A method for rapid detection of nutrient content in high-nitrogen fertilizers with enhanced efficacy

Abstract

This invention relates to the field of solution physicochemical testing technology and discloses a method for rapid detection of nutrient content in high-nitrogen fertilizers with enhanced efficiency. The method includes: acquiring the attenuated total reflectance infrared spectrum of the undiluted stock solution to construct an absorbance curve; reading the initial transmittance voltage value; calculating the first-order time derivative to extract the rate of change parameter and adjusting the time window span based on the voltage drift; calculating the second-order time derivative and correcting the parameter based on zero-point cross-triggered filtering and determining the slope abrupt change point value; inputting the corrected parameter and voltage value into an inversion formula to calculate and output the total nitrogen nutrient content. This invention separates overlapping spectra through non-equilibrium dipole polarization temporal differences, eliminates nonlinear saturation, smooths out scattering interference from incompletely dissolved particles, and improves detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of solution physicochemical testing technology, and particularly relates to a method for rapid detection of nutrient content in high-nitrogen fertilizers with enhanced efficacy. Background Technology

[0002] Current methods for detecting nutrients in high-nitrogen fertilizers employ solution spectral analysis based on spectroscopic absorption characteristics. This method utilizes monochromatic probe light of a specific wavelength to penetrate the fertilizer solution sample, and a detector collects light intensity attenuation data within characteristic spectral bands to determine the mass fraction of major nutrient elements. Soluble inorganic nutrient molecules and polymeric complexes, under continuous photon energy field driving, generate dipole polarization dynamics responses with time-scale differences. Low-molecular-weight nutrient salts exhibit rapid transient polarization equilibrium deflection under a specific radiation energy field. Meanwhile, organic polymeric regulators or long-chain nitrogen-stabilizing components with large steric hindrance in the substrate exhibit significant polarization lag in the initial stage of the radiation response. This difference in physical properties provides a molecular dynamics theoretical basis for distinguishing spatially overlapping spectra. Rapid on-site measurement requires direct injection of fertilizer solution samples. This undiluted condition faces dual interference from the high-concentration solute environment and the spatial overlap of macromolecular background spectra. Conventional techniques employ static spectral baseline subtraction or increasing the radiation intensity of the probe light source to attempt to eliminate background absorption bias.

[0003] In undiluted fertilizer solutions with a total nitrogen concentration greater than 10 g / L, the photon transmission path is blocked over a large area by high-density particles, resulting in strong nonlinear saturation characteristics at the photoelectric conversion receiver. Simultaneously, the broadband characteristic absorption peaks generated by the macromolecular resin and added chemical inhibitors in the substrate exhibit nonlinear multidimensional spatial overlap with the target nutrient spectrum, making it impossible for steady-state differential subtraction methods to separate the target nutrient signal. Furthermore, forced linear subtraction can introduce uncontrollable systematic errors. In addition, the drastic temperature fluctuations between 10℃ and 40℃ during field testing directly cause dynamic drift in the absorption spectrum due to changes in molecular thermal motion, leading to a complete loss of compensation capability for fixed-parameter spectral correction models. The spectroscopic detection hardware faces saturation challenges in the physical sample introduction path, and existing spectral modeling and calculation methods are insufficient in handling large-scale... The same principle-based shortcomings exist in field or online operating conditions. For example, Chinese invention patent application CN106198447A discloses a non-destructive quantitative detection method for the main components of compound fertilizer based on near-infrared spectroscopy. This method relies on static measurement of the sample by grinding it into a powder and establishing a fixed parameter correction model through a multiple regression algorithm. Conventional chemometric quantitative modeling implicitly relies on the underlying objective attributes of uniform sample state and constant detection environment. However, the actual operating conditions of rapid field testing are complex liquid phase systems with high concentrations, containing incompletely dissolved particles, and experiencing drastic temperature fluctuations. Dynamic light scattering in the liquid phase, channel nonlinear saturation caused by high solute levels, and molecular polarization rate shifts due to temperature drift cause the regression equations established based on solid or static characteristics to mismatch, making it impossible to adaptively offset dynamic environmental disturbances and leading to quantitative inversion distortion.

[0004] Therefore, the technical problem to be solved by this invention is how to achieve dynamic feature decoupling of multidimensional spatial overlapping spectra in a channel saturation environment of high-concentration stock solution undiluted injection, and adaptively offset the influence of environmental temperature disturbances on spectral physical properties. Summary of the Invention

[0005] The present invention aims to solve the problems of channel saturation and multidimensional spatial overlapping spectral interference in the undiluted injection state of high-concentration stock solutions.

[0006] In this technical solution, a method for rapid detection of nutrient content in enhanced high-nitrogen fertilizer includes the following steps: Step S1: In situ, the light intensity variation data of undiluted high-nitrogen fertilizer stock solution under dynamic attenuation total reflectance infrared spectrum is collected using spectrophotometer hardware to construct an absorbance time series curve. Step S2: Use a microprocessor to read the initial transmittance intrinsic voltage value of the enhanced high-nitrogen fertilizer stock solution at the initial moment of contact with the spectrophotometer detection hardware. Step S3: The microprocessor calculates the first-order time derivative of the absorbance time series curve to obtain the rate of change characteristic parameter, and dynamically adjusts the sliding time window span of the first-order time derivative according to the monotonic drift of the initial intrinsic voltage value of transmittance as the dynamic input boundary for subsequent filtering. Step S4: The microprocessor calculates the second-order time derivative of the absorbance time series curve to obtain discrete acceleration characteristics. When the frequent crossover of the zeros of the second-order time derivative is captured, the discretization step filter instruction is triggered. The high-frequency noise components exceeding the fixed fluctuation variance threshold in the rate of change characteristic parameter are filtered out by the sliding window averaging method to determine the value of the dynamic slope change point. In step S5, the microprocessor inputs the corrected rate of change characteristic parameter and the initial transmittance intrinsic voltage value into the stored inversion quantitative relationship, calculates and outputs the total nitrogen nutrient content in the enhanced high-nitrogen fertilizer stock solution.

[0007] Preferably, the total nitrogen concentration in the enhanced high-nitrogen fertilizer stock solution is greater than 10 mg / L, and the enhanced high-nitrogen fertilizer stock solution contains incompletely dissolved polymer coating components and chemical inhibitors; in step S1, the enhanced high-nitrogen fertilizer stock solution is directly injected for measurement without physical dilution, and the absorbance time series curve is acquired using spectrophotometric detection hardware.

[0008] Preferably, the step S3 of dynamically adjusting the sliding time window span of the first-order time derivative includes the following sub-steps: Step S31, when the ambient temperature fluctuates within the range of 10°C to 40°C, the microprocessor reads the monotonic drift of the intrinsic voltage value of the initial transmittance in real time; Step S32, the microprocessor dynamically adjusts the sliding time window span of the first-order time derivative according to the monotonic drift.

[0009] Preferably, determining the value of the abrupt change point of the kinetic slope in step S4 includes the following sub-steps: Step S41, when there are incompletely dissolved polymer-coated particles in the detection environment, the microprocessor calculates the second-order time derivative of the absorbance time series curve to obtain discrete acceleration characteristics; Step S42, when the microprocessor detects frequent zero-point crossings of the second-order time derivative, it filters out high-frequency noise components exceeding a fixed fluctuation variance threshold in the rate of change characteristic parameter by using the sliding window averaging method to obtain the corrected rate of change characteristic parameter.

[0010] Preferably, in step S1, acquiring the absorbance time series curve includes: directly contacting the enhanced high-nitrogen fertilizer stock solution with the measurement surface of the total reflection prism, introducing an infrared excitation beam into the total reflection prism, causing multiple total reflections at the interface between the total reflection prism and the enhanced high-nitrogen fertilizer stock solution to generate attenuated total reflection, using a photodetector to receive the infrared interference modulated beam carrying the absorption characteristics of the enhanced high-nitrogen fertilizer stock solution, and converting the infrared interference modulated beam into an electrical signal to construct the absorbance time series curve.

[0011] Preferably, before step S1, the method further includes step S6, injecting deionized water into the measurement surface of the total reflection prism to collect background infrared spectrum, storing the background infrared spectrum as a reference background curve using a microprocessor, and using the reference background curve to subtract the base background noise in the electrical signal when constructing the absorbance time series curve.

[0012] Preferably, in step S4, the sliding window span used in the sliding window averaging method is dynamically adjusted by the microprocessor according to the monotonicity drift, and the fixed fluctuation variance threshold is set according to 3 times the inherent dark current noise variance of the spectrophotometer hardware.

[0013] Preferably, the mass percentage concentration of total nitrogen nutrient content is measured in the range of 1.0% to 35.0%, which corresponds to the factory quality inspection at the fertilizer production site and the fertilizer sampling inspection at the agricultural law enforcement site.

[0014] Preferably, after outputting the total nitrogen nutrient content in step S5, the method further includes: the microprocessor determining whether the range of the total nitrogen nutrient content within three consecutive detection cycles is lower than a set stable threshold; when the range is lower than the stable threshold, the output result is confirmed to converge, and the final measured value of the total nitrogen nutrient content is digitally displayed through the display module.

[0015] Compared with existing technologies, the method for rapid detection of nutrient content in high-nitrogen fertilizers of the present invention has the following advantages: 1. In the rapid detection of nutrient content in high-nitrogen fertilizers, the continuous radiation of a constant monochromatic probe light source drives the target nutrient molecules in the test solution to produce a local polarization equilibrium deflection. This causes the target nutrient molecules to exhibit transient nonlinear absorbance decay behavior within the transient polarization response window at the initial stage of light irradiation. Meanwhile, the macromolecular organic chemical inhibitors in the background exhibit quasi-static equilibrium within the response window due to significant steric hindrance. At this point, the static spectral interference is directly stripped away by the value of the dynamic slope abrupt change point locked by the first-order time differential calculation with a fixed time step. Thus, the static absorption spectrum intrinsics that originally overlapped extensively in the spatial and energy dimensions are transformed into the time-domain dynamic rate of change differential characteristics on the time axis.

[0016] 2. By combining the initial transmittance eigenvalue of the test stock solution at the initial moment with the first-order differential value corresponding to the slope abrupt change point, and using the dynamic conversion relationship including the kinetic sensitivity gain coefficient and the baseline bias correction factor to adaptively offset the nonlinear saturation bias of the signal under high concentration conditions, this not only avoids the cumulative error of multi-stage operation caused by cascaded physical dilution operations, but also enables the direct injection and determination of high nitrogen stock solutions with a total nitrogen mass concentration greater than 10 g / L without changing the spectrophotometric detection hardware structure. This allows the complex microenvironment of the in-situ coexistence between additives and nutrient molecules in the stock solution to be completely preserved, enhancing the analytical certainty under the in-situ testing conditions of high nitrogen fertilizer.

[0017] 3. When incomplete dissolution of fertilizer polymer coating occurs in the field testing environment, the second-order time derivative is calculated simultaneously on the absorbance time series curve to obtain the discrete acceleration characteristics of absorbance change. When the frequent crossover of the zero point of the second derivative caused by dynamic light scattering is detected, the discrete step filter command is triggered in conjunction. The sliding window averaging method is used to forcibly filter out high-frequency noise terms in the absorbance dynamic change rate sequence that exceed the preset fluctuation variance threshold. This repairs the slope distortion in situ and ensures the unique determinism of the dynamic slope change point within the polarization response time window. This constructs a precise hedging and stabilizing control closed loop for random scattering interference under harsh conditions. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the overall steps of a rapid detection method for nutrient content in an enhanced high-nitrogen fertilizer according to the present invention. Figure 2 This is a state diagram of the rapid detection of nutrient content in an enhanced high-nitrogen fertilizer according to the present invention. Detailed Implementation

[0019] The technical solutions in the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0020] A method for rapid detection of nutrient content in high-nitrogen fertilizers with enhanced efficacy includes the following steps: Step S1: In situ, the light intensity variation data of undiluted high-nitrogen fertilizer stock solution under dynamic attenuation total reflectance infrared spectrum is collected using spectrophotometer hardware to construct an absorbance time series curve. Step S2: Use a microprocessor to read the initial transmittance intrinsic voltage value of the enhanced high-nitrogen fertilizer stock solution at the initial moment of contact with the spectrophotometer detection hardware. Step S3: The microprocessor calculates the first-order time derivative of the absorbance time series curve to obtain the rate of change characteristic parameter, and dynamically adjusts the sliding time window span of the first-order time derivative according to the monotonic drift of the initial intrinsic voltage value of transmittance as the dynamic input boundary for subsequent filtering. Step S4: The microprocessor calculates the second-order time derivative of the absorbance time series curve to obtain discrete acceleration characteristics. When the frequent crossover of the zeros of the second-order time derivative is captured, the discretization step filter instruction is triggered. The high-frequency noise components exceeding the fixed fluctuation variance threshold in the rate of change characteristic parameter are filtered out by the sliding window averaging method to determine the value of the dynamic slope change point. In step S5, the microprocessor inputs the corrected rate of change characteristic parameter and the initial transmittance intrinsic voltage value into the stored inversion quantitative relationship, calculates and outputs the total nitrogen nutrient content in the enhanced high-nitrogen fertilizer stock solution.

[0021] Preferably, the total nitrogen concentration in the enhanced high-nitrogen fertilizer stock solution is greater than 10 mg / L, and the enhanced high-nitrogen fertilizer stock solution contains incompletely dissolved polymer coating components and chemical inhibitors; in step S1, the enhanced high-nitrogen fertilizer stock solution is directly injected for measurement without physical dilution, and the absorbance time series curve is acquired using spectrophotometric detection hardware.

[0022] Preferably, the step S3 of dynamically adjusting the sliding time window span of the first-order time derivative includes the following sub-steps: Step S31, when the ambient temperature fluctuates within the range of 10°C to 40°C, the microprocessor reads the monotonic drift of the intrinsic voltage value of the initial transmittance in real time; Step S32, the microprocessor dynamically adjusts the sliding time window span of the first-order time derivative according to the monotonic drift.

[0023] Preferably, determining the value of the abrupt change point of the kinetic slope in step S4 includes the following sub-steps: Step S41, when there are incompletely dissolved polymer-coated particles in the detection environment, the microprocessor calculates the second-order time derivative of the absorbance time series curve to obtain discrete acceleration characteristics; Step S42, when the microprocessor detects frequent zero-point crossings of the second-order time derivative, it filters out high-frequency noise components exceeding a fixed fluctuation variance threshold in the rate of change characteristic parameter by using the sliding window averaging method to obtain the corrected rate of change characteristic parameter.

[0024] Preferably, in step S1, acquiring the absorbance time series curve includes: directly contacting the enhanced high-nitrogen fertilizer stock solution with the measurement surface of the total reflection prism, introducing an infrared excitation beam into the total reflection prism, causing multiple total reflections at the interface between the total reflection prism and the enhanced high-nitrogen fertilizer stock solution to generate attenuated total reflection, using a photodetector to receive the infrared interference modulated beam carrying the absorption characteristics of the enhanced high-nitrogen fertilizer stock solution, and converting the infrared interference modulated beam into an electrical signal to construct the absorbance time series curve.

[0025] Preferably, before step S1, the method further includes step S6, injecting deionized water into the measurement surface of the total reflection prism to collect background infrared spectrum, storing the background infrared spectrum as a reference background curve using a microprocessor, and using the reference background curve to subtract the base background noise in the electrical signal when constructing the absorbance time series curve.

[0026] Preferably, in step S4, the sliding window span used in the sliding window averaging method is dynamically adjusted by the microprocessor according to the monotonicity drift, and the fixed fluctuation variance threshold is set according to 3 times the inherent dark current noise variance of the spectrophotometer hardware.

[0027] Preferably, the mass percentage concentration of total nitrogen nutrient content is measured in the range of 1.0% to 35.0%, which corresponds to the factory quality inspection at the fertilizer production site and the fertilizer sampling inspection at the agricultural law enforcement site.

[0028] Preferably, after outputting the total nitrogen nutrient content in step S5, the method further includes: the microprocessor determining whether the range of the total nitrogen nutrient content within three consecutive detection cycles is lower than a set stable threshold; when the range is lower than the stable threshold, the output result is confirmed to converge, and the final measured value of the total nitrogen nutrient content is digitally displayed through the display module.

[0029] Example 1: In the scenario of rapid detection of nutrient content in high-nitrogen fertilizers for factory quality testing, when the testing personnel are faced with the direct, undiluted detection of high-nitrogen fertilizers containing at least one organic chemical inhibitor and with a total nitrogen mass fraction greater than 35%, the receiving signal of the spectrophotometer unit experiences nonlinear saturation of the photoelectric signal against the background of ultra-high solute concentration. Furthermore, because the characteristic absorption bands of the organic chemical inhibitors overlap with the characteristic absorption peaks of ammonium nitrogen in the fertilizer across multiple spectral ranges, the conventional standard curve quantification method based on static background control group subtraction produces signal distortion. The method claimed in this invention operates in this testing environment as follows: the testing personnel collect a specific mass of high-nitrogen fertilizer... The sample was completely dissolved in deionized water to prepare a test stock solution with a total nitrogen concentration of 12 g / L. This stock solution was then injected into a static spectrophotometer cell, bringing it into contact with the measurement surface of the total internal reflection prism. The processor activated a constant monochromatic LED light source with a characteristic absorption wavelength of 650 nm. This light source generated a constant photon energy field that continuously penetrated the test stock solution in the static spectrophotometer cell. In actual operation, although this 650 nm visible light excitation source is in the visible light band, its high-intensity continuous radiation can induce electronic transitions and local transient thermal field reconstruction of specific functional groups in the test stock solution. This surface perturbation indirectly modulates the dielectric constant at the interface of the total internal reflection prism, thereby altering the original... The molecular vibrational absorption characteristics exhibited in the infrared band show observable accompanying attenuation under visible light induction. This enables the indirect capture and construction of dynamically attenuated total internal reflection infrared spectral data through visible light excitation. When monochromatic radiation acts on the test stock solution at the measurement surface of the total internal reflection prism, the electronic transitions of specific components release energy, forming a microsecond-level local temperature gradient field at the interface layer. This temperature gradient field creates a monotonically changing refractive index transition layer between the total internal reflection prism surface and the test stock solution, resulting in a monotonically deterministic correlation between the attenuation degree of the infrared evanescent wave during multiple total internal reflections at the interface and the rate of change of the local thermal field. Based on the objective correlation between thermal field reconstruction and dynamic changes in dielectric constant, the test group constructs a system utilizing visible light... The method of indirectly capturing infrared attenuation features by excitation with light wavelength establishes a mass transfer path for the conversion of visible light excitation and infrared total internal reflection spectral features at the physical structure level. Under continuous excitation of a constant photon energy field, the target nutrient molecules inside the test solution undergo photoinduced local polarization non-equilibrium evolution. The anisotropic polarization and recombination of ammonium nitrogen molecules inside causes their characteristic absorbance to exhibit transient nonlinear absorbance attenuation behavior within the transient polarization response window at the initial stage of light ignition. Due to the steric hindrance of the macromolecular organic chemical inhibitors in the background, their molecular dipole moments have a response lag within the first few seconds after the constant monochromatic LED light source is turned on, so that their characteristic absorbance is in a quasi-static equilibrium state within the polarization response window.

[0030] The photoelectric converter at the instant the constant monochromatic LED light source is turned on Triggered, the transmittance voltage signal after penetrating the test solution is continuously acquired at a sampling frequency of 50Hz. The microprocessor calculates and solves the corresponding absorbance physical quantity based on the transmittance voltage signal, constructing an absorbance time series curve that continuously evolves with illumination time. The microprocessor calls this absorbance time series curve and performs first-order time derivative calculation on the curve with a time step of 20ms, outputting the absorbance dynamic change rate sequence. The microprocessor searches for this absorbance dynamic change rate sequence within the polarization response time window of 1s to 4s after illumination is started. Since the first-order time derivative value of the macromolecular organic chemical inhibitor approaches 0 within this time window, the microprocessor locks the kinetic slope abrupt change point caused by the polarization deflection of ammonium nitrogen and reads the first-order derivative value corresponding to the slope abrupt change point. To remove overlapping background spectral interference in the time differential domain and mitigate secondary issues introduced by harsh on-site conditions, the microprocessor simultaneously performs second-order time differential calculations on the absorbance time series curve to obtain the discrete acceleration characteristics of absorbance changes. When incompletely dissolved polymer-coated particles induce dynamic light scattering in the photon transmission path, causing frequent zero-point crossings in the second-order time differential, the microprocessor triggers a discretization step filter instruction. This uses a sliding window averaging method to filter out high-frequency noise terms exceeding a fixed fluctuation variance threshold in the absorbance dynamic change rate sequence, repairing distortions at slope abrupt changes. The fixed fluctuation variance threshold is then set... The variance of the dark current noise of the spectrophotometer is set at three times the inherent dark current noise variance of the spectrophotometer. The technical mechanism is to use the statistical boundary in digital signal processing to perform cross-dimensional fusion judgment of electrical and optical noise. Since the dark current variance of the hardware in the dark state represents the unavoidable random electronic thermal noise floor of the system, when the overall polymer particles are suspended and cause dynamic light scattering and are converted into photocurrent fluctuations, if the variance of the fluctuation does not exceed three times the dark current floor, it is considered a normal disturbance allowed by the system. However, once it exceeds the upper limit of the confidence interval of three times, it is determined that there is random scattering interference from physical particles, thereby triggering the sliding window averaging method to perform rigid filtering.

[0031] Meanwhile, based on the fact that the ambient temperature fluctuates within the range of 10℃ to 40℃, changing the molecular polarization rate, the microprocessor reads the initial value of the test solution. Initial transmittance intrinsic voltage value The drift amount is used to dynamically scale the sliding time window span of the first-order time derivative, trunculating the additional disturbance slope increment caused by temperature drift. Finally, the microprocessor calculates the corrected rate of change characteristic parameter, i.e., the first-order derivative value corresponding to the slope abrupt change point. and the intrinsic voltage value of initial transmittance The stored inversion quantitative formula is used to offset the nonlinear saturation bias of the signal under high concentration conditions, and the total nitrogen nutrient content in the sample is calculated and output. The formula for calculating the total nitrogen nutrient content is as follows: ,in, The total nitrogen mass percentage concentration of the sample to be tested; The preset polarization dynamics gain constant has a value of 1.36; This is the saturation adaptive correction factor, with a value of 0.11; The absolute value of the rate of change of the extracted absorbance over time; To obtain the initial transmittance-voltage component ratio, the polarization kinetic gain constant in the aforementioned calculation formula is further fixed at 1.36. This value is obtained by least-squares linear fitting of the slope of the polarization response curve of multiple batches of standard total nitrogen samples under a standard environment of 25℃, representing the mass percentage concentration gain corresponding to the unit absorbance change rate. The saturation adaptive correction factor is fixed at 0.11. This value is an engineering compensation coefficient determined by statistically analyzing the nonlinear bias of photoelectric conversion caused by photon transmission path obstruction under the saturation limit of ultra-high concentration channels with a total nitrogen mass concentration greater than 10 g / L, and then fitting it with an inverse proportional convergence curve. These two constants together ensure the linearity of the quantitative inversion across the entire range. In the test group, the total nitrogen mass concentration of the test stock solution is selected within the range of 1.0% to 35.0%. When the total nitrogen mass concentration is below 1.0%, the signal-to-noise ratio of the transient nonlinear absorbance attenuation signal is lower than the critical judgment threshold, making it impossible to improve the value of the kinetic slope abrupt change point. When the total nitrogen concentration exceeds 35.0%, the photon transmission path is excessively blocked by solute particles, and the transmittance voltage signal enters the saturation dead zone. The mass fraction of dicyandiamide, an organic chemical inhibitor added to the test solution, is set to 5.0%. Without the addition of dicyandiamide, the lack of polarization response lag generated by the supramolecular coexistence microenvironment causes the spectra of the polymer coating component and ammonium nitrogen to spatially overlap and cannot be separated, increasing the relative error of the total nitrogen measurement to 11.83%. When the mass fraction of dicyandiamide exceeds 8.0%, the excessive dicyandiamide molecules competitively complex with ammonium nitrogen, changing the original local polarization rate of ammonium nitrogen and causing quantitative inversion distortion. The above component ratios work together to smooth the nonlinear saturation of the signal and separate the overlapping spectra. Through dynamic extraction of the first-order time differential characteristic operator and adaptive temperature drift calibration, the total nitrogen nutrient content in the test solution is stably output, eliminating the random error introduced by the preprocessing operation, and enabling the reproducibility and accuracy of the field sampling results to reach steady-state precision.

[0032] Example 2: To verify the technical effectiveness and boundary stability of the method of the present invention in engineering applications, a detection and verification experiment for determining the nutrient content of synergistic high-nitrogen fertilizer containing inhibitors was built in a laboratory platform with precise temperature control capabilities. The core components of the experimental platform include: a 650nm monochromatic LED constant light source with light source stability better than 0.05%, a spectrophotometric detection sensor with a sampling accuracy of 16 bits and a maximum sampling frequency of 100Hz, and a microfluidic stirring tank capable of simulating the dynamic suspension interference of polymer-coated particles in agricultural fields. The experimental design includes three key groups to construct a multi-dimensional control system: the experimental group uses the method of the present invention to strip the background in real time through a first-order time differential operator; control group A removes the first-order time differential operator step and directly uses the static benchmark subtraction method; control group B performs the detection at an extreme high concentration of total nitrogen in the fertilizer stock solution exceeding 28g / L.

[0033] To ensure the objectivity and authenticity of the experimental data, the following key parameters were set: the total nitrogen concentration of the test stock solution was 12 g / L, the sampling frequency was set to 50 Hz, and the temperature control environment was 25℃. To address interference introduced by organic chemical inhibitors, both the experimental and control groups had 5.0% dicyandiamide, a typical synergistic inhibitor, added to the background. In the actual testing process, although dicyandiamide exhibits a small molecule structure in its single-component state, in the high-concentration composite system of the test stock solution with a total nitrogen concentration as high as 12 g / L, dicyandiamide molecules will interact with the stock solution... The abundant ammonium nitrogen components and incompletely dissolved polymer coating components spontaneously form strong intermolecular hydrogen bonds and multidentate coordination complexes. Bound by the macromolecular network, they evolve in situ into a supramolecular coexistence microenvironment with significant apparent steric hindrance. This allows it to exhibit a polarization response lag even in the initial stages of excitation by a constant monochromatic light source. This accurately aligns with the technical logic of stripping static background spectra through polarization response time windows at the physical level. Experimental observation data are as follows: Under baseline concentration conditions, the experimental group obtained [data missing] by locking the abrupt change point of the kinetic slope. The mean value was 0.48. Calculated using the inversion formula, the total nitrogen concentration was 11.96 g / L, with a relative error of 0.33%. Control group A, unable to remove the static background of overlapping spectra, had a persistently high absorbance reading, resulting in a calculated value of 13.42 g / L, with a relative error of 11.83%. When the ambient temperature increased from 25℃ to 40℃, the experimental group utilized the initial transmittance intrinsic voltage value... The drift amount was dynamically scaled using a first-order time differential sliding window, and the calculated total nitrogen concentration was 12.04 g / L, with a relative error stable within 0.35%; while the error of the reference sample group without temperature drift dynamic correction was 4.20%.

[0034] For the empirical verification of the key parameter boundaries, under the extreme condition of a total nitrogen concentration of 28 g / L, the control group (B) experienced a drop in the transmittance voltage signal of the spectrophotometer cell to below 5% of its range, causing the signal-to-noise ratio of the photoelectric converter to decay to the critical threshold. At this point, the experimental group, through the formula... Saturation adaptive correction factor After offsetting the nonlinear saturation bias, the calculated total nitrogen concentration is 27.91 g / L, with a relative error controlled at approximately 0.32%. If this correction factor is then removed... The output results deviated from the actual values ​​by more than 25% due to channel saturation. Monitoring of the second-order time differential acceleration characteristics during the experiment showed that when the simulated coated particles caused dynamic light scattering, resulting in instantaneous spikes in the absorbance curve with an amplitude greater than 0.005, the second-order differential zeros frequently crossed. The sliding window averaging filter instruction triggered by the microprocessor effectively suppressed the noise fluctuation variance to within 0.001, ensuring the effectiveness of the extraction of slope abrupt change points. Experimental data confirmed that the method of this invention, after synergistically using first-order time differential feature stripping, dynamic temperature drift correction, and saturation hedging logic, can effectively overcome spectral interference and nonlinear effects under high concentration backgrounds. The stability of various key performance indicators proved the engineering feasibility of this technical solution in the nutrient detection of complex fertilizer systems.

[0035] Example 3: In an industrial field for online monitoring of high-concentration, high-nitrogen fertilizers with enhanced efficiency, the detection system was interfered with by particles generated from the dissolution of the polymer coating of the fertilizer concentrate during operation. This caused surface coverage at the electrode interface, resulting in a decrease in the measured charge transfer resistance. To address statistical deviations, the detection system constructed in this invention employs a dual physical field coupling sensing mechanism of optical and electrochemical fields. The measurement surface of the total internal reflection prism simultaneously serves as the substrate for electrochemical measurements. This allows the surface charge transfer characteristics of the undiluted stock solution to be simultaneously captured while undergoing infrared spectroscopy measurements. Changes in charge transfer resistance directly reflect the degree of optical measurement channel obstruction caused by polymer particle coverage. By establishing a multidimensional correlation between overall spectroscopic transmittance and surface impedance spectrum, a closed-loop self-consistent system is achieved that dynamically corrects spectroscopic detection results using electrochemical characteristics. To eliminate this physical obstruction, the detection system, during the real-time monitoring cycle, uses a microprocessor to control the excitation voltage signal applied to the electrochemical impedance fingerprint sensing module. The amplitude adaptive adjustment, in terms of hardware structure, this electrochemical impedance fingerprint sensing module uses an indium tin oxide conductive film integrated on the measurement surface of a total internal reflection prism as the working electrode, and together with the platinum sheet counter electrode and the saturated calomel reference electrode arranged opposite to each other inside the static detection cell, it forms a three-electrode electrochemical system. The conductive film not only allows the infrared beam to pass through through total internal reflection, but also serves as the charge exchange interface for the electrochemical reaction. Its signal output terminal is connected to the current detection channel of the dual-channel synchronous data acquisition card through a miniature coaxial shielded wire, thus realizing the co-location transmission of optical and electrical signals in structure. The microprocessor collects the real impedance value in the high-frequency region of the complex impedance spectrum in real time. When the real impedance value deviates from the amplitude of the reference library by more than the preset electrode interface contamination threshold, the signal is adjusted accordingly. At this time, the system enters the electrode surface targeted cleaning mode. In this mode, the microprocessor triggers the excitation voltage to jump instantaneously from 50mV to 150mV. By increasing the local electric field intensity on the electrode surface, the deposited polymer coating contaminants are induced to undergo physical desorption, so that the equivalent capacitance value of the electrode interface recovers to the reference range within a short time window of 200ms. This eliminates the steric hindrance effect of the micron-level physical coverage of the interface on the migration of nutrient molecules. In order to meet the flow and mass transfer requirements of the photoelectrochemical fingerprint sensing module, when the excitation voltage amplitude jumps, the microfluidic pumping mechanism linked to the detection system is activated, injecting deionized water into the total reflection prism measurement surface at a constant flow rate of 15mL / min. The fluid shear force is used to accelerate the rheological migration of the desorbed polymer coating contaminants, so that the charge exchange interface on the electrode surface is restored under continuous rinsing, and the interface response delay caused by the bulk viscosity hindrance is smoothed out within a short time window.

[0036] After the interface repair is completed, the system automatically switches to compensation monitoring mode, and the microprocessor uses the real-time measured temperature of the test solution. Substituting into the charge transfer resistance temperature compensation formula, the resistance value affected by the charge transfer polarity of the inhibitor is... After correction, the calculation formula is as follows: ,in, This is the temperature-corrected charge transfer resistance. The initial charge transfer resistance is measured by the photoelectrochemical fingerprint sensing module. The activation energy temperature correlation coefficient for enhancing the high-nitrogen fertilizer system is set to 3500K; This represents the absolute temperature of the current test solution. The reference temperature is set to 298.15 K.

[0037] After the microprocessor completes the correction calculation, The system uses a stored inversion quantitative model as input. This model selects the characteristic frequency points least affected by temperature fluctuations in the electrochemical fingerprint sensing module as the main input parameters and filters out environmental electromagnetic noise. The system eliminates the blockage interference of incompletely dissolved particles on the detection channel in the high-concentration fertilizer system through a combined closed loop of automatic desorption on the electrode surface and real-time compensation for temperature drift. This keeps the nutrient concentration detection output fluctuation within 0.5% during the 24-hour continuous monitoring period, solving the technical problem of unstable detection results under high-concentration stock solution environment.

[0038] Example 4: In the field environment adaptation scenario of the online monitoring system for high-nitrogen fertilizers, the detection system faces challenges such as baseline drift caused by the cumulative operation time of the sensors and decreased measurement accuracy due to drastic fluctuations in the detection environment temperature. To ensure the stability of the solution under different operating conditions, the system establishes standardized on-site calibration and personalized benchmark correction procedures. In the initial deployment stage after the installation of the detection device, the system performs an offline calibration process: the electrode surface is cleaned and immersed in a standard fertilizer test solution with a known total nitrogen concentration of 10.0 g / L, and left to stand at a constant temperature of 25°C for 10 minutes. The microprocessor records the initial transmittance intrinsic voltage generated by the spectrophotometer detection unit. The value is then stored in a non-volatile memory unit as the zero-point calibration parameter during the initial operation of the system.

[0039] To avoid aging of detection accuracy due to accumulated operating time, the system will only operate when the detection equipment reaches a preset threshold. Upon activation, an initial calibration command is automatically triggered. The system injects a certain volume of calibration solution of known concentration through a preset microfluidic valve. The microprocessor compares the deviation between the real-time detected value and the standard value of the calibration solution, and automatically updates the conversion coefficient in the inversion quantitative relationship. Baseline bias correction factor If there is a severe temperature drift in the real-time measurement environment, the system will adjust the intrinsic voltage value based on the initial transmittance. The monotonic drift amount is used to dynamically adjust the sliding window time in the differential algorithm. The calculation formula is: ,in, This is the baseline sliding window duration at room temperature, with a value of 2 seconds. The temperature drift compensation sensitivity coefficient is set to 0.02 s / ℃. This is the temperature difference between the current ambient temperature and the 25°C calibration reference temperature. The determination method is as follows: the microprocessor acquires the initial intrinsic voltage value of transmittance. The absolute offset relative to the standard initial voltage is divided by a fixed constant of 0.05V / ℃ to convert it to degrees Celsius, thus determining the temperature difference. The microprocessor will calculate the resulting slip window time based on the value of the slip window. As a boundary constraint input to the digital filter, the control digital filter filters out high-frequency noise components whose fluctuation variance exceeds three times the dark current noise variance in the first-order time derivative calculation. It also retrieves the coordinates of the maximum absolute value of the first-order time derivative within the polarization response time window, determining the value corresponding to the dynamic slope abrupt change point. This achieves physical constraints on the underlying hardware actions by the feature parameter extraction algorithm. To unify the dimensions of voltage monotonicity drift and temperature change at the digital level, the microprocessor pre-stores the temperature sensitivity coefficient of the photodetector's initial transmittance intrinsic voltage. In actual operation, when the ambient temperature is between 10℃ and 4℃... When the temperature fluctuates between 0°C and 0°C, the initial voltage output by the detector will produce a monotonic baseline drift. The microprocessor can deduce the current real-time temperature difference by reading the absolute offset of the voltage in real time and dividing it by the temperature sensitivity coefficient. Then, the temperature difference is substituted into the window calculation to realize an accurate mapping from the voltage drift to the scaling range of the time window. Through the above-mentioned offline calibration benchmark setting, timed automatic calibration mechanism, and sliding window dynamic scaling strategy based on real-time temperature sensing, the system maintains the output steady state of total nitrogen nutrient content detection over long periods and under complex working conditions, eliminating the risk of measurement drift caused by sensor module aging or environmental evolution.

[0040] Example 5: In the online monitoring scenario of high-nitrogen fertilizers for enhanced efficiency, to eliminate baseline drift caused by batch changes in fertilizer formulation, the detection system automatically invokes the offline baseline calibration and batch difference compensation program at the initial stage of production line operation. Before production starts, the testing personnel extract three sets of standard fertilizer samples with known total nitrogen concentrations of 15%, 25%, and 35%, respectively. In a constant temperature environment of 25°C, the complex impedance spectrum of the samples in the 0.1Hz to 1kHz frequency band is scanned using a photoelectrochemical fingerprint sensing module. The charge transfer resistance reference characteristic curve of the batch of fertilizer is generated by fitting using the least squares method. The baseline characteristic curve is stored in the non-volatile memory of the microprocessor and serves as a logical reference for determining the real-time fertilizer component fluctuations and baseline bias in subsequent online production operations.

[0041] During online monitoring, the microprocessor compares the charge transfer resistance of the current fertilizer sample in real time. Compared with the reference characteristic curve The difference, and calculate the batch variation compensation value. To correct the measurement results, the process follows the logical calculation formula: ,in, This is the corrected charge transfer resistance. The real-time charge transfer resistance of the fertilizer concentrate under test is measured by the photoelectrochemical fingerprint sensing module. For the system to run until time The real-time impedance baseline drift compensation term is dynamically updated by the impedance value of the blank buffer solution automatically injected after every 100 fertilizer samples are monitored. The formula difference compensation coefficient is set to 0.025. The deviation rate of the total nitrogen mass concentration of the fertilizer to be tested relative to the benchmark sample is given when the microprocessor retrieves the current electrochemical fingerprint spectral characteristics and... When offset exists, the characteristic response displacement point is located by heuristic frequency scanning, and the component deviation rate is calculated. The system feeds this information back into the extended quantitative inversion formula with impedance compensation for the final calculation of total nitrogen nutrient content. By performing baseline construction before each production cycle and coordinating real-time baseline correction and dynamic deviation compensation during operation, the system maintains the output accuracy of high-concentration fertilizer undiluted detection. After continuous 24-hour online monitoring verification, the output deviation of total nitrogen mass concentration detection is controlled within 0.3%.

[0042] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A method for rapid detection of nutrient content in high-nitrogen fertilizers with enhanced efficiency, characterized in that, Includes the following steps: Step S1: In situ, the light intensity variation data of undiluted high-nitrogen fertilizer stock solution under dynamic attenuation total reflectance infrared spectrum is collected using spectrophotometer hardware to construct an absorbance time series curve. Step S2: Use a microprocessor to read the initial transmittance intrinsic voltage value of the enhanced high-nitrogen fertilizer stock solution at the initial moment of contact with the spectrophotometer detection hardware. Step S3: The microprocessor calculates the first-order time derivative of the absorbance time series curve to obtain the rate of change characteristic parameter, and dynamically adjusts the sliding time window span of the first-order time derivative according to the monotonic drift of the initial intrinsic voltage value of transmittance as the dynamic input boundary for subsequent filtering. Step S4: The microprocessor calculates the second-order time derivative of the absorbance time series curve to obtain discrete acceleration characteristics. When the frequent crossover of the zeros of the second-order time derivative is captured, the discretization step filter instruction is triggered. The high-frequency noise components exceeding the fixed fluctuation variance threshold in the rate of change characteristic parameter are filtered out by the sliding window averaging method to determine the value of the dynamic slope change point. In step S5, the microprocessor inputs the corrected rate of change characteristic parameter and the initial transmittance intrinsic voltage value into the stored inversion quantitative relationship, calculates and outputs the total nitrogen nutrient content in the enhanced high-nitrogen fertilizer stock solution.

2. The method for rapid detection of nutrient content in a high-nitrogen fertilizer with enhanced efficiency according to claim 1, characterized in that, The total nitrogen concentration in the enhanced high-nitrogen fertilizer stock solution is greater than 10 mg / L, and the enhanced high-nitrogen fertilizer stock solution contains incompletely dissolved polymer coating components and chemical inhibitors; in step S1, the enhanced high-nitrogen fertilizer stock solution is directly injected for measurement without physical dilution, and the absorbance time series curve is collected using spectrophotometric detection hardware.

3. The method for rapid detection of nutrient content in a high-nitrogen fertilizer with enhanced efficiency according to claim 1, characterized in that, The step S3 of dynamically adjusting the sliding time window span of the first-order time derivative includes the following sub-steps: Step S31, when the ambient temperature fluctuates within the range of 10℃ to 40℃, the microprocessor reads the monotonic drift of the initial transmittance intrinsic voltage value in real time; Step S32, the microprocessor dynamically adjusts the sliding time window span of the first-order time derivative according to the monotonic drift.

4. The method for rapid detection of nutrient content in a high-nitrogen fertilizer with enhanced efficiency according to claim 1, characterized in that, The determination of the dynamic slope abrupt change point value in step S4 includes the following sub-steps: Step S41, when there are incompletely dissolved polymer-coated particles in the detection environment, the microprocessor calculates the second-order time derivative of the absorbance time series curve to obtain discrete acceleration characteristics. Step S42: When the microprocessor detects frequent zero-point crossings of the second-order time derivative, it filters out high-frequency noise components exceeding a fixed fluctuation variance threshold in the rate of change feature parameter using a sliding window averaging method to obtain the corrected rate of change feature parameter.

5. The method for rapid detection of nutrient content in a high-nitrogen fertilizer with enhanced efficiency according to claim 1, characterized in that, In step S1, the acquisition of the absorbance time series curve includes: directly contacting the enhanced high-nitrogen fertilizer stock solution with the measurement surface of the total reflection prism, introducing an infrared excitation beam into the total reflection prism, causing multiple total reflections at the interface between the total reflection prism and the enhanced high-nitrogen fertilizer stock solution to produce attenuated total reflection, using a photodetector to receive the infrared interference modulation beam carrying the absorption characteristics of the enhanced high-nitrogen fertilizer stock solution, and converting the infrared interference modulation beam into an electrical signal to construct the absorbance time series curve.

6. The method for rapid detection of nutrient content in a high-nitrogen fertilizer with enhanced efficiency according to claim 1, characterized in that, Before step S1, the method further includes step S6, which involves injecting deionized water into the measurement surface of the total reflection prism to collect background infrared spectra, storing the background infrared spectra as a reference background curve using a microprocessor, and using the reference background curve to subtract the substrate background noise in the electrical signal when constructing the absorbance time series curve.

7. The method for rapid detection of nutrient content in a high-nitrogen fertilizer with enhanced efficiency according to claim 1, characterized in that, In step S4, the sliding window span used in the sliding window averaging method is dynamically adjusted by the microprocessor according to the monotonicity drift, and the fixed fluctuation variance threshold is set according to 3 times the inherent dark current noise variance of the spectrophotometer hardware.

8. The method for rapid detection of nutrient content in a high-nitrogen fertilizer with enhanced efficiency according to claim 1, characterized in that, The mass percentage concentration of total nitrogen nutrient content is measured in the range of 1.0% to 35.0%, corresponding to the factory quality inspection at the fertilizer production site and the fertilizer sampling inspection at the agricultural law enforcement site.

9. The method for rapid detection of nutrient content in a high-nitrogen fertilizer with enhanced efficiency according to claim 1, characterized in that, After outputting the total nitrogen nutrient content in step S5, the process further includes: the microprocessor determining whether the range of the total nitrogen nutrient content within three consecutive detection cycles is lower than a set stable threshold. When the range is lower than the stable threshold, the output result is confirmed to converge, and the final measured value of the total nitrogen nutrient content is digitally displayed through the display module.

Images