Method and system for detecting concentration of trace elements in water

Abstract

The invention relates to the field of trace element detection, in particular to a system for detecting the concentration of trace elements in water. The gas chamber is connected with the atomization device, is internally provided with a light path capable of dynamically adjusting the White cell, and is used for enhancing a spectral absorption signal of the low-concentration trace elements; the light path modulation module is mounted on the side wall of the gas chamber; the temperature control module is used for adjusting the temperature of the optical element and the air chamber; the spectrum detection module is arranged behind the light outlet of the gas chamber and is used for detecting a spectrum signal after the aerosol is absorbed; the ionization and mass spectrum module comprises an ionization source and a mass spectrometer, the ionization source is used for ionizing the aerosol in the gas chamber into ions, and the mass spectrometer is used for separating the ions according to the mass-to-charge ratio and detecting the ions. According to the invention, a spectrum and mass spectrum combined technology is adopted, a water sample to be detected is atomized into aerosol water drops, and high-sensitivity detection of trace elements in water is realized by enhancing a spectrum absorption signal of low-concentration trace elements.

Description

Technical Field

[0001] The present invention relates to the field of trace element detection, and particularly to a method and system for detecting the concentration of trace elements in water. Background Art

[0002] In China, water quality detection is a key link in ensuring the quality of domestic water and the safety of the ecological environment. At present, China's water quality detection standards mainly cover microbial indicators and toxicological indicators. Among them, toxicological indicators involve various heavy metals and harmful substances, such as arsenic, cadmium, chromium, etc. However, traditional water quality detection methods have certain limitations in terms of detection sensitivity, accuracy, and stability, and it is difficult to meet the increasingly strict water quality standards and people's demand for high-precision water quality detection.

[0003] Traditional spectroscopic analysis methods, such as atomic absorption spectrometry and inductively coupled plasma emission spectrometry, although widely used in the detection of trace elements in water, for the detection of ultra-low concentration trace elements, their detection limits are often relatively high, generally above dozens of ppm, and it is difficult to accurately detect trace harmful substances in water. Some detection methods based on optical principles are easily affected by environmental factors, such as temperature changes and light intensity fluctuations, resulting in unstable detection signals, poor repeatability and reproducibility. For example, in a detection system with a long optical path, a small temperature change may cause thermal expansion or contraction of the optical path, thereby leading to spectral drift and affecting the accuracy of the detection results.

[0004] In view of the many problems existing in the above-mentioned existing water trace element detection technologies, it is urgent to develop a water trace element concentration detection method and system with a low detection limit, high stability, strong anti-interference ability, simple operation and low cost to meet the urgent need for high-precision detection technologies in the current water quality monitoring and environmental protection fields. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for detecting the concentration of trace elements in water. By using the combined technology of spectroscopy and mass spectrometry, and combining components such as an atomizing device, a dynamically adjustable White cell optical path, an ionization and mass spectrometry module, etc., the water sample to be measured is atomized into aerosol water droplets, and by enhancing the spectral absorption signal of low-concentration trace elements, high-sensitivity detection of trace elements in water is achieved.

[0006] The technical solution adopted by the present invention to solve its technical problems is to provide a system for detecting the concentration of trace elements in water, which is characterized by including: an atomization device for atomizing a water sample to be measured into aerosol water droplets; a gas chamber connected to the atomization device, with a White cell optical path arranged inside it for enhancing the spectral absorption signal of trace elements at low concentrations; an optical path modulation module installed on the side wall of the gas chamber for modulating an incident light source and guiding it to the White cell optical path inside the gas chamber; a temperature control module connected to the bottom of the gas chamber for controlling the temperature of the gas chamber; a spectral detection module arranged behind the light outlet of the gas chamber for detecting the spectral signal after absorbing the aerosol; an ionization and mass spectrometry module including an ion source and a mass spectrometer, where the ion source is used to ionize the aerosol in the gas chamber into ions, and the mass spectrometer is used to separate the ions by mass-to-charge ratio and perform detection; and a result output module connected to the spectral detection module and the ionization and mass spectrometry module for processing the spectral signal and mass spectrometry data and outputting the detection result of the trace element concentration.

[0007] Further, the optical path modulation module includes a front seat, a rear seat, a light source, a chopper, an air inlet wheel, a driving device, and a filter; the driving device is fixed on one side of the rear seat; a central hole is provided at the central position of the air inlet wheel; the air inlet wheel is arranged on the other side of the rear seat; the output end of the driving device passes through the circular through hole of the rear seat and the central hole of the air inlet wheel and is connected to the chopper for driving the chopper to rotate; a light source incident hole is provided on the rear seat; the light source is fixed on the rear seat; an air inlet hole is provided on the side surface of the air inlet wheel; the front seat is installed on the side wall of the gas chamber; a filter is further fixed at the bottom of the front seat; an air inlet valve is installed on the side wall of the front seat; one end of the air inlet valve is connected to the air inlet hole of the air inlet wheel.

[0008] Further, a reflection unit and a White cell optical path unit are installed inside the gas chamber; the reflection unit includes a first plane mirror and a second plane mirror; the first plane mirror is arranged on the side wall of the light inlet of the gas chamber with an adjustable angle for reflecting the incident light to the third concave mirror B of the White cell optical path; the second plane mirror is arranged at the end of the White cell optical path for reflecting the light that has fully absorbed the gas to the spectral detection module; the White cell optical path unit is composed of a first concave mirror A, a second concave mirror A', and a third concave mirror B, where: the first concave mirror A and the second concave mirror A' are symmetrically arranged on one side inside the gas chamber, and the third concave mirror B is arranged on the other side inside the gas chamber.

[0009] Further, the spectral detection module includes a grating spectroscopy unit, a photodetector, and a signal processing unit; the grating spectroscopy unit disperses the mixed light after absorbing the aerosol according to wavelengths; the photodetector receives the dispersed light and converts it into an electrical signal; the signal processing unit performs denoising processing on the electrical signal based on the wavelet transform algorithm, and calibrates the spectral intensity of the denoised signal.

[0010] Furthermore, a piezoelectric ceramic actuator is also installed on the back of the third concave mirror B for adjusting the tilt angle θ of the third concave mirror B.

[0011] Furthermore, the ionization and mass spectrometry module further includes an electron multiplier for amplifying and detecting the ion signals separated by the mass spectrometer.

[0012] Furthermore, the temperature control module includes: A power supply connected to the input end of the DC-DC converter; The DC-DC converter, whose output end is connected to the heater through an LC filter circuit, and the LC filter circuit is used to suppress the high-frequency noise of the power supply; A temperature sensing unit including a temperature sensor attached to the bottom of the gas chamber for real-time monitoring of the gas chamber temperature; its output end is connected to the input end of the ADC module for converting the temperature analog signal into a digital signal; A control unit using an FPGA or a W806 microcontroller, whose input end is connected to the output end of the ADC module to receive the digital temperature signal and output a control signal through the PWM drive module; A temperature regulation unit including: A TEC element, whose drive end is connected to the output end of the PWM drive module to receive the PWM signal to achieve refrigeration or heating; A heater, whose power supply end is connected to the output end of the LC filter circuit and the control end is connected to the PWM signal output end of the FPGA or the W806 microcontroller; The heater and the TEC element are installed at the bottom of the gas chamber; A communication unit including an isolated serial port TTL circuit, whose input end is connected to the communication interface of the FPGA or the W806 microcontroller and the output end is connected to an external main control system to achieve electrically isolated data transmission.

[0013] Furthermore, the temperature control module uses a fuzzy PID control algorithm for temperature control, and dynamically adjusts the parameters of the traditional PID controller through fuzzy inference.

[0014] The present invention also provides a method for detecting the concentration of trace elements in water, including the following steps: S1. Convert the water sample to be tested into aerosol droplets through an atomization device and introduce them into the gas chamber; S2. Generate incident light through a light source, convert it into pulsed light through an air turbine and a chopper, and use a filter to select the target wavelength; guide the modulated incident light to the dynamic adjustment White cell optical path in the gas chamber; S3. Guide the light through the White cell optical path to the spectral detection module, and use the spectral detection module to capture the spectral signal absorbed by the aerosol; S4. Introduce the aerosol in the gas chamber into the ionization source to generate gaseous ions through ionization; separate the ions by mass-to-charge ratio using a mass spectrometer, and amplify the detection signal using an electron multiplier; S5. Perform Fourier transform and low-pass filtering on the spectral signal to remove high-frequency noise; calculate the concentration of trace elements in water by combining with the mass spectrometry data based on the standard curve method.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention adopts the technology of combining spectroscopy and mass spectrometry, and combines components such as an atomization device, a dynamically adjustable White cell optical path, an ionization and mass spectrometry module, etc. to atomize the water sample to be measured into aerosol water droplets, and realizes the high-sensitivity detection of trace elements in water by enhancing the spectral absorption signal of low-concentration trace elements. Its detection limit can be as low as 1 PPM or even lower, solving the problem of high detection limit of traditional detection methods and difficulty in accurately detecting ultra-low concentration trace elements, and can accurately detect trace harmful substances in water, such as various heavy metals such as arsenic, cadmium, and chromium.

[0016] 2. The chopper and inflatable wheel in the optical path modulation module, as well as the optimized design of the reflection unit and the White cell optical path unit in the gas chamber, make the optical path more stable and reliable. Dynamically adjust the tilt angle of the third concave mirror of the White cell optical path, and combine with the angle sensor to monitor the angle change amount in real time, which can flexibly adjust the optical path length and the light reflection path according to the actual detection requirements, ensure multiple reflections and effective absorption of light in the gas chamber, and enhance the stability and repeatability of the spectral signal.

[0017] 3. The present invention introduces a temperature control module, which can adjust and control the temperature of the gas chamber. Adopt the fuzzy PID control algorithm to achieve high-precision constant temperature control of ±0.1 °C, effectively eliminate the influence of temperature fluctuations on the detection results, ensure the stability of the gas chamber temperature, thereby improving the stability and reliability of spectral detection, avoiding problems such as spectral drift or resolution decline caused by temperature changes, and ensuring the data stability and consistency during long-term detection.

[0018] 4. The present invention introduces the application of an isolated serial port TTL circuit, which provides electrical isolation and noise suppression functions for the system. In a complex detection environment, it effectively protects sensitive circuits, avoids signal loss and circuit damage caused by electrical interference, voltage fluctuations or noise, ensures the stability and reliability of data transmission between system modules, and enhances the anti-interference ability of the entire detection system.

[0019] 5. The present invention adds a filter before the light enters the gas chamber, which can effectively remove the scattering and absorption interference of particulate matter in the water sample on the spectral signal. Description of the Drawings

[0020] Figure 1It is a schematic structural diagram of a system for detecting the concentration of trace elements in water according to the present invention; Figure 2 It is a partial schematic structural diagram of a system for detecting the concentration of trace elements in water according to the present invention; Figure 3 It is a cross-sectional view of an air chamber of a system for detecting the concentration of trace elements in water according to the present invention; Figure 4 It is a schematic structural diagram of an optical path modulation module of a system for detecting the concentration of trace elements in water according to the present invention; Figure 5 It is a physical diagram of an optical path modulation module, an air chamber and a spectral analysis module of a system for detecting the concentration of trace elements in water according to the present invention from one angle; Figure 6 It is a physical diagram of an optical path modulation module, an air chamber and a spectral analysis module of a system for detecting the concentration of trace elements in water according to the present invention from another angle; Figure 7 It is a physical diagram of an optical path modulation module, an air chamber and a spectral analysis module of a system for detecting the concentration of trace elements in water according to the present invention from another angle; Figure 8 It is a schematic structural diagram of a temperature control module of a system for detecting the concentration of trace elements in water according to the present invention; Figure 9 It is a circuit diagram of a TTL circuit of a system for detecting the concentration of trace elements in water according to the present invention; Figure 10 It is a schematic flow diagram of a method for detecting the concentration of trace elements in water according to the present invention;

[0021] The markings of each component in the drawings are as follows: 1. Optical path modulation module; 11. Front seat, 12. Rear seat; 13. Light source; 14. Chopper; 15. Inflation wheel; 16. Driving device; 17. Filter; 18. Inflation valve; 2. Air chamber; 21. First plane mirror; 22. Second plane mirror; 23. First concave mirror A; 24. Second concave mirror A'; 25. Third concave mirror B; 3. Spectral detection module; 4. Temperature control module. Detailed implementation manners

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Embodiment 1: The present invention provides a system for detecting the concentration of trace elements in water, such asFigure 1 The following are included: Atomization device: The water sample to be measured is converted into micron-sized aerosol water droplets through an ultrasonic atomizer, with an atomization efficiency ≥ 95% to ensure that the water sample is evenly dispersed into an aerosol state.

[0024] Gas chamber and White cell optical path, as Figures 2-7 shown: A dynamically adjustable White cell optical path unit is set in the gas chamber, including a first concave mirror A, a second concave mirror A', and a third concave mirror B. The third concave mirror B adjusts the tilt angle θ in real time through a piezoelectric ceramic driver, and cooperates with an angle sensor to monitor Δθ to achieve dynamic optimization of the optical path length to enhance the spectral absorption signal of low-concentration elements. The reflection unit includes two plane mirrors, one of which is located on the side wall of the light inlet of the gas chamber with an adjustable angle (adjustable range ±5°) for reflecting the incident light to the third concave mirror; the other plane mirror is located at the end of the optical path to reflect the absorbed light to the spectral detection module.

[0025] Optical path modulation module: As Figure 4 shown, an infrared light source is used as the light source, and the continuous light is converted into pulsed light through a chopper with a frequency of 1 - 100 Hz to reduce noise interference. The inflation wheel is filled with CO2 or N2. The filter is fixed at the bottom of the front seat to screen the characteristic absorption wavelength of the target element.

[0026] Temperature control module: As Figure 5 shown, a two-way temperature control using a TEC element and a heater is adopted. The temperature is dynamically adjusted through a fuzzy PID algorithm to ensure the stability of the optical elements and the optical path. The PT1000 sensor monitors the temperature in real time. After the data is converted into digital signals by the ADC module, it is processed by the FPGA microcontroller, and a PWM signal is output to drive the temperature control unit.

[0027] Spectral detection module: The grating spectroscopy unit disperses the absorbed mixed light by wavelength, and it is converted into an electrical signal by a photodetector. The signal processing unit uses a wavelet transform algorithm to denoise the electrical signal and calibrates the spectral intensity through the standard curve method.

[0028] Ionization and mass spectrometry module: It includes an ionization source and a mass spectrometer. The ionization source is used to ionize the aerosol in the gas chamber into ions, and the mass spectrometer is used to separate and detect the ions according to the mass-to-charge ratio; it also includes an electron multiplier, which is used to amplify and detect the ion signal separated by the mass spectrometer. The aerosol enters an inductively coupled plasma ionization source with an ionization efficiency ≥ 99% to generate gaseous ions. The mass spectrometer separates the ions according to the mass-to-charge ratio, and the electron multiplier amplifies the signal and then outputs the detection data.

[0029] Furthermore, as Figure 4 and Figure 5As shown in the figure, the optical path modulation module 1 includes a front seat 11, a rear seat 12, a light source 13, a chopper 14, an inflatable wheel 15, a driving device 16, and a filter 17; the driving device 16 is fixed to one side of the rear seat 12; a central hole is provided at the central position of the inflatable wheel 15; the inflatable wheel 15 is installed on the other side of the rear seat 12; a circular through hole is provided at the central position of the rear seat 12; the output end of the driving device 16 passes through the circular through hole of the rear seat 12 and the central hole of the inflatable wheel 15 and is connected to the chopper 14 for driving the chopper 14 to rotate; a light source incident hole is provided on the rear seat 12; the light source 13 is fixed to the rear seat; an inflation hole is provided on the side surface of the inflatable wheel 15; the front seat 11 is installed on the side wall of the air chamber 2; a filter 17 is further fixed to the bottom of the front seat 11; an inflation valve 18 is installed on the side wall of the front seat 11; one end of the inflation valve 18 is connected to the inflation hole of the inflatable wheel 15.

[0030] As Figure 4 shown, the optical path modulation module of the present invention is specifically as follows: The optical path modulation module includes a front seat, a rear seat, a light source, a chopper, an inflatable wheel, and a driving device; the driving device is fixed to one side of the rear seat; the rear seat is made of high-strength aluminum alloy, and a circular through hole is machined at the central position, and the inner wall of the through hole is plated with a wear-resistant coating. The driving device is a stepper motor, fixed to one side of the rear seat, and its output shaft is rigidly connected to the inflatable wheel and the chopper through a coupling. The stepper motor is controlled by a microcontroller, and can achieve a stepping accuracy of 0.1°, and drive the chopper to rotate synchronously at a preset speed, with a range of 10 - 200 rpm.

[0031] The inflatable wheel is of a disc-shaped structure, and the central hole is coaxially assembled with the circular through hole of the rear seat. An inflation hole is provided on the side surface of the inflatable wheel, and the inflation hole is connected to the inflation valve through a flexible air pipe. The chopper is a metal disc with evenly distributed slots, coaxially fixed with the inflatable wheel, and is used to modulate the continuous light source into pulsed light.

[0032] The light source uses a high-stability infrared light source, and is vertically incident on the inflatable wheel through the light source incident hole on the rear seat. The front seat is fixed to the side wall of the air chamber by bolts, and a band-pass filter is installed at the bottom, which is used to screen the characteristic absorption wavelength of the target element. The inflation valve is integrated on the side wall of the front seat, and the inflation valve is connected to the inflation hole of the inflatable wheel through a polytetrafluoroethylene hose, and the opening and closing of the valve body are controlled by an FPGA to ensure the synchronization of gas switching and optical path modulation.

[0033] Optical path modulation working process: The continuous light emitted by the light source is converted into pulsed light by the chopper, and the pulse frequency is controlled by the rotation speed of the stepper motor; the inflation valve synchronously switches the gas supply according to the window position to avoid cross-contamination; the target wavelength light screened by the filter enters the White cell optical path in the air chamber through the front seat to complete signal enhancement.

[0034] Further, as Figure 3 and Figure 6As shown in the figure, a reflection unit and a White cell optical path unit are installed in the gas chamber 2; the reflection unit includes a first plane mirror 21 and a second plane mirror 22; the first plane mirror 21 is arranged on the side wall of the light inlet of the gas chamber, with an adjustable angle, and is used to reflect the incident light to the third concave mirror B25 of the White cell optical path; the second plane mirror is arranged at the end of the White cell optical path and is used to reflect the light that has fully absorbed the gas to the spectral detection module; the White cell optical path unit is composed of a first concave mirror A23, a second concave mirror A'24, and a third concave mirror B25, where: the first concave mirror A23 and the second concave mirror A'24 are symmetrically arranged on one side inside the gas chamber, and the third concave mirror B is arranged on the other side inside the gas chamber; a piezoelectric ceramic driver is installed on the back of the third concave mirror B25 and is used to adjust the tilt angle θ of the third concave mirror B25.

[0035] The first plane mirror is fixed to the side wall of the light inlet of the gas chamber by a knob. The knob is equipped with a stepper motor, and the pitch angle of the plane mirror is controlled by a microcontroller. The adjustment range is ±5°, and it is used to accurately reflect the incident light to the third concave mirror B. The second plane mirror is fixed at the end of the White cell optical path, and the mirror surface forms a 45° angle with the optical path, and reflects the absorbed light to the grating spectroscopic unit of the spectral detection module.

[0036] The first concave mirror A and the second concave mirror A': are symmetrically arranged on the left side inside the gas chamber, and the surface is coated with a high-reflection dielectric film. The distance between the two mirrors is adjustable and is used to form a multiple reflection optical path. The third concave mirror B: is arranged on the right side of the gas chamber, with a radius of curvature R = 1000 mm. A piezoelectric ceramic driver is integrated on the back, and the tilt angle θ of the mirror surface is adjusted by the driving voltage to optimize the optical path collimation in real time.

[0037] The incident light is reflected by the first plane mirror to the third concave mirror B, and then multiple reflections are formed between A, A', and B. By increasing the optical path length, the absorption signal of low-concentration elements is enhanced; the piezoelectric ceramic driver dynamically adjusts the tilt angle θ of the third concave mirror B according to the aerosol concentration to compensate for the optical path offset caused by temperature or mechanical vibration; the second plane mirror guides the absorbed light to the spectral detection module.

[0038] Further, as Figure 8 shown, the temperature control module includes: A power supply, connected to the input end of the DC-DC converter; The DC-DC converter, the output end is connected to the heater through an LC filter circuit, and the LC filter circuit is used to suppress the high-frequency noise of the power supply; The temperature sensing unit, including a PT1000 sensor, whose output end is connected to the input end of the ADC module, and is used to convert the temperature analog signal into a digital signal; The control unit, using an FPGA or a W806 microcontroller, whose input end is connected to the output end of the ADC module, receives the digital temperature signal, and outputs a control signal through the PWM drive module; A temperature regulation unit, comprising: A TEC element, whose driving end is connected to the output end of the PWM driving module, and receives a PWM signal to achieve refrigeration or heating; A heater, whose power supply end is connected to the output end of the LC filter circuit, and whose control end is connected to the PWM signal output end of the FPGA or the W806 microcontroller; A communication unit, comprising an isolated serial port TTL circuit, whose input end is connected to the communication interface of the FPGA or the W806 microcontroller, and whose output end is connected to an external main control system to achieve electrically isolated data transmission.

[0039] Furthermore, the temperature control module uses a fuzzy PID control algorithm for temperature control, dynamically adjusts the parameters of the traditional PID controller through fuzzy inference, and the control process includes: First, collect the real-time temperature value of the temperature sensing unit , and compare it with the set temperature target value to obtain the temperature error , and the error change rate , where is the temperature error at the previous moment, is the sampling period; Take the temperature error and the error change rate as the inputs of the fuzzy controller, and perform fuzzy quantization on them respectively. The quantization factors are and respectively, to obtain the fuzzy input variables and ; According to the pre-established fuzzy rule base, perform fuzzy inference on the fuzzy input variables and to determine the fuzzy value of the output control increment ; Perform defuzzification on the fuzzy value of the control increment to obtain the actual control increment , where is corresponding fuzzy membership degree, is the candidate control increment value; Update the output of the PID controller according to the control increment , that is , and then control the working power of the heater or the TEC element to achieve the control of the temperature of the optical element and the gas chamber.

[0040] The input power supply of the temperature control module uses a 24V DC power supply, which is stepped down to 5V by a DC-DC converter to supply power to the FPGA microcontroller and its peripheral circuits. The output terminal is connected to the heater and the TEC element through an LC filter circuit to suppress the influence of high-frequency noise on the temperature control elements.

[0041] The temperature sensor uses a PT1000 platinum resistance temperature sensor, which is installed at the bottom of the gas chamber to collect temperature signals in real time; after the output of the sensor is conditioned by a differential amplification circuit, it is input to a 24-bit ADC module to convert the analog signal into a digital temperature value T actual 。

[0042] The FPGA microcontroller embeds a fuzzy PID control algorithm and outputs a control signal to the TEC element and the heater through a PWM drive module.

[0043] The communication unit uses an isolated serial port TTL circuit to realize data interaction between the FPGA and the external main control system, and transmits temperature data and control instructions.

[0044] Implementation process of the fuzzy PID control algorithm: a: Temperature error calculation: Set the target temperature T target , and read the actual temperature T actual output by the ADC module at 25°C, and calculate the error and the error change rate , where Δt is the sampling period.

[0045] b: Fuzzification processing: The quantization factors are set as =0.5, =0.2, and the error and are converted into fuzzy input variables and .

[0046] The input variables are divided into 7 fuzzy sets: negative big NB, negative medium NM, negative small NS, zero ZO, positive small PS, positive medium PM, positive big PB.

[0047] c: Fuzzy rule base and inference: 49 fuzzy rules are preset, and the Mamdani inference method is adopted to calculate the output membership degree in combination with the triangular membership function.

[0048] d: Defuzzification and PID parameter adjustment: Through the centroid method for defuzzification, calculate the actual control increment , where the candidate control increment value covers the PWM duty cycle range from -100% to +100%.

[0049] Update the PID output: , and drive the TEC component (cooling / heating) or the heater to adjust the power.

[0050] As Figure 9 shown, it is the circuit diagram of the isolated serial port TTL. The isolated serial port TTL circuit mainly includes two parts: transmission and reception. In the transmission part, the +5V power supply is connected to the base of the triode Q2 through the resistor R18 (4K7). The collector of Q2 is connected to the TX terminal through the resistor R20 (4K7). The emitter of Q2 is connected to the JP2 RS232 interface through the resistor R24 (1K2) and is in parallel with the diode D3 (IN4148). One end of the capacitor C5 (10uF) is connected between the anode of D3 and R24, and the other end is grounded. In the reception part, the RX terminal is connected to the base of the triode Q3 through the resistor R23 (1K2). The emitter of Q3 is grounded, and the collector is connected to the JP2 RS232 interface through the resistor R25 (4K7). And a diode D4 (IN4148) is connected in parallel between the collector and the emitter of Q3. The entire circuit is connected to an external device through JP2 for signal transmission to achieve the serial port isolation function.

[0051] Furthermore, the spectral detection module includes a grating spectroscopy unit, a photodetector, and a signal processing unit; the grating spectroscopy unit disperses the mixed light after passing through the absorption aerosol according to the wavelength; the photodetector receives the dispersed light and converts it into an electrical signal; the signal processing unit performs denoising processing on the electrical signal based on the wavelet transform algorithm, and calibrates the spectral intensity of the denoised signal.

[0052] The grating spectroscopy unit uses a planar holographic diffraction grating with a line density of 1200 lines / mm, a blazing wavelength of λ = 500 nm, a wavelength range covering 200 - 1000 nm, and a resolution of 0.1 nm. The grating is fixed behind the light outlet of the gas chamber, with an incident angle θ = 30°, ensuring that the grating diffraction efficiency is ≥80%. The surface of the grating is coated with an enhanced aluminum film, and a slit is set at the light path outlet to suppress the interference of stray light.

[0053] After the incident light enters the grating spectroscopy unit through the light outlet of the gas chamber, it is dispersed into a continuous spectrum according to the wavelength, and the dispersion angle range is ±15°. The precise alignment of the target wavelength is achieved by adjusting the grating angle.

[0054] The photodetector uses a back-illuminated CCD array, model Hamamatsu S7031 - 1006. The CCD array is installed on the focal plane of the grating spectroscopy unit and matches the distance from the grating.

[0055] Signal reading and conversion: The CCD drive circuit reads the pixel signal at a clock frequency of 10 kHz, amplifies it through a low-noise amplifier, and then inputs it to a 24-bit ADC module with a sampling rate of 50 kSPS to output a digital spectral signal.

[0056] The signal processing unit includes: (1) Wavelet transform denoising process: Decomposition and reconstruction: Using the Daubechies5 wavelet basis, perform 5-layer multi-resolution decomposition on the original spectral signal, and extract the high-frequency detail coefficients D1 - D5 and the low-frequency approximation coefficient A5.

[0057] Threshold processing: Perform soft threshold denoising on the high-frequency coefficients. The threshold calculation formula is:

[0058] where σ is the noise standard deviation and N is the signal length.

[0059] Reconstructed signal: Retain the low-frequency approximation coefficient A5, and perform inverse wavelet transform on the denoised high-frequency coefficients and A5 to obtain the denoised spectral signal.

[0060] (2) Spectral intensity calibration method: Standard curve method: Use Hg and Pb standard solutions with known concentrations to establish an absorbance-concentration curve. The fitting equation is a quadratic polynomial: ; where I is the calibrated intensity, C is the element concentration, and a, b, c are the fitting coefficients of the calibration curve, which are determined by fitting experimental data. a: Quadratic term coefficient, reflecting the contribution of the concentration square term to the response value. b: Linear term coefficient, reflecting the contribution of the concentration linear term to the response value. c: Constant term, representing the background signal or baseline offset.

[0061] Experimental steps: Prepare standard solutions with concentrations of Na, Ca, Mg, and K, measure their spectral intensity I, and obtain a, b, and c through fitting.

[0062] During detection: Measure the I of the unknown sample and substitute it into the formula to reverse-calculate the concentration C.

[0063] Real-time calibration: Before each detection, calibrate the response characteristics of the grating spectroscopic unit and the CCD through the built-in reference light source to ensure that the wavelength positioning error < ±0.05 nm.

[0064] Example 2: The present invention also provides a method for detecting the concentration of trace elements in water, as Figure 10 shown, including the following steps: S1. Convert the water sample to be measured into aerosol water droplets through an atomization device and introduce them into the gas chamber; S2. Generate incident light through a light source, convert it into pulsed light through a chopper, and use a filter to select the target wavelength; Guide the modulated incident light to the dynamic adjustable White cell optical path in the gas chamber; S3, using a spectral detection module to capture the spectral signal after aerosol absorption; S4, passing the aerosol in the gas chamber into an ionization source to ionize and generate gaseous ions; separating the ions according to the mass-to-charge ratio by a mass spectrometer, and amplifying the detection signal by an electron multiplier; S5. Perform Fourier transform and low-pass filtering on the spectral signal to remove high-frequency noise; calculate the concentration of trace elements in water based on the standard curve method combined with mass spectrometry data.

[0065] Step S1: Use an ultrasonic atomizer with an atomization frequency of 1.7MHz to convert the water sample to be tested into aerosol droplets with a particle size of 1-5μm, and the atomization efficiency is ≥98%. The aerosol is transported to the air chamber to ensure uniform aerosol distribution.

[0066] Step S2: Optical path modulation and background interference elimination; Light source and chopper: Use an infrared light source with a wavelength range of 200-1000nm and a power of 150W, which is modulated into pulse light by a chopper to reduce thermal noise; Install a bandpass filter to screen the characteristic absorption wavelength of the target element. Dynamic White cell optical path: The piezoelectric ceramic driver is used to adjust the tilt angle of the third concave mirror in real time, adjust the optical path, and enhance weak absorption signals. The synchronization signal triggers the spectrum detection module through the magnetic encoder to collect the reference signal and the measurement signal in time, and eliminates the background gas absorption interference through the differential algorithm.

[0067] Step S3: The spectrum detection module uses a grating spectrometer and a back-illuminated CCD array with a spectral resolution of 0.1 nm to capture the absorption spectrum at 253.7 nm in real time; the CCD output signal is converted by a 24-bit ADC and input into the FPGA for baseline correction and noise suppression.

[0068] Step S4: Using inductively coupled plasma (ICP) with a power of 1.2 kW and an argon flow rate of 12 L / min, the aerosol is ionized into gaseous ions. A quadrupole mass spectrometer is used to separate the target ions according to the mass-to-charge ratio (m / z), and an electron multiplier amplifies the signal and outputs the ion current intensity data.

[0069] Step S5: Fourier transform and filtering: Fast Fourier transform the spectral signal, use a low-pass filter to remove high-frequency noise, and retain the effective absorption peak. Spectral data: Calculate the preliminary concentration based on the standard curve method. Mass spectrometry data: Perform secondary verification through the ion current intensity and concentration calibration curve. The final concentration takes the weighted average of the spectrum and mass spectrometry results, with a weight ratio of 6:4 and a comprehensive error of <±5%.

[0070] Example 3: (1) A system for detecting trace element concentration in water, the system configuration comprising: Atomization device: Ultrasonic nebulizer, model Sono-Tek 8700-120, atomization frequency 1.7 MHz, aerosol particle size 1-5 μm, atomization efficiency ≥98%.

[0071] Gas chamber.

[0072] Optical path system: Dynamically adjust the White cell optical path, equipped with a piezoelectric ceramic driver, angle adjustment accuracy of ±0.001° and a high-reflectivity concave mirror with a reflectivity ≥99.9%.

[0073] Spectral detection module: Grating spectroscopy unit, 1200 lines / mm, resolution 0.1 nm; back-illuminated CCD, quantum efficiency ≥90%, dynamic range 16 bit.

[0074] Mass spectrometry module: Inductively coupled plasma mass spectrometer ICP-MS, mass resolution 0.1 amu, electron multiplier gain 10 6 .

[0075] (2) Experimental parameters: High-purity N2: Purity ≥99.99%, flow rate 0.5 L / min.

[0076] Ionization source: ICP power 1.2 kW, argon flow rate 12 L / min.

[0077] Signal processing: FPGA hardware acceleration, processing delay <2 ms.

[0078] (3) Implementation steps and test data of the detection method.

[0079] Step 1: Establishment of the standard curve.

[0080] Standard solution: Prepare standard solutions of Na, Ca, Mg, and K with a concentration range of 0.01-50 mg / L.

[0081] Through ICP-MS analysis, the standard curves of each element were obtained. The correlation coefficients (R²) of the standard curves were all greater than 0.99, indicating a good linear relationship.

[0082] As shown in Table 1, the standard curve equations and correlation coefficients of each element are presented, and the data results are as follows:

[0083] Step 2: Detection of the water sample to be measured.

[0084] Sample source: 3 different water sources (numbered 1-3), each detected 3 times repeatedly.

[0085] As shown in Table 2, the concentration detection results of each trace element in the water sample to be measured are presented, and the detection results are as follows:

[0086] Step 3: Repeatability and stability tests.

[0087] Repeatability: The water sample 1 was detected 5 times repeatedly, and RSD < 5%.

[0088] As shown in Table 3, the repeatability test results of repeated detection of water sample 1 are as follows:

[0089] Stability: The water sample 1 was detected continuously for 5 days, and the concentration fluctuation < 5%.

[0090] Step 4: Detection limit and noise level.

[0091] As shown in Table 4, the detection limits LOD of each element are shown:

[0092] Noise level: The average background noise is 50 counts / s, and the fluctuation range is ±10 counts / s.

[0093] 3. Data analysis and verification.

[0094] Multimodal data fusion: Combined use of spectroscopy and mass spectrometry: The spectral data (absorbance) and mass spectrometry data (ion current intensity) were calculated with weighted calculation, and the weight ratio was 6:4. The results showed that the RSD of the concentration of each element was less than 5%, indicating that the method has good repeatability.

[0095] Through this experiment, the effectiveness and performance indicators of the method and system for detecting the concentration of trace elements in water proposed in this patent were verified. This method and system can accurately and stably detect the concentration of various trace elements in water, and have a low detection limit and a small noise level, meeting the requirements of practical applications.

[0096] In this article, specific examples were used to elaborate on the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A system for detecting trace element concentration in water, characterized in that: include: Atomizing device, used for atomizing the water sample to be tested into aerosol water droplets; The gas chamber is connected to the atomization device and is provided with a White cell optical path inside thereof for enhancing the spectral absorption signal of low-concentration trace elements; An optical path modulation module is installed on the side wall of the air chamber and is used to modulate the incident light source and guide it to the White cell optical path in the air chamber; A temperature control module, connected to the bottom of the air chamber, for controlling the temperature of the air chamber; The spectrum detection module is arranged behind the light outlet of the air chamber and is used to detect the spectrum signal after the aerosol is absorbed; An ionization and mass spectrometry module, including an ionization source and a mass spectrometer, wherein the ionization source is used to ionize the aerosol in the gas chamber into ions, and the mass spectrometer is used to separate the ions according to the mass-to-charge ratio and perform detection; The result output module is connected with the spectrum detection module and the ionization and mass spectrometry module, and is used to process the spectrum signal and mass spectrum data, and output the trace element concentration detection result.

2. A system for detecting trace element concentration in water according to claim 1, characterized in that: The optical path modulation module comprises a front seat, a rear seat, a light source, a chopper, an inflatable wheel, a driving device and a filter; the driving device is fixed on one side of the rear seat; a center hole is opened at the center position of the inflatable wheel; the inflatable wheel is arranged on the other side of the rear seat; the output end of the driving device passes through the circular through hole of the rear seat and the center hole of the inflatable wheel and is connected with the chopper for driving the chopper to rotate; a light source incident hole is arranged on the rear seat; the light source is fixed on the rear seat; an inflatable hole is arranged on the side of the inflatable wheel; the front seat is installed on the side wall of the air chamber; a filter is also fixed on the bottom of the front seat; an inflatable valve is installed on the side wall of the front seat; one end of the inflatable valve is connected with the inflatable hole of the inflatable wheel.

3. A system for detecting trace element concentration in water according to claim 1, characterized in that: A reflection unit and a White pool optical path unit are installed in the air chamber; The reflection unit includes a first plane mirror and a second plane mirror; The first plane mirror is arranged on the side wall of the light entrance of the air chamber, and the angle is adjustable, and is used to reflect the incident light to the third concave mirror B of the light path of the White pool; The second plane mirror is arranged at the end of the light path of the White cell, and is used to reflect the light fully absorbed by the gas to the spectrum detection module; The White pool optical path unit consists of a first concave mirror A, a second concave mirror A' and a third concave mirror B, where: The first concave mirror A and the second concave mirror A' are symmetrically arranged on one side of the interior of the air chamber, and the third concave mirror B is arranged on the other side of the interior of the air chamber.

4. A system for detecting trace element concentration in water according to claim 1, characterized in that: The spectral detection module includes a grating spectrometer, a photodetector and a signal processing unit; the grating spectrometer disperses the mixed light after absorbing the aerosol according to the wavelength; the photodetector receives the dispersed light and converts it into an electrical signal; the signal processing unit denoises the electrical signal based on the wavelet transform algorithm, and performs spectral intensity calibration on the denoised signal.

5. A system for detecting trace element concentration in water according to claim 3, characterized in that: A piezoelectric ceramic driver is also installed on the back of the third concave mirror B to adjust the tilt angle θ of the third concave mirror B.

6. A system for detecting trace element concentration in water according to claim 1, characterized in that: The ionization and mass spectrometry module also includes an electron multiplier, which is used to amplify and detect ion signals separated by the mass spectrometer.

7. A system for detecting trace element concentration in water according to claim 1, characterized in that: The temperature control module includes: A power supply connected to the input of the DC-DC converter; A DC-DC converter, the output end of which is connected to the heater via an LC filter circuit, and the LC filter circuit is used to suppress high-frequency noise of the power supply; The temperature sensing unit includes a temperature sensor, which is attached to the bottom of the air chamber and is used to monitor the temperature of the air chamber in real time; its output end is connected to the input end of the ADC module and is used to convert the temperature analog signal into a digital signal; The control unit adopts FPGA or W806 microcontroller, whose input end is connected to the output end of the ADC module, receives the digital temperature signal, and outputs the control signal through the PWM drive module; Temperature regulating unit, comprising: The TEC element, whose driving end is connected to the output end of the PWM driving module, receives the PWM signal to achieve cooling or heating; A heater, whose power supply end is connected to the output end of the LC filter circuit, and whose control end is connected to the PWM signal output end of the FPGA or W806 microcontroller; The heater and TEC element are installed at the bottom of the air chamber; The communication unit includes an isolated serial port TTL circuit, an input end of which is connected to the communication interface of the FPGA or W806 microcontroller, and an output end of which is connected to an external main control system to realize electrically isolated data transmission.

8. A system for detecting trace element concentration in water according to claim 7, characterized in that: The temperature control module uses fuzzy pid control algorithm to control temperature and dynamically adjusts the parameters of the traditional pid controller through fuzzy reasoning.

9. A method for detecting the concentration of trace elements in water applied to the system for detecting the concentration of trace elements in water according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. The water sample to be tested is converted into aerosol water droplets through an atomization device and passed into the air chamber; S2, generating incident light through a light source, converting it into pulsed light through an inflatable wheel and a chopper, and using a filter to select a target wavelength; guiding the modulated incident light to a dynamically adjusted White cell optical path in the air chamber; S3, the light is guided to the spectrum detection module through the White cell optical path, and the spectrum detection module is used to capture the spectrum signal after aerosol absorption; S4, passing the aerosol in the gas chamber into an ionization source to ionize and generate gaseous ions; separating the ions according to the mass-to-charge ratio by a mass spectrometer, and amplifying the detection signal by an electron multiplier; S5, performing Fourier transform and low-pass filtering on the spectral signal to remove high-frequency noise; The concentration of trace elements in water was calculated based on the standard curve method combined with mass spectrometry data.

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