Soil weakly acidic soluble heavy metal detection system and detection method

Abstract

This invention discloses a detection system and method for weakly acidic soluble heavy metals in soil, relating to the field of soil research technology. It includes a main frame, a control system, and a pretreatment device, a detection device, and a transport device set within the main frame and controlled by the control system. The transport device includes a three-dimensional moving component, an injection device, and a gripper device, with the injection device and gripper device located at the moving ends of the three-dimensional moving component. The pretreatment device includes a pretreatment microfluidic chip and a rotation drive device. The pretreatment microfluidic chip can be placed at the output end of the rotation drive device and includes a vortex mixing zone, a filtration separation zone, and a centrifugal enrichment zone. The detection device includes an electrode connection area and a detection microfluidic chip based on electrochemical detection. The electrodes within the detection microfluidic chip can contact the electrode connection area, and the electrode connection area can output an electrical signal. This invention enables one-stop processing, has a high degree of automation, and high experimental efficiency.

Description

Technical Field

[0001] This invention relates to the field of soil research technology, and in particular to a detection system and method for detecting soluble heavy metals in weakly acidic soil. Background Technology

[0002] Traditional soil heavy metal detection mainly relies on large laboratory instruments, such as atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS). While these techniques excel in detection accuracy and sensitivity, they generally suffer from high costs, long detection cycles, and inconvenience in portability. To address these issues, electrochemical analysis methods, particularly anodic stripping voltammetry (ASV), are now widely used. This method involves smaller and lower-cost equipment. However, before using stripping voltammetry, an extraction process is required. Traditional stepwise extraction methods based on classic fractional extraction techniques such as BCR or Tessier are time-consuming. Furthermore, current experiments are often conducted in stages using multiple machines. After each machine completes its operation, the processed sample is manually transferred to the next machine for the next step, consuming significant manpower and resources, resulting in long overall processing times and low experimental efficiency. The multi-machine setup is also inconvenient to carry, has low automation, and is very difficult to implement in field experiments. Therefore, there is an urgent need for a detection system and method for soluble heavy metals in weakly acidic soil to solve the above-mentioned technical problems. Summary of the Invention

[0003] The purpose of this invention is to provide a detection system and method for soluble heavy metals in weakly acidic soil, in order to solve the problems existing in the prior art. It can achieve one-stop processing, has a high degree of automation, and has high experimental efficiency.

[0004] To achieve the above objectives, the present invention provides the following solution: This invention provides a soil weakly acidic soluble heavy metal detection system, comprising a main frame, a control system, and a pretreatment device, a detection device, and a transport operation device disposed within the main frame and controlled by the control system; wherein; The transfer operation device includes a three-dimensional moving component, an injection device, and a gripper device. The injection device and the gripper device are disposed at the moving end of the three-dimensional moving component, and the moving end of the three-dimensional moving component is capable of three-dimensional movement within the main frame. The pretreatment device includes a pretreatment microfluidic chip and a rotary drive device. The pretreatment microfluidic chip can contain soil samples and weak acid extract. The gripper device can grasp the pretreatment microfluidic chip and place it at the output end of the rotary drive device. The rotary drive device can drive the pretreatment microfluidic chip to rotate. The pretreatment microfluidic chip includes at least a vortex mixing zone, a filtration separation zone, and a centrifugal enrichment zone from the inside out. Under the action of the rotary drive device, the experimental sample can sequentially reach the vortex mixing zone, the filtration separation zone, and the centrifugal enrichment zone. The detection device includes a detection microfluidic chip and an electrode connection area. The detection microfluidic chip uses electrochemical detection. The gripper device can move the detection microfluidic chip and make the electrodes in the detection microfluidic chip contact the electrode connection area. The injection device can transfer the experimental sample processed by the pretreatment device to the detection microfluidic chip. The electrode connection area can output an electrical signal.

[0005] In some embodiments, the pretreatment microfluidic chip includes a sealing membrane layer, a main chamber layer, a filter membrane layer, a secondary chamber layer, and a base plate connected sequentially from top to bottom. Each of the sealing layer, the main chamber layer, the filter membrane layer, and the secondary chamber layer has multiple processing spaces radially, and when stacked, there are at least three processing spaces radially, which, from the inside out, are the vortex mixing zone, the filtration separation zone, and the centrifugal enrichment zone. The sealing layer has an inlet near its center and an outlet near its edge. The sample to be tested can enter through the inlet and flow into the vortex mixing zone for vortex extraction. After extraction, the sample can pass through the filter membrane layer and, under external force, from the main chamber layer to the filtration separation zone, and finally reach the centrifugal enrichment zone and be removed through the outlet.

[0006] In some embodiments, the sealing layer, the main chamber layer, the filter membrane layer, and the secondary chamber layer have multiple independent processing units along the circumferential direction, and each processing unit includes the vortex mixing zone, the filtration separation zone, the centrifugation enrichment zone, the sample inlet, and the sample outlet.

[0007] In some embodiments, the sealing layer includes a sealing upper layer, a sealing middle layer, and a sealing lower layer that are sequentially bonded together from top to bottom; The filter membrane layer includes an upper filter membrane layer, a middle filter membrane layer, and a lower filter membrane layer that are sequentially bonded together from top to bottom. The upper filter membrane layer and the lower filter membrane layer can support the middle filter membrane layer.

[0008] In some embodiments, the device further includes a first substrate holder, a first substrate tray, a second substrate holder, and a second substrate tray. The first substrate tray is used to support the pre-processing microfluidic chip and is slidably connected to the first substrate holder. The second substrate tray is used to support the detection microfluidic chip. The electrode connection area is fixedly disposed on the second substrate holder, and the second substrate tray is slidably connected to the second substrate holder. Push rods are provided on both the first and second substrate trays. A magnet is fixedly disposed in the sealing middle layer. The gripping device is a magnetic push block, which can push the push rods and attract the pre-processing microfluidic chip.

[0009] In some embodiments, the detection microfluidic chip comprises, from top to bottom, a sealing film layer, a channel layer, a detection layer, an electrode layer, a waste liquid layer, and a bottom layer. The channel layer, the detection layer, the electrode layer, and the waste liquid layer each have interconnected waste liquid ports, collectively forming a waste liquid chamber. The channel layer is provided with an inlet channel, a detection hole, and an outlet channel. The sealing layer has an inlet hole; one end of the inlet channel communicates with the inlet hole, and the other end communicates with the detection hole. One end of the outlet channel communicates with the detection hole, and the other end communicates with the waste liquid chamber. The electrode layer is provided with a reference electrode, a working electrode, and a counter electrode. One end of each of the reference electrode, working electrode, and counter electrode extends into the detection hole, and the other end is used to connect to the electrode connection area.

[0010] In some embodiments, the three-dimensional moving component includes a first carriage, a second carriage, and a third carriage. The first carriage and the second carriage are both horizontally arranged. The second carriage is slidably disposed on the first carriage and can slide along a first direction. The third carriage is vertically arranged and slidably disposed on the second carriage and can slide along a second direction. A slider is slidably disposed on the third carriage. The slider can slide along a third direction. The first direction, the second direction, and the third direction are perpendicular to each other. There are two third carriages. The sliders on the two third carriages are respectively used to connect to the gripper device and the injection device.

[0011] This invention also provides a method for detecting soluble heavy metals in weakly acidic soil, implemented using the soil weakly acidic soluble heavy metal detection system described above, and comprising the following steps: S1: Prepare experimental samples according to the preset ratio. The experimental samples are a mixture of soil samples and weak acid extract. S2: The rotary drive device includes a vortex device and a centrifugal device. The gripper device grabs the pre-treatment microfluidic chip and places it on the vortex device. The injection device draws up the experimental sample and injects it into the pre-treatment microfluidic chip. The vortex device is started to perform vortex mixing and extraction. S3: The gripper device grabs the pre-processed microfluidic chip from step S2 and places it onto the centrifuge device, then starts the centrifuge device to perform solid-liquid separation and heavy metal enrichment. S4: The gripper pushes the detection microfluidic chip to connect to the electrode connection area, and the injection device extracts the clarified extract from the pretreatment microfluidic chip in step S3 and injects it into the detection microfluidic chip to start electrochemical detection; S5: The electrode connection area outputs a signal to the electrochemical workstation, which transmits the detection results to the host computer for data recording, display, and report generation; S6: Replace the pretreatment microfluidic chip and the detection microfluidic chip, and repeat steps S2-S4.

[0012] In some embodiments, initiating electrochemical detection in step S4 specifically includes: S41: The host computer software sets electrochemical detection parameters according to user input and sends the electrochemical detection parameters to the lower-level electrochemical workstation via serial port; the electrochemical detection parameters include enrichment potential, enrichment time, settling time, starting potential, ending potential, step size, amplitude and frequency. S42: The lower-level electrochemical workstation outputs a constant enrichment potential to the working electrode of the detection microfluidic chip during the enrichment stage according to the received electrochemical detection parameters, so that the target heavy metal ions are reduced and deposited on the surface of the working electrode. S43: After enrichment is completed, the lower electromechanical workstation enters the settling stage, maintaining the initial potential and the set settling time. S44: After the settling period, the lower electrochemical workstation enters the dissolution scanning stage. Based on the starting potential, ending potential, step size, amplitude and frequency, a square wave step scanning potential is generated and applied to the working electrode to cause the heavy metal deposited on the working electrode to oxidize and dissolve and generate a current signal. S45: At the end of each voltage pulse of the square wave stepped scanning potential, the analog-to-digital converter is triggered to collect the current signal through the timer-analog-to-digital converter-direct memory access hardware linkage mechanism, and the converted digital quantity is stored in the memory buffer through direct memory access. S46: The lower-level electrochemical workstation will upload the collected current signal and corresponding real-time potential data to the upper-level computer in real time via serial port; S47: The host computer receives and parses the real-time potential data and current signal, and displays the potential-current volt-ampere diagram in the form of a real-time curve in the graphical user interface.

[0013] In some implementations, in step S5, the electrochemical workstation transmits the detection results to the host computer for data recording, display, and report generation, specifically including: S51: After the dissolution scanning stage is completed or the user actively stops the detection, the host computer processes the cached raw potential-current data using the Savitzky-Gore smoothing filter algorithm to obtain the smoothed potential-current curve; the Savitzky-Gore smoothing filter algorithm uses local polynomial least squares fitting, and its convolution coefficient is [-3, 12, 17, 12, -3] / 35; S52: The host computer, according to the data processing command triggered by the user, identifies the peak position, extracts the peak height and calculates the peak area of ​​the dissolution peak on the smoothed potential-current curve. It performs qualitative analysis of the heavy metal to be tested based on the peak position and quantitative analysis of the heavy metal to be tested based on the peak height or peak area in combination with the pre-stored standard curve. S53: The host computer saves the original potential-current data and / or the smoothed potential-current curve as a universal format file according to the user-triggered save command; S54: After the detection is completed or when the electrode needs to be regenerated, the host computer sends a cleaning command to the lower-level electrochemical workstation according to the cleaning voltage and cleaning time set by the user. S55: The lower-level electrochemical workstation outputs a cleaning voltage according to the cleaning command to dissolve the heavy metal deposits or contaminants remaining on the surface of the working electrode, thereby regenerating the electrode. During the cleaning process, the cleaning current is collected in real time and uploaded to the upper-level computer for display. S56: After the cleaning time is completed, the lower-level electrochemical workstation stops outputting the cleaning voltage and resets the relevant status flag bits.

[0014] The present invention achieves the following technical effects compared to the prior art: The soil weakly acidic soluble heavy metal detection system provided by this invention requires no manual intervention throughout the entire process, from chip loading, sample and extraction solution injection, pretreatment chip positioning and driving, precise extraction solution transfer, automatic electrode docking of the detection chip, to chip waste disposal after detection. The single-batch sample processing cycle is shortened from over ten hours to minutes, while enabling continuous batch sample detection, resulting in an order-of-magnitude increase in throughput. The high degree of automation avoids problems such as volume deviation, sample loss, and poor contact caused by manual liquid handling, sample transfer, and electrode docking, improving the reproducibility and reliability of the detection results. The three core pretreatment steps—vortex extraction, solid-liquid separation, and heavy metal enrichment—which traditionally require multiple devices such as vortex mixers, centrifuges, and filters, are highly integrated into a single microfluidic chip. The entire sample processing is completed within the chip's closed flow channel, eliminating the need for transfer between different containers / devices, avoiding cross-contamination, minimizing sample loss, and ensuring the accuracy of the detection results. A single rotary drive unit provides power for the entire process of extraction, separation, and enrichment, eliminating the need for multiple independent drive devices and reducing equipment complexity and failure rate. Simultaneously, rotational parameters (speed and time) can be precisely digitally controlled, ensuring consistent pretreatment results for different samples. Employing microfluidic chip-based vortex extraction technology, a rapid vortex flow field is generated within micron-level channels through precisely controlled fluid dynamics. This microscale convective mass transfer effect is far superior to macroscopic stirring, significantly accelerating the mass transfer rate between soil particles and the weakly acidic extract, thereby drastically reducing the traditional 16-hour extraction time to 10 minutes. Furthermore, samples can be tested immediately after pretreatment, all within a single main frame. The compact and lightweight design allows for both batch testing in laboratories and direct deployment to contaminated sites for in-situ detection. This embodiment precisely targets weakly acid-soluble heavy metals, employing a mild weakly acid extraction strategy, making the test results more reflective of actual environmental risks and biological exposure levels. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the soil weak acid soluble heavy metal detection system in some embodiments of the present invention; Figure 2 This is an exploded view of the soil weak acid soluble heavy metal detection system in some embodiments of the present invention; Figure 3This is a schematic diagram of the pre-processing microfluidic chip structure in some embodiments of the present invention; Figure 4 This is an exploded view of the pre-processing microfluidic chip in some embodiments of the present invention; Figure 5 This is a schematic diagram of the structure of the detection microfluidic chip in some embodiments of the present invention; Figure 6 This is an exploded view of a microfluidic chip being inspected in some embodiments of the present invention; Figure 7 This is a schematic diagram of the vortex device in some embodiments of the present invention; Figure 8 This is an exploded view of the vortex device in some embodiments of the present invention; Figure 9 This is a schematic diagram of the centrifuge device in some embodiments of the present invention; Figure 10 This is an exploded view of the centrifuge device in some embodiments of the present invention; Figure 11 This is a schematic diagram illustrating the combination of the first substrate holder and the first substrate disk in some embodiments of the present invention; Figure 12 This is a schematic diagram illustrating the separation of the first substrate holder and the first substrate disk in some embodiments of the present invention; Figure 13 This is a schematic diagram illustrating the combination of the second substrate holder and the second substrate disk in some embodiments of the present invention; Figure 14 This is a schematic diagram illustrating the separation of the second substrate holder and the second substrate disk in some embodiments of the present invention; Figure 15 This is a schematic diagram of the interface of the soil heavy metal square wave leaching voltammetry detection software in some embodiments of the present invention.

[0017] In the diagram: 1-Main frame; 101-Base; 102-Cube frame; 2-Three-dimensional moving component; 201-First slide; 202-Second slide; 203-Third slide; 204-Slider; 3-Rotation drive device; 31-Vortex device; 311-Vortex base; 312-Eccentric shaft; 32-Centrifuge device; 321-Centrifuge base; 4-First substrate holder; 5-Second substrate holder; 6-Detection microfluidic chip; 61-Liquid inlet; 62-Waste liquid chamber; 63-Liquid inlet channel; 64-Second air pressure balance port; 65-Reference electrode; 66-Working electrode; 67-Counter electrode; 601-Upper layer of rubber mold; 602-Middle layer of rubber film; 603-Lower layer of rubber film; 604-Channel layer; 605-Detection layer; 606-Electrode layer; 607- 608 - Upper waste liquid layer; 609 - Lower waste liquid layer; 7 - Bottom layer; 8 - Gripper device; 9 - Injection device; 9 - Pretreatment microfluidic chip; 91 - Vortex mixing zone; 92 - First filtration separation zone; 93 - Second filtration separation zone; 94 - Centrifugation enrichment zone; 95 - Sample inlet; 96 - Sample outlet; 97 - First pressure balance port; 98 - Positioning hole; 901 - Upper sealing layer; 902 - Middle sealing layer; 903 - Lower sealing layer; 904 - First chamber layer; 905 - Main chamber layer; 906 - Upper filter membrane layer; 907 - Middle filter membrane layer; 908 - Lower filter membrane layer; 909 - Second chamber layer; 910 - Base plate; 10 - Motor box; 11 - Motor; 12 - Positioning column; 13 - First slide tray; 14 - Push rod; 15 - Second slide tray; 16 - Electrode connection area. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The purpose of this invention is to provide a detection system and method for soluble heavy metals in weakly acidic soil, in order to solve the problems existing in the prior art. It can achieve one-stop processing, has a high degree of automation, and has high experimental efficiency.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 like Figures 1-14As shown, the present invention provides a soil weak acid soluble heavy metal detection system, including a main frame 1, a control system, and a pretreatment device, a detection device, and a transfer operation device set in the main frame 1 and controlled by the control system. The main frame 1 preferably includes a base 101 and a cubic frame 102 fixedly set on the base 101. The transfer operation device includes a three-dimensional moving component 2, an injection device 8, and a gripper device 7. The injection device 8 and the gripper device 7 are located at the moving end of the three-dimensional moving component 2, and the moving end of the three-dimensional moving component 2 can perform three-dimensional movement within the main frame 1. The pretreatment device includes a pretreatment microfluidic chip 9 and a rotary drive device 3. The pretreatment microfluidic chip 9 can contain soil samples and weak acid extract. The gripper device 7 can grip the pretreatment microfluidic chip 9 and place it at the output end of the rotary drive device 3. The rotary drive device 3 can drive the pretreatment microfluidic chip 9 to rotate. The pretreatment microfluidic chip 9 includes at least a vortex mixing zone 91, a filtration separation zone, and a centrifugal enrichment zone 94 from the inside out. Under the action of the rotary drive device 3, the experimental sample can sequentially reach the vortex mixing zone 91, the filtration separation zone, and the centrifugal enrichment zone 94. The detection device includes a detection microfluidic chip 6 and an electrode connection area 16. The detection microfluidic chip 6 uses electrochemical detection. The gripper device 7 can move the detection microfluidic chip 6 and make the electrode in the detection microfluidic chip 6 contact the electrode connection area 16. The injection device 8 can transfer the experimental sample processed by the pretreatment device to the detection microfluidic chip 6. The electrode connection area 16 can output an electrical signal.

[0022] From chip loading, sample and extraction solution injection, pretreatment chip positioning and driving, precise extraction solution transfer, and automatic electrode docking of the detection chip, to chip waste disposal after detection, the entire process requires no manual intervention. The processing time for a single batch of samples is reduced from over ten hours to minutes, while continuous batch sample detection is possible, resulting in an order-of-magnitude increase in throughput. This high degree of automation avoids problems such as volume deviation, sample loss, and poor contact caused by manual pipetting, sample transfer, and electrode docking, improving the reproducibility and reliability of test results. The three core pretreatment steps—vortex extraction, solid-liquid separation, and heavy metal enrichment—that traditionally required multiple devices such as vortex mixers, centrifuges, and filters, are highly integrated into a single microfluidic chip. The entire sample processing is completed within the chip's closed flow channels, eliminating the need for transfer between different containers / devices, avoiding cross-contamination, minimizing sample loss, and ensuring the accuracy of test results. A single rotary drive unit 3 provides power for the entire process of extraction, separation, and enrichment, eliminating the need for multiple independent drive devices and reducing equipment complexity and failure rate. Simultaneously, rotational parameters (speed and time) can be precisely and digitally controlled, ensuring consistent pretreatment results for different samples. Employing microfluidic chip-based vortex extraction technology, a rapid vortex flow field is generated within micron-level channels through precisely controlled fluid dynamics. This microscale convective mass transfer effect is far superior to macroscopic stirring, significantly accelerating the mass transfer rate between soil particles and the weakly acidic extract, thereby drastically reducing the traditional 16-hour extraction time to 10 minutes.

[0023] Furthermore, the experimental samples can be tested immediately after complete pretreatment, all within the same main frame 1. The entire unit is small in size and lightweight, meeting both the needs of batch testing in laboratories and allowing for direct deployment to contaminated sites for in-situ testing. This embodiment precisely targets weakly acid-soluble heavy metals and employs a mild weak acid extraction strategy, making the test results more reflective of actual environmental risks and biological exposure levels.

[0024] In some embodiments, the pretreatment microfluidic chip 9 includes a sealing layer, a main chamber layer 905, a filter membrane layer, a secondary chamber layer 909, and a base plate 910 connected sequentially from top to bottom. The sealing layer, the main chamber layer 905, the filter membrane layer, and the secondary chamber layer 909 each have multiple processing spaces in the radial direction, and after being stacked, there are at least three processing spaces in the radial direction, which are, from the inside to the outside, a vortex mixing zone 91, a filtration separation zone, and a centrifugal enrichment zone 94. The sealing layer has an inlet 95 near the center and an outlet 96 near the edge. The sample to be tested can enter through the inlet 95 and flow into the vortex mixing zone 91 for vortex extraction. After extraction, the sample to be tested can pass through the filter membrane layer and reach the filtration separation zone from the main chamber layer 905 under the action of external force, and finally reach the centrifugal enrichment zone 94 and be taken out through the outlet 96. By utilizing high-speed vortex mixing within a microfluidic chip, the extraction time required by traditional methods (such as vortex mixing) of 16 hours or even longer is significantly reduced to less than 10 minutes, resulting in a substantial increase in efficiency. Multiple independent and time-consuming operations, such as vortexing, filtration, and centrifugation, are integrated into a single microfluidic chip, reducing sample transfer and intermediate steps, greatly improving the overall process efficiency. No back-and-forth transport is required, resulting in a high degree of automation. The automated execution of extraction, filtration, and centrifugation steps reduces manual intervention and operational complexity. Furthermore, compared to the bulky and immobile nature of traditional vortex mixers or ultrasonic devices, this embodiment, based on a microfluidic chip, features a compact and lightweight system that is easy to carry and deploy in the field, providing significant convenience for field or mobile laboratories. Furthermore, the extract first undergoes primary filtration by trapping large soil particles through a filter membrane layer. Then, high-speed centrifugation further clarifies the pre-filtered extract, removing ultrafine suspended particles. This results in a higher clarity extract that can be directly applied to electrochemical and spectroscopic detection methods, avoiding issues such as solid particle contamination of the detection electrode and baseline drift, thus improving the sensitivity and accuracy of subsequent detections. It should be noted that a primary chamber layer 904 is also located above the main chamber layer 905.

[0025] In some embodiments, the sealing layer, main chamber layer 905, filter membrane layer, and secondary chamber layer 909 contain multiple independent processing units along the circumference. Each processing unit includes a vortex mixing zone 91, a filtration separation zone, a centrifugal enrichment zone 94, an inlet 95, and an outlet 96. Preferably, four processing units are provided. The microfluidic chip is disk-shaped, and the four processing units are located in four quadrants, enabling simultaneous processing of multiple soil samples. The four independent processing units arranged in a four-quadrant configuration can simultaneously complete the entire pretreatment process of vortex extraction, filtration separation, and centrifugal enrichment on the same chip, and can process four soil samples simultaneously with a single startup. Each processing unit is equipped with an independent sample inlet 95, vortex mixing zone 91, filtration and separation zone, centrifugation enrichment zone 94, and sample outlet 96. The chambers and flow channels between units are completely independent, with no shared structures or connecting flow paths. Even if the heavy metal concentrations of soil samples from different units vary greatly (such as samples from heavily polluted sites and clean control sites), there will be no sample cross-contamination or contamination issues. This avoids the contamination risks associated with shared flow channels in traditional multi-channel chips, ensuring the authenticity and accuracy of the test results for each sample. The four processing units are integrated on the same disc chip and driven synchronously by the same motor. Key parameters such as vortex rotation speed, vortex time, centrifugal force, and extraction environment are completely uniform for all samples, eliminating systematic errors caused by different equipment and different batch operations in traditional methods. The relative standard deviation (RSD) of parallel sample test results is significantly reduced, and data repeatability and reliability are greatly improved. With just one clamping, one injection, and one start-up, the entire pretreatment process for four samples can be completed simultaneously, reducing the number of repetitive manual operations, lowering the labor intensity of operators, and reducing random errors caused by manual operation at the source. Even non-professionals can complete the standardized pretreatment of large batches of samples.

[0026] As a preferred embodiment, each processing unit is provided with a first air pressure balance port 97. Each processing unit independently provides a first air pressure balance port 97, which can discharge the air in the chamber in real time during sample injection and replenish the air pressure simultaneously during sample discharge to eliminate air resistance.

[0027] In some embodiments, the sealing layer includes a sealing upper layer 901 (1 mm thick), a sealing middle layer 902 (2 mm thick), and a sealing lower layer 903 (1 mm thick), which are sequentially bonded together from top to bottom. All three layers are made of rubber. Since all three layers are made of rubber, their coefficients of thermal expansion and elastic moduli are completely identical, preventing issues such as warping, separation, and gaps caused by temperature changes and uneven stress in plastic-rubber hybrid structures. The flexible bonding of the three layers completely fills the microscopic gaps between the chip layers, achieving a 360° full-coverage seal to prevent leakage at points prone to leakage, such as the sample inlet 95, flow channel interface, and chamber edges. Throughout the entire process from sample injection, vortex mixing, low-speed filtration to high-speed centrifugation, the internal fluid pressure is dynamically changing. The superimposed elasticity of the three-layer rubber structure has greater deformation and better resilience than that of a single-layer rubber. It can adaptively expand and contract with changes in internal pressure, withstand the instantaneous impact of vortex turbulence, and also withstand the continuous high pressure of centrifugal process. It will not have problems such as high pressure bursting or low pressure rebound failure, and maintains stable sealing of the interface throughout the process, ensuring the continuous operation of the pretreatment process.

[0028] The filter membrane layer comprises, from top to bottom, an upper filter membrane layer 906, a middle filter membrane layer 907, and a lower filter membrane layer 908, which are sequentially bonded together. The upper filter membrane layer 906 and the lower filter membrane layer 908 can support the middle filter membrane layer 907. The upper filter membrane layer 906 and the lower filter membrane layer form a symmetrical rigid clamping structure, fixing the functional middle filter membrane layer 907 in the middle, restricting its deformation space, and avoiding unsupported / one-sided support of the filter membrane.

[0029] In a preferred embodiment, the filtration separation zone includes a first filtration separation zone 92 and a second filtration separation zone 93 along the radial direction. Both the first filtration separation zone 92 and the second filtration separation zone 93 are embedded with a two-stage hydrophilic polytetrafluoroethylene (PTFE) filter membrane. The dual filtration zones connected in series from the inside to the outside along the radial direction form a two-stage gradient interception system of coarse filtration and fine filtration. The inner first filtration separation zone 92 is responsible for primary coarse filtration, which uses the secondary filter membrane to intercept large-particle aggregates of soil, sand, gravel, plant residues and other large-particle impurities, avoiding damage and blockage caused by large particles directly impacting the fine filter membrane. The outer second filtration separation zone 93 is responsible for deep fine filtration, which uses the secondary filter membrane to further remove ultrafine suspended particles, humic colloids, clay particles and other tiny impurities that are easy to interfere with detection in the leachate after primary filtration.

[0030] In some embodiments, the soil weakly acidic soluble heavy metal detection system further includes a first substrate holder 4, a first substrate tray 13, a second substrate holder 5, and a second substrate tray 15. The first substrate tray 13 is used to support the pretreatment microfluidic chip 9. The first substrate tray 13 is slidably connected to the first substrate holder 4, specifically, the first substrate holder 4 is provided with a groove, and the left and right ends of the first substrate tray 13 are slidably disposed in the groove. The second substrate tray 15 is used to support the detection microfluidic chip 6, and the electrode connection area 16 is fixedly disposed. On the second wafer carrier 5, the second wafer tray 15 is slidably connected to the second wafer carrier 5. Specifically, the second wafer carrier 5 is provided with a sliding groove, and the left and right ends of the second wafer tray 15 are slidably disposed in the sliding groove. Both the first wafer tray 13 and the second wafer tray 15 are provided with push rods 14, which are located on the side near the end face. A magnet is fixedly disposed in the sealing middle layer 902. The gripper device 7 is a magnetic push block, which can push the push rod 14 and can attract the pre-processing microfluidic chip 9. The magnetic push block replaces the traditional complex mechanical gripper with an independent pushing mechanism. With only one actuator, the four core actions of pushing the wafer tray push rod 14, attracting and gripping the pre-processing chip, accurately transferring and placing the chip, and recycling the waste chip can be completed simultaneously. There is no need to set up additional auxiliary mechanisms such as gripper opening and closing, and pushing extension and retraction. The motion end structure of the three-dimensional moving component 2 is extremely simple, reducing the number of parts and mechanical complexity, and reducing the equipment failure rate and maintenance costs. The magnetic pusher, integrated with the magnet within the 902 sealed middle layer of the pretreatment microfluidic chip 9, achieves stable chip adsorption through uniform magnetic force. This eliminates the rigid clamping action of mechanical grippers, preventing damage to the multi-layered bonding structure, microchannels, and sealing structure of the microfluidic chip. It also avoids chip deformation, leakage, and channel blockage caused by improper gripping force. The entire chip is pre-loaded into the wafer tray. From loading, transfer, docking to waste recycling, no manual contact with the chip's sample inlet channels, detection electrodes, reaction chambers, or other core areas is required throughout the process. This avoids sample and electrode contamination from human contact and prevents cross-contamination between different samples, ensuring the accuracy of the test results.

[0031] In some embodiments, the detection microfluidic chip 6 comprises, from top to bottom, a sealing film layer, a channel layer 604, a detection layer 605, an electrode layer 606, a waste liquid layer, and a bottom layer 609. The channel layer 604, the detection layer 605, the electrode layer 606, and the waste liquid layer are all provided with interconnected waste liquid ports, which together form a waste liquid chamber 62. The channel layer 604 is provided with an inlet channel 63, a detection hole, and an outlet channel. The sealing layer is provided with an inlet hole 61. One end of the inlet channel 63 is connected to the inlet hole 61, and the other end is connected to the detection hole. One end of the outlet channel is connected to the detection hole, and the other end is connected to the waste liquid chamber 62. The electrode layer 606 is provided with a reference electrode 65, a working electrode 66, and a counter electrode 67. One end of the reference electrode 65, the working electrode 66, and the counter electrode 67 extends into the detection hole, and the other end is used to connect to the electrode connection area 16. The reaction ends of the reference electrode 65, working electrode 66, and counter electrode 67 extend directly into the detection aperture, achieving unobstructed full contact with the test liquid. This minimizes the electron transfer path and ensures more complete enrichment, reduction, and oxidative dissolution reactions of heavy metal ions, significantly improving detection sensitivity. The reaction ends of the three electrodes are located within the closed solution environment of the detection aperture, while the electrical connection ends extend to the chip edge and connect with the electrode connection area 16. Physical isolation prevents the test liquid and waste liquid from contacting the electrical connection ends, avoiding short circuits, corrosion, and contact resistance fluctuations caused by weak acid extraction solutions. This also avoids baseline drift and signal distortion issues in electrochemical detection. The detection microfluidic chip 6, excluding the bottom layer 609, is composed of eight layers of polymethyl methacrylate (PMMA) material of varying thicknesses bonded together. A polyimide film is embedded between the fifth layer (detection layer 605) and the sixth layer (electrode layer 606) of PMMA material. The polyimide film (0.2 mm thick) was induced in situ by a 10640 nm wavelength laser to form a graphene three-electrode system, including a working electrode 66, a reference electrode 65, and a counter electrode 67. A second pressure balancing port 64 was provided on the detection microfluidic chip 6.

[0032] As a preferred embodiment, the reference electrode 65 is coated with nano-silver material, which further improves the stability and reproducibility of the electrode, ensuring reliability for long-term use. In a stable acetic acid / sodium acetate weak acid buffer environment (pH 5.0), the nano-silver coating can establish a thermodynamically stable reversible redox couple, providing a constant potential reference. Compared to the pure graphene reference electrode 65, its potential drift is reduced, and potential fluctuations during continuous batch detection can be controlled within a small range, avoiding the problem of the pure carbon-based reference electrode 65 lacking a fixed redox couple and having a potential that easily drifts with the environment.

[0033] More specifically, the sealing membrane layer includes an upper rubber layer 601, a middle rubber layer 602, and a lower rubber layer 603. The waste liquid layer includes an upper waste liquid layer 607 and a lower waste liquid layer 608. The magnet can be completely embedded in the middle rubber layer 602. Through the full-wrap sealing of the upper and lower rubber membranes, dual physical isolation is achieved between the magnet and the sample solution and the external environment. This solves the problems of unstable embedding of magnets in a single sealing membrane and easy magnet detachment, and also avoids the risk of corrosion and heavy metal precipitation contamination of the sample caused by contact between the magnet and the weak acid leaching solution of acetate-sodium acetate.

[0034] In some embodiments, the three-dimensional moving component 2 includes a first slide 201, a second slide 202, and a third slide 203. The first slide 201 and the second slide 202 are both horizontally arranged. The second slide 202 is slidably mounted on the first slide 201 and can slide along a first direction. The third slide 203 is vertically arranged and slidably mounted on the second slide 202, and can slide along a second direction. A slider 204 is slidably mounted on the third slide 203, and the slider 204 can slide along a third direction. The first direction, the second direction, and the third direction are perpendicular to each other. There are two third slides 203, and the sliders 204 on the two third slides 203 are respectively used to connect to the gripper device 7 and the injection device 8. Under the premise of synchronous X-axis coverage of the entire workstation, the second and third direction strokes of the gripper device 7 and the injection device 8 are completely independently controlled, allowing for synchronous parallel actions without sequential waiting. For example, while the gripper device 7 completes the pretreatment chip gripping and vortex / centrifugation station placement, the injection device 8 can simultaneously complete the precise aspiration of soil samples and weak acid extract, the transfer of extract after pretreatment, and the quantitative injection of detection chips; it can even complete the chip loading and extraction operation of the next sample while the current sample is being electrochemically detected, thus improving the experimental speed.

[0035] Example 2 This embodiment also provides a method for detecting soluble heavy metals in weakly acidic soil, implemented using the soil weakly acidic soluble heavy metal detection system described in Embodiment 1, and includes the following steps: S1: Prepare experimental samples according to the preset ratio. The experimental samples are a mixture of soil samples and weak acid extract. Specifically, the soil samples to be tested and the weak acid extract (0.6M acetic acid / sodium acetate solution, pH 5.0) are prepared separately according to the preset solid-liquid ratio (1:40). Using weak acids such as acetate as extractants avoids the problems of high operational risks and complex waste liquid treatment caused by strong corrosive reagents compared with traditional strong acid (such as nitric acid and perchloric acid) digestion methods. It significantly improves the safety of operators and environmental friendliness, which is in line with the development trend of green analytical chemistry.

[0036] S2: The rotary drive device 3 includes a vortex device 31 and a centrifuge device 32. The gripper device 7 grips the pretreatment microfluidic chip 9 and places it on the vortex device 31. The injection device 8 aspirates the experimental sample (3.2 ml) and injects it into the pretreatment microfluidic chip 9. The vortex device 31 is started to perform vortex mixing and extraction. The vortex time is set to the optimized parameters (10 minutes), and the vortex speed is also adjusted to the optimized parameters (2000 rpm). Compared with ultrasonic extraction (which generates a lot of noise and equipment vibration during operation), the vortex extraction mechanism of this embodiment has extremely low noise and weak vibration, which greatly improves the comfort of the laboratory and on-site testing environment, avoids the negative impact of vibration on precision instruments, and improves the long-term stability of the system.

[0037] S3: The gripper device 7 grabs the pre-processing microfluidic chip 9 from step S2 and places it onto the centrifuge device 32, and starts the centrifuge device 32 to perform solid-liquid separation and heavy metal enrichment. S4: The gripper device 7 pushes the detection microfluidic chip 6 to connect to the electrode connection area 16. The injection device 8 extracts the clarified extract from the pretreatment microfluidic chip 9 in step S3 and injects it into the detection microfluidic chip 6, initiating electrochemical detection. The electrode connection area 16 applies the potential scanning program required for Square Wave Anodic Stripping Voltammetry (SWASV). During the enrichment stage, as the injection pump precisely and slowly injects the aspirated extract into the detection microfluidic chip 6, the target heavy metal ions are electrodeposited on the surface of the working electrode 66 as the solution flows through the detection orifice. The enrichment time is equal to the injection time of the injection device 8, which is 180 s, followed by a 5 s settling period. During the dissolution stage, the heavy metals are oxidized and dissolved on the surface of the working electrode 66 within the detection orifice, generating a current signal. The electrode connection area 16 collects and analyzes these current signals, performing qualitative (based on peak potential) and quantitative (based on peak current intensity) analysis of the heavy metals by peak current or peak area. A rapid and highly sensitive detection of heavy metals is achieved by combining a low-cost graphene three-electrode on a microfluidic chip 6 with the SWASV method. The miniaturization and integration of the chip further reduce reagent consumption and detection time. Most importantly, on the one hand, a syringe pump replaces traditional magnetic stirring, enabling micro-quantity detection; on the other hand, differential enrichment and dissolution achieve signal amplification.

[0038] Combining square wave pulse stripping voltammetry (SWASV), this system enables rapid enrichment and highly sensitive detection of trace (ppb level) heavy metals in leachates. SWASV effectively suppresses non-Radidaic currents (double-layer charging currents) through differential pulse waveforms, significantly improving the signal-to-noise ratio and allowing clear differentiation of the target heavy metal's stripping peak even against complex soil matrix backgrounds. Furthermore, the inherent multiple detection capability of electrochemical methods allows the system to perform qualitative and quantitative analysis of multiple heavy metal ions (such as Pb²⁺ and Cd²⁺) in a single scan. The core of the detection microfluidic chip 6 is a laser-induced graphene three-electrode system. Graphene three electrodes (working electrode 66, reference electrode 65, and counter electrode 67) are directly prepared in situ on a polyimide (PI) film using a 10640nm laser. This process not only significantly simplifies the electrode preparation process but also significantly reduces production costs. Graphene itself possesses excellent conductivity, a large specific surface area, and abundant defect sites, enhancing the electrode's ability to enrich heavy metal ions and its electrochemical reactivity. In particular, coating the reference electrode 65 with nano-silver material further improves the stability and reproducibility of the electrode, ensuring reliability for long-term use.

[0039] S5: Electrode connection area 16 outputs signals to the electrochemical workstation, which transmits the detection results to the host computer for data recording, display, and report generation; S6: Replace the pretreatment microfluidic chip 9 and the detection microfluidic chip 6, and repeat steps S2-S4.

[0040] Furthermore, initiating electrochemical detection in step S4 includes the following sub-steps: Step a1: The user starts the host computer software, which is designed based on Qt Creator and is used for human-computer interaction in the square wave stripping voltammetry detection of heavy metals in soil. In the serial port settings area of ​​the software interface, the user selects the serial communication port for communication with the lower-level electrochemical workstation and clicks the "Open Serial Port" button to establish a connection. The lower-level electrochemical workstation is built based on an STM32F103RCT6 microcontroller. The host computer and the lower-level computer communicate bidirectionally through a fixed-length frame protocol, with a frame length of 35 bytes.

[0041] Step a2: In the square wave stripping voltammetry parameter area of ​​the software interface, the user sets or confirms the electrochemical detection parameters according to the type and concentration range of the heavy metal to be tested. The electrochemical detection parameters include enrichment potential, enrichment time, settling time, starting potential, ending potential, step size, amplitude and frequency. In the electrode cleaning area, the user sets or confirms the cleaning voltage and cleaning time required for electrode cleaning.

[0042] Step a3: When the user clicks the Start Test button, the host computer software packages the square wave stripping voltammetry parameters set in step a2 into a fixed-length frame protocol data packet and sends it to the lower-level electrochemical workstation in a multi-threaded manner through the serial communication port.

[0043] Step a4: After receiving the instruction, the lower-level electrochemical workstation performs frame header verification, frame tail verification, and instruction parsing through the universal asynchronous transceiver interrupt service routine; if the parsing result is a square wave stripping voltammetry test instruction, then it enters the enrichment stage.

[0044] Step a5: During the enrichment stage, the digital-to-analog converter of the lower-level electrochemical workstation outputs a constant enrichment potential and precisely maintains the set enrichment time, so that the target heavy metal ions are reduced and electrodeposited on the working electrode surface of the detection microfluidic chip.

[0045] Step a6: After enrichment, the lower electrochemical workstation enters the settling stage, maintaining the initial potential and the set settling time to allow the electrode-solution interface to reach equilibrium.

[0046] Step a7: After the settling period, the lower-level electrochemical workstation enters the dissolution scanning stage. The bipolar potentiostat accurately generates a bipolar square wave step scan potential from the starting potential to the ending potential under single power supply according to the square wave dissolution voltammetry parameters set by the upper-level computer, and applies it to the working electrode.

[0047] Step a8: At the end of each square wave voltage pulse, the analog-to-digital converter is triggered to perform non-blocking high-speed synchronous acquisition through the timer-analog-to-digital converter-direct memory access hardware linkage mechanism. The analog-to-digital converter is directly started by the capture and compare event of the timer to convert the current signal output by the transimpedance amplifier into a digital quantity.

[0048] Step a9: The analog-to-digital conversion result is automatically moved to the ring buffer in memory through direct memory access loop mode. Within each voltage step, the system performs 100 times oversampling and calculates the arithmetic mean of the 100 data points as the current value at that moment to suppress power frequency interference.

[0049] Step a10: The data monitoring and tracking counter of the lower-level electrochemical workstation provides nanosecond-level precision blocking delay to ensure the accurate phase difference between the square wave forward pulse and the reverse pulse, thereby enabling accurate calculation of the differential current and eliminating interference from the double-layer charging current.

[0050] Step a11: The lower-level electrochemical workstation packages the calculated real-time potential data and differential current data into a data packet and uploads it to the upper-level computer in real time through the serial communication port. The potential-current voltammogram is then displayed in the graphical user interface as a real-time curve.

[0051] Furthermore, in step S5, the electrochemical workstation transmits the detection results to the host computer for data recording, display, and report generation, including the following sub-steps: Step b1: In an independent data receiving and parsing thread, the host computer software receives real-time data packets uploaded by the slave computer through the serial communication port. After the received data undergoes frame verification, the potential and current values ​​are parsed and stored in a temporary buffer.

[0052] Step b2: The parsed data is transmitted to the main thread of the user interface in real time. The potential-current voltammetry diagram is displayed in the plotting area of ​​the main interface in the form of a real-time curve. The plotting area supports real-time rendering and dynamic scaling of tens of thousands of data points.

[0053] Step b3: During the test, the user can click the stop button at any time. The host computer software will immediately send a stop command to the lower-level electrochemical workstation. After receiving the command, the lower-level electrochemical workstation will end the current test task, the digital-to-analog converter output will return to zero, and the relevant flag bits will be reset.

[0054] Step b4: Display the remaining time of the current test stage in real time on the software interface. The remaining time includes the remaining time of the square wave stripping voltammetry enrichment stage, the remaining time of the scanning stage, or the remaining time of the cleaning stage.

[0055] Step b5: After the square wave stripping voltammetry test process is completed or the user actively stops the test, the host computer enters the data post-processing stage.

[0056] Step b6: The host computer software processes the raw potential-current data in the cache using the Savitzky-Gore smoothing filter algorithm. The Savitzky-Gore smoothing filter algorithm uses local polynomial least squares fitting with convolution coefficients of [-3, 12, 17, 12, -3] / 35 to obtain the smoothed potential-current curve, thereby removing high-frequency random noise in the original spectrum while retaining the peak height and half-width of the heavy metal leaching peaks.

[0057] Step b7: The smoothed curve after Savitzky-Gore smoothing filter is displayed in the plotting area with different colors covering the original data.

[0058] Step b8: The user clicks the data processing button, and the host computer software automatically identifies the peak position, extracts the peak height, and calculates the peak area of ​​the dissolution peak on the smoothed potential-current curve; qualitative analysis of heavy metals is achieved by identifying the peak position of the dissolution peak, and the peak position corresponds to the characteristic potential of a specific heavy metal; quantitative analysis of heavy metals is achieved by measuring the peak height or peak area and combining it with a pre-established standard curve.

[0059] Step b9: The user clicks the Save Data button to save the raw potential-current data and / or the smoothed potential-current curve as a universal format file, which is convenient for subsequent external analysis and report generation.

[0060] Step b10: The user reads the historically saved data file through the Load File function in the File menu, and performs Savitzky-Gore smoothing filtering for noise reduction, peak height extraction, and peak area extraction on the read data file to achieve historical data backtracking and reanalysis.

[0061] Step b11: After the test is completed or when the electrode needs to be regenerated, the user sets the cleaning voltage and cleaning time in the electrode cleaning area of ​​the host computer software and clicks the start cleaning button. The host computer sends the cleaning command and related parameters to the lower-level electrochemical workstation.

[0062] Step b12: The lower-level electrochemical workstation enters the cleaning stage. The digital-to-analog converter outputs the set cleaning voltage, which is a strong oxidation potential, to dissolve the heavy metal deposits or organic pollutants remaining on the surface of the working electrode, thereby achieving electrode regeneration.

[0063] Step b13: During the cleaning process, the lower-level electrochemical workstation collects the cleaning current in real time and uploads it to the upper-level computer through the serial communication port. The upper-level computer displays the current-time curve of current decay over time in real time. The user judges whether the electrode cleaning and regeneration is complete based on whether the current returns to the baseline.

[0064] Step b14: After the cleaning time is over, the lower-level electrochemical workstation stops outputting the cleaning voltage and resets the relevant status flag bits, and the digital-to-analog converter output returns to zero.

[0065] It should be noted that there are two rotary drive devices 3: a vortex device 31 and a centrifugal device 32. Both the vortex device 31 and the centrifugal device 32 use high-precision brushless DC motors or stepper motors, and the motors 11 are installed inside the motor housing 10. An eccentric shaft 312 and a vortex base 311 are located above the motor of the vortex device 31, and a centrifugal base 321 is located above the motor of the centrifugal device 32. The pretreatment microfluidic chip 9 has multiple positioning holes 98 distributed along the diameter of the microfluidic chip, with one positioning hole 98 at the center. Positioning posts 12 are provided on the vortex base 311 and the centrifugal base 321, and these posts 12 can be inserted into the positioning holes 98. The positioning posts 12 and the positioning holes 98 adopt a tool-less plug-in design; simply align the positioning hole 98 of the chip with the positioning post 12 of the base and insert it, making the operation simple and quick. The centrally located multi-positioning holes 98 distributed along the diameter ensure that the fixing force is evenly distributed along the diameter after the chip is clamped, preventing problems such as one-sided force or clamping misalignment. This allows the chip's three-layer all-rubber sealing layer to be evenly pressurized, ensuring a tight seal at the sealing interface throughout the process. Even under conditions of high-speed rotation and internal pressure fluctuations, there will be no problems such as local sealing failure or sample leakage.

[0066] The interface of the soil heavy metal square wave leaching voltammetry detection software is as follows: Figure 15 As shown.

[0067] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A soil weakly acidic soluble heavy metal detection system, characterized in that: It includes a main frame, a control system, and a pre-processing device, a detection device, and a transfer operation device disposed within the main frame and controlled by the control system, wherein; The transfer operation device includes a three-dimensional moving component, an injection device, and a gripper device. The injection device and the gripper device are disposed at the moving end of the three-dimensional moving component, and the moving end of the three-dimensional moving component is capable of three-dimensional movement within the main frame. The pretreatment device includes a pretreatment microfluidic chip and a rotary drive device. The pretreatment microfluidic chip can contain soil samples and weak acid extract. The gripper device can grasp the pretreatment microfluidic chip and place it at the output end of the rotary drive device. The rotary drive device can drive the pretreatment microfluidic chip to rotate. The pretreatment microfluidic chip includes at least a vortex mixing zone, a filtration separation zone, and a centrifugal enrichment zone from the inside out. Under the action of the rotary drive device, the experimental sample can sequentially reach the vortex mixing zone, the filtration separation zone, and the centrifugal enrichment zone. The detection device includes a detection microfluidic chip and an electrode connection area. The detection microfluidic chip uses electrochemical detection. The gripper device can move the detection microfluidic chip and make the electrodes in the detection microfluidic chip contact the electrode connection area. The injection device can transfer the experimental sample processed by the pretreatment device to the detection microfluidic chip. The electrode connection area can output an electrical signal.

2. The soil weakly acidic soluble heavy metal detection system according to claim 1, characterized in that: The pretreatment microfluidic chip includes a sealing layer, a main chamber layer, a filter membrane layer, a secondary chamber layer, and a base plate connected sequentially from top to bottom. Each of the sealing layer, the main chamber layer, the filter membrane layer, and the secondary chamber layer has multiple processing spaces along the radial direction, and when stacked, there are at least three processing spaces along the radial direction, which, from the inside out, are the vortex mixing zone, the filtration separation zone, and the centrifugal enrichment zone. The sealing layer has an inlet near its center and an outlet near its edge. The sample to be tested can enter through the inlet and flow into the vortex mixing zone for vortex extraction. After extraction, the sample can pass through the filter membrane layer and, under external force, from the main chamber layer to the filtration separation zone, and finally reach the centrifugal enrichment zone and be removed through the outlet.

3. The soil weakly acidic soluble heavy metal detection system according to claim 2, characterized in that: The sealing layer, the main chamber layer, the filter membrane layer, and the second chamber layer have multiple independent processing units along the circumference. Each processing unit includes the vortex mixing zone, the filtration separation zone, the centrifugation enrichment zone, the sample inlet, and the sample outlet.

4. The soil weakly acidic soluble heavy metal detection system according to claim 2, characterized in that: The sealing layer comprises a sealing upper layer, a sealing middle layer, and a sealing lower layer that are sequentially bonded together from top to bottom; The filter membrane layer includes an upper filter membrane layer, a middle filter membrane layer, and a lower filter membrane layer that are sequentially bonded together from top to bottom. The upper filter membrane layer and the lower filter membrane layer can support the middle filter membrane layer.

5. The soil weakly acidic soluble heavy metal detection system according to claim 4, characterized in that: It also includes a first substrate holder, a first substrate tray, a second substrate holder, and a second substrate tray. The first substrate tray is used to carry the pre-processing microfluidic chip and is slidably connected to the first substrate holder. The second substrate tray is used to carry the detection microfluidic chip. The electrode connection area is fixedly disposed on the second substrate holder. The second substrate tray is slidably connected to the second substrate holder. Push rods are provided on both the first and second substrate trays. A magnet is fixedly disposed in the sealing middle layer. The gripping device is a magnetic push block. The magnetic push block can push the push rod and can attract the pre-processing microfluidic chip.

6. The soil weakly acidic soluble heavy metal detection system according to claim 1, characterized in that: The detection microfluidic chip comprises, from top to bottom, a sealing layer, a channel layer, a detection layer, an electrode layer, a waste liquid layer, and a bottom layer. The channel layer, detection layer, electrode layer, and waste liquid layer each have interconnected waste liquid ports, forming a waste liquid chamber. The channel layer has an inlet channel, a detection port, and an outlet channel. The sealing layer has an inlet port; one end of the inlet channel communicates with the inlet port, and the other end communicates with the detection port. One end of the outlet channel communicates with the detection port, and the other end communicates with the waste liquid chamber. The electrode layer has a reference electrode, a working electrode, and a counter electrode. One end of each of the reference electrode, working electrode, and counter electrode extends into the detection port, and the other end is used to connect to the electrode connection area.

7. The soil weakly acidic soluble heavy metal detection system according to claim 1, characterized in that: The three-dimensional moving component includes a first carriage, a second carriage, and a third carriage. The first carriage and the second carriage are both horizontally arranged. The second carriage is slidably mounted on the first carriage and can slide along a first direction. The third carriage is vertically arranged and slidably mounted on the second carriage and can slide along a second direction. A slider is slidably mounted on the third carriage. The slider can slide along a third direction. The first direction, the second direction, and the third direction are perpendicular to each other. There are two third carriages. The sliders on the two third carriages are respectively used to connect to the gripper device and the injection device.

8. A method for detecting soluble heavy metals in weakly acidic soil, characterized in that: The detection system for weakly acidic soluble heavy metals in soil, as described in any one of claims 1-7, is implemented by the following steps: S1: Prepare experimental samples according to the preset ratio. The experimental samples are a mixture of soil samples and weak acid extract. S2: The rotary drive device includes a vortex device and a centrifugal device. The gripper device grabs the pre-treatment microfluidic chip and places it on the vortex device. The injection device draws up the experimental sample and injects it into the pre-treatment microfluidic chip. The vortex device is started to perform vortex mixing and extraction. S3: The gripper device grabs the pre-processed microfluidic chip from step S2 and places it onto the centrifuge device, then starts the centrifuge device to perform solid-liquid separation and heavy metal enrichment. S4: The gripper pushes the detection microfluidic chip to connect to the electrode connection area, and the injection device extracts the clarified extract from the pretreatment microfluidic chip in step S3 and injects it into the detection microfluidic chip to start electrochemical detection; S5: The electrode connection area outputs a signal to the electrochemical workstation, which transmits the detection results to the host computer for data recording, display, and report generation; S6: Replace the pretreatment microfluidic chip and the detection microfluidic chip, and repeat steps S2-S4.

9. The method for detecting soluble heavy metals in weakly acidic soil according to claim 8, characterized in that: The electrochemical detection process initiated in step S4 specifically includes: S41: The host computer software sets electrochemical detection parameters according to user input and sends the electrochemical detection parameters to the lower-level electrochemical workstation via serial port; the electrochemical detection parameters include enrichment potential, enrichment time, settling time, starting potential, ending potential, step size, amplitude and frequency. S42: The lower-level electrochemical workstation outputs a constant enrichment potential to the working electrode of the detection microfluidic chip during the enrichment stage according to the received electrochemical detection parameters, so that the target heavy metal ions are reduced and deposited on the surface of the working electrode. S43: After enrichment is completed, the lower electromechanical workstation enters the settling stage, maintaining the initial potential and the set settling time. S44: After the settling period, the lower electrochemical workstation enters the dissolution scanning stage. Based on the starting potential, ending potential, step size, amplitude and frequency, a square wave step scanning potential is generated and applied to the working electrode to cause the heavy metal deposited on the working electrode to oxidize and dissolve and generate a current signal. S45: At the end of each voltage pulse of the square wave stepped scanning potential, the analog-to-digital converter is triggered to collect the current signal through the timer-analog-to-digital converter-direct memory access hardware linkage mechanism, and the converted digital quantity is stored in the memory buffer through direct memory access. S46: The lower-level electrochemical workstation will upload the collected current signal and corresponding real-time potential data to the upper-level computer in real time via serial port; S47: The host computer receives and parses the real-time potential data and current signal, and displays the potential-current volt-ampere diagram in the form of a real-time curve in the graphical user interface.

10. The method for detecting soluble heavy metals in weakly acidic soil according to claim 9, characterized in that: In step S5, the electrochemical workstation transmits the detection results to the host computer for data recording, display, and report generation, specifically including: S51: After the dissolution scanning stage is completed or the user actively stops the detection, the host computer processes the cached raw potential-current data using the Savitzky-Gore smoothing filter algorithm to obtain the smoothed potential-current curve; the Savitzky-Gore smoothing filter algorithm uses local polynomial least squares fitting, and its convolution coefficient is [-3, 12, 17, 12, -3] / 35; S52: The host computer, according to the data processing command triggered by the user, identifies the peak position, extracts the peak height and calculates the peak area of ​​the dissolution peak on the smoothed potential-current curve. It performs qualitative analysis of the heavy metal to be tested based on the peak position and quantitative analysis of the heavy metal to be tested based on the peak height or peak area in combination with the pre-stored standard curve. S53: The host computer saves the original potential-current data and / or the smoothed potential-current curve as a universal format file according to the user-triggered save command; S54: After the detection is completed or when the electrode needs to be regenerated, the host computer sends a cleaning command to the lower-level electrochemical workstation according to the cleaning voltage and cleaning time set by the user. S55: The lower-level electrochemical workstation outputs a cleaning voltage according to the cleaning command to dissolve the heavy metal deposits or contaminants remaining on the surface of the working electrode, thereby regenerating the electrode. During the cleaning process, the cleaning current is collected in real time and uploaded to the upper-level computer for display. S56: After the cleaning time is completed, the lower-level electrochemical workstation stops outputting the cleaning voltage and resets the relevant status flag bits.

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