Sequential injection analysis method for nitrate / nitrite in water

Abstract

The invention discloses a sequential injection analysis method for nitrate / nitrite in water. Through the arrangement of the bubble detector and the application of the air column, accurate sample introduction can be realized, complete reaction is ensured, a water sample and a reagent are not in contact with pure water, diffusion and dilution are avoided, and thus the accuracy and reliability of a detection result are improved. By using the air inlet action bag, accurate sample introduction of liquid is further ensured, complete reaction is ensured, and a water sample and a reagent are not in contact with pure water and are not diffused and diluted, so that the accuracy and the reliability of a detection result are improved. The sequential injection module, the detection unit and the control unit all adopt modular design, a user can flexibly replace a detector and reaction conditions according to detection requirements, the detection requirements of different water quality parameters are met, and the adaptability and expansibility of the system are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of water quality monitoring, and in particular relates to a sequential injection analysis method for nitrate / nitrite in water quality. Background Art

[0002] Nitrate and nitrite in nutrients are important indicators for water quality monitoring and evaluation of water eutrophication. Traditional laboratories use manual measurements, which are prone to sample contamination, take a long time to measure, and are not suitable for long-term on-site monitoring. The emergence of flow analysis technology has realized the automation and miniaturization of fluid control, reducing the risk of sample contamination and reagent consumption. The development of flow analysis technology has greatly promoted the development of automatic nutrient detection technology. Among them, Sequential Injection Analysis (SIA) has gradually been used in water quality nutrient monitoring due to its advantages such as simple and reliable hardware, good versatility of injection pipelines, and low sample and reagent consumption.

[0003] The sequential injection analysis system mainly includes a pump, a multi-channel selection valve, and a liquid storage ring therebetween. Each channel of the multi-channel selection valve is respectively connected to a sample channel, a reagent channel, a waste liquid channel, a detector channel, and the like.

[0004] For example, the invention application with publication number CN102980858A discloses a small sequential injection nitrite analysis system, in which the first solenoid valve is connected to the nitrite standard solution, the second solenoid valve is connected to the color developer and deionized water, the first solenoid valve and the second solenoid valve are commonly connected to the third solenoid valve, the third solenoid valve is connected to the fourth solenoid valve connected to the water sample, the fifth solenoid valve is connected to the deionized water and the waste liquid bottle equipped with a liquid level detection device, the fourth solenoid valve and the fifth solenoid valve are connected to the six-way valve through the first peristaltic pump and the second peristaltic pump respectively, and the six-way valve is connected to the waste liquid, the quantitative ring and the colorimetric cell respectively.

[0005] For another example, the invention application with publication number CN117517227A discloses a micro gas phase molecular absorption spectrum online detection device and detection method for nitrite in environmental water. The device is based on the principle of gas phase molecular absorption spectrum, and integrates the carrier gas system, reaction system and detection system through a sequential injection analysis system, which improves the sensitivity of nitrite detection at visible wavelengths, reduces the interference of water vapor in the gas phase on detection, reduces the energy consumption requirements and production costs of the nitrite gas phase molecular absorption measurement and analysis device, reduces the size of the detection device, and realizes the trace level detection of nitrite in complex matrices.

[0006] In order to achieve accurate detection of nutrients in water samples, it is necessary to accurately control the volume of the test water sample and reagent, as well as the mixing procedure of the two, which requires precise control of the flow path to achieve sample control. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention provides a sequential injection analysis method for nitrate / nitrite in water quality, so as to achieve efficient and accurate detection of water nutrients such as nitrate and nitrite.

[0008] A sequential injection analysis method for nitrate / nitrite in water quality uses a sequential injection analysis system, the sequential injection analysis system comprising:

[0009] A sequential injection module, comprising a multi-channel selection valve, a plunger pump and a liquid storage ring, wherein the multi-channel selection valve comprises a common end interface and a plurality of inlet and outlet interfaces, wherein the common end interface is connected to an injection pipeline, wherein the liquid storage ring and the plunger pump are sequentially arranged on the injection pipeline from close to the common end interface to far from the common end interface, and the free end of the injection pipeline is used to connect to a pure water bottle; and a bubble detector is arranged on the common end interface of the multi-channel selection valve;

[0010] A water sample collection unit, comprising a water sample collection tube, one end of which is used to suck the water sample to be tested, and the other end of which is connected to one of the inlet and outlet interfaces of the multi-channel selection valve;

[0011] A reagent unit, comprising a reagent inlet tube, one end of which is connected to a reagent bottle, and the other end of which is connected to one of the inlet and outlet interfaces of the multi-channel selection valve;

[0012] A reaction unit, comprising a mixing tube, one end of which is connected to one of the inlet and outlet ports of the multi-channel selection valve;

[0013] A detection unit, comprising a detection tube, one end of which is connected to one of the inlet and outlet interfaces of the multi-channel selection valve;

[0014] A waste liquid pipe, one end of which is connected to one of the inlet and outlet interfaces of the multi-channel selection valve;

[0015] One of the inlet and outlet interfaces of the multi-channel selector valve is used as an air end for air intake;

[0016] The sequential injection analysis method includes an initialization phase, a sampling phase, a reaction phase, a detection phase, and a cleaning phase.

[0017] During the initialization stage and the cleaning stage, the pump is reset, cleaned, and reset in turn; during the reset, the pure water in the plunger pump is emptied to restore the initial position, and the liquid storage ring is filled with pure water, but a section of air column is left at the end of the injection line connected to the common end interface;

[0018] During the sampling stage, the common end interface is connected to the water sample collection tube, and the plunger pump extracts the water sample to be tested until the state of the bubble detector changes from no liquid to liquid, and the water sample of the volume required for sampling or the water sample larger than the volume required for sampling is continuously extracted, and then the common end interface is connected to the mixing tube, and the liquid of the volume required for sampling is pushed into the mixing tube; the common end interface is connected to the waste liquid tube, and the excess water sample to be tested is discharged; then the common end interface is connected to the air end, and sufficient air is extracted, and the common end interface is connected to the mixing tube, and the water sample is completely pushed into the mixing tube by injecting air;

[0019] In the reaction stage, the common end interface is connected to the reagent inlet tube, and the plunger pump extracts the detection reagent in the reagent bottle until the state of the bubble detector changes from no liquid to liquid, and the detection reagent of the volume required for the reaction or the detection reagent larger than the volume required for the reaction is continuously extracted, and then the common end interface is connected to the mixing tube, and the detection reagent of the volume required for the reaction is pushed into the mixing tube; the common end interface is connected to the waste liquid tube, and the excess water sample to be tested is discharged; then the common end interface is connected to the air end, and sufficient air is extracted, and the common end interface is connected to the mixing tube, and the detection reagent is completely pushed into the mixing tube by injecting air, so that the detection reagent is mixed with the water sample to be tested to obtain a mixed reaction liquid;

[0020] During the detection stage, the common end interface is connected to the mixing tube, and the mixed reaction liquid in the mixing tube is extracted by the plunger pump until the state of the bubble detector changes from no liquid to liquid, and the mixed reaction liquid of the volume required for detection or the mixed reaction liquid larger than the volume required for detection is continuously extracted, and then the common end interface is connected to the detection tube, and the mixed reaction liquid of the volume required for detection is pushed into the detection tube; the common end interface is connected to the waste liquid pipe to discharge the excess mixed reaction liquid; then the common end interface is connected to the air end to extract enough air, and the common end interface is connected to the detection tube to completely push the detection reagent into the detection tube by injecting air.

[0021] The sequential injection analysis method of the present application can be used to directly detect and analyze water samples at a site such as a riverside. At this time, one end of the water sample collection tube is directly inserted into the position where the water sample to be tested needs to be sucked; the water sample to be tested can also be collected and brought back for testing in the laboratory.

[0022] During the detection stage, only a portion of the mixed reaction liquid can be drawn into the detection tube for detection, and the excess mixed reaction liquid can be discharged to ensure that the mixed reaction liquid is sufficient for detection.

[0023] Preferably, the sequential injection analysis system further comprises a control unit, and the control unit is used to control the operation of each component;

[0024] Integrate and package the control programs of some repetitive actions into action packages, wherein the action packages include a reset action package, a cleaning action package, a liquid inlet action package, and an air inlet action package;

[0025] The reset action package includes a control program for the following actions performed in sequence: emptying the pure water in the plunger pump to restore the initial position, and filling the liquid storage ring with pure water, but leaving a section of air column at the end of the injection pipeline connected to the common end interface;

[0026] The cleaning action package includes a control program for sequentially performing the following actions: connecting the common end interface to the waste liquid pipe, extracting pure water from the pure water bottle through the plunger pump, and cleaning the liquid storage ring;

[0027] The liquid inlet action package includes a control program for the following actions performed in sequence: the plunger pump extracts liquid until the state of the bubble detector changes from no liquid to liquid, and continues to extract a required volume of liquid or liquid greater than the required volume, and then connects the common end interface to the pipeline that needs to be inlet, and pushes the required volume of liquid into the corresponding pipeline; connects the common end interface to the waste liquid pipe to discharge excess liquid;

[0028] The air intake action package includes a control program for performing the following actions in sequence: connecting the common end interface to the air end, extracting enough air, connecting the common end interface to the pipeline that needs to be filled with liquid, and completely pushing the liquid into the corresponding pipeline by injecting air.

[0029] The present invention realizes high automation and standardization of operations at each stage in the water quality detection process through the design of action packages (reset action package, cleaning action package, liquid intake action package, and air intake action package), reduces the need for manual intervention, and reduces the possibility of human error.

[0030] More preferably, during the initialization phase, the reset action package is used during resetting, and the cleaning action package is used during cleaning.

[0031] More preferably, during the sample introduction stage, the liquid introduction action pack is used first, and then the air introduction action pack is used.

[0032] More preferably, during the reaction phase, the liquid action pack is used first, and then the air action pack is used.

[0033] More preferably, during the detection phase, a liquid-intake action pack is used, followed by an air-intake action pack.

[0034] Preferably, the detection unit is provided with a detector on the detection tube, and the detector includes one or more detectors, each of which is selected from an optical detector, a conductivity detector or an electrochemical detector.

[0035] More preferably, the optical detector is used to measure the absorbance of certain components in the water sample or the generated fluorescent signal, and the optical detector includes a flow cuvette connected to the detection tube;

[0036] The flow cuvette is provided with a shading structure on the outside, the shading structure includes two shading sheets that are buckled with each other, and the buckling surfaces of the two shading sheets after being buckled with each other are provided with a first receiving groove for accommodating the flow cuvette and a second receiving groove for installing a detection light source, and one side of the second receiving groove is provided with a first detection port that is connected to the first receiving groove and faces the side of the flow cuvette;

[0037] A third receiving groove for mounting a detector is provided on one of the light shielding sheets, and a second detection port connected to the first receiving groove and facing the side of the flow cuvette is provided on one side of the third receiving groove;

[0038] The first containing tank is also provided with a avoidance hole for avoiding the inlet end and the outlet end of the flow cuvette;

[0039] The engaging surfaces of the two shading sheets after being buckled together are provided with mating protrusions and grooves on both axial sides of the first receiving groove, wherein each shading sheet is provided with a protrusion and a groove on each side of the first receiving groove.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention can accurately inject samples and ensure complete reaction through the provision of a bubble detector and the application of an air column, and the water sample and the reagent do not come into contact with pure water, and there is no diffusion dilution, thereby improving the accuracy and reliability of the test results.

[0042] By using the air inlet action package, the precise injection of liquid is further guaranteed, the reaction is complete, and the water sample and reagent do not come into contact with pure water, and there is no diffusion dilution, thereby improving the accuracy and reliability of the test results.

[0043] 2. The sequential injection module, detection unit and control unit of the present invention all adopt a modular design. Users can flexibly replace detectors and reaction conditions according to detection requirements to adapt to the detection requirements of different water quality parameters, thereby improving the adaptability and scalability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the structure of the sequential injection analysis system of the present invention.

[0045] Figure 2 Schematic diagram of the partial structure of the reaction unit.

[0046] Figure 3 It is a structural schematic diagram of the shading structure in the detection unit.

[0047] Figure 4 A schematic diagram of the exploded structure of the light-shielding structure in the detection unit from a first perspective.

[0048] Figure 5 A schematic diagram of the exploded structure of the light-shielding structure in the detection unit from a second viewing angle.

[0049] Figure 6 Schematic diagram of the structure of the flow cuvette.

[0050] Reference numerals: multi-channel selector valve 1, common end interface 11, inlet and outlet interface 12, inlet and outlet interface 13, inlet and outlet interface 14, inlet and outlet interface 15, inlet and outlet interface 16, inlet and outlet interface 17,

[0051] Injection pipeline 2, plunger pump 21, liquid storage ring 22, pure water bottle 23, bubble detector 24,

[0052] Water sample collection tube 3, automatic water sample collection device 31, water sample bottle 32,

[0053] Into the reagent tube 4, reagent bottle 41,

[0054] Mixing tube 5, heating wire 51, temperature sensor 52,

[0055] Detection tube 6, detector 61, optical detector 62, flow cuvette 621, light shielding sheet 622, first receiving groove 623, second receiving groove 624, first detection port 625, avoidance hole 626, protrusion 627, groove 628, third receiving groove 629, second detection port 6210,

[0056] Waste liquid tube 7, waste liquid bottle 71. DETAILED DESCRIPTION

[0057] like Figure 1 to Figure 6 As shown, a sequential injection analysis system is used for sequential injection analysis of nitrate / nitrite in water quality. The sequential injection analysis system includes a sequential injection module, a water sample collection unit, a reagent unit, a reaction unit, a detection unit and a waste liquid pipe 7.

[0058] The sequential injection module includes a multi-channel selection valve 1, which includes a common end interface 11 and multiple inlet and outlet interfaces. The common end interface 11 is connected to an injection pipeline 2. A liquid storage ring 22 and a plunger pump 21 are sequentially arranged on the injection pipeline 2 from close to the common end interface 11 to far away from the common end interface 11. The free end of the injection pipeline 2 is used to connect to a pure water bottle 23; a bubble detector 24 is arranged at the common end interface 11 of the multi-channel selection valve 1.

[0059] The plunger pump 21 is used to accurately control the volume and flow rate of samples and reagents. It is driven by a motor and controlled by a solenoid valve. When the solenoid valve is closed (power off), the plunger cylinder in the pump is connected to the liquid storage ring 22. When the solenoid valve is opened (power on), the plunger cylinder in the pump is connected to the pure water bottle. The other end of the liquid storage ring 22 is connected to the common end of the multi-channel selection valve to store liquid to prevent samples and reagents from being sucked into the pump, so as to prevent the reagents from contaminating the pump or corrosive reagents from damaging the pump.

[0060] The inlet and outlet interfaces on the multi-channel selection valve 1 include inlet and outlet interfaces 12, inlet and outlet interfaces 13, inlet and outlet interfaces 14, inlet and outlet interfaces 15, inlet and outlet interfaces 16, and inlet and outlet interfaces 17. There are two unused inlet and outlet interfaces in the structure shown in the figure.

[0061] The bubble detector 24 can be used to detect bubbles. When bubbles are detected, it is in the liquid-free state; when no bubbles are detected, that is, there is liquid, it is in the liquid-existing state.

[0062] By discharging liquid to one side of the pure water bottle 23 through the plunger pump 21, the corresponding liquid can enter the liquid storage ring 22 from the common end interface 11 for temporary storage. By reverse driving the plunger pump 21, the liquid temporarily stored in the liquid storage ring 22 can enter the corresponding unit again through the common end interface 11.

[0063] The water sample collection unit includes a water sample collection tube 3, one end of which is used to suck the water sample to be tested, and the other end is connected to the inlet and outlet interface 12 of the multi-channel selection valve 1. The water sample collection tube 3 is connected to an automatic water sample collection device 31, which has sample pretreatment functions such as filtering and temperature control to remove suspended matter.

[0064] The sequential injection analysis method of the present application can be used to directly perform water sample detection and analysis at a site such as a riverside. At this time, one end of the water sample collection tube 3 is directly inserted into the position where the water sample to be tested needs to be sucked; the water sample to be tested can also be collected and tested in the laboratory. Figure 1 The structure shown in the figure shows that the test is carried out in the laboratory, and one end of the water sample collection tube 3 extends into the water sample bottle 32, and the water sample to be tested is stored in the water sample bottle 32.

[0065] The reagent unit comprises a reagent inlet tube 4 , one end of which is connected to a reagent bottle 41 , and the other end of which is connected to an inlet and outlet interface 16 of the multi-channel selection valve 1 .

[0066] The reaction unit includes a mixing tube 5, one end of which is connected to the inlet and outlet interface 13 of the multi-channel selection valve 1. Figure 2 As shown, the reaction unit further includes a heating device, and the heating device includes a heating wire 51 wound around the surface of the mixing tube 5. The reaction unit further includes a temperature sensor 52 for detecting the temperature of the liquid in the mixing tube 5.

[0067] The detection unit includes a detection tube 6, one end of which is connected to the inlet and outlet interface 14 of the multi-channel selector valve 1. The detection unit is provided with a detector 61 on the detection tube 6, and the detector 61 includes one or more detectors, each of which is selected from an optical detector, a conductivity detector or an electrochemical detector.

[0068] The optical detector 62 is used to measure the absorbance of certain components in the water sample or the generated fluorescent signal. The optical detector 62 includes a flow cuvette 621 connected to the detection tube 6. The structure of the flow cuvette 621 is as follows: Figure 6 As shown, the flow cuvette 621 is an existing structure and can be purchased directly. The two ends of the flow cuvette 621 are an inlet end and an outlet end respectively.

[0069] A light shielding structure is provided outside the flow cuvette 621. The structural schematic diagram of the light shielding structure in the detection unit is shown in FIG. Figure 3 to Figure 5 As shown, the light shielding structure includes two light shielding sheets 622 that are buckled with each other. The buckled surfaces of the two light shielding sheets 622 are provided with a first receiving groove 623 for receiving the flow cuvette 621 and a second receiving groove 624 for installing the detection light source. One side of the second receiving groove 624 has a first detection port 625 that is connected to the first receiving groove 623 and faces the side of the flow cuvette 621. A third receiving groove 629 for installing a detector is provided on one of the light shielding sheets 622. One side of the third receiving groove 629 has a second detection port 6210 that is connected to the first receiving groove 623 and faces the side of the flow cuvette 621. The first receiving groove 623 is also provided with a avoidance hole 626 that avoids the inlet and outlet ends of the flow cuvette 621.

[0070] The buckling surfaces of the two light shielding sheets 622 after buckling with each other are provided with mutually matching protrusions 627 and grooves 628 on both axial sides of the first receiving groove 623, wherein each light shielding sheet 622 is provided with a protrusion 627 and a groove 628 on each side of the first receiving groove 623. The setting of the light shielding structure, especially the protrusions 627 and grooves 628 staggered and matched on the two light shielding sheets 622, can effectively prevent the leakage of ambient light at the interface, making the detection more accurate.

[0071] Conductivity detectors are used to detect the ion concentration of the solution. Electrochemical detectors are used to detect specific targets such as heavy metals. The detection unit is modularly designed, and users can flexibly replace the detector according to actual detection needs to cope with different water quality analysis scenarios.

[0072] One end of the waste liquid pipe 7 is connected to the inlet and outlet interface 15 of the multi-channel selection valve 1, and the other end is connected to the waste liquid bottle 71. The waste liquid pipe 7 is used to receive the waste liquid discharged from each unit, and the waste liquid is collected in the waste liquid bottle 71.

[0073] The inlet and outlet interfaces 17 of the multi-channel selector valve 1 are used as air ends for air intake.

[0074] The sequential injection analysis system of the present invention also includes a control unit, which is used to control the operation of each component. The control programs of some repeated actions are integrated and packaged into action packages, which include reset action packages, cleaning action packages, liquid inlet action packages, and air inlet action packages.

[0075] The reset action package includes a control program for the following actions in sequence: emptying the pure water in the plunger pump 21 to restore the initial position, and filling the liquid storage ring 22 with pure water, but leaving a section of air column at the end of the injection line 2 connected to the common end interface 11. Leaving a section of air column can prevent the water sample or reagent from contacting the pure water, and eliminate the influence of diffusion movement on the test results or contamination of the plunger pump 21, thereby affecting the life of the equipment.

[0076] The cleaning action package includes a control program for the following actions in sequence: connecting the common port 11 to the waste liquid pipe 7, extracting pure water from the pure water bottle 23 through the plunger pump 21, and cleaning the liquid storage ring 22. Avoiding reagents or water samples from remaining in the liquid storage ring 22 and other places of the injection line 2.

[0077] The liquid inlet action package includes a control program for the following actions performed in sequence: liquid is extracted by the plunger pump 21 until the state of the bubble detector 24 changes from no liquid to liquid, and the required volume of liquid or liquid greater than the required volume is continued to be extracted, and then the common end interface 11 is connected to the pipeline that needs to be inlet, and the required volume of liquid is pushed into the corresponding pipeline; the common end interface 11 is connected to the waste liquid pipe 7 to discharge excess liquid.

[0078] The liquid inlet action package can be used for single precise sample injection. Due to different equipment or scene changes, the length of the tube connecting the multi-channel selection valve 1 and the water sample bottle 32 or the reagent bottle 41 will change. If the quantitative volume is extracted according to the traditional method, the volume of liquid in the mixing tube 5 entering the reaction unit will change, which may cause the amount of test reagent or the water sample to be tested to be too little, and the reaction is incomplete, so that the result is low and the accuracy of the test result is affected. The above problem can be solved by setting the bubble detector 24 and the operation method of the liquid inlet action package, so that the liquid inlet volume is accurate and the accuracy of the test result is ensured.

[0079] The air intake action package includes a control program for the following actions in sequence: connecting the common end interface 11 to the air end (inlet and outlet interface 17), extracting enough air, connecting the common end interface 11 to the pipeline that needs to be filled with liquid, and completely pushing the liquid into the corresponding pipeline by injecting air. Since there is a connecting pipe between the mixing tube 5 and the multi-channel selection valve 1, when the water sample or reagent is pushed into the mixing tube 5, part of the liquid will remain in the connecting pipe, and air is needed to push this section of liquid into the reaction tube 5 for reaction. In addition, the air can also play a "stirring" role between the water sample and the reagent, fully mixing and reacting, and the excess gas is discharged from the sample outlet at the top of the mixing tube 5.

[0080] The present invention realizes high automation and standardization of operations at each stage in the water quality detection process through the design of action packages (reset action package, cleaning action package, liquid intake action package, and air intake action package), reduces the need for manual intervention, and reduces the possibility of human error.

[0081] The sequential injection analysis method for nitrate / nitrite in water quality of the present application comprises an initialization stage, a sampling stage, a reaction stage, a detection stage, and a cleaning stage.

[0082] During the initialization phase, reset, clean, and reset are performed in sequence. The reset action package is used during reset, and the clean action package is used during cleansing.

[0083] In the sampling stage, the liquid injection action package is used first, and then the air injection action package is used. Specifically, in the sampling stage, the common end interface 11 is connected to the water sample collection tube 3, and the plunger pump 21 extracts the water sample to be tested until the state of the bubble detector 24 changes from no liquid to liquid state, and the water sample of the volume required for sampling or the water sample larger than the volume required for sampling is continuously extracted, and then the common end interface 11 is connected to the mixing tube 5, and the liquid of the volume required for sampling is pushed into the mixing tube 5; the common end interface 11 is connected to the waste liquid tube 7, and the excess water sample to be tested is discharged; then the common end interface 11 is connected to the air end, and enough air is extracted, and the common end interface 11 is connected to the mixing tube 5, and the water sample is completely pushed into the mixing tube 5 by injecting air.

[0084] In the reaction stage, the liquid-intake action package is used first, and then the air-intake action package is used. Specifically, in the reaction stage, the common end interface 11 is connected to the reagent tube 4, and the detection reagent in the reagent bottle 41 is extracted by the plunger pump 21 until the state of the bubble detector 24 changes from no liquid to a liquid state, and the detection reagent of the volume required for the reaction or the detection reagent greater than the volume required for the reaction is continuously extracted, and then the common end interface 11 is connected to the mixing tube 5, and the detection reagent of the volume required for the reaction is pushed into the mixing tube 5; the common end interface 11 is connected to the waste liquid pipe 7, and the excess water sample to be detected is discharged; then the common end interface 11 is connected to the air end, and enough air is extracted, and the common end interface 11 is connected to the mixing tube 5, and the detection reagent is completely pushed into the mixing tube 5 by injecting air, so that the detection reagent is mixed with the water sample to be tested to obtain a mixed reaction liquid. In the reaction stage, if it is necessary to carry out under specific temperature conditions, the heating wire 51 at the mixing tube 5 heats the mixing tube 5, and the temperature is detected by the temperature sensor 52.

[0085] In the detection stage, the liquid inlet action package is used, and then the air inlet action package is used. Specifically, in the detection stage, the common end interface 11 is connected to the mixing tube 5, and the plunger pump 21 extracts the mixed reaction liquid in the mixing tube 5 until the state of the bubble detector 24 changes from no liquid to liquid, and the mixed reaction liquid of the volume required for detection or the mixed reaction liquid greater than the volume required for detection is continuously extracted, and then the common end interface 11 is connected to the detection tube 6, and the mixed reaction liquid of the volume required for detection is pushed into the detection tube 6; the common end interface 11 is connected to the waste liquid tube 7 to discharge the excess mixed reaction liquid; then the common end interface 11 is connected to the air end, and enough air is extracted, and the common end interface 11 is connected to the detection tube 6, and the detection reagent is completely pushed into the detection tube 6 by injecting air.

[0086] During the detection stage, only a portion of the mixed reaction liquid can be drawn into the detection tube for detection, and the excess mixed reaction liquid can be discharged to ensure that the mixed reaction liquid is sufficient for detection.

[0087] During the cleaning phase, reset, clean, and reset are performed in sequence. The reset action package is used during reset, and the cleaning action package is used during cleaning. The system is reset and all pipes and reaction channels in contact with samples and reagents are cleaned to ensure the accuracy and effectiveness of the next test.

Claims

1. A sequential injection analysis method for nitrate / nitrite in water, characterized in that: A sequential injection analysis system is used, the sequential injection analysis system comprising: A sequential injection module, comprising a multi-channel selection valve, a plunger pump and a liquid storage ring, wherein the multi-channel selection valve comprises a common end interface and a plurality of inlet and outlet interfaces, wherein the common end interface is connected to an injection pipeline, wherein the liquid storage ring and the plunger pump are sequentially arranged on the injection pipeline from close to the common end interface to far from the common end interface, and the free end of the injection pipeline is used to connect to a pure water bottle; and a bubble detector is arranged on the common end interface of the multi-channel selection valve; A water sample collection unit, comprising a water sample collection tube, one end of which is used to suck the water sample to be tested, and the other end of which is connected to one of the inlet and outlet interfaces of the multi-channel selection valve; A reagent unit, comprising a reagent inlet tube, one end of which is connected to a reagent bottle, and the other end of which is connected to one of the inlet and outlet interfaces of the multi-channel selection valve; A reaction unit, comprising a mixing tube, one end of which is connected to one of the inlet and outlet ports of the multi-channel selection valve; A detection unit, comprising a detection tube, one end of which is connected to one of the inlet and outlet interfaces of the multi-channel selection valve; A waste liquid pipe, one end of which is connected to one of the inlet and outlet interfaces of the multi-channel selection valve; One of the inlet and outlet interfaces of the multi-channel selector valve is used as an air end for air intake; The sequential injection analysis method includes an initialization phase, a sampling phase, a reaction phase, a detection phase, and a cleaning phase. During the initialization stage and the cleaning stage, the pump is reset, cleaned, and reset in turn; during the reset, the pure water in the plunger pump is emptied to restore the initial position, and the liquid storage ring is filled with pure water, but a section of air column is left at the end of the injection line connected to the common end interface; During the sampling stage, the common end interface is connected to the water sample collection tube, and the plunger pump extracts the water sample to be tested until the state of the bubble detector changes from no liquid to liquid, and the water sample of the volume required for sampling or the water sample larger than the volume required for sampling is continuously extracted, and then the common end interface is connected to the mixing tube, and the liquid of the volume required for sampling is pushed into the mixing tube; the common end interface is connected to the waste liquid tube, and the excess water sample to be tested is discharged; then the common end interface is connected to the air end, and sufficient air is extracted, and the common end interface is connected to the mixing tube, and the water sample is completely pushed into the mixing tube by injecting air; In the reaction stage, the common end interface is connected to the reagent inlet tube, and the plunger pump extracts the detection reagent in the reagent bottle until the state of the bubble detector changes from no liquid to liquid, and the detection reagent of the volume required for the reaction or the detection reagent larger than the volume required for the reaction is continuously extracted, and then the common end interface is connected to the mixing tube, and the detection reagent of the volume required for the reaction is pushed into the mixing tube; the common end interface is connected to the waste liquid tube, and the excess water sample to be tested is discharged; then the common end interface is connected to the air end, and sufficient air is extracted, and the common end interface is connected to the mixing tube, and the detection reagent is completely pushed into the mixing tube by injecting air, so that the detection reagent is mixed with the water sample to be tested to obtain a mixed reaction liquid; During the detection stage, the common end interface is connected to the mixing tube, and the mixed reaction liquid in the mixing tube is extracted by the plunger pump until the state of the bubble detector changes from no liquid to liquid, and the mixed reaction liquid of the volume required for detection or the mixed reaction liquid larger than the volume required for detection is continuously extracted, and then the common end interface is connected to the detection tube, and the mixed reaction liquid of the volume required for detection is pushed into the detection tube; the common end interface is connected to the waste liquid pipe to discharge the excess mixed reaction liquid; then the common end interface is connected to the air end to extract enough air, and the common end interface is connected to the detection tube to completely push the detection reagent into the detection tube by injecting air.

2. The sequential injection analysis method for nitrate / nitrite in water according to claim 1, characterized in that: The sequential injection analysis system further comprises a control unit, which is used to control the operation of each component; Integrate and package the control programs of some repetitive actions into action packages, wherein the action packages include a reset action package, a cleaning action package, a liquid inlet action package, and an air inlet action package; The reset action package includes a control program for the following actions performed in sequence: emptying the pure water in the plunger pump to restore the initial position, and filling the liquid storage ring with pure water, but leaving a section of air column at the end of the injection pipeline connected to the common end interface; The cleaning action package includes a control program for sequentially performing the following actions: connecting the common end interface to the waste liquid pipe, extracting pure water from the pure water bottle through the plunger pump, and cleaning the liquid storage ring; The liquid inlet action package includes a control program for the following actions performed in sequence: the plunger pump extracts liquid until the state of the bubble detector changes from no liquid to liquid, and continues to extract a required volume of liquid or liquid greater than the required volume, and then connects the common end interface to the pipeline that needs to be inlet, and pushes the required volume of liquid into the corresponding pipeline; connects the common end interface to the waste liquid pipe to discharge excess liquid; The air intake action package includes a control program for performing the following actions in sequence: connecting the common end interface to the air end, extracting enough air, connecting the common end interface to the pipeline that needs to be filled with liquid, and completely pushing the liquid into the corresponding pipeline by injecting air.

3. The sequential injection analysis method for nitrate / nitrite in water according to claim 2, characterized in that: In the initialization phase, the reset action package is used during resetting, and the cleansing action package is used during cleansing.

4. The sequential injection analysis method for nitrate / nitrite in water according to claim 2, characterized in that: During the injection phase, the liquid injection action pack is used first, followed by the air injection action pack.

5. The sequential injection analysis method for nitrate / nitrite in water according to claim 2, characterized in that: During the reaction phase, use the liquid action pack first, then the air action pack.

6. The sequential injection analysis method for nitrate / nitrite in water according to claim 2, characterized in that: During the detection phase, the liquid action pack is used, followed by the air action pack.

7. The sequential injection analysis method for nitrate / nitrite in water according to claim 1, characterized in that: The detection unit is provided with a detector on the detection tube, and the detector includes one or more detectors, each of which is selected from an optical detector, a conductivity detector or an electrochemical detector.

8. The sequential injection analysis method for nitrate / nitrite in water according to claim 7, characterized in that: The optical detector is used to measure the absorbance of certain components in the water sample or the generated fluorescent signal, and the optical detector includes a flow cuvette connected to the detection tube; The flow cuvette is provided with a shading structure on the outside, the shading structure includes two shading sheets that are buckled with each other, and the buckling surfaces of the two shading sheets after being buckled with each other are provided with a first receiving groove for accommodating the flow cuvette and a second receiving groove for installing a detection light source, and one side of the second receiving groove is provided with a first detection port that is connected to the first receiving groove and faces the side of the flow cuvette; A third receiving groove for mounting a detector is provided on one of the light shielding sheets, and a second detection port connected to the first receiving groove and facing the side of the flow cuvette is provided on one side of the third receiving groove; The first containing tank is also provided with a avoidance hole for avoiding the inlet end and the outlet end of the flow cuvette; The engaging surfaces of the two shading sheets after being buckled together are provided with mating protrusions and grooves on both axial sides of the first receiving groove, wherein each shading sheet is provided with a protrusion and a groove on each side of the first receiving groove.

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