Method and system for detecting trace element concentration in water

Abstract

The present invention relates to the field of trace element detection, and in particular to a system for detecting trace element concentrations in water, comprising an atomizing device; an air chamber connected to the atomizing device, the interior of which is provided with a dynamically adjustable White cell optical path for enhancing spectral absorption signals of low-concentration trace elements; an optical path modulation module installed on the side wall of the air chamber; a temperature control module for adjusting the temperature of the optical element and the air chamber; a spectral detection module arranged behind the light outlet of the air chamber for detecting spectral signals after absorbing aerosol; an ionization and mass spectrometry module comprising an ionization source and a mass spectrometer, the ionization source being used to ionize the aerosol in the air chamber into ions, and the mass spectrometer being used to separate the ions according to the mass-to-charge ratio and perform detection. The present invention adopts a spectral and mass spectrometry-combined technology to atomize a water sample to be tested into aerosol droplets, and by enhancing the spectral absorption signals of low-concentration trace elements, achieves high-sensitivity detection of trace elements in water.

Description

Technical Field

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

[0002] In my country, water quality testing is crucial for ensuring the quality of domestic drinking water and ecological safety. Currently, water quality testing standards primarily cover microbiological and toxicological indicators, with toxicological indicators involving a variety of heavy metals and hazardous substances, such as arsenic, cadmium, and chromium. However, traditional water quality testing methods have limitations in sensitivity, accuracy, and stability, making them unable to meet increasingly stringent water quality standards and the demand for high-precision water quality testing.

[0003] Traditional spectroscopic analysis methods, such as atomic absorption spectroscopy and inductively coupled plasma optical emission spectroscopy, are widely used for trace element detection in water. However, their detection limits for ultra-low concentrations of trace elements are often high, typically exceeding tens of ppm, making it difficult to accurately detect trace amounts of harmful substances in water. Some optical-based detection methods are susceptible to environmental factors such as temperature changes and fluctuations in light intensity, resulting in unstable detection signals and poor repeatability and reproducibility. For example, in detection systems with long optical paths, slight temperature changes can cause thermal expansion or contraction of the optical path, leading to spectral drift and compromising the accuracy of test results.

[0004] In view of the many problems existing in the above-mentioned existing trace element detection technology in water, there is an urgent need to develop a method and system for detecting trace element concentrations in water with a low detection limit, high stability, strong anti-interference ability, simple operation and low cost, so as to meet the urgent demand for high-precision detection technology 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. The method adopts the technology of combining spectroscopy and mass spectrometry, combines components such as an atomization device, a dynamically adjustable White cell optical path, an ionization and mass spectrometry module, and atomizes the water sample to be tested into aerosol droplets. 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 problem is: to provide a system for detecting the concentration of trace elements in water, characterized by comprising: an atomization device for atomizing a water sample to be tested into aerosol droplets; an air chamber connected to the atomization device, wherein a White cell optical path is arranged inside the air chamber for enhancing the spectral absorption signal of low-concentration trace elements; an optical path modulation module installed on the side wall of the air chamber for modulating the incident light source and guiding 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; a spectral detection module arranged behind the light outlet of the air chamber for detecting the spectral signal after absorbing the aerosol; 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 air chamber into ions, and the mass spectrometer is used to separate the ions according to the 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 spectrum data and outputting the trace element concentration detection result.

[0007] Furthermore, the optical path modulation module includes 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 to 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 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 inflation hole is provided 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 to the bottom of the front seat; an inflation valve is installed on the side wall of the front seat; one end of the inflation valve is connected to the inflation hole of the inflatable wheel.

[0008] Furthermore, 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 inlet of the air chamber, and its angle is adjustable, and is used to reflect the incident light to the third concave mirror B of the White pool optical path; the second plane mirror is arranged at the end of the White pool optical path, and is used to reflect the light that has fully absorbed 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, wherein: 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.

[0009] Furthermore, 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 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.

[0010] Furthermore, a piezoelectric ceramic driver is installed on the back of the third concave mirror B to adjust the tilt angle θ of the third concave mirror B.

[0011] Furthermore, the ionization and mass spectrometry module also includes an electron multiplier, which is used to amplify and detect the ion signals separated by the mass spectrometer.

[0012] Furthermore, the temperature control module includes:

[0013] A power supply connected to the input of the DC-DC converter;

[0014] 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;

[0015] The temperature sensing unit includes a temperature sensor, which is attached to the bottom of the gas chamber and is used to monitor the gas chamber temperature in real time; its output end is connected to the input end of the ADC module, which is used to convert the temperature analog signal into a digital signal;

[0016] The control unit uses 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;

[0017] Temperature regulation unit, comprising:

[0018] The TEC element has its driving end connected to the output end of the PWM driving module and receives the PWM signal to achieve cooling or heating;

[0019] The heater has a power supply terminal connected to the output terminal of the LC filter circuit and a control terminal connected to the PWM signal output terminal of the FPGA or W806 microcontroller;

[0020] The heater and TEC element are installed at the bottom of the air chamber;

[0021] The communication unit includes an isolated serial port TTL circuit, the input end of which is connected to the communication interface of the FPGA or W806 microcontroller, and the output end is connected to the external main control system to achieve electrically isolated data transmission.

[0022] Furthermore, the temperature control module adopts fuzzy PID control algorithm to perform temperature control, and dynamically adjusts the parameters of the traditional PID controller through fuzzy reasoning.

[0023] The present invention also provides a method for detecting the concentration of trace elements in water, comprising the following steps:

[0024] S1. The water sample to be tested is converted into aerosol droplets through an atomization device and passed into the air chamber;

[0025] 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 the target wavelength; guiding the modulated incident light to the dynamically adjusted White cell optical path in the air chamber;

[0026] 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 spectral signal after aerosol absorption;

[0027] S4. Passing the aerosol in the chamber into an ionization source to ionize and generate gaseous ions; separating the ions according to their mass-to-charge ratio using a mass spectrometer, and amplifying the detection signal using an electron multiplier;

[0028] 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 and combined with the mass spectrometry data.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention utilizes spectroscopy and mass spectrometry, combining components such as an atomizer, a dynamically adjustable White cell optical path, and an ionization and mass spectrometry module to atomize the water sample to be tested into aerosol droplets. By enhancing the spectral absorption signal of low-concentration trace elements, it achieves highly sensitive detection of trace elements in water. Its detection limit can be as low as 1 PPM or even lower, resolving the problem of traditional detection methods with high detection limits and difficulty in accurately detecting ultra-low concentrations of trace elements. It can accurately detect trace amounts of harmful substances in water, such as arsenic, cadmium, chromium, and other heavy metals.

[0031] 2. The optimized design of the chopper and pneumatic wheel in the optical path modulation module, as well as the reflection unit and White cell optical path unit within the air chamber, makes the optical path more stable and reliable. Dynamic adjustment of the tilt angle of the third concave mirror in the White cell optical path, combined with an angle sensor to monitor the angle change in real time, allows for flexible adjustment of the optical path length and light reflection path based on actual detection requirements, ensuring multiple reflections and effective absorption of light within the air chamber, enhancing the stability and repeatability of the spectral signal.

[0032] 3. This invention introduces a temperature control module that can regulate and control the temperature of the gas chamber. Using a fuzzy PID control algorithm, it achieves high-precision constant temperature control within ±0.1°C, effectively eliminating the impact of temperature fluctuations on test results and ensuring the stability of the gas chamber temperature. This improves the stability and reliability of spectral detection, avoids spectral drift or resolution degradation caused by temperature changes, and ensures data stability and consistency during long-term testing.

[0033] 4. This invention incorporates an isolated serial port TTL circuit, providing electrical isolation and noise suppression for the system. This effectively protects sensitive circuits in complex detection environments, preventing signal loss and circuit damage caused by electrical interference, voltage fluctuations, or noise. This ensures stable and reliable data transmission between system modules and enhances the anti-interference capability of the entire detection system.

[0034] 5. The present invention adds a filter before the light enters the air chamber, which can effectively remove the scattering and absorption interference of particulate matter in the water sample on the spectral signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic structural diagram of a system for detecting trace element concentrations in water according to the present invention;

[0036] Figure 2 This is a partial structural diagram of a system for detecting trace element concentrations in water according to the present invention;

[0037] Figure 3 is a cross-sectional view of an air chamber of a system for detecting trace element concentration in water according to the present invention;

[0038] Figure 4 This is a structural schematic diagram of an optical path modulation module of a system for detecting trace element concentrations in water according to the present invention;

[0039] Figure 5 This is a physical diagram from one angle of the optical path modulation module, gas chamber, and spectrum analysis module of a system for detecting trace element concentrations in water according to the present invention;

[0040] Figure 6 This is a physical diagram from another angle of the optical path modulation module, gas chamber, and spectrum analysis module of a system for detecting trace element concentrations in water according to the present invention;

[0041] Figure 7 This is a physical diagram from another angle of the optical path modulation module, gas chamber, and spectrum analysis module of a system for detecting trace element concentrations in water according to the present invention;

[0042] Figure 8 This is a schematic structural diagram of a temperature control module of a system for detecting trace element concentrations in water according to the present invention;

[0043] Figure 9 This is a circuit diagram of a TTL circuit of a system for detecting trace element concentration in water according to the present invention;

[0044] Figure 10 It is a schematic flow chart of a method for detecting trace element concentration in water according to the present invention;

[0045] The components in the accompanying drawings are marked as follows: 1. Optical path modulation module; 11. Front seat, 12. Rear seat; 13. Light source; 14. Chopper; 15. Inflatable wheel; 16. Driving device; 17. Filter; 18. Inflating 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 DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] Example 1: The present invention provides a system for detecting trace element concentration in water, such as Figure 1 Shown include:

[0048] Atomization device: The water sample to be tested is converted into micron-sized aerosol droplets through an ultrasonic atomizer, with an atomization efficiency of ≥95%, ensuring that the water sample is evenly dispersed into an aerosol state.

[0049] The light path between the gas chamber and the White pool, such as Figure 2-7 Figure 2 shows a dynamically adjustable White cell optical path unit within the gas chamber, comprising a first concave mirror A, a second concave mirror A', and a third concave mirror B. The third concave mirror B uses a piezoelectric ceramic driver to adjust its tilt angle θ in real time, and an angle sensor monitors Δθ to dynamically optimize the optical path length and enhance the spectral absorption signal of low-concentration elements. The reflective unit comprises two plane mirrors, one of which is located on the sidewall of the gas chamber's light inlet and has an adjustable angle (±5°) to reflect incident light toward the third concave mirror. The other plane mirror, located at the end of the optical path, reflects absorbed light toward the spectral detection module.

[0050] Optical path modulation module: such as Figure 4 As shown, the light source uses an infrared light source, which is converted into pulsed light via a chopper at a frequency of 1-100Hz to reduce noise interference. The inflatable wheel is filled with CO2 or N2. The filter is fixed to the bottom of the front seat to select the characteristic absorption wavelength of the target element.

[0051] Temperature control module: Figure 5 As shown, dual temperature control using a TEC element and heater is employed. A fuzzy PID algorithm dynamically adjusts the temperature to ensure the stability of the optical components and optical path. A PT1000 sensor monitors the temperature in real time. The data is converted to a digital signal by an ADC module and then processed by an FPGA microcontroller, which then outputs a PWM signal to drive the temperature control unit.

[0052] Spectral Detection Module: The grating spectrometer disperses the absorbed mixed light according to wavelength, which is then converted into an electrical signal by a photodetector. The signal processing unit uses a wavelet transform algorithm to remove noise from the electrical signal and calibrates the spectral intensity using a standard curve method.

[0053] The Ionization and Mass Spectrometry Module includes an ionization source and a mass spectrometer. The ionization source ionizes the aerosol in the chamber into ions, and the mass spectrometer separates and detects the ions based on their mass-to-charge ratio. The module also includes an electron multiplier, which amplifies and detects the ion signals separated by the mass spectrometer. Aerosol enters the inductively coupled plasma ionization source, generating gaseous ions with an ionization efficiency of ≥99%. The mass spectrometer separates the ions based on their mass-to-charge ratio, and the electron multiplier amplifies the signals and outputs the detection data.

[0054] Furthermore, if Figure 4 and Figure 5 As shown, 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 center hole is provided at the center 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 center 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 center 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 of the inflatable wheel 15; the front seat 11 is installed on the side wall of the air chamber 2; a filter 17 is also 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.

[0055] like Figure 4 As shown, the optical path modulation module of the present invention is specifically as follows:

[0056] The optical path modulation module consists of a front seat, a rear seat, a light source, a chopper, an inflatable wheel, and a drive unit. The drive unit is fixed to one side of the rear seat. The rear seat is made of high-strength aluminum alloy and features a circular through-hole in the center, coated with a wear-resistant coating. The drive unit uses a stepper motor, fixed to one side of the rear seat. Its output shaft is rigidly connected to the inflatable wheel and chopper via a coupling. The stepper motor is controlled by a microcontroller and achieves 0.1° step accuracy. It drives the chopper to rotate synchronously at a preset speed ranging from 10 to 200 rpm.

[0057] The pneumatic wheel is a disc-shaped structure with a central hole coaxially mounted with the circular through-hole in the rear seat. Inflation holes are located on the side of the wheel, connected to the inflation valve via a flexible air tube. The chopper, a metal disc with uniform grooves coaxially mounted on the wheel, modulates the continuous light source into pulsed light.

[0058] The light source uses a highly stable infrared source, which is incident vertically onto the pneumatic wheel through the light source entrance hole on the rear seat. The front seat is bolted to the side wall of the air chamber, and a bandpass filter is installed at the bottom to screen for the characteristic absorption wavelength of the target element. The inflation valve is integrated into the side wall of the front seat and connected to the inflation hole of the pneumatic wheel via a polytetrafluoroethylene hose. The valve body is controlled by an FPGA to ensure the synchronization of gas switching and optical path modulation.

[0059] Optical path modulation workflow:

[0060] The continuous light emitted by the light source is converted into pulsed light by a chopper, and the pulse frequency is controlled by the speed of the stepper motor; the inflation valve switches the gas supply synchronously according to the window position to avoid cross contamination; the target wavelength light after being screened by the filter enters the White pool optical path in the gas chamber through the front seat to complete the signal enhancement.

[0061] Furthermore, if Figure 3 and Figure 6 As shown, a reflection unit and a White pool optical path unit are installed in the air 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 air chamber, and its angle is adjustable, and is used to reflect the incident light to the third concave mirror B25 of the White pool optical path; the second plane mirror is arranged at the end of the White pool optical path, and is used to reflect the light that has fully absorbed the gas to the spectrum detection module; the White pool optical path unit consists of a first concave mirror A23, a second concave mirror A'24 and a third concave mirror B25, wherein: the first concave mirror A23 and the second concave mirror A'24 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; a piezoelectric ceramic driver is installed on the back of the third concave mirror B25, which is used to adjust the inclination angle θ of the third concave mirror B25.

[0062] The first plane mirror is fixed to the side wall of the air chamber light entrance by a knob equipped with a stepper motor. The microcontroller controls the plane mirror's pitch angle within a ±5° adjustment range, precisely reflecting the incident light to the third concave mirror B. The second plane mirror is fixed at the end of the White cell optical path, with the mirror surface forming a 45° angle with the optical path, reflecting the absorbed light to the grating spectrometer unit of the spectrum detection module.

[0063] The first and second concave mirrors A and A' are symmetrically positioned on the left side of the air chamber. Coated with a highly reflective dielectric film, the distance between the mirrors is adjustable, creating a multi-reflection optical path. The third concave mirror B, positioned on the right side of the air chamber, has a curvature radius of R = 1000mm and an integrated piezoelectric ceramic driver on its back. The drive voltage adjusts the mirror's tilt angle θ, optimizing the optical path's collimation in real time.

[0064] The incident light is reflected by the first plane mirror to the third concave mirror B, and then forms multiple reflections between A, A', and B, enhancing the absorption signal of low-concentration elements by increasing the optical path length. The piezoelectric ceramic driver dynamically adjusts the tilt angle θ of the third concave mirror B according to the aerosol concentration to compensate for optical path deviation caused by temperature or mechanical vibration. The second plane mirror guides the absorbed light to the spectral detection module.

[0065] Furthermore, if Figure 8 As shown, the temperature control module includes:

[0066] A power supply connected to the input of the DC-DC converter;

[0067] 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;

[0068] The temperature sensing unit includes a PT1000 sensor, the output end of which is connected to the input end of the ADC module for converting the temperature analog signal into a digital signal;

[0069] The control unit uses 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;

[0070] Temperature regulation unit, comprising:

[0071] The TEC element has its driving end connected to the output end of the PWM driving module and receives the PWM signal to achieve cooling or heating;

[0072] The heater has a power supply terminal connected to the output terminal of the LC filter circuit and a control terminal connected to the PWM signal output terminal of the FPGA or W806 microcontroller;

[0073] The communication unit includes an isolated serial port TTL circuit, the input end of which is connected to the communication interface of the FPGA or W806 microcontroller, and the output end is connected to the external main control system to achieve electrically isolated data transmission.

[0074] Furthermore, the temperature control module uses a fuzzy PID control algorithm to perform temperature control, and dynamically adjusts the parameters of the traditional PID controller through fuzzy reasoning. The control process includes:

[0075] First, collect the real-time temperature value of the temperature sensing unit , and the set temperature target value Compare and get the temperature error , and the error rate of change ,in is the temperature error at the previous moment, is the sampling period;

[0076] The temperature error and error rate of change As the input of the fuzzy controller, it is fuzzy quantized and the quantization factors are and , get the fuzzy input variable and ;

[0077] According to the pre-established fuzzy rule base, the fuzzy input variables and Perform fuzzy reasoning to determine the output control increment The fuzzy value of

[0078] Control increment The fuzzy value is defuzzified to obtain the actual control increment ,in for The corresponding fuzzy membership is is the candidate control increment value;

[0079] According to the control increment Update the output of the pid controller, i.e. , and then control the working power of the heater or tec element to achieve control of the temperature of the optical element and the gas chamber.

[0080] The temperature control module's input power source is a 24V DC power supply, which is stepped down to 5V by a DC-DC converter to power the FPGA microcontroller and peripheral circuits. The output is connected to the heater and TEC element via an LC filter circuit to suppress the impact of high-frequency noise on the temperature control element.

[0081] 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. The sensor output is conditioned by the differential amplifier circuit and input into the 24-bit ADC module to convert the analog signal into a digital temperature value T. actual .

[0082] The FPGA microcontroller has a built-in fuzzy PID control algorithm, which outputs control signals to the TEC element and heater through the PWM drive module.

[0083] The communication unit uses an isolated serial TTL circuit to realize data interaction between FPGA and external main control system, and transmit temperature data and control instructions.

[0084] Fuzzy PID control algorithm implementation process:

[0085] a: Temperature error calculation:

[0086] Set target temperature Ttarget , read the actual temperature T output by the ADC module at 25℃ actual , calculation error and error change rate , where Δt is the sampling period.

[0087] b: Fuzzy processing:

[0088] The quantization factor is set to =0.5, =0.2, the error and Convert to fuzzy input variables and .

[0089] The input variables are divided into 7 fuzzy sets: negative large NB, negative medium NM, negative small NS, zero ZO, positive small PS, positive medium PM, and positive large PB.

[0090] c: Fuzzy rule base and reasoning:

[0091] 49 fuzzy rules are preset, and the Mamdani reasoning method is used in combination with the triangular membership function to calculate the output membership.

[0092] d: Defuzzification and PID parameter adjustment:

[0093] Defuzzification is performed by the center of gravity method to calculate the actual control increment , where the candidate control increment value is Covers a PWM duty cycle range of -100% to +100%.

[0094] Update PID output: , drive TEC element (cooling / heating) or heater to adjust power.

[0095] like Figure 9 Figure 2 shows the circuit diagram for an isolated serial TTL interface. This circuit primarily consists of two parts: the transmitter and receiver. In the transmitter, the +5V power supply is connected to the base of transistor Q2 via resistor R18 (4K7). Q2's collector is connected to the TX terminal via resistor R20 (4K7). Q2's emitter is connected to the RS232 interface on JP2 via resistor R24 ​​(1K2) and in parallel with diode D3 (IN4148). Capacitor C5 (10µF) is connected between the anode of D3 and R24, with the other end grounded. In the receiver, the RX terminal is connected to the base of transistor Q3 via resistor R23 (1K2). Q3's emitter is grounded, and its collector is connected to the RS232 interface on JP2 via resistor R25 (4K7). Diode D4 (IN4148) is connected in parallel between Q3's collector and emitter. The entire circuit connects to external devices via JP2 for signal transmission, achieving serial port isolation.

[0096] Furthermore, 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 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.

[0097] The grating spectrometer utilizes a planar holographic diffraction grating with a line density of 1200 lines / mm, a blaze wavelength of λ=500nm, a wavelength range of 200-1000nm, and a resolution of 0.1nm. The grating is fixed behind the light exit of the gas chamber, with an incident angle of θ=30°, ensuring a diffraction efficiency of ≥80%. The grating surface is coated with an enhanced aluminum film, and a slit is placed at the light exit to suppress stray light interference.

[0098] After the incident light enters the grating spectrometer through the light outlet of the gas chamber, it is dispersed into a continuous spectrum according to wavelength. The dispersion angle range is ±15°. The target wavelength can be precisely aligned by adjusting the grating angle.

[0099] The photodetector is a back-illuminated CCD array, model Hamamatsu S7031-1006. The CCD array is mounted on the focal plane of the grating spectrometer and matches the grating spacing.

[0100] Signal readout and conversion:

[0101] The CCD driver circuit reads the pixel signal at a 10kHz clock frequency, amplifies it through a low-noise amplifier, and then inputs it into a 24-bit ADC module with a sampling rate of 50kSPS to output a digital spectrum signal.

[0102] The signal processing unit includes:

[0103] (1) Wavelet transform denoising process:

[0104] Decomposition and reconstruction: Using the Daubechies5 wavelet basis, the original spectral signal is decomposed into 5 layers of multi-resolution to extract high-frequency detail coefficients D1-D5 and low-frequency approximation coefficient A5.

[0105] Threshold processing: Soft threshold denoising is performed on high-frequency coefficients. The threshold calculation formula is:

[0106]

[0107] Where σ is the standard deviation of the noise and N is the signal length.

[0108] Reconstruct the signal: retain the low-frequency approximate coefficient A5, perform inverse wavelet transform on the denoised high-frequency coefficient and A5 to obtain the denoised spectral signal.

[0109] (2) Spectral intensity calibration method:

[0110] Standard curve method: Use Hg and Pb standard solutions of known concentration to establish an absorbance-concentration curve, and the fitting equation is a quadratic polynomial:

[0111] ;

[0112] Where I is the calibrated intensity, C is the element concentration, and a, b, and c are the calibration curve fitting coefficients, determined by fitting experimental data. a is the quadratic coefficient, reflecting the contribution of the squared concentration term to the response. b is the linear coefficient, reflecting the contribution of the linear concentration term to the response. c is the constant term, representing background signal or baseline shift.

[0113] Experimental steps: Prepare standard solutions of Na, Ca, Mg, and K concentrations, measure their spectral intensity I, and obtain a, b, and c through fitting.

[0114] During detection: measure the I of the unknown sample and substitute it into the formula to reverse calculate the concentration C.

[0115] Real-time calibration: Before each test, the response characteristics of the grating spectrometer and CCD are calibrated using a built-in reference light source to ensure that the wavelength positioning error is less than ±0.05nm.

[0116] Example 2: The present invention also provides a method for detecting the concentration of trace elements in water, such as Figure 10 As shown, the following steps are included:

[0117] S1. The water sample to be tested is converted into aerosol droplets through an atomization device and passed into the air chamber;

[0118] S2, generating incident light through a light source, converting it into pulsed light through a chopper, and using a filter to select the target wavelength; guiding the modulated incident light to the dynamically adjusted White cell optical path in the gas chamber;

[0119] S3, using a spectral detection module to capture the spectral signal after aerosol absorption;

[0120] S4. Passing the aerosol in the chamber into an ionization source to ionize and generate gaseous ions; separating the ions according to their mass-to-charge ratio using a mass spectrometer, and amplifying the detection signal using an electron multiplier;

[0121] 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 and combined with the mass spectrometry data.

[0122] Step S1: Use an ultrasonic atomizer with an atomization frequency of 1.7 MHz to convert the water sample to aerosol droplets with a particle size of 1-5 μm, with an atomization efficiency of ≥98%. The aerosol is transported to the air chamber to ensure uniform aerosol distribution.

[0123] Step S2: Optical Path Modulation and Background Interference Elimination; Light Source and Chopper: An infrared light source with a wavelength range of 200-1000nm and a power of 150W is used, modulated into pulsed light by a chopper to reduce thermal noise. A bandpass filter is installed to select the characteristic absorption wavelength of the target element. Dynamic White Cell Optical Path: A piezoelectric ceramic driver adjusts the tilt angle of the third concave mirror in real time, adjusting the optical path and enhancing weak absorption signals. A synchronization signal, via a magnetic encoder, triggers the spectral detection module to time-share the reference and measurement signals. Background gas absorption interference is eliminated using a differential algorithm.

[0124] 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.

[0125] Step S4: Ionize the aerosol into gaseous ions using an inductively coupled plasma (ICP) at 1.2 kW power and an argon flow rate of 12 L / min. A quadrupole mass spectrometer separates the target ions by mass-to-charge ratio (m / z). An electron multiplier amplifies the signal and outputs ion current intensity data.

[0126] Step S5: Fourier Transform and Filtering: Perform a fast Fourier transform on the spectral signal, apply a low-pass filter to remove high-frequency noise, and retain the significant absorption peaks. Spectral data: Preliminary concentrations are calculated based on a standard curve. Mass spectrometric data: Secondary verification is performed using a calibration curve of ion current intensity and concentration. The final concentration is the weighted average of the spectral and mass spectrometric results, with a weighting ratio of 6:4 and a combined error of <±5%.

[0127] Example 3: (1) A system for detecting trace element concentration in water, the system configuration comprising:

[0128] Atomization device: ultrasonic nebulizer, model Sono-Tek8700-120, atomization frequency 1.7 MHz, aerosol particle size 1-5 μm, atomization efficiency ≥98%.

[0129] Air chamber.

[0130] Optical path system: Dynamically adjusted White cell optical path, equipped with piezoelectric ceramic driver, angle adjustment accuracy ±0.001° and high reflectivity concave mirror, reflectivity ≥99.9%.

[0131] Spectral detection module: grating spectrometer, 1200 lines / mm, resolution 0.1 nm; back-illuminated CCD, quantum efficiency ≥ 90%, dynamic range 16 bits.

[0132] Mass spectrometry module: Inductively coupled plasma mass spectrometer ICP-MS, mass resolution 0.1amu, electron multiplier gain 10 6 .

[0133] (2) Experimental parameters:

[0134] High-purity N2: purity ≥99.99%, flow rate 0.5L / min.

[0135] Ionization source: ICP power 1.2 kW, argon flow rate 12 L / min.

[0136] Signal processing: FPGA hardware acceleration, processing delay <2ms.

[0137] (3) Implementation steps and test data of the detection method.

[0138] Step 1: Establish a standard curve.

[0139] Standard solution: Prepare standard solutions of Na, Ca, Mg, and K with a concentration range of 0.01-50 mg / L.

[0140] ICP-MS analysis yielded calibration curves for each element. The correlation coefficients (R²) of the calibration curves were all greater than 0.99, indicating good linear relationships.

[0141] As shown in Table 1, the standard curve equations and correlation coefficients of each element are as follows:

[0142]

[0143] Step 2: Testing of water samples to be tested.

[0144] Sample source: 3 different water sources (numbered 1-3), each tested 3 times.

[0145] As shown in Table 2, the concentration test results of each trace element in the water sample to be tested are as follows:

[0146]

[0147] Step 3: Repeatability and stability test.

[0148] Repeatability: Water sample 1 was tested 5 times with RSD < 5%.

[0149] As shown in Table 3, the repeatability test results of repeated testing of water sample 1 are as follows:

[0150]

[0151] Stability: When water sample 1 was tested for 5 consecutive days, the concentration fluctuation was less than 5%.

[0152] Step 4: Detection limit and noise level.

[0153] As shown in Table 4, the detection limit LOD of each element is shown:

[0154]

[0155] Noise level: The average background noise is 50 counts / s, with a fluctuation range of ±10 counts / s.

[0156] 3. Data analysis and verification.

[0157] Multimodal data fusion:

[0158] Combination of spectroscopy and mass spectrometry: Spectral data (absorbance) and mass spectrometry data (ion current intensity) were weighted and calculated with a weight ratio of 6:4. The results showed that the RSD of each element concentration was less than 5%, indicating that the method has good repeatability.

[0159] This experiment verified the effectiveness and performance of the proposed method and system for detecting trace element concentrations in water. The method and system can accurately and stably detect the concentrations of multiple trace elements in water, with low detection limits and minimal noise, meeting the needs of practical applications.

[0160] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting 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 droplets; The gas chamber is connected to the atomization device and has a White cell optical path inside for enhancing the spectral absorption signal of low-concentration trace elements; The optical path modulation module is installed on the side wall of the gas chamber and is used to modulate the incident light source and guide it to the White cell optical path in the gas chamber; A temperature control module is connected to the bottom of the air chamber and is used to control the temperature of the air chamber; The spectrum detection module is located behind the light outlet of the gas chamber and is used to detect the spectrum signal after the aerosol is absorbed; Ionization and mass spectrometry module, including 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 the ions according to the mass-to-charge ratio and detect them; The result output module is connected to the spectrum detection module and the ionization and mass spectrometry module to process the spectrum signal and mass spectrometry data. The spectrum data is used to calculate the initial concentration based on the standard curve method. The mass spectrometry data is secondary verified by the ion current intensity and concentration calibration curve. The final concentration is the weighted average of the spectrum and mass spectrometry results, and the trace element concentration detection result is output. 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 gas chamber and is used to monitor the gas chamber temperature in real time; its output end is connected to the input end of the ADC module, which is used to convert the temperature analog signal into a digital signal; The control unit uses 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 regulation unit, comprising: The TEC element has its driving end connected to the output end of the PWM driving module and receives the PWM signal to achieve cooling or heating; The heater has a power supply terminal connected to the output terminal of the LC filter circuit and a control terminal connected to the PWM signal output terminal 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, the input end of which is connected to the communication interface of the FPGA or W806 microcontroller, and the output end is connected to the external main control system to achieve electrically isolated data transmission; The isolated serial port TTL circuit includes: a transmitting part, a +5V power supply is connected to the base of transistor Q2 via resistor R18, the collector of Q2 is connected to the TX terminal via resistor R20, the emitter of Q2 is connected to the JP2RS232 interface via resistor R24, and is connected in parallel with diode D3, one end of capacitor C5 is connected between the anode of D3 and R24, and the other end is grounded; a receiving part, an RX terminal is connected to the base of transistor Q3 via resistor R23, the emitter of Q3 is grounded, the collector is connected to the JP2RS232 interface via resistor R25, and a diode D4 is connected in parallel between the collector and emitter of Q3; Among them, the temperature control module adopts fuzzy pid control algorithm to control the temperature, and dynamically adjusts the parameters of the traditional pid controller through fuzzy reasoning; First, collect the real-time temperature value of the temperature sensing unit , and the set temperature target value Compare and get the temperature error , and the error rate of change ,in is the temperature error at the previous moment, is the sampling period; The temperature error and error rate of change As the input of the fuzzy controller, it is fuzzy quantized and the quantization factors are and , get the fuzzy input variable and ; According to the pre-established fuzzy rule base, the fuzzy input variables and Perform fuzzy reasoning to determine the output control increment The fuzzy value of Control increment The fuzzy value is defuzzified to obtain the actual control increment ,in for The corresponding fuzzy membership is is the candidate control increment value; According to the control increment Update the output of the pid controller, i.e. , and then control the working power of the heater or tec element to achieve control of the temperature of the optical element and the gas chamber.

2. A system for detecting trace element concentration in water according to claim 1, characterized in that: The optical path modulation module includes 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 to 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 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 to the rear seat; an inflation hole is provided 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 to the bottom of the front seat; an inflation valve is installed on the side wall of the front seat; one end of the inflation valve is connected to the inflation 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 reflecting unit includes a first plane mirror and a second plane mirror; The first plane mirror is set on the side wall of the light entrance of the air chamber, with an adjustable angle, and is used to reflect the incident light to the third concave mirror B in 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 that has fully absorbed 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, wherein the first concave mirror A and the second concave mirror A' are symmetrically arranged on one side of the air chamber, and the third concave mirror B is arranged on the other side of the air chamber.

4. The 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 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. The 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 the ion signals separated by the mass spectrometer.

7. A method for detecting trace element concentration in water applied to the system for detecting trace element concentration in water according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. The water sample to be tested is converted into aerosol 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 the target wavelength; guiding the modulated incident light to the dynamically adjusted White cell optical path in the air chamber; S3. Light is guided through the White cell optical path to the spectral detection module, which captures the spectral signal after aerosol absorption. S4. The aerosol in the chamber is passed through an ionization source to ionize and generate gaseous ions. The ions are separated by mass-to-charge ratio using a mass spectrometer, and the detection signal is amplified using an electron multiplier. S5. The spectral signal is Fourier transformed and low-pass filtered to remove high-frequency noise. The concentrations of trace elements in water were calculated based on the standard curve method and combined with mass spectrometry data.

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