Electrochemical detection method and device for pollutant concentration in water environment

Abstract

This invention discloses an electrochemical detection method and a matching detection device for pollutant concentration in aquatic environments. The method measures the electrochemical responses of environmental water samples, diluted environmental water samples, and environmental water samples with added pollutants. The steady-state output current obtained from these electrochemical responses is then input into a specific algorithm to calculate the concentration of the pollutant in the environmental water sample. Compared to traditional electrochemical detection methods, the electrochemical detection method and device of this invention simultaneously perform calibration and measurement in complex aquatic environments, avoiding measurement errors introduced by differences between laboratory calibration conditions and field measurement conditions. It also reduces measurement errors caused by performance shifts due to contamination during multiple measurements and measurement errors due to aging over time, making it particularly suitable for detection in complex aquatic environments.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring technology, specifically relating to an electrochemical detection method and apparatus for the concentration of pollutants in an aquatic environment. Background Technology

[0002] The development of industry, agriculture, and fisheries has discharged large amounts of pollutants into the aquatic environment, such as nutrients, pesticides and veterinary drugs, heavy metal ions, microplastics, and antibiotics, creating a complex aquatic environment containing a variety of pollutants. Accurate monitoring of the concentrations of these pollutants is of great significance for public health and environmental protection. Standard methods for measuring these pollutants largely rely on laboratory instruments, which are insufficient to meet the needs of real-time, long-term on-site monitoring.

[0003] Electrochemical detection methods are small in size and fast in detection, making them a commonly used technique for on-site monitoring. The principle is that trace pollutants undergo an electrochemical reaction with a sensitive material on the working electrode, and the output electrochemical response signal (voltage, current) has a definite relationship with the concentration of the pollutant within a certain range. Therefore, the concentration of the pollutant can be calculated from the output of the electrochemical reaction. In practice, solutions containing different concentrations of the pollutant need to be prepared in the laboratory first. A calibration curve is formed by measuring the correlation between the electrochemical output of these solutions and the different pollutant concentrations. Then, the electrochemical output value of the actual water sample to be tested is measured, and the corresponding concentration of the pollutant is found on the calibration curve as the measurement result.

[0004] However, due to the increasing complexity of aquatic environments, which often contain a variety of different pollutants, their electrochemical reactions often differ from those of solutions prepared in the laboratory. Using calibration curves obtained in the laboratory for measurement introduces additional errors. Another important source of error is the performance shift and aging of electrochemical sensing materials when measuring complex aquatic environments, resulting in different errors from multiple measurements or measurements taken at different times. The more types and complex the composition of pollutants in the aquatic environment, the greater the error. Summary of the Invention

[0005] One of the objectives of this invention is to overcome the deficiencies of the prior art and provide an electrochemical detection method for pollutant concentration in an aquatic environment.

[0006] Another object of the present invention is to provide an electrochemical detection device for detecting pollutant concentrations in complex aquatic environments using the above-described electrochemical detection method.

[0007] The technical solution of the present invention is as follows:

[0008] An electrochemical detection method for pollutant concentrations in complex aquatic environments includes the following steps:

[0009] (1) Prepare diluted water samples, water samples to be tested, and enriched water samples to be tested;

[0010] The diluted water sample to be tested was obtained by mixing environmental water sample and deionized water, and the volume ratio of the environmental water sample in the diluted water sample to be tested was 85-95%.

[0011] The water samples to be tested are environmental water samples;

[0012] The enriched water sample was obtained by mixing the pollutant solution and the environmental water sample. The ratio of the concentration of the pollutant in the pollutant solution to the maximum allowable concentration of the pollutant in the corresponding water environment in the national standard is 5-30:1. The volume ratio of the environmental water sample in the enriched water sample is the same as the volume ratio of the environmental water sample in the diluted water sample.

[0013] (2) The diluted water sample, the water sample to be tested, and the enriched water sample to be tested of equal volume are tested in three identical detection units respectively, and the steady-state output current of the diluted water sample, the water sample to be tested, and the enriched water sample to be tested is obtained.

[0014] (3) Calculate the concentration of the pollutant to be tested in the above water sample. The calculation formula is as follows:

[0015] The concentration of the pollutant to be tested in the water sample = the concentration of the pollutant to be tested added to the enriched water sample * (steady-state output current of the water sample to be tested - steady-state output current of the diluted water sample to be tested) / (steady-state output current of the enriched water sample to be tested - steady-state output current of the water sample to be tested).

[0016] A detection device for the above-described electrochemical detection method includes:

[0017] The detection cell includes a reference electrode cell located in the middle and at least three sample cells arranged around the reference electrode cell. The sample cells are made of the same material and have the same structure. The reference electrode cell and the sample cells are connected vertically. The sample cells and the reference electrode cell are connected through a current through hole. The current through hole is filled with conductive silicone.

[0018] An electrode substrate is provided with at least three sets of electrochemical detection electrodes, each set of electrochemical detection electrodes including a working electrode and a counter electrode;

[0019] The detection cell is sealed on the electrode substrate. The electrode substrate and the sample cell form a cavity for holding the water sample to be tested. The electrode substrate and the reference electrode cell cooperate to form a cavity for holding the reference electrode and the electrolyte that cooperates with the reference electrode. Each set of electrochemical detection electrodes, the cavity for holding the water sample to be tested on it, and the shared reference electrode constitute a detection unit. Their number and position correspond one-to-one with the sample cells.

[0020] In some possible implementations, the detection device also includes a top cover plate that is detachably fitted onto the end of the detection slot away from the electrode substrate. The top cover plate has an insertion hole through which a reference electrode passes, and the end of the reference electrode away from the detection slot can be connected to a current detection device.

[0021] In some possible implementations, the electrode substrate also includes multiple solder joints. The area of ​​the electrode substrate is larger than the orthographic projection of the detection groove onto the plane of the electrode substrate. The solder joints are not covered by the orthographic projection. Each solder joint is electrically connected to a working electrode or a counter electrode. The solder joints can be connected to a current detection device.

[0022] In some possible implementations, the working electrode is an LSM / rGO composite material.

[0023] More preferably, LSM is La 0.8 Sr 0.2 MnO3.

[0024] Furthermore, the mass ratio of LSM to rGO is 17:3.

[0025] In some possible implementations, the reference electrode is an Ag / AgCl electrode and the electrolyte is a KCl gel.

[0026] In some possible implementations, the counter electrode is a platinum electrode.

[0027] In some possible implementations, the analyte is nitrite, the reference electrode is an Ag / AgCl electrode, the electrolyte is a KCl gel, the working electrode is an LSM / rGO composite material, and the counter electrode is a platinum electrode.

[0028] The present invention has at least the following beneficial effects:

[0029] (1) The electrochemical detection method of the present invention can detect the concentration of pollutants in the water environment at the same time, and can perform calibration and detection simultaneously, avoiding the measurement error caused by the difference between laboratory calibration conditions and field measurement conditions. Especially in complex water environments, its accuracy is significantly better than that of traditional electrochemical calibration methods.

[0030] (2) The electrochemical detection device of the present invention has multiple detection units with identical materials, structures and processes, and each detection unit is connected to the same reference electrode. The counter electrode and working electrode used are the same. When the electrochemical detection device of the present invention is used for detection, the storage conditions, storage time, measurement conditions and measurement time of each detection unit are the same, which reduces the performance deviation caused by contamination of the detection unit during measurement and the measurement error caused by aging.

[0031] (3) The electrochemical detection device of the present invention has low manufacturing cost and small size, making it easy to carry.

[0032] (4) The electrochemical detection method of the present invention has the advantages of good detection accuracy, as well as fast and simple operation. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the electrochemical detection device according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the assembly of the electrochemical detection device according to an embodiment of the present invention;

[0035] Figure 3 for Figure 1 The electrochemical detection device shown is a cross-sectional view along AA'.

[0036] Figure 4 Here is a photograph of the electrochemical detection device according to an embodiment of the present invention;

[0037] Figure 5 This is a calculation method for the electrochemical detection method in this embodiment of the invention;

[0038] Figure 6 The current-time curves of four water samples measured in the example are shown.

[0039] Figure 7 This is a comparison chart showing the results of nitrite concentration measurements in four water samples obtained using laboratory standard methods, traditional electrochemical calibration methods, and the methods described in the embodiments of this invention.

[0040] The reference numerals in the figure are as follows: 1-Electrode substrate; 11-Electrochemical detection electrode; 12-Working electrode; 13-Counter electrode; 14-Solder joint; 2-Detection tank; 21-Reference electrode tank; 22-Reference electrode; 23-Sample tank; 24-Current through-hole; 3-Upper cover plate; 31-Socket. Detailed Implementation

[0041] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0042] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. In this invention, the terms "upper," "lower," "bottom," "rear," "side," "length direction," and "width direction," etc., indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, and are only for the purpose of simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the following embodiments, "width" refers to the distance between the left and right sides of the supporting panel.

[0043] In the following examples, the water used is deionized water; unless otherwise specified, the detection methods in the following examples are conventional detection methods; unless otherwise specified, the reagents in the following examples were purchased from commercial channels.

[0044] The specific implementation first provides an electrochemical detection device for pollutant concentration in an aquatic environment. Then, it provides an electrochemical detection method for pollutant concentration in a water sample and uses this method to detect the concentration of the pollutant in four water samples (collected from Wenqing Lake in Xiamen, the estuary, a sewage outlet, and a farmland ditch). The pollutant reacts with the working electrode in the sample tank of the electrochemical detection device to generate an output current. Within a certain concentration range, this output current is directly proportional to the concentration of the pollutant. In this embodiment, the electrochemical detection device is used to simultaneously measure the output current of the water sample containing three different concentrations of the pollutant. The actual concentration of the pollutant in the water sample is then calculated. Specifically, the pollutant in this embodiment is nitrite.

[0045] Example 1: Structure of the Electrochemical Detection Device

[0046] The following is combined Figure 1-Figure 4 The specific structure of the electrochemical detection device provided in this embodiment will be described. First, as... Figures 1-3 As shown, the electrochemical detection device includes an upper cover plate 3, a detection tank 2, and an electrode substrate 1 connected in sequence from top to bottom.

[0047] The detection groove 2 includes a reference electrode groove 21 located in the middle and five sample grooves 23 arranged around the reference electrode groove 21. The sample grooves 23 and the reference electrode groove 21 are connected by a current through hole 24, which is filled with conductive silicone.

[0048] Electrochemical detection electrodes 11 are disposed on the electrode substrate 1. Each set of electrochemical detection electrodes 11 includes a working electrode 12 and a counter electrode 13. The position and number of the electrochemical detection electrodes 11 correspond one-to-one with the sample cell 23. The electrode substrate 1 also includes a plurality of solder joints 14. The area of ​​the electrode substrate 1 is larger than the orthographic projection of the detection cell 2 onto the plane of the electrode substrate 1. The solder joints 14 are not covered by the orthographic projection. Each solder joint 14 is electrically connected to a working electrode 12 or a counter electrode 13. The solder joints 14 can be connected to a current detection device.

[0049] The electrode substrate 1 and the sample tank 23 form a cavity for holding the water sample to be tested. The electrode substrate 1 and the reference electrode tank 21 cooperate to form a cavity for holding the reference electrode 22 and the electrolyte (not shown in the figure) that cooperates with the reference electrode 22.

[0050] The aforementioned upper cover plate 3 has an insertion hole 31. The upper cover plate 3 is detachably fitted onto the end of the detection groove 2 away from the electrode substrate 1. The upper cover plate 3 has an insertion hole 31 in the middle, and the position of the insertion hole 31 corresponds to the reference electrode groove 21. The reference electrode 22 passes through the insertion hole 31, and the end of the reference electrode 22 away from the detection groove 2 can be connected to a current detection device.

[0051] In this embodiment, the reference electrode 22 is an Ag / AgCl electrode, and the electrolyte is a KCl gel. In other possible implementations, other commonly used electrodes and electrolytes can be used depending on the characteristics of the water sample being tested. For example, when the water sample is neutral, the reference electrode 22 can be a saturated calomel electrode; when the water sample is acidic, a mercurous sulfate reference electrode 22 can be used with a saturated potassium sulfate solution (or gel) as the electrolyte; and when the water sample is alkaline, a mercury / mercuric oxide reference electrode 22 can be used with potassium hydroxide as the electrolyte. The above combinations of reference electrode 22 and electrolyte are common practices in the art and should not be construed as limiting the structure of the electrochemical detection device provided by this invention.

[0052] In this embodiment, the detection cell 2 includes five sample cells 23 arranged in a ring of reference electrode cells 21. These five sample cells 23 are made of the same material, structure, and size, and are centrally symmetrically distributed to minimize measurement errors caused by inconsistencies in the sample cells. Each sample cell 23 can hold water samples to be tested at different dilution ratios or water samples to be tested with different concentrations of the analyte, so as to obtain the output current of the water samples to be tested at different concentrations of the analyte, thereby enabling more accurate detection of the concentration of the analyte. However, in other possible implementations, the detection cell 2 only needs to have at least three sample cells 23. The sample cells 23 and the reference electrode cells 21 in the detection cell 2 are vertically connected, and the electrolyte and water sample contained or filled in the detection cell 2 are in direct contact with the electrode substrate 1.

[0053] In this embodiment, the pollutant to be tested is nitrite, and the working electrode 12 is La. 0.8 Sr 0.2 The MnO3 / rGO electrode has a platinum electrode as the counter electrode 13. In other possible implementations, those skilled in the art may replace the counter electrode 13 with other commonly used counter electrodes in the art, such as a carbon rod electrode; those skilled in the art may also replace the working electrode 12 with other existing electrodes depending on the different contaminants to be measured.

[0054] In this embodiment, the upper cover plate 3 and the detection groove 2 are made of acrylic sheet, and the electrode substrate 1 is made of glass. The glass surface is formed sequentially through photolithography, vapor deposition, and cleaning. Figure 2 and Figure 3 The working electrode 12 and counter electrode 13 shown are made with the above-mentioned precise micro-machining process to ensure a high degree of consistency in the electrode materials, shapes and processes of each detection unit.

[0055] Specifically, in this embodiment, the method for forming the working electrode 12 on the electrode substrate 1 is as follows:

[0056] (1) Take 50mg of La 0.8 Sr 0.2 MnO3 powder was dispersed in 25 mL of deionized water and ultrasonically treated for 2 h to obtain a dispersed LSM solution. rGO was added to the dispersed LSM solution to make the rGO concentration in the LSM solution 15 wt%. Then, the solution was ultrasonically stirred in a water bath for 6 h to obtain an LSM / rGO mixture.

[0057] (2) The above LSM / rGO mixture was washed three times with deionized water and ethanol respectively, and dried at 60°C for 12 h to obtain LSM / rGO nanocomposite material.

[0058] (3) Mix 1 mg of the above LSM / rGO nanocomposite material, 2 μL of Nafion solution and 10 mL of ethanol to obtain LSM / rGO mixed solution;

[0059] (4) The electrode substrate 1 is shielded and masked, and then the LSM / rGO mixture solution is sprayed evenly onto the surface of the electrode substrate 1 using a spray gun. During the spraying process, the electrode substrate 1 is kept at 150°C and rotated at a speed of 60 rpm.

[0060] The method for forming the counter electrode 13 is the same as that for forming the working electrode 12. The materials, shapes (including thicknesses) and processes of each detection unit 11 obtained by the above-mentioned forming method are the same, ensuring that the performance of each detection unit is highly consistent and reducing the measurement error of the electrochemical detection device for the water sample in each sample tank 23.

[0061] In summary, the above-mentioned electrochemical detection device has multiple sample cells 23, and each sample cell 23 is connected to the same reference electrode 22. The counter electrode 13 and the working electrode 12 used are the same. When the above-mentioned electrochemical detection device is used for detection, the storage conditions, storage time, measurement conditions and measurement time of each detection unit are the same, which reduces the performance deviation caused by contamination of the detection device during measurement and the measurement error caused by the aging of the materials used in the detection device. This electrochemical detection device is used for the electrochemical detection of pollutant concentration in the water environment, has high accuracy and is simple in structure and easy to operate.

[0062] In addition, if Figure 4 As shown, in this embodiment, the electrode substrate 1 has a thickness of 0.5 mm and a side length of 30 mm; the detection groove 2 has a height of 8 mm, an outer diameter of 24 mm, a side wall thickness of 2 mm, and an inner diameter of 6 mm for the reference electrode groove; the upper cover plate 3 has a thickness of 2 mm, an outer diameter of 24 mm, and a jacking hole 31 with a diameter of 6 mm. The electrochemical detection device is small in size and easy to carry.

[0063] Example 2 Electrochemical Detection Method

[0064] Using a water sample from Wenqing Lake in Xiamen as the environmental water sample / test sample, and nitrite as the pollutant to be tested, this embodiment describes the electrochemical detection method provided. The electrochemical detection method specifically includes the following steps:

[0065] (1) Prepare diluted water samples, water samples to be tested, and enriched water samples to be tested;

[0066] The diluted water sample was obtained by mixing 370 μL of environmental water sample and 30 μL of deionized water.

[0067] The water sample to be tested was a 400 μL environmental water sample;

[0068] The enriched water sample was obtained by mixing 30 μL of 200 μM nitrite solution with 370 μL of environmental water sample.

[0069] (3) The output current of the diluted water sample, the water sample to be tested and the enriched water sample to be tested of equal volume are detected in three sample cells respectively, and the steady-state output current of the diluted water sample, the water sample to be tested and the enriched water sample to be tested in the electrochemical detection device is obtained.

[0070] In this embodiment, the method for detecting the output current is the It method. Specifically, this involves measuring the electrochemical cyclic voltammetry curves of the water sample to be tested, the diluted water sample to be tested, and the enriched water sample to be tested, obtaining the peak potentials of these three samples. In this embodiment, the peak potentials of all three are 0.90V. Then, using this peak potential as the operating voltage, the output current of the water sample to be tested, the diluted water sample to be tested, and the enriched water sample to be tested are measured over time to obtain the steady-state output current.

[0071] (4) Calculate the concentration of the pollutant to be tested in the above-mentioned water sample. The calculation formula is as follows, and the derivation method of the calculation formula is as follows: Figure 5 As shown:

[0072] The concentration of the pollutant to be tested in the water sample = the concentration of the pollutant to be tested added to the enriched water sample * (steady-state output current of the water sample to be tested - steady-state output current of the diluted water sample to be tested) / (steady-state output current of the enriched water sample to be tested - steady-state output current of the water sample to be tested).

[0073] Subsequently, using water samples from the estuary, sewage outlet, and farmland ditches as environmental water samples, the above electrochemical detection method was repeated, and the current-time curves of the four types of water samples were obtained, as shown below. Figure 6 As shown; the concentrations of nitrite in the four water samples tested were obtained using this method, as shown below. Figure 7 As shown.

[0074] Comparative Example 1

[0075] The concentrations of nitrite in water samples from Wenqing Lake, the estuary of the sea, the sewage outlet, and farmland ditch in Xiamen were tested using GB 7493-87 "Determination of Nitrite Nitrogen in Water Quality - Spectrophotometric Method". The nitrite concentrations in these samples were 7.51, 12.42, 29.61, and 35.62 μM, respectively.

[0076] Comparative Example 2

[0077] The concentration of nitrite in water samples from Wenqing Lake, the estuary of the sea, the sewage outlet, and farmland ditches in Xiamen was tested using traditional electrochemical calibration methods.

[0078] The test method is as follows: (1) Prepare standard solutions of nitrite at different concentrations; (2) Continuously and gradually add the above standard solutions of different nitrite concentrations, and obtain the laboratory calibration curve by continuous chronoamperometry analysis, that is, the relationship curve between nitrite concentration Cx and output current Icx. The linear detection range of this sensor is 5~100μM, and the corresponding regression equation can be expressed as Icx(μA)=0.003Cx(μM)+0.084(R2 =0.996). (3) The output current of the four environmental water samples was detected and substituted into the above regression equation to calculate the nitrite concentration in the four environmental water samples. The nitrite concentrations of the water samples from Wenqing Lake in Xiamen, the estuary, the sewage outlet, and the farmland ditch were 9.63, 14.77, 53.13, and 70.80 μM, respectively.

[0079] The concentrations of nitrite in the water samples tested in Example 2, Comparative Example 1, and Comparative Example 2 are as follows: Figure 7 As shown, in complex aquatic environments, such as sewage outlets containing various pollutants from domestic wastewater and farmland ditches containing various pollutants from fertilizer and pesticide residues, the detection results of traditional electrochemical calibration methods show a widening gap compared to laboratory standard methods. This indicates that the detection accuracy of traditional electrochemical calibration methods in complex aquatic environments is low and cannot meet the requirements. In contrast, the detection method provided in Example 2 shows a smaller difference between the detection results of traditional electrochemical calibration methods and laboratory standard methods in complex aquatic environments, meeting the accuracy requirements for on-site testing. Therefore, the detection method provided in Example 2 has the advantage of high accuracy in complex aquatic environments.

[0080] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. An electrochemical detection method for the concentration of pollutants in aquatic environments, characterized in that, Includes the following steps: (1) Prepare diluted water samples, water samples to be tested, and enriched water samples to be tested; The diluted water sample was obtained by mixing environmental water sample and deionized water, with the environmental water sample accounting for 85-95% of the volume of the diluted water sample. The water samples to be tested are environmental water samples; The enriched water sample was obtained by mixing the pollutant solution and the environmental water sample. The ratio of the concentration of the pollutant in the pollutant solution to the maximum allowable concentration of the pollutant in the corresponding water environment in the national standard is 5-30:

1. The volume ratio of the environmental water sample in the enriched water sample is the same as the volume ratio of the environmental water sample in the diluted water sample. (2) The diluted water sample, the water sample to be tested, and the enriched water sample to be tested of equal volume are tested in three identical detection units respectively, and the steady-state output current of the diluted water sample, the water sample to be tested, and the enriched water sample to be tested is obtained. (3) Calculate the concentration of the pollutant to be tested in the above water sample. The calculation formula is as follows: The concentration of the pollutant to be tested in the water sample = the concentration of the pollutant to be tested added to the enriched water sample × (steady-state output current of the water sample to be tested - steady-state output current of the diluted water sample to be tested) / (steady-state output current of the enriched water sample to be tested - steady-state output current of the water sample to be tested).

2. A detection device for the electrochemical detection method according to claim 1, characterized in that, include: The detection cell includes a reference electrode cell located in the middle and at least three sample cells arranged around the reference electrode cell. The sample cells are made of the same material and have the same structure. The reference electrode cell and the sample cells are connected vertically. The sample cells and the reference electrode cell are connected through a current through hole. The current through hole is filled with conductive silicone. An electrode substrate is provided with at least three sets of electrochemical detection electrodes, each set of electrochemical detection electrodes including a working electrode and a counter electrode; The detection cell is sealed on the electrode substrate. The electrode substrate and the sample cell form a cavity for holding the water sample to be tested. The electrode substrate and the reference electrode cell cooperate to form a cavity for holding the reference electrode and the electrolyte that cooperates with the reference electrode. Each set of the electrochemical detection electrodes, the cavity for holding the water sample to be tested on it, and the shared reference electrode constitute a detection unit. The number and position of the detection unit correspond one-to-one with the sample cells.

3. The detection device as described in claim 2, characterized in that, It also includes an upper cover plate, which is detachably fitted onto the end of the detection groove away from the electrode substrate. The upper cover plate has an insertion hole through which the reference electrode passes and the end of the reference electrode away from the detection groove can be connected to a current detection device.

4. The detection device as described in claim 2 or 3, characterized in that, The electrode substrate further includes multiple solder joints. The area of ​​the electrode substrate is larger than the orthographic projection of the detection groove onto the plane of the electrode substrate. The solder joints are not covered by the orthographic projection. Each solder joint is electrically connected to a working electrode or a counter electrode. The solder joints can be connected to a current detection device.

5. The detection device as described in claim 2 or 3, characterized in that, The working electrode is an LSM / rGO composite material.

6. The detection device as described in claim 5, characterized in that, The LSM is La 0.8 Sr 0.2 MnO3.

7. The detection device as described in claim 6, characterized in that, The mass ratio of LSM to rGO is 17:

3.

8. The detection device as described in claim 2 or 3, characterized in that, The reference electrode is an Ag / AgCl electrode, and the electrolyte is a KCl gel.

9. The detection device as described in claim 2 or 3, characterized in that, The counter electrode is a platinum electrode.

10. The detection device as described in claim 2 or 3, characterized in that, The analyte is nitrite, the reference electrode is an Ag / AgCl electrode, the electrolyte is KCl gel, the working electrode is an LSM / rGO composite material, and the counter electrode is a platinum electrode.

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