Chemical oxygen demand detection method and detection equipment

Abstract

The present application relates to a method and equipment for detecting chemical oxygen demand, and relates to the field of detection technology, wherein the method for detecting chemical oxygen demand comprises the following steps: detecting the chloride ion content in the water sample to be tested, selecting reagent one according to the chloride ion content; injecting, injecting reagent one and the water sample to be tested into a digestion cup; heating and stirring, heating the digestion cup to the temperature of the water sample to be tested to 95°C-98°C, and digesting at a constant temperature for 15 minutes after heating; cooling by heat dissipation, cooling the substance in the digestion cup to 35°C-80°C; titration, adding reagent two and reagent three to the cooled digestion cup, standing for three minutes, adding reagent four for titration, and determining the titration amount of reagent four by a redox electrode. Water samples to be tested with different chloride ion concentrations enter the digestion cup, and reagents are selected according to the chloride ion concentration in the water sample to be tested to enter the digestion cup for detection, thereby improving the detection effect of chemical oxygen demand.

Description

Technical Field

[0001] The present application relates to the field of detection technology, and in particular to a chemical oxygen demand detection method and detection equipment. Background Art

[0002] The Chemical Oxygen Demand (COD) of water quality refers to the amount of oxygen consumed by chemical oxidants when oxidizing organic pollutants in water under certain conditions. It is a comprehensive indicator for evaluating the degree of organic pollution in water in environmental monitoring and an indicator for measuring the amount of organic matter in water. The larger the chemical oxygen demand, the more serious the organic pollution in the water.

[0003] In coastal waters (at the mouth of a river), the alternation of fresh and salt water is complex and turbulent, and the salinity is always changing. Therefore, in water quality monitoring and water environment investigation, it is particularly important to select appropriate monitoring methods to analyze COD in coastal waters and accurately assess the degree of pollution. Summary of the invention

[0004] The purpose of the present application is to provide a chemical oxygen demand detection method and detection equipment, wherein the chemical oxygen demand detection method can detect the chemical oxygen demand of water bodies with different chloride ion contents.

[0005] To this end, in the first aspect, an embodiment of the present application provides a detection method for a chemical oxygen demand detection device, comprising the following steps: detecting the chloride ion content in a water sample to be tested, and selecting reagent one according to the chloride ion content; injecting, injecting reagent one and the water sample to be tested into a digestion cup; heating and stirring, heating the digestion cup to a temperature of 95°C-98°C for the water sample to be tested, and digesting at a constant temperature for 15 minutes after heating; cooling by heat dissipation, cooling the substance in the digestion cup to 35°C-80°C; titrating, adding reagent two and reagent three to the cooled digestion cup, letting it stand for three minutes, adding reagent four for titration, and determining the titration amount of reagent four by a redox electrode.

[0006] In one possible implementation, when the chloride ion content in the water sample to be tested is greater than 1000 mg / L, reagent one is an alkaline solution of potassium permanganate, reagent two is a potassium iodide solution, reagent three is a sulfuric acid solution, reagent four is a sodium thiosulfate solution, and during heat dissipation cooling, the material in the digestion cup is cooled to 35°C-40°C.

[0007] In one possible implementation, when the chloride ion content in the water sample to be tested is less than 300 mg / L, reagent one is an acidic solution of potassium permanganate, reagent two is a sodium oxalate solution, reagent three is none, reagent four is a potassium permanganate solution, and during heat dissipation cooling, the material in the digestion cup is cooled to 70°C-80°C.

[0008] In one possible implementation, when the chloride ion content in the water sample to be tested is greater than or equal to 300 mg / L and less than or equal to 1000 mg / L, the sample is diluted through a dilution tank to a chloride ion content of 300 mg / L in the water sample to be tested, and during heat dissipation cooling, the material in the digestion cup is cooled to 70°C-80°C.

[0009] In a second aspect, an embodiment of the present application provides a chemical oxygen demand detection device, comprising:

[0010] A chloride ion detection component comprises a chloride ion detector; a ten-way exhaust valve provided with a central interface and a plurality of common interfaces, wherein one of the common interfaces is used to draw a water sample to be tested; a plunger pump connected to the central interface; a digestion component comprises a digestion cup and a redox electrode, wherein the digestion cup is connected to one of the common interfaces of the ten-way exhaust valve, and the redox electrode extends into the digestion cup and is used to detect the chemical oxygen demand in the digestion cup.

[0011] In a possible implementation, the chloride ion detection component also includes a dilution box, which includes: a mixing zone, the chloride ion detector includes a detection probe, the detection probe extends into the mixing zone, and the sample outlet end of the mixing zone is connected to the ten-way exhaust valve; a pure water zone, the water outlet of the pure water zone is connected to the mixing zone, and a plurality of pure water zones are provided, and the volumes of the plurality of pure water zones gradually increase; the dilution box is transparent, and the pure water zone and / or the mixing zone are provided with scales.

[0012] In a possible implementation, the dilution tank also includes: a water storage area for storing pure water; a water pipe, including a main pipe and multiple branch pipes, the multiple branch pipes are respectively connected to the multiple pure water areas, the main pipe is connected to the water storage area, and a valve switch is also provided at the main pipe.

[0013] In a possible implementation manner, a first stirring member is further provided in the mixing zone, and the first stirring member is used to stir the substance in the mixing zone.

[0014] In a possible implementation, the digestion component also includes: a second stirring member, used to stir the substance in the digestion cup; a heating plate, arranged around the digestion cup and used to heat the substance in the digestion cup; a temperature probe, extending into the digestion cup and used to detect the temperature in the digestion cup; a condenser, connected to the digestion cup, a closed inner tube is arranged in the condenser, and a condensing agent is filled in the inner tube; a cooling fan is arranged on the outer wall of the condenser, and the cooling fan blows air toward the condenser; a peristaltic pump is connected to the digestion cup through a pipeline; the chloride ion detector includes a detection probe, and the detection probe extends into the digestion cup.

[0015] In a possible implementation, two digestion components are provided, and the two digestion cups are connected to a common interface of the ten-way exhaust valve.

[0016] According to the chemical oxygen demand detection method and detection equipment provided by the embodiment of the present application, the chemical oxygen demand detection method includes the following steps: detecting the chloride ion content in the water sample to be tested, selecting reagent one according to the chloride ion content; injecting, injecting reagent one and the water sample to be tested into the digestion cup; heating and stirring, heating the digestion cup to the temperature of the water sample to be tested to 95°C-98°C, and digesting at a constant temperature for 15 minutes after heating; cooling by heat dissipation, cooling the substance in the digestion cup to 35°C-80°C; titration, adding reagent two and reagent three to the cooled digestion cup, standing for three minutes, adding reagent four for titration, and determining the titration amount of reagent four by the redox electrode. Water samples to be tested with different chloride ion concentrations enter the digestion cup, and reagents are selected according to the chloride ion concentration in the water sample to be tested to enter the digestion cup for detection, thereby improving the detection effect of chemical oxygen demand. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In addition, in the drawings, the same components are marked with the same reference numerals, and the drawings are not drawn according to the actual scale.

[0018] Figure 1 A schematic diagram showing the structure of a chemical oxygen demand detection device provided in an embodiment of the present application Figure 1 ;

[0019] Figure 2 A schematic structural diagram of a dilution box provided in an embodiment of the present application is shown;

[0020] Figure 3 A schematic diagram showing the structure of a chemical oxygen demand detection device provided in an embodiment of the present application Figure 2 .

[0021] Description of reference numerals:

[0022] 1. Chloride ion detection component; 11. Chloride ion detector; 12. Dilution box; 121. Mixing area; 122. Pure water area; 123. Water storage area; 124. Water pipe;

[0023] 2. Ten-way exhaust valve; 21. Center interface; 22. Public interface;

[0024] 3. Plunger pump;

[0025] 4. Digestion assembly; 41. Digestion cup; 42. Redox electrode; 43. Second stirring element; 44. Heating plate; 45. Temperature probe; 46. Condenser; 47. Peristaltic pump;

[0026] 5. The first stirring member. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0028] When detecting the chemical oxygen demand in water bodies, the potassium permanganate index method is usually used. The potassium permanganate index method is suitable for testing the chemical oxygen demand in relatively clean water bodies such as drinking water and surface water due to the weak oxidation ability of potassium permanganate, and the measurement range is 0.5-4.5 mg / L. At the same time, when the chloride ion concentration is higher than 300 mg / L, the determination method of oxidation in alkaline medium is adopted. Literature shows that when the chloride ion content in the water body is greater than 300 mg / L, the acidic potassium permanganate method will be interfered by chloride ions; when the chloride ion content is greater than 8000 mg / L, the alkaline potassium permanganate method will be interfered by chloride ions, so in fact only freshwater wastewater with slightly higher chloride ions can be analyzed. However, the test range of chemical oxygen demand of nearshore water bodies, that is, water bodies located at the estuary of the sea, is between 0.5 and 4.5 mg / L, but the concentration of chloride ions is fluctuating.

[0029] like Figure 1 As shown, Figure 1 A schematic diagram of the structure of a chemical oxygen demand detection device provided in an embodiment of the present application is shown. The embodiment of the present application provides a chemical oxygen demand detection device, including a chloride ion detection component 1, a ten-way drain valve 2, a plunger pump 3 and a digestion component 4. The chloride ion detection component 1 includes a chloride ion detector 11, the ten-way drain valve 2 is provided with a central interface 21 and a plurality of common interfaces 22, and a common interface 22 is used to suck the water sample to be tested; the plunger pump 3 is connected to the central interface 21; the digestion component 4 includes a digestion cup 41 and a redox electrode 42, the digestion cup 41 is connected to a common interface 22 of the ten-way drain valve 2, and the redox electrode 42 extends into the digestion cup 41 and is used to detect the chemical oxygen demand in the digestion cup 41.

[0030] It should be understood that the chloride ion detection component 1 includes a chloride ion detector 11, and the chloride ion detector 11 includes a detection probe and a display. The detection probe is placed in the water sample to be tested for detection, and the chloride ion content detection result is displayed on the display, thereby detecting the chloride ion content in the water sample to be tested. The ten-way exhaust valve 2 is provided with a central interface 21 and ten common interfaces 22, wherein the ten common interfaces 22 are respectively connected to a variety of reagents, but one of the common interfaces 22 is connected to the water sample to be tested, and one of the common interfaces 22 is connected to the digestion cup 41. The central interface 21 is connected to a port of the plunger pump 3, and the plunger pump 3 draws the water sample to be tested and various reagents into the digestion cup 41 through the ten-way exhaust valve 2 for reaction, thereby completing the test of the water sample to be tested; there are ten common interfaces 22, so that a variety of reagents can be connected.

[0031] When in use, the water sample to be tested is tested by the chloride ion detector 11, and the water sample to be tested enters the digestion cup 41 through the ten-way drain valve 2. The ten-way drain valve 2 selects a suitable reagent for detection according to the chloride ion content in the water sample to be tested and puts it into the digestion cup 41 for digestion detection, thereby improving the detection effect of chemical oxygen demand. The redox electrode 42 extends into the digestion cup 41 to judge the potential value of the liquid after the reagent titration. Compared with the traditional colorimetric titration, the redox electrode 42 improves the accuracy of titration.

[0032] Reference Figure 2 , showing a structural schematic diagram of a dilution box provided in an embodiment of the present application. In some optional examples, the chloride ion detection component 1 also includes a dilution box 12, the dilution box 12 includes a mixing area 121 and a pure water area 122, the chloride ion detector 11 includes a detection probe, the detection probe extends into the mixing area 121, the water outlet of the pure water area 122 is connected to the mixing area 121, and a plurality of pure water areas 122 are provided, and the volume of the plurality of pure water areas 122 gradually increases.

[0033] The pure water in the pure water zone 122 can be distilled water or deionized water. The pure water zone 122 can be set at any position above, below, left or right of the mixing zone 121. In one example, the pure water zone 122 is set above the mixing zone 121, and the lower end of the pure water zone 122 is an outlet, so that the pure water in the pure water zone 122 can enter the mixing zone 121 by its own gravity, which is convenient for users to operate.

[0034] In order to reduce the residual water in the pure water zone 122, the lower end of the pure water zone 122 can be set in a cone shape, the large end of the cone is connected to the pure water zone 122, and the small end of the cone is connected to the mixing zone 121 through a pipe. A valve can be set at the pipe to facilitate the user to control the pure water zone 122.

[0035] In order to increase the speed at which pure water flows from the pure water zone 122 into the mixing zone 121, a small hole may be opened above the pure water zone 122. The small hole penetrates the top wall of the pure water zone 122 so that the internal and external air pressures of the pure water zone 122 are the same, thereby facilitating the flow of pure water.

[0036] When the water sample to be tested needs to be diluted, the water sample to be tested is added to the mixing area 121, and the pure water in the pure water area 122 enters the mixing area 121, and the pure water is mixed with the water sample to be tested, so as to dilute the chloride ions in the water sample to be tested. The diluted water sample to be tested is then tested for the concentration of chloride ions by the chloride ion detector 11. When the chloride ions in the water sample meet the detection standard, they enter the digestion cup 41 through the ten-way drain valve 2, and then the chemical oxygen demand in the water sample to be tested is detected.

[0037] In order to improve the mixing effect of the water sample to be tested and the pure water, the water sample to be tested may be introduced into the mixing zone 121 from the side so that the water sample to be tested and the outlet water are offset, thereby improving the dilution effect of the water sample to be tested.

[0038] There are multiple pure water areas 122, and the volumes of the multiple pure water areas 122 gradually increase. In one example, the volumes of the multiple pure water areas 122 are 10ml, 20ml, 30ml, 40ml and 50ml, respectively, so that the user can choose the volume of pure water to be added to the water sample to be tested, thereby improving the dilution effect and the convenience of operation for the operator.

[0039] For example, when the volume of the water sample to be tested is 20 ml, 10 ml, 20 ml, 30 ml, 40 ml or 50 ml of pure water is selected according to the chloride ion concentration of the water sample to be tested and added to any one of the water samples to be tested and added to the mixing area 121. The user no longer needs to measure the volume of the added pure water, thereby improving the convenience of the operator and reducing the dilution time.

[0040] In some optional examples, the dilution box 12 is transparent, and the pure water area 122 and / or the mixing area 121 are provided with scales. The dilution box 12 is made of a transparent material, such as a glass material or a transparent plastic material, so that the user can observe the situation of the pure water area 122 and the situation of the mixing area 121. In some optional examples, the outer shells of the plurality of pure water areas 122 are provided with scale labels, so that the user can know the amount of pure water added and calculate the dilution ratio. In some optional examples, the mixing area 121 is provided with a scale bar, so that the user can understand the amount of water sample to be tested and the amount of pure water added. In some optional examples, both the pure water area 122 and the mixing area 121 are provided with scale bars.

[0041] Furthermore, the water sample to be tested enters the mixing zone 121 through the pipeline, and the diluted water sample in the mixing zone 121 flows into the ten-way exhaust valve 2 through the pipeline. In order to reduce the flow time of the water sample, a pump body can be added to each pipeline.

[0042] In some optional examples, the dilution tank 12 further includes a water storage area 123 and a water delivery pipe 124. The water storage area 123 is arranged above the pure water area 122, and a large amount of pure water is contained in the water storage area 123. The water delivery pipe 124 includes a main pipe and a plurality of branch pipes, the main pipe is connected to the branch pipes, the plurality of branch pipes are respectively connected to the plurality of pure water areas 122, the main pipe is connected to the water storage area 123, and the main pipe is also provided with a valve switch.

[0043] The setting of the water storage area 123 can provide a water source for the pure water area 122. When the pure water in the pure water area 122 is used, the valve switch at the main pipe can be opened to allow the pure water in the water storage area 123 to enter the pure water area 122, thereby replenishing the pure water area 122 with pure water; when the replenishment is completed, the valve switch at the main pipe will be closed. The setting of the water supply pipe 124 makes it more convenient to replenish the water source for the pure water area 122.

[0044] In one example, a filter box may be provided, in which an ion exchange resin is provided to remove chloride ions in water. When the chemical oxygen demand detection device is moved to a site, the water on site may be directly filtered, and there is no need to carry deionized water or distilled water, thereby improving the convenience of carrying for users.

[0045] Reference Figure 1 and Figure 2 In some optional examples, a first stirring member 5 is further provided in the mixing zone 121, and the first stirring member 5 is used to stir the substances in the mixing zone 121. The first stirring member 5 can be a magnetic stirrer, which is provided below the mixing zone 121, and the stirring bar in the magnetic stirrer is located in the mixing zone 121, so as to stir the substances in the mixing zone 121, that is, the pure water and the water sample to be tested, thereby improving the mixing effect of the pure water and the water sample to be tested, and improving the dilution effect of the water sample to be tested.

[0046] In some optional examples, the digestion assembly 4 further includes a second stirring member 43, a heating plate 44, a temperature probe 45, a condenser 46, a cooling fan and a peristaltic pump 47. The second stirring member 43 is used to stir the substance in the digestion cup 41; the heating plate 44 is arranged around the digestion cup 41; the temperature probe 45 extends into the digestion cup 41 and is used to detect the temperature in the digestion cup 41; the condenser 46 is connected to the digestion cup 41, and a closed inner tube is arranged in the condenser 46, and a condensing agent is filled in the inner tube; the cooling fan is arranged on the outer wall of the condenser 46, and the cooling fan blows air toward the condenser 46; the peristaltic pump 47 is connected to the digestion cup 41 through a pipeline.

[0047] The second stirring member 43 may be a magnetic stirrer, which is located below the digestion cup 41 , and the stirrer is located in the digestion cup 41 . When stirring is required, the magnetic stirrer is started, so that the stirrer stirs in the digestion cup 41 .

[0048] The setting of the heating plate 44, when heating is needed, starts the heating plate 44 to heat the digestion cup 41, and the heating plate 44 is arranged around the digestion cup 41, so that the heating plate 44 heats the digestion cup 41 more evenly, and improves the effect of the heating plate 44 on the digestion cup 41. The temperature probe 45 is arranged inside the digestion cup 41, so that the user can understand the temperature in the digestion cup 41. The temperature probe 45 is used in conjunction with the heating plate 44, so that the user can better control the temperature in the digestion cup 41.

[0049] Furthermore, in order to prevent the water sample to be tested from evaporating during the heating process, the mouth of the digestion cup 41 is closed, but an injection hole is provided at the top of the digestion cup 41 for placing the injection pipe; the digestion cup 41 is also provided with an electrode hole for inserting the redox electrode 42, and the top of the digestion cup 41 is also provided with a reserved opening for inserting other equipment. The reserved opening is closed when not in use, and the top of the digestion cup 41 is also provided with a condensation port for inserting the condensation tube 46.

[0050] The condenser 46 is provided with an interlayer to form a closed inner tube, and a condensing agent is provided in the inner tube of the condenser 46. When the water sample to be tested evaporates, the gas formed enters the condenser 46 for cooling and refluxes into the digestion cup 41. In order to further improve the cooling effect of the water sample to be tested, a cooling fan is added to the outside of the condenser 46, and the cooling fan blows air to cool the surface of the condenser 46, further improving the cooling effect of the condenser 46.

[0051] The bottom of the digestion cup 41 is also connected to a peristaltic pump 47 through a pipeline. After the digestion cup 41 is digested, the liquid in the digestion cup 41 can be discharged through the peristaltic pump 47, so as to be cleaned and used next time.

[0052] Reference Figure 3 , Figure 3 A schematic diagram showing the structure of a chemical oxygen demand detection device provided in an embodiment of the present application Figure 2 In one example, the probe of the chloride ion detector 11 extends into the mixing zone 121 of the dilution tank 12, the mixing zone 121 is connected to the ten-way drain valve 2 through a pipeline, and a common interface 22 of the ten-way drain valve 2 is connected to the digestion cup 41. When in use, the water sample to be tested enters the mixing zone 121 of the dilution tank 12, and the chloride ion detector 11 detects the water sample to be tested. If dilution is required, the pure water in the pure water zone 122 is added to the dilution tank 12. If dilution is not required, the water sample to be tested enters the digestion cup 41 from the mixing zone 121 through the ten-way drain valve 2.

[0053] In another example, the chemical oxygen demand detection equipment is not provided with a dilution box 12, and the probe of the chloride ion detector 11 extends into the digestion cup 41. When in use, the water sample to be tested is transferred to the digestion cup 41 through the ten-way drain valve 2, and detected by the chloride ion detector 11. If dilution is not required, the reagent is directly introduced into the water sample to be tested for detection; if dilution is required, pure water can be first introduced through the ten-way drain valve 2 for dilution and then other reagents can be added for detection. During operation, the second stirring member 43 is used for stirring so that the pure water and the water sample to be tested are mixed more evenly, but in the process of adding pure water, the operator needs to pause the second stirring member 43 several times to facilitate the chloride ion detector 11 to detect the chloride ion concentration in the water sample to be tested, so as to meet the dilution effect of the water sample to be tested. The detection equipment of the present application reduces the volume of the chemical oxygen demand detection equipment relative to the detection equipment provided with a dilution box 12.

[0054] Furthermore, two digestion components 4 are provided, and the two digestion cups 41 are both connected to a common interface 22 of the ten-way exhaust valve 2 .

[0055] The digestion component 4 is provided with two methods of use: the first method is to pass the same water sample to be tested into two digestion cups 41 and to detect them simultaneously with the same reagent, thereby improving the detection accuracy of the water sample to be tested. The second method is that when multiple water samples to be tested are needed, different water samples to be tested can be passed into the two digestion cups 41 respectively to improve the detection efficiency. The third method is to put the water sample to be tested with a high chloride ion concentration into one of the digestion cups 41 for detection with some reagents, and put the water sample to be tested with a high chloride ion concentration into the other digestion cup 41 for dilution and detection with another part of the reagents, thereby improving the detection effect.

[0056] Reference Figure 1 , Figure 2 as well as Figure 3 , a detection method of a chemical oxygen demand detection device, comprising the following steps:

[0057] Detect the chloride ion content in the sample to be tested, and select reagent one according to the chloride ion content;

[0058] Injection: inject reagent 1 and the water sample to be tested into the digestion cup 41;

[0059] Heat and stir, heat the digestion cup 41 to the temperature of the water sample to be tested to 95°C-98°C, and digest at a constant temperature for 15 minutes after heating;

[0060] Heat dissipation cooling, cooling the material in the digestion cup 41 to 35°C-80°C;

[0061] For titration, reagent 2 and reagent 3 are added, and the mixture is allowed to stand for three minutes. Then, reagent 4 is added for titration, and the titration amount of reagent 4 is determined by the redox electrode 42 .

[0062] As shown in Table 1, the acid solution (1+3) of potassium permanganate (0.8 g / L) means that the concentration of potassium permanganate is 0.8 g / L, and the acid solution can be a sulfuric acid solution, and the ratio with pure water is 1:3.

[0063] The alkaline solution (50 g / L) of potassium permanganate (0.128 g / L) means that the concentration of potassium permanganate is 0.128 g / L, and the alkaline solution can be sodium hydroxide and the concentration is 50 g / L.

[0064] The meaning of sulfuric acid solution 1+3 is: the ratio of sulfuric acid to pure water is 1:3.

[0065] Table 1 Detection reagents

[0066]

[0067] It should be understood that there are multiple ways to detect the chloride ion concentration. In the first way, the water sample to be tested can be passed into the dilution box 12, and the probe of the chloride ion detector 11 can be inserted into the dilution box 12, and the chloride ion detector 11 can detect the chloride ion concentration. In the second way, the water sample to be tested can be passed into the digestion cup 41, and the probe of the chloride ion detector 11 can be inserted into the digestion cup 41 to detect the digestion cup 41. The third way is to perform manual detection.

[0068] Prepare multiple test samples with a COD of 3 mg / l using glucose, redistilled water and sodium chloride to simulate seawater. Seawater can also be simulated using artificial seawater.

[0069] Among them, the chloride ion concentration in the first test product is 1200 mg / L, the chloride ion concentration in the second test product is 1000 mg / l, the chloride ion concentration in the third test product is 700 mg / l, the chloride ion concentration in the fourth test product is 300 mg / l, and the chloride ion concentration in the fifth test product is 200 mg / l.

[0070] Multiple test samples with a COD of 3 mg / l were prepared using sodium oxalate, double distilled water and sodium chloride to simulate fresh water.

[0071] Among them, the chloride ion concentration in the sixth test product is 1200 mg / L, the chloride ion concentration in the seventh test product is 1000 mg / l, the chloride ion concentration in the eighth test product is 700 mg / l, the chloride ion concentration in the ninth test product is 300 mg / l, and the chloride ion concentration in the tenth test product is 200 mg / l.

[0072] The first method is selected below to detect the chloride ion concentration, but the second and third methods are also applicable.

[0073] Example 1

[0074] In one example, the first test product is placed in the mixing zone 121 for chloride ion concentration detection, and the chloride ion content of the first test product is greater than 1000 mg / L. After the detection is completed, the first test product enters the digestion cup 41 through the ten-way drain valve 2. At this time, reagent 1 is an alkaline solution of potassium permanganate, reagent 2 is a potassium iodide solution, reagent 3 is a sulfuric acid solution, and reagent 4 is a sodium thiosulfate solution.

[0075] The plunger pump 3 pumps 20 ml of the first test product and 4 ml of the alkaline solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the first test product and the alkaline solution of potassium permanganate evenly.

[0076] The digestion cup 41 is heated by the heating sheet 44 until the temperature reaches 98°C and the temperature is kept constant for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred, so that potassium permanganate partially oxidizes some organic matter and inorganic reducing substances in the first test product. Under alkaline conditions, a known amount of excess potassium permanganate is used to oxidize oxygen-demanding substances in the water body.

[0077] The liquid in the digestion cup 41 is cooled to 35°C, 37°C, or 40°C, and potassium iodide reagent and sulfuric acid reagent are added. The manganese dioxide produced by the oxidation process of the excess potassium permanganate is reduced by potassium iodide; after three minutes of reaction, sodium thiosulfate solution is added to titrate the free iodine produced, and the titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the first test product is determined according to the amount of sodium thiosulfate consumed during the titration.

[0078] Example 2

[0079] In one example, the second test product enters the mixing area 121 for chloride ion concentration detection. The chloride ion content in the second test product is 1000 mg / L. After the detection is completed, the second test product needs to be diluted. At this time, reagent 1 is an acid solution of potassium permanganate, reagent 2 is a sodium oxalate solution, reagent 3 is non-existent, and reagent 4 is a potassium permanganate solution.

[0080] At this time, the second test product enters the mixing area 121 of the dilution box 12, and the chloride ion content is detected by the chloride ion detector 11. According to the chloride ion content, pure water in one or more pure water areas 122 is selected to be added to the mixing area 121 for stirring and mixing. After mixing, the diluted second test product is tested. When the chloride ion content of the diluted second test product is lower than 300 mg / L, the second test product enters the digestion cup 41 through the ten-way drain valve 2 for digestion.

[0081] The plunger pump 3 pumps 20 ml of the diluted second test product and 4 ml of the acidic potassium permanganate solution into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring member 43 to mix the second test product with the acidic potassium permanganate solution.

[0082] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the second test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the second test product is determined by the back titration amount of potassium permanganate.

[0083] Example 3

[0084] In one example, the third test product enters the mixing zone 121 for chloride ion concentration detection. The chloride ion content in the third test product is less than 1000 mg / L but greater than 300 mg / L. After the detection is completed, the third test product needs to be diluted. At this time, reagent 1 is an acid solution of potassium permanganate, reagent 2 is a sodium oxalate solution, reagent 3 is non-existent, and reagent 4 is a potassium permanganate solution.

[0085] At this time, the third test product enters the mixing area 121 of the dilution box 12, and the chloride ion content is detected by the chloride ion detector 11. According to the chloride ion content, pure water in one or more pure water areas 122 is selected to be added to the mixing area 121 for stirring and mixing. After mixing, the diluted third test product is tested. When the chloride ion content of the diluted third test product is lower than 300 mg / L, the third test product enters the digestion cup 41 through the ten-way drain valve 2 for digestion.

[0086] The plunger pump 3 pumps 20 ml of the diluted third test product and 4 ml of the acidic potassium permanganate solution into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the third test product with the acidic potassium permanganate solution.

[0087] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the third test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the third test product is determined by the back titration amount of potassium permanganate.

[0088] Example 4

[0089] In one example, the fourth test product enters the mixing area 121 for chloride ion concentration detection. The chloride ion content in the fourth test product is 300 mg / L. After the detection is completed, the fourth test product needs to be diluted. At this time, reagent one is an acid solution of potassium permanganate, reagent two is a sodium oxalate solution, reagent three is non-existent, and reagent four is a potassium permanganate solution.

[0090] At this time, the fourth test product enters the mixing area 121 of the dilution box 12, and the chloride ion content is detected by the chloride ion detector 11. According to the chloride ion content, pure water in one or more pure water areas 122 is selected to be added to the mixing area 121 for stirring and mixing. After mixing, the diluted fourth test product is tested. When the chloride ion content of the diluted fourth test product is lower than 300 mg / L, the fourth test product enters the digestion cup 41 through the ten-way drain valve 2 for digestion.

[0091] The plunger pump 3 pumps 20 ml of the diluted fourth test product and 4 ml of the acidic potassium permanganate solution into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the fourth test product with the acidic potassium permanganate solution.

[0092] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the fourth test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the fourth test product is determined by the back titration amount of potassium permanganate.

[0093] Example 5

[0094] In one example, the fifth test product enters the mixing zone 121 for chloride ion concentration detection. The chloride ion content in the fifth test product is less than 300 mg / L. After the detection is completed, the fifth test product enters the digestion cup 41 through the ten-way exhaust valve 2. At this time, reagent 1 is an acid solution of potassium permanganate, reagent 2 is a sodium oxalate solution, reagent 3 is non-existent, and reagent 4 is a potassium permanganate solution.

[0095] The plunger pump 3 pumps 20 ml of the fifth test product and 4 ml of the acidic solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the fifth test product with the acidic solution of potassium permanganate.

[0096] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the fifth test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the fifth test product is determined by the back titration amount of potassium permanganate.

[0097] In some embodiments, when the chloride ion concentration in the water sample to be tested is greater than or equal to 300 mg / L and less than or equal to 1000 mg / L, the chloride ion concentration in the water sample to be tested can be further divided.

[0098] Example 6

[0099] In one example, the sixth test product is placed in the mixing zone 121 for chloride ion concentration detection, and the chloride ion content of the sixth test product is greater than 1000 mg / L. After the detection is completed, the sixth test product enters the digestion cup 41 through the ten-way drain valve 2. At this time, reagent 1 is an alkaline solution of potassium permanganate, reagent 2 is a potassium iodide solution, reagent 3 is a sulfuric acid solution, and reagent 4 is a sodium thiosulfate solution.

[0100] The plunger pump 3 pumps 20 ml of the sixth test product and 4 ml of the alkaline solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring member 43 to mix the sixth test product and the alkaline solution of potassium permanganate evenly.

[0101] The digestion cup 41 is heated by the heating sheet 44 until the temperature reaches 98°C and the temperature is kept constant for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred, so that potassium permanganate partially oxidizes some organic matter and inorganic reducing substances in the sixth test product. Under alkaline conditions, a known amount of excess potassium permanganate is used to oxidize oxygen-demanding substances in the water body.

[0102] The liquid in the digestion cup 41 is cooled to 35°C, 37°C, or 40°C, and potassium iodide reagent and sulfuric acid reagent are added. The manganese dioxide produced by the oxidation process of the excess potassium permanganate is reduced by potassium iodide; after three minutes of reaction, sodium thiosulfate solution is added to titrate the free iodine produced, and the titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the sixth test product is determined according to the amount of sodium thiosulfate consumed during the titration.

[0103] Example 7

[0104] In one example, the seventh test product enters the mixing area 121 for chloride ion concentration detection. The chloride ion content in the seventh test product is 1000 mg / L. After the detection is completed, the seventh test product needs to be diluted. At this time, reagent one is an acid solution of potassium permanganate, reagent two is a sodium oxalate solution, reagent three is non-existent, and reagent four is a potassium permanganate solution.

[0105] At this time, the seventh test product enters the mixing area 121 of the dilution box 12, and the chloride ion content is detected by the chloride ion detector 11. According to the chloride ion content, pure water in one or more pure water areas 122 is selected to be added to the mixing area 121 for stirring and mixing. After mixing, the diluted seventh test product is tested. When the chloride ion content of the diluted seventh test product is lower than 300 mg / L, the seventh test product enters the digestion cup 41 through the ten-way drain valve 2 for digestion.

[0106] The plunger pump 3 pumps 20 ml of the diluted seventh test product and 4 ml of the acidic solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the seventh test product with the acidic solution of potassium permanganate.

[0107] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the seventh test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the seventh test product is determined by the back titration amount of potassium permanganate.

[0108] Example 8

[0109] In one example, the eighth test product enters the mixing zone 121 for chloride ion concentration detection. The chloride ion content in the eighth test product is less than 1000 mg / L but greater than 300 mg / L. After the detection is completed, the eighth test product needs to be diluted. At this time, reagent 1 is an acid solution of potassium permanganate, reagent 2 is a sodium oxalate solution, reagent 3 is non-existent, and reagent 4 is a potassium permanganate solution.

[0110] At this time, the eighth test product enters the mixing area 121 of the dilution box 12, and the chloride ion content is detected by the chloride ion detector 11. According to the chloride ion content, pure water in one or more pure water areas 122 is selected to be added to the mixing area 121 for stirring and mixing. After mixing, the diluted eighth test product is tested. When the chloride ion content of the diluted eighth test product is lower than 300 mg / L, the eighth test product enters the digestion cup 41 through the ten-way drain valve 2 for digestion.

[0111] The plunger pump 3 pumps 20 ml of the diluted eighth test product and 4 ml of the acidic potassium permanganate solution into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the eighth test product with the acidic potassium permanganate solution.

[0112] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the eighth test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the eighth test product is determined by the back titration amount of potassium permanganate.

[0113] Example 9

[0114] In one example, the ninth test product enters the mixing area 121 for chloride ion concentration detection. The chloride ion content in the ninth test product is 300 mg / L. After the detection is completed, the ninth test product needs to be diluted. At this time, reagent one is an acid solution of potassium permanganate, reagent two is a sodium oxalate solution, reagent three is non-existent, and reagent four is a potassium permanganate solution.

[0115] At this time, the ninth test product enters the mixing area 121 of the dilution box 12, and the chloride ion content is detected by the chloride ion detector 11. According to the chloride ion content, pure water in one or more pure water areas 122 is selected to be added to the mixing area 121 for stirring and mixing. After mixing, the diluted ninth test product is tested. When the chloride ion content of the diluted ninth test product is lower than 300 mg / L, the ninth test product enters the digestion cup 41 through the ten-way drain valve 2 for digestion.

[0116] The plunger pump 3 pumps 20 ml of the diluted ninth test product and 4 ml of the acidic potassium permanganate solution into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the ninth test product with the acidic potassium permanganate solution.

[0117] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the ninth test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the ninth test product is determined by the back titration amount of potassium permanganate.

[0118] Example 10

[0119] In one example, the tenth test product enters the mixing zone 121 for chloride ion concentration detection. The chloride ion content in the tenth test product is less than 300 mg / L. After the detection is completed, the tenth test product enters the digestion cup 41 through the ten-way exhaust valve 2. At this time, reagent 1 is an acid solution of potassium permanganate, reagent 2 is a sodium oxalate solution, reagent 3 is non-existent, and reagent 4 is a potassium permanganate solution.

[0120] The plunger pump 3 pumps 20 ml of the tenth test product and 4 ml of the acidic potassium permanganate solution into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the tenth test product with the acidic potassium permanganate solution.

[0121] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the tenth test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the tenth test product is determined by the back titration amount of potassium permanganate.

[0122] In some embodiments, when the chloride ion concentration in the water sample to be tested is greater than or equal to 300 mg / L and less than or equal to 1000 mg / L, the chloride ion concentration in the water sample to be tested can be further divided.

[0123] Comparative Example 1

[0124] In one example, the second test product enters the mixing zone 121 for chloride ion concentration detection. The chloride ion content in the second test product is equal to 1000 mg / L. After the detection is completed, the second test product enters the digestion cup 41 through the ten-way exhaust valve 2. At this time, reagent 1 is an acid solution of potassium permanganate, reagent 2 is a sodium oxalate solution, reagent 3 is non-existent, and reagent 4 is a potassium permanganate solution.

[0125] The plunger pump 3 pumps 20 ml of the second test product and 4 ml of the acidic potassium permanganate solution into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring member 43 to mix the second test product with the acidic potassium permanganate solution.

[0126] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the second test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the second test product is determined by the back titration amount of potassium permanganate.

[0127] Comparative Example 2

[0128] In one example, the seventh test product enters the mixing zone 121 for chloride ion concentration detection. The chloride ion content in the seventh test product is equal to 1000 mg / L. After the detection is completed, the seventh test product enters the digestion cup 41 through the ten-way exhaust valve 2. At this time, reagent 1 is an acid solution of potassium permanganate, reagent 2 is a sodium oxalate solution, reagent 3 is non-existent, and reagent 4 is a potassium permanganate solution.

[0129] The plunger pump 3 pumps 20 ml of the seventh test product and 4 ml of the acidic solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring member 43 to mix the seventh test product with the acidic solution of potassium permanganate.

[0130] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the seventh test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the seventh test product is determined by the back titration amount of potassium permanganate.

[0131] Comparative Example 3

[0132] In one example, the third test product enters the mixing zone 121 for chloride ion concentration detection. The chloride ion content in the third test product is greater than 300 mg / L and less than 1000 mg / L. After the detection is completed, the third test product enters the digestion cup 41 through the ten-way exhaust valve 2. At this time, reagent 1 is an acid solution of potassium permanganate, reagent 2 is a sodium oxalate solution, reagent 3 is non-existent, and reagent 4 is a potassium permanganate solution.

[0133] The plunger pump 3 pumps 20 ml of the third test product and 4 ml of the acidic solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring element 43 to mix the third test product with the acidic solution of potassium permanganate.

[0134] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the third test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the third test product is determined by the back titration amount of potassium permanganate.

[0135] Comparative Example 4

[0136] In one example, the eighth test product enters the mixing zone 121 for chloride ion concentration detection, and the chloride ion content in the eighth test product is greater than 300 mg / L and less than 1000 mg / L. After the detection is completed, the eighth test product enters the digestion cup 41 through the ten-way exhaust valve 2. At this time, reagent one is an acid solution of potassium permanganate, reagent two is a sodium oxalate solution, reagent three is non-existent, and reagent four is a potassium permanganate solution.

[0137] The plunger pump 3 pumps 20 ml of the eighth test product and 4 ml of the acidic solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring member 43 to mix the eighth test product with the acidic solution of potassium permanganate.

[0138] The digestion cup 41 is heated by the heating plate 44 until the temperature reaches 98°C and kept at a constant temperature for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred so that potassium permanganate partially oxidizes certain organic matter and inorganic reducing substances in the eighth test product. When the temperature in the digestion cup 41 is cooled to 70°C, 75°C or 80°C, sodium oxalate solution is added to reduce the remaining potassium permanganate. After three minutes of reaction, potassium permanganate solution is added for back titration. The titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the eighth test product is determined by the back titration amount of potassium permanganate.

[0139] Comparative Example 5

[0140] In one example, the eighth test product is placed in the mixing zone 121 for chloride ion concentration detection, and the chloride ion content of the eighth test product is less than 1000 mg / L and greater than 300 mg / L. After the detection is completed, the eighth test product enters the digestion cup 41 through the ten-way drain valve 2. At this time, reagent 1 is an alkaline solution of potassium permanganate, reagent 2 is a potassium iodide solution, reagent 3 is a sulfuric acid solution, and reagent 4 is a sodium thiosulfate solution.

[0141] The plunger pump 3 pumps 20 ml of the eighth test product and 4 ml of the alkaline solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring member 43 to mix the eighth test product and the alkaline solution of potassium permanganate evenly.

[0142] The digestion cup 41 is heated by the heating sheet 44 until the temperature reaches 98°C and the temperature is kept constant for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred, so that potassium permanganate partially oxidizes some organic matter and inorganic reducing substances in the eighth test product. Under alkaline conditions, a known amount of excess potassium permanganate is used to oxidize oxygen-demanding substances in the water body.

[0143] The liquid in the digestion cup 41 is cooled to 35°C, 37°C, or 40°C, and potassium iodide reagent and sulfuric acid reagent are added. The manganese dioxide produced by the oxidation process of the excess potassium permanganate is reduced by potassium iodide; after three minutes of reaction, sodium thiosulfate solution is added to titrate the free iodine produced, and the titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the eighth test product is determined according to the amount of sodium thiosulfate consumed during the titration.

[0144] Comparative Example 6

[0145] In one example, the tenth test product is placed in the mixing zone 121 for chloride ion concentration detection, and the chloride ion content of the tenth test product is less than 300 mg / L. After the detection is completed, the tenth test product enters the digestion cup 41 through the ten-way drain valve 2. At this time, reagent 1 is an alkaline solution of potassium permanganate, reagent 2 is a potassium iodide solution, reagent 3 is a sulfuric acid solution, and reagent 4 is a sodium thiosulfate solution.

[0146] The plunger pump 3 pumps 20 ml of the tenth test product and 4 ml of the alkaline solution of potassium permanganate into the digestion cup 41 through the ten-way exhaust valve 2, and starts the second stirring member 43 to mix the tenth test product and the alkaline solution of potassium permanganate evenly.

[0147] The digestion cup 41 is heated by the heating sheet 44 until the temperature reaches 98°C and the temperature is kept constant for 15 minutes. During the heating process, the substances in the digestion cup 41 are still stirred, so that potassium permanganate partially oxidizes some organic matter and inorganic reducing substances in the tenth test product. Under alkaline conditions, a known amount of excess potassium permanganate is used to oxidize oxygen-demanding substances in the water body.

[0148] The liquid in the digestion cup 41 is cooled to 35°C, 37°C, or 40°C, and potassium iodide reagent and sulfuric acid reagent are added. The manganese dioxide produced by the oxidation process of the excess potassium permanganate is reduced by potassium iodide; after three minutes of reaction, sodium thiosulfate solution is added to titrate the free iodine produced, and the titration end point is determined by the potential change of the redox electrode 42, and the chemical oxygen demand in the tenth test product is determined according to the amount of sodium thiosulfate consumed during the titration.

[0149] Test results

[0150] Referring to Table 2, Table 2 is a test result table of Examples 1-10 and Comparative Examples 1-4, and the COD value in the test in the table is the average value taken after multiple tests of Examples 1-10 and Comparative Examples 1-4.

[0151] Table 2 Test results

[0152] Theoretical COD value Chloride ion concentration COD value during the test Example 1 3mg / l 1200mg / l 3.05mg / L Example 2 3mg / l 1000mg / l 2.92mg / L Example 3 3mg / l 700mg / l 2.97mg / L Example 4 3mg / l 300mg / l 2.98mg / L Example 5 3mg / l 200mg / l 3.09mg / L Example 6 3mg / l 1200mg / l 3.03mg / L Example 7 3mg / l 1000mg / l 3.18mg / L Example 8 3mg / l 700mg / l 3.15mg / L Example 9 3mg / l 300mg / l 3.06mg / L Example 10 3mg / l 200mg / l 3.11mg / L Comparative Example 1 3mg / l 1000mg / l 3.38mg / L Comparative Example 2 3mg / l 1000mg / l 3.45mg / L Comparative Example 3 3mg / l 700mg / l 3.34mg / L Comparative Example 4 3mg / l 700mg / l 3.35mg / L Comparative Example 5 3mg / l 700mg / l 2.82mg / L Comparative Example 6 3mg / l 200mg / l 2.80mg / L

[0153] According to Table 2, when the chloride ion concentration in the test product is greater than 1000 mg / l, both Example 1 and Example 6 use an alkaline solution of potassium permanganate, potassium iodide, a sulfuric acid solution, and sodium thiosulfate to detect the COD value in the simulated seawater test product and the simulated freshwater test product. The test value is close to the theoretical value, and the COD value of the near-coastal water body can be detected by this method, and it is closest to the theoretical COD value compared with other test methods.

[0154] When the chloride ion concentration in the test product is between 300mg / l-1000mg / l, Examples 2-4 and 7-9 are all diluted first and then the COD values ​​in the simulated seawater test product and the simulated freshwater test product are detected using potassium permanganate acid solution, sodium oxalate solution and potassium permanganate solution. The test value is close to the theoretical value, and the COD value of seawater can be detected by this method. However, when the chloride ion concentration is higher, the gap between the test value and the theoretical value gradually increases.

[0155] When the chloride ion concentration in the test product is less than 300 mg / l, potassium permanganate acid solution, sodium oxalate solution and potassium permanganate solution are directly used to detect the COD value in the simulated seawater test product and the simulated freshwater test product. The test value is close to the theoretical value. This method can be used to detect the COD value of near-coastal water bodies.

[0156] It can be seen from the results of Comparative Examples 1-4 that when the chloride ion content is greater than 300 mg / l, the test results of the seawater simulation test products and the freshwater simulation test products are not accurate enough if the potassium permanganate acid solution, sodium oxalate solution and potassium permanganate solution are directly used without dilution.

[0157] It can be seen from the results of Comparative Examples 5-6 that when the chloride ion content is less than 1000 mg / l, the test results of the freshwater simulation test products using potassium permanganate alkaline solution, potassium iodide, sulfuric acid solution and sodium thiosulfate are not accurate enough.

[0158] It should be noted that the phrases "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments", etc. mentioned in the specification indicate that the described embodiments may include certain features, structures or characteristics, but not every embodiment may include the certain features, structures or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when describing certain features, structures or characteristics in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such features, structures or characteristics in conjunction with other embodiments, whether explicitly or not explicitly described.

[0159] It should be easily understood that “on,” “above,” and “over” in the present disclosure should be interpreted in the broadest manner, so that “on” not only means “directly on something,” but also includes the meaning of “on something” with intervening features or layers therebetween, and “above” or “over” not only includes the meaning of “above” or “over,” but also may include the meaning of “above” or “over something” with no intervening features or layers therebetween (i.e., directly on something).

[0160] In addition, spatially relative terms, such as "below," "below," "beneath," "above," "above," etc., may be used herein for ease of description to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may have other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0161] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0162] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A detection method for chemical oxygen demand detection equipment, characterized in that: The following steps are involved: Detect the chloride ion content in the water sample to be tested, and select reagent 1 according to the chloride ion content; Inject, inject reagent 1 and the water sample to be tested into the digestion cup; Heat and stir, heat the digestion cup to the temperature of the water sample to be tested to 95℃-98℃, and digest at a constant temperature for 15 minutes after heating; Heat dissipation cooling, cool the material in the digestion cup to 35℃-80℃; Titration: add reagent 2 and reagent 3 to the cooled digestion cup, let stand for three minutes, add reagent 4 for titration, and determine the titration amount of reagent 4 by the redox electrode; Wherein, when the chloride ion content in the water sample to be tested is greater than 1000 mg / L, reagent one is an alkaline solution of potassium permanganate, reagent two is a potassium iodide solution, reagent three is a sulfuric acid solution, reagent four is a sodium thiosulfate solution, and during heat dissipation cooling, the material in the digestion cup is cooled to 35°C-40°C; Wherein, when the chloride ion content in the water sample to be tested is less than 300 mg / L, reagent one is an acidic solution of potassium permanganate, reagent two is a sodium oxalate solution, reagent three is none, reagent four is a potassium permanganate solution, and during heat dissipation cooling, the material in the digestion cup is cooled to 70°C-80°C; Among them, when the chloride ion content in the water sample to be tested is greater than or equal to 300 mg / L and less than or equal to 1000 mg / L, it is diluted through a dilution box to a chloride ion content of 300 mg / L in the water sample to be tested, and during heat dissipation cooling, the material in the digestion cup is cooled to 70°C-80°C.

2. A chemical oxygen demand detection device for implementing the detection method according to claim 1, characterized in that: include: Chloride ion detection components, including chloride ion detectors; A ten-way exhaust valve is provided with a central interface and a plurality of common interfaces, wherein one of the common interfaces is used to draw a water sample to be tested; A plunger pump, connected to the central interface; A digestion component, comprising a digestion cup and a redox electrode, wherein the digestion cup is connected to one of the common interfaces of the ten-way exhaust valve, and the redox electrode extends into the digestion cup and is used to detect the chemical oxygen demand in the digestion cup; Wherein, the chloride ion detection component also includes a dilution box, and the dilution box includes: A mixing zone, the chloride ion detector comprises a detection probe, the detection probe extends into the mixing zone, and the sample outlet end of the mixing zone is connected to the ten-way exhaust valve; A pure water zone, wherein the water outlet of the pure water zone is connected to the mixing zone, and a plurality of the pure water zones are provided, and the volumes of the plurality of the pure water zones gradually increase; The dilution box is transparent, and the pure water area and / or the mixing area are provided with scales; Wherein, the digestion component also includes: a second stirring member, used for stirring the substances in the digestion cup; A heating plate, arranged around the digestion cup and used for heating the substance in the digestion cup; A temperature probe, extending into the digestion cup and used to detect the temperature in the digestion cup; A condenser tube is connected to the digestion cup, wherein a closed inner tube is arranged in the condenser tube, and a condensing agent is contained in the inner tube; A cooling fan is arranged on the outer wall of the condenser tube, and the cooling fan blows air toward the condenser tube; A peristaltic pump connected to the digestion cup through a pipeline; The chloride ion detector comprises a detection probe, and the detection probe extends into the digestion cup.

3. The chemical oxygen demand detection device according to claim 2, characterized in that: The dilution box also includes: Water storage area, used to store pure water; The water delivery pipe comprises a main pipe and a plurality of branch pipes, wherein the plurality of branch pipes are respectively connected to the plurality of pure water areas, the main pipe is connected to the water storage area, and a valve switch is also arranged at the main pipe.

4. The chemical oxygen demand detection device according to claim 3, characterized in that: A first stirring member is also provided in the mixing zone, and the first stirring member is used to stir the material in the mixing zone.

5. The chemical oxygen demand detection device according to claim 2, characterized in that: The digestion components are provided with two, and the two digestion cups are connected to a common interface of the ten-way exhaust valve.

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