertz time-domain detection device, reference optical parameters and changing optical parameters are obtained, and the concentration is measured using the real-time relative change of optical parameters, thus reducing the impact of system variations on the accuracy of the measurement results. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a schematic diagram of the solvent water content detection system based on the terahertz time-domain decay total reflection method of the present invention;

[0059] Figure 2 This is a schematic diagram of the ATR sensor module of the present invention;

[0060] Figure 3 This is a schematic diagram of the online liquid collection device of the present invention;

[0061] Figure 4This is a flowchart of the solvent water content detection method based on terahertz time-domain decay total reflection method of the present invention.

[0062] Symbol explanation:

[0063] 1-Femtosecond laser, 2-First beam splitter, 3-First reflector, 4-First terahertz emitter, 5-First condenser lens, 6-First ATR sensor module, 7-Peristaltic pump, 8-Solvent for sample to be tested, 9-First terahertz receiver, 10-Optical delay line, 11-Second ATR sensor module, 12-Data processing terminal, 13-Sample inlet, 14-Sample outlet, 15-Sample chamber sealing layer, 16-Sample cavity, 17-Incident surface, 18-Outlet surface, 20-Input pipeline, 21-Output pipeline, 22-Second beam splitter, 23-Second reflector, 24-Third reflector, 25-Fourth reflector, 26-Third beam splitter, 27-Fifth reflector, 28-Second terahertz emitter, 29-Second condenser lens, 30-Second terahertz receiver, 31-Sixth reflector, 32-Seventh reflector, 33-Eighth reflector, 34-Ninth reflector. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] The purpose of this invention is to provide a solvent water content detection system and method based on terahertz time-domain attenuated total internal reflection method. By detecting the correspondence between the sample solvent water content and its optical parameters at a preset concentration gradient, the system utilizes an online sample solvent sampling device to sample the solvent of the sample to be tested online, enabling online non-destructive testing of the solvent water content.

[0066] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] Example 1

[0068] like Figure 1 As shown, the present invention provides a solvent water content detection system based on terahertz time-domain attenuated total reflection method, characterized in that the system includes a terahertz time-domain detection device, an ATR sensor module, an online sample solvent sampling device, and a data processing terminal 12.

[0069] The terahertz time-domain detection device is connected to the ATR sensor module and the data processing terminal 12 respectively; the terahertz time-domain detection device is used to transmit terahertz signals to the ATR sensor module and receive terahertz total reflection signals emitted from the ATR sensor module, and is also used to transmit the terahertz total reflection signals to the data processing terminal 12.

[0070] Specifically, the terahertz time-domain detection device includes a femtosecond laser 1, a first beam splitter 2, a first reflector 3, a first terahertz emitter 4, a first focusing lens 5, a first terahertz receiver 9, a second reflector 23, a second beam splitter 22, a third reflector 24, a fourth reflector 25, a third beam splitter 26, a fifth reflector 27, a second terahertz emitter 28, a second focusing lens 29, a second terahertz receiver 30, a sixth reflector 31, a seventh reflector 32, an eighth reflector 33, and a ninth reflector 34.

[0071] The femtosecond laser 1 produces a first laser and a second laser after passing through the first beam splitter 2; the first reflector 3 and the first terahertz emitter 4 are arranged in the first laser emission path; the first laser is reflected by the first reflector 3 and then incident on the first terahertz emitter 4, causing the first terahertz emitter 4 to emit a terahertz signal; the terahertz signal is incident on the first condenser lens 5, and after exiting the first condenser lens 5, the terahertz signal is incident on the incident surface 17 of the first ATR sensor module 6, reflected by the reflecting surface of the first ATR sensor module 6, and then emitted from the exit surface 18 of the first ATR sensor module 6, resulting in a first terahertz total internal reflection signal, which is received by the first terahertz receiver 9.

[0072] The second laser beam passes through the third beam splitter 26 to obtain the third and fourth laser beams. The third laser beam is incident on the optical delay line 10 and then emitted. The emitted laser beam is incident on the second beam splitter 22 to obtain the fifth and sixth laser beams. The optical delay line 10 includes a sixth reflector 31, a seventh reflector 32, an eighth reflector 33, and a ninth reflector 34. The third laser beam is reflected sequentially by the sixth reflector 31, the seventh reflector 32, the eighth reflector 33, and the ninth reflector 34 before being emitted. The fifth laser beam is reflected by the second reflector 23 and then incident on the first terahertz receiver 9.

[0073] The fourth laser beam is incident on the fifth reflecting mirror 27, and after being reflected by the fifth reflecting mirror 27, it is incident on the second terahertz transmitter 28, causing the second terahertz transmitter 28 to emit a terahertz signal. The terahertz signal is incident on the second condenser lens 29, and after exiting the second condenser lens 29, the terahertz signal is incident on the incident surface 17 of the second ATR sensor module 11, reflected by the reflecting surface of the second ATR sensor module 11, and exited from the exit surface 18 of the second ATR sensor module 11, resulting in a second terahertz total internal reflection signal, which is received by the second terahertz receiver 30. The sixth laser beam is reflected by the third reflecting mirror 24 and then incident on the fourth reflecting mirror 25, and after being reflected by the fourth reflecting mirror 25, it is incident on the second terahertz receiver 30.

[0074] The first terahertz receiver 9 and the second terahertz receiver 30 transmit the received first terahertz total internal reflection signal and second terahertz total internal reflection signal to the data processing terminal 12.

[0075] The ATR sensor module includes a first ATR sensor module 6 and a second ATR sensor module 11. The first ATR sensor module 6 is the ATR sensor module for the sample solvent to be detected; the second ATR sensor module 11 is the ATR sensor module for the reference solvent, that is, the ATR sensor module for the standard sample solvent.

[0076] The first ATR sensor module 6 is connected to the online sample solvent sampling device; the first ATR sensor module 6 is used to receive the sample solvent 8 to be tested delivered by the online sample solvent sampling device, and to use the sample solvent 8 to be tested to perform total reflection of the terahertz signal.

[0077] The second ATR sensor module 11 is used to perform total reflection of the terahertz signal using a standard sample solvent.

[0078] The online sample solvent sampling device is used to control the flow of the sample solvent 8 to be tested through the first ATR sensor module 6.

[0079] The data processing terminal 12 is used to calculate the water content of the solvent 8 in the sample to be tested based on the terahertz total internal reflection signal. Specifically, the data processing terminal 12 is a computer. Further, the data processing terminal 12 calculates the water content of the solvent 8 in the sample to be tested based on the first terahertz total internal reflection signal and the second terahertz total internal reflection signal.

[0080] like Figure 3 As shown, the online sample solvent extraction device includes a peristaltic pump 7, an input line 20, and an output line 21. The input line 20 is the solvent inflow conduit; the output line 21 is the solvent outflow conduit.

[0081] The peristaltic pump 7 is installed in the input pipeline 20 or the output pipeline 21; the peristaltic pump 7 is used to control the flow of the solvent 8 of the sample to be tested through the first ATR sensor module 6.

[0082] One end of the input pipe 20 is connected to the solvent 8 of the sample to be tested; the other end of the input pipe 20 is connected to the sample inlet 13 of the first ATR sensor module 6; the solvent 8 of the sample to be tested flows into the first ATR sensor module 6 through the input pipe 20.

[0083] One end of the output pipe 21 is connected to the solvent 8 of the sample to be tested; the other end of the output pipe 21 is connected to the sample outlet 14 of the first ATR sensor module 6; the solvent 8 of the sample to be tested flows out of the first ATR sensor module 6 through the output pipe 21.

[0084] like Figure 2 As shown, the ATR sensor module includes a sample chamber, a sample inlet 13, a sample outlet 14, a sample cavity 16, and a silicon prism.

[0085] The reflecting surface of the silicon prism is the bottom surface of the sample chamber.

[0086] The bottom surface of the sample chamber 16 is in contact with the reflective surface of the silicon prism; the sample chamber 16 is provided with a sample inlet 13 and a sample outlet 14; the sample solvent flows into the sample chamber 16 through the sample inlet 13; the sample solvent flows out of the sample chamber 16 through the sample outlet 14. Specifically, the sample chamber 16 is located at the contact surface between the reflective surface of the ATR sensor module and the sample chamber, and the upper end of the chamber is provided with a sample inlet 13 and a sample outlet 14. The first ATR sensor module 6 uses a liquid peristaltic pump 7 to draw liquid from the ethanol solvent to be tested, and transfers the ethanol solvent into the sample chamber 16 in real time through the sample inlet 13, while simultaneously returning the ethanol solvent to be tested to the original solvent through the sample outlet 14. The second ATR sensor is used to measure the terahertz time-domain signal of a fixed high-concentration ethanol solvent (ethanol solvent standard sample solution). Set the system parameters as follows: initial scan time is 350ps, scan width is 100ps, and scan speed is 10 (0.061mm / s).

[0087] In addition, the ATR sensor module also includes a sample chamber sealing layer 15; the sample chamber sealing layer 15 and the reflective surface of the silicon prism together constitute a hollow sample chamber; the sample outlet 14 and the sample inlet 13 extend from the upper surface of the sample chamber; further, the sample chamber is a hollow cuboid space; the sample cavity 16 is a hollow cuboid space.

[0088] The terahertz signal is incident on the incident surface 17 of the silicon prism and reflected by the reflecting surface of the silicon prism to obtain the terahertz total internal reflection signal; the terahertz total internal reflection signal is emitted from the exit surface 18 of the silicon prism.

[0089] Specifically, the optical parameters of the ATR sensor module satisfy formula (1):

[0090]

[0091] Wherein, θ1 is the incident angle of the terahertz wave at the reflecting surface of the ATR sensor, n1 is the refractive index of the ATR sensor medium, and n2 is the maximum refractive index of the solvent 8 of the sample to be detected. Further, the apex angle of the silicon prism is 51.6°, and the refractive index of the silicon prism is 3.42.

[0092] This invention utilizes terahertz attenuated total internal reflection time-domain spectroscopy, which has the advantages of simple device, high detection accuracy and sensitivity. It can reflect the changes in optical parameter characteristics caused by changes in solvent water content in real time, and then, based on the relationship between the dielectric constant, refractive index and absorption coefficient of the solvent sample and the solvent water content, the real-time water content of the solvent in the sample to be tested can be obtained.

[0093] Example 2

[0094] To implement the system corresponding to Embodiment 1 above and achieve the corresponding functions and technical effects, a method for detecting solvent water content based on terahertz time-domain attenuated total internal reflection is provided below. Figure 4 As shown, the method includes:

[0095] Step S1: Obtain the multiple linear regression model for the water content of the sample solvent; the output of the multiple linear regression model is the water content of the sample solvent; the inputs of the multiple linear regression model are the change in the absorption coefficient of the sample solvent and the change in the refractive index of the sample solvent. Specifically, the multiple linear regression model is shown in formula (2):

[0096] B=β0+β1Δα+β2Δn+ε (2)

[0097] Where B is the output of the multiple linear regression model, β0 is the linear regression constant, β1 is the linear regression coefficient of the change in absorption coefficient, β2 is the linear regression coefficient of the change in refractive index, and ε is a random variable.

[0098] Furthermore, β0, β1, β2, and ε are obtained as follows:

[0099] Linear fitting was performed on Δα and Δn at different concentrations to obtain the coefficients β0, β1 and β2 of the binary linear regression model of formula (2); the solvent water content was inverted using the model of formula (2) to determine the random variable ε corresponding to Δα and Δn at different concentrations.

[0100] S1 specifically includes:

[0101] Step S11: Acquire the first terahertz total internal reflection signal of the ATR sensor module in a solvent-free state to obtain the terahertz time-domain reference signal. Specifically, set the experimental environment temperature to 23℃ and the humidity to less than 1%, and measure the terahertz time-domain reference signal E of the system in a sample-free state. reference (t).

[0102] Step S12: Obtain the second terahertz total reflection signal after total reflection of the terahertz signal by sample solvents of different concentrations, thus obtaining the terahertz time-domain signal of sample solvents of different concentrations. Specifically, the experimental environment temperature is set to 23℃ and the humidity is less than 1%, and the terahertz time-domain signal E of sample solvents with different concentration gradients is measured. sample (t).

[0103] Step S13: Based on the terahertz time-domain signals of the sample solvents of different concentrations and the terahertz time-domain reference signal, obtain the transfer function of the ATR sensor module corresponding to the sample solvents of different concentrations.

[0104] Specifically, the corresponding frequency domain signal E is obtained by performing Fast Fourier Transform on the terahertz time-domain reference signal and the sample signal that undergoes total reflection of the terahertz signal. reference (ω) and E sample (ω). The optical parameters of the ATR sensor module are extracted, and the transfer function of the ATR sensor module is obtained as shown in formula (3).

[0105]

[0106] Among them, E in (ω) represents the frequency domain signal of the terahertz wave incident on the ATR sensor module, r is the total reflection coefficient of the prism-sample interface of the ATR sensor module, and r′ is the total reflection coefficient of the prism-air interface of the ATR sensor module. The frequency domain signal E of the terahertz wave incident on the ATR sensor module is... in (ω) and the output signal of the ATR sensor module satisfy formula (4):

[0107] E out (ω)=E in (ω)r (4)

[0108] Where E out (ω) is the reference frequency domain signal E reference(ω) and the frequency domain signal E that undergoes total reflection of the terahertz signal. sample (ω).

[0109] The amplitude ρ(ω) and phase of the ATR sensor transfer function can be obtained from equation (3), as shown in equations (5) and (6).

[0110]

[0111]

[0112] Step S14: Based on the transfer function of the ATR sensor module corresponding to the sample solvent of different concentrations, apply the Fresnel equation to calculate the total reflection coefficient and dielectric constant of the sample solvent of different concentrations.

[0113] Specifically, this invention uses S-polarized terahertz waves and utilizes Fresnel's formula to obtain the calculation formula for the total reflection coefficient r, as shown in formula (7).

[0114]

[0115] Based on the prism parameters, the prism base angle θ = 51.6°, and the refractive index of the silicon prism is... (The absorption coefficient of a silicon prism is much smaller than its refractive index and can be ignored), while the refractive index of air is taken as... The total reflection coefficient of the terahertz frequency domain signal can be solved from formulas (3), (5), (6), and (7) as shown in formula (8), and the dielectric constant is shown in formula (9).

[0116] r sample =ρ(ω)e -j(φ(ω+1.73)) (8)

[0117]

[0118] Step S15: Determine the change in refractive index and the change in absorption coefficient based on the total reflection coefficient and dielectric constant of the sample solvents of different concentrations.

[0119] Based on the total reflection coefficient and dielectric constant of the sample solvents at different concentrations, the refractive index n of the sample solvent that exhibits total reflection of the terahertz signal is obtained. sample and absorption coefficient α sample The calculation formulas are shown in formulas (10) and (11):

[0120]

[0121]

[0122] Where Re(ε2) is the real part of the dielectric constant ε2, Im(ε2) is the imaginary part of the dielectric constant ε2, ω is the angular frequency corresponding to the terahertz frequency domain signal, and c is the speed of light, taken as c = 3 × 10⁻⁶. 8 m / s.

[0123] According to formulas (10) and (11), the refractive index n of the solvent of the sample to be tested is obtained. sample1 and absorption coefficient α sample1 and the refractive index n of the solvents in samples with different concentration gradients sample2 and absorption coefficient α sample2 Thus, the change in refractive index Δn of the sample can be obtained. sample and the change in absorption coefficient Δα sample As shown in formulas (12) and (13):

[0124] Δn sample =n sample1 -n sample2 (12)

[0125] Δα sample =α sample1 -α sample2 (13)

[0126] Where, n sample1 n represents the refractive index of a solvent with varying concentrations. sample2 The refractive index of the reference concentration solvent; α sample1 α is the absorption coefficient of the solvent with varying concentrations. sample2 The absorption coefficient is for a reference concentration of solvent.

[0127] Step S16: Perform principal component analysis on the refractive index change and the absorption coefficient change to determine the refractive index change and absorption coefficient change with cumulative contributions exceeding a set threshold, and obtain the final refractive index change and the final absorption coefficient change.

[0128] S16 specifically includes:

[0129] Step S161: Perform principal component analysis on the changes in refractive index and absorption coefficient to determine the covariance matrices of the changes in refractive index and absorption coefficient. Specifically, principal component analysis is used to extract key information from the spectral data to obtain a concentration-optical parameter data table. Principal component analysis is performed on the initial data of the solvent sample's refractive index and absorption coefficient in the 0.2THz-1THz band. Taking the absorption coefficient as an example, its spectral data is {Δα1,Δα2,Δα3,...,Δα...} n}, forming a sample matrix α, and standardizing each sample data as shown in formula (14):

[0130]

[0131] α(λ) represents the normalized spectral data; Δα max and Δα min These are the maximum and minimum values ​​for each sample of the spectral data. The covariance matrix of the sample matrix Δα is calculated as shown in formula (15):

[0132]

[0133] Step S162: Determine the refractive index eigenvalue of the covariance matrix of the refractive index change and the absorption coefficient eigenvalue of the covariance matrix of the absorption coefficient change.

[0134] Step S163: Arrange the refractive index eigenvalues ​​from largest to smallest to obtain a refractive index eigenvalue matrix.

[0135] Step S164: Arrange the absorption coefficient eigenvalues ​​from largest to smallest to obtain the absorption coefficient eigenvalue matrix.

[0136] Step S165: Based on the refractive index eigenvalue matrix, determine the refractive index change corresponding to the eigenvalue with a cumulative contribution rate greater than the first set threshold as the final refractive index change.

[0137] Step S166: Based on the absorption coefficient eigenvalue matrix, determine the change in absorption coefficient corresponding to the eigenvalue with a cumulative contribution rate greater than the second set threshold as the final change in absorption coefficient.

[0138] Specifically, the eigenvalues ​​of c are arranged from largest to smallest to form an eigenvalue matrix. The changes in the absorption coefficient corresponding to the first k eigenvalues ​​with a cumulative contribution rate greater than 85% are taken as the final changes in the absorption coefficient. Similarly, the final changes in refractive index can be obtained.

[0139] Step S17: Based on the final change in refractive index and the final change in absorption coefficient, the water content of the sample solvent at different concentrations is inverted using multiple linear regression to obtain a multiple linear regression model.

[0140] In practical applications, this invention utilizes high-concentration solvents and distilled water to prepare standard solvent samples with a certain concentration gradient according to the calculation formula for the water content of standard solvent samples; the calculation formula for the water content of standard solvent samples is shown in (16):

[0141]

[0142] Where V0 is the volume of the high-concentration solvent, C0% is the concentration of the high-concentration solvent, and C n % represents the concentration of the solvent to be prepared, V n To configure a concentration of C nThe volume of water required to add to a % solvent.

[0143] Furthermore, taking the online rapid detection of ethanol water content as an example, using anhydrous ethanol with a concentration higher than 99.7% and distilled water, according to the calculation formula of the water content of standard solvent samples, ethanol solvent standard sample solutions with equal concentration gradients of 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, and 10% are prepared.

[0144] In practical applications, the terahertz attenuation total internal reflection time-domain spectroscopy detection system provided by this invention is used to conduct a reference calibration experiment on the solvent-free experimental system under a constant temperature and dehumidification environment (23℃, humidity less than 1%). The reference calibration experiment method is as follows:

[0145] The ATR sensor was placed in the sample test chamber, and dry air was introduced. Once the chamber temperature stabilized at 23°C and the humidity dropped below 1%, the reference calibration experiment was initiated. The measurements were repeated 2000 times, and the average value of the obtained signals was taken as the terahertz time-domain reference signal E. reference (t).

[0146] Using the terahertz attenuation total internal reflection time-domain spectroscopy detection system provided by this invention, standard sample solvent determination experiments were conducted on standard ethanol solvents of different concentrations under a constant temperature and dehumidification environment (23℃, humidity less than 1%). The standard sample determination experimental method is as follows:

[0147] The first ATR sensor was placed inside the sample testing chamber, and dry air was introduced. Once the chamber temperature stabilized at 23°C and the humidity dropped below 1%, the standard sample determination experiment began. A peristaltic pump was started to uniformly transfer the ethanol standard solution to one ATR sensor module, while simultaneously returning it to the original solvent through sample outlet 14. Online detection was performed on the flowing standard ethanol solvent at each concentration. Each concentration of standard ethanol solvent was measured 2000 times, and the average value of the obtained signals was taken to obtain the terahertz time-domain sample signal E for each concentration of standard ethanol solvent. sample (t).

[0148] Based on the terahertz time-domain reference signal E reference (t) and terahertz time-domain sample signal E sample (t) is used to obtain the ATR sensor transfer function corresponding to different concentrations of standard ethanol solvent, and then to obtain the multiple linear regression model of water content of standard ethanol solvent at different concentrations.

[0149] Step S2: Obtain the third terahertz total reflection signal of the terahertz signal by the solvent of the sample to be tested, and obtain the first terahertz time-domain sample signal.

[0150] Step S3: Obtain the fourth terahertz total reflection signal by total reflection of the terahertz signal by the standard sample solvent, and obtain the second terahertz time-domain sample signal.

[0151] In one specific implementation, the band frequency of the first terahertz time-domain sample signal and the band frequency of the second terahertz time-domain sample signal are both 0.2THz-1THz.

[0152] Step S4: Determine the transfer function of the first ATR sensor module based on the terahertz time-domain reference signal and the first terahertz time-domain sample signal.

[0153] Step S5: Determine the transfer function of the second ATR sensor module based on the terahertz time-domain reference signal and the second terahertz time-domain sample signal.

[0154] Step S6: Based on the transfer function of the first ATR sensor module, apply the Fresnel equation to obtain the total reflection coefficient and dielectric constant of the solvent of the sample to be detected.

[0155] Step S7: Based on the transfer function of the second ATR sensor module, apply the Fresnel equation to obtain the total reflection coefficient and dielectric constant of the standard sample solvent.

[0156] Step S8: Determine the refractive index and absorption coefficient of the solvent of the sample to be tested based on the total reflection coefficient and dielectric constant of the solvent of the sample to be tested.

[0157] Step S9: Determine the refractive index and absorption coefficient of the standard sample solvent based on the total reflection coefficient and dielectric constant of the standard sample solvent.

[0158] Step S10: Determine the change in refractive index and the change in absorption coefficient based on the refractive index and absorption coefficient of the solvent in the standard sample and the solvent in the sample to be tested. Specifically, the change in refractive index is the refractive index of the solvent in the sample to be tested minus the refractive index of the solvent in the standard sample; the change in absorption coefficient is the absorption coefficient of the solvent in the sample to be tested minus the absorption coefficient of the solvent in the standard sample.

[0159] Step S11: Based on the change in refractive index and the change in absorption coefficient, the water content of the solvent in the sample to be tested is determined using the multiple linear regression model.

[0160] Specifically, the change in refractive index and the change in absorption coefficient are input into a multiple linear regression model of the water content of standard ethanol solvents at different concentrations to obtain the water content of the solvent in the sample to be tested.

[0161] Compared with the prior art, the advantages of the present invention are as follows:

[0162] 1. This invention can achieve non-destructive online rapid detection of solvent water content. By selecting ATR sensor modules with different parameters, rapid detection of water content in various solvents can be achieved.

[0163] 2. The solvent water content detection method provided by the present invention, through a peristaltic pump online sampling device, can achieve rapid online detection of the water content of volatile solvents without affecting the solvent composition.

[0164] 3. This invention combines a dual ATR sensor module with a single probe optical path. By acquiring reference optical parameters and changing optical parameters, it innovatively uses the real-time relative change of optical parameters to measure concentration, which can reduce the impact of system variation factors on the accuracy of measurement results.

[0165] 4. This invention is based on a terahertz time-domain spectroscopy system and uses attenuated total reflection technology to obtain the real-time spectrum of solvent water content, acquire relevant optical parameters of solvent water content, and combine principal component analysis and multiple linear regression algorithm to achieve non-destructive online rapid detection of solvent water content.

[0166] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0167] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A solvent water content detection system based on terahertz time-domain decay total internal reflection method, characterized in that, The system includes a terahertz time-domain detection device, an ATR sensor module, an online sample solvent extraction device, and a data processing terminal. The terahertz time-domain detection device is connected to the ATR sensor module and the data processing terminal respectively; the terahertz time-domain detection device is used to transmit terahertz signals to the ATR sensor module and receive terahertz total internal reflection signals emitted from the ATR sensor module, and is also used to transmit the terahertz total internal reflection signals to the data processing terminal. The ATR sensor module includes a first ATR sensor module and a second ATR sensor module; The ATR sensor module includes a sample chamber, a sample inlet, a sample outlet, a sample volume chamber, and a silicon prism; The reflecting surface of the silicon prism is the bottom surface of the sample chamber; The bottom surface of the sample chamber is in contact with the reflective surface of the silicon prism; the sample chamber is provided with a sample inlet and a sample outlet; the sample solvent flows into the sample chamber through the sample inlet; the sample solvent flows out of the sample chamber through the sample outlet; The terahertz signal is incident on the incident surface of the silicon prism and reflected by the reflecting surface of the silicon prism to obtain the terahertz total internal reflection signal; the terahertz total internal reflection signal is emitted from the exit surface of the silicon prism. The optical parameters of the ATR sensor module satisfy: ； in, The angle of incidence of the terahertz wave on the reflecting surface of the ATR sensor is given. The refractive index of the ATR sensor medium. The maximum refractive index of the solvent in the sample to be tested; The apex angle of the silicon prism is 51.6°. The first ATR sensor module is connected to the online sample solvent sampling device; the first ATR sensor module is used to receive the sample solvent to be tested delivered by the online sample solvent sampling device, and to use the sample solvent to be tested to perform total reflection of the terahertz signal; The second ATR sensor module is used to perform total internal reflection of the terahertz signal using a standard sample solvent; The online sample solvent sampling device is used to control the flow of the sample solvent to be tested through the first ATR sensor module; The data processing terminal is used to calculate the water content of the solvent in the sample to be tested based on the terahertz total reflection signal.

2. The solvent water content detection system based on terahertz time-domain attenuated total internal reflection method according to claim 1, characterized in that, The online sample solvent extraction device includes a peristaltic pump, an input pipeline, and an output pipeline; The peristaltic pump is installed in the input pipeline or the output pipeline; the peristaltic pump is used to control the flow of the solvent of the sample to be tested through the first ATR sensor module; One end of the input line is connected to the solvent of the sample to be tested; the other end of the input line is connected to the sample inlet of the first ATR sensor module; the solvent of the sample to be tested flows into the first ATR sensor module through the input line; One end of the output pipeline is connected to the solvent of the sample to be tested; the other end of the output pipeline is connected to the sample outlet of the first ATR sensor module; the solvent of the sample to be tested flows out of the first ATR sensor module through the output pipeline.

3. The solvent water content detection system based on terahertz time-domain decay total internal reflection method according to claim 1, characterized in that, The refractive index of the silicon prism is 3.

42.

4. A method for detecting solvent water content based on terahertz time-domain decaying total internal reflection method, applied to the solvent water content detection system based on terahertz time-domain decaying total internal reflection method as described in any one of claims 1-3, characterized in that, The method includes: A multiple linear regression model for obtaining the water content of the sample solvent is specifically included: acquiring the first terahertz total internal reflection signal of the ATR sensor module in a solvent-free state to obtain a terahertz time-domain reference signal; acquiring the second terahertz total internal reflection signals of the terahertz signal by sample solvents of different concentrations to obtain terahertz time-domain signals of sample solvents of different concentrations; obtaining the transfer function of the ATR sensor module corresponding to the sample solvents of different concentrations based on the terahertz time-domain signals of the sample solvents of different concentrations and the terahertz time-domain reference signal; and calculating the total internal reflection coefficient and dielectric constant of the sample solvents of different concentrations based on the transfer function of the ATR sensor module corresponding to the sample solvents of different concentrations using the Fresnel equation. Based on the total reflection coefficient and dielectric constant of the sample solvents at different concentrations, the changes in refractive index and absorption coefficient are determined. Principal component analysis is performed on these changes to identify those with cumulative contributions exceeding a set threshold, yielding the final changes in refractive index and absorption coefficient. Based on these final changes in refractive index and absorption coefficient, the water content of the sample solvents at different concentrations is inverted using multiple linear regression, resulting in a multiple linear regression model. The output of the multiple linear regression model is the water content of the sample solvent; the inputs to the multiple linear regression model are the changes in the absorption coefficient and refractive index of the sample solvent. The third terahertz total reflection signal of the sample solvent to be tested is obtained to obtain the first terahertz time-domain sample signal. The fourth terahertz total reflection signal, obtained by total reflection of the terahertz signal by the standard sample solvent, is used to obtain the second terahertz time-domain sample signal. The transfer function of the first ATR sensor module is determined based on the terahertz time-domain reference signal and the first terahertz time-domain sample signal. The transfer function of the second ATR sensor module is determined based on the terahertz time-domain reference signal and the second terahertz time-domain sample signal. Based on the transfer function of the first ATR sensor module, the Fresnel equation is applied to obtain the total reflection coefficient and dielectric constant of the solvent of the sample to be detected; Based on the transfer function of the second ATR sensor module, the Fresnel equation is applied to obtain the total reflection coefficient and dielectric constant of the standard sample solvent; The refractive index and absorption coefficient of the solvent in the sample to be tested are determined based on the total reflection coefficient and dielectric constant of the solvent in the sample to be tested. Based on the total reflection coefficient and dielectric constant of the standard sample solvent, determine the refractive index and absorption coefficient of the standard sample solvent; The changes in refractive index and absorption coefficient are determined based on the refractive index and absorption coefficient of the solvent in the standard sample and the solvent in the sample to be tested. Based on the change in refractive index and the change in absorption coefficient, the water content of the solvent in the sample to be tested is determined using the multiple linear regression model.

5. The method for detecting solvent water content based on terahertz time-domain decay total internal reflection method according to claim 4, characterized in that, The step of performing principal component analysis on the refractive index change and the absorption coefficient change to determine the refractive index change and absorption coefficient change whose cumulative contribution exceeds a set threshold, and obtaining the final refractive index change and the final absorption coefficient change, specifically includes: Principal component analysis is performed on the change in refractive index and the change in absorption coefficient to determine the covariance matrix of the change in refractive index and the covariance matrix of the change in absorption coefficient. Determine the refractive index eigenvalues ​​of the covariance matrix of the refractive index change and the absorption coefficient eigenvalues ​​of the covariance matrix of the absorption coefficient change; Arrange the refractive index eigenvalues ​​from largest to smallest to obtain a refractive index eigenvalue matrix; Arrange the absorption coefficient eigenvalues ​​from largest to smallest to obtain the absorption coefficient eigenvalue matrix; Based on the refractive index eigenvalue matrix, the refractive index change corresponding to the eigenvalue with a cumulative contribution rate greater than a first set threshold is determined as the final refractive index change. Based on the absorption coefficient eigenvalue matrix, the change in absorption coefficient corresponding to the eigenvalue with a cumulative contribution rate greater than the second set threshold is determined as the final change in absorption coefficient.

6. The method for detecting solvent water content based on terahertz time-domain attenuated total internal reflection method according to claim 4, characterized in that, The multiple linear regression model is as follows: ； in, B This is the output of the multiple linear regression model. The linear regression constant is... The linear regression coefficient represents the change in the absorption coefficient. The linear regression coefficients for the change in refractive index are... It is a random variable.

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