An automated ammonia nitrogen analysis system and instrument based on flow analysis technology

Abstract

The present invention discloses an automated analysis system and instrument for ammonia nitrogen based on flow analysis technology, and belongs to the technical field of chemical analysis and quantitative detection. The instrument developed by the present invention can realize automatic and rapid determination of ammonia nitrogen in different detection ranges in various water quality samples, and the obtained results are accurate and reliable. The characteristics of the present invention are that, firstly, a new type of flow analysis system is designed and established, which, on the basis of inheriting the advantages of traditional flow injection analysis and sequential injection analysis technology, solves many problems existing in these technologies, such as the inconvenience of using peristaltic pumps, high cost of using rotary valves, and inability to be used for online monitoring and unattended operation. The automated analysis instrument developed based on this can realize true one-button start-up; secondly, based on the analysis system, a dedicated analysis flow path is designed for the salicylic acid reaction system involving ammonia nitrogen, and after optimizing the system parameters and reaction conditions, the obtained detection performance indicators all perform well.

Description

Technical Field

[0001] The invention relates to an automated analysis system and instrument for quantitative detection of ammonia nitrogen in water quality, belonging to the technical field of chemical analysis and quantitative detection. The instrument is suitable for automatic determination of ammonia nitrogen in different detection ranges in various water quality samples, and can quickly obtain accurate and reliable quantitative results. Background Art

[0002] In the field of chemical analysis, for automated analytical instruments, a series of operations such as sample pretreatment, dilution, pipetting, reagent mixing, reaction, timing, detection, data processing, etc. are implemented through instruments, so as to achieve the goals of less human intervention, less human error, lower labor costs, and improved detection precision and accuracy. At present, the technical solutions for realizing chemical analysis automation are roughly divided into two categories: "discrete" and "flow". Among them, discrete is to imitate manual operation by means of automatic control of robotic arms, similar to assembly line operation; flow analysis is to merge, react, and detect samples and reagents in a flowing state, which is specifically divided into technical branches such as continuous flow analysis, flow injection analysis, sequential injection analysis, and microfluidics.

[0003] Ammonia nitrogen is present in water as free ammonia (NH3) or ammonium ions (NH4 + ) is an important nutrient in water bodies, but excessive ammonia nitrogen will lead to eutrophication of water bodies and become a major oxygen-consuming pollutant, which is toxic to fish and other aquatic organisms. In addition, ammonia nitrogen in water can be converted into nitrite under certain conditions, which will form nitrites, a strong carcinogen, when combined with proteins, posing a threat to human health. For a long time, the ammonia nitrogen content in the water environment has been an important monitoring indicator. Therefore, an automated analysis method that can quickly, automatically and accurately determine the ammonia nitrogen content is of great practical application value and can be used as a research tool related to ammonia nitrogen.

[0004] In the national standard (GB) and the industry standard (HJ), the chemical reactions involved in the visible spectrophotometric detection method for ammonia nitrogen are mainly the salicylic acid method (HJ 536-2009) and the Nessler reagent method (HJ 535-2009). According to different implementation schemes, the automated analysis methods developed based on these two reactions mainly include the ammonia nitrogen water quality online monitor (HJ 101-2019), the ammonia nitrogen continuous flow analysis method (HJ 665-2013), and the ammonia nitrogen flow injection analysis method (HJ 666-2013).

[0005] Among them, the ammonia nitrogen water quality online monitor is similar to other water quality online monitors. It imitates the design concept of sequential injection analysis technology. It uses a peristaltic pump in combination with a photoelectric quantitative tube or an injection pump to push samples and different reagents into the reaction chamber (which is also the detection chamber) in turn through a two-way solenoid valve group or a multi-position rotary switching valve, and detects after a chemical color development reaction occurs therein. This method has the disadvantages of slow analysis speed (the sample needs to be mixed evenly and the reaction needs to be balanced before detection), large consumption of reagents and carrier current (large internal volume of the reaction chamber / detection chamber), and the need to perform additional "emptying-cleaning" repeated operations on the detection chamber after each analysis is completed.

[0006] The above-mentioned ammonia nitrogen flow analysis method (HJ 665-2013, HJ 666-2013) is no different from the implementation methods of conventional continuous flow analysis technology and flow injection analysis technology. All of them use peristaltic pumps to combine multiple continuously flowing reagents with continuously flowing samples (in continuous flow analysis) or sample plugs after volume quantification driven by a continuously flowing carrier (in flow injection analysis), and a chemical color reaction occurs during the flow process. Its characteristics are that the sample solution enters the flow cuvette (also called flow cell) of the detector under physical mixing non-equilibrium, chemical reaction non-equilibrium and flow state to detect the response signal. This type of technology provides a solution for rapid analysis. However, the prerequisite for its detection precision and accuracy is that the flow rate of all solutions must remain stable. The peristaltic pump needs to be preheated for a long time during use, and the elastic pump tube used will affect the flow rate as it wears out. Therefore, the standard curve needs to be updated frequently or the peristaltic pump tube needs to be replaced, which leads to high learning costs, usage costs, and maintenance costs of the instrument. At the same time, the continuous flow of reagents also causes a large waste of it. In addition, the two-position multi-channel rotary valve used in the flow injection analysis system has the limitations of difficult manufacturing process, dependence on imports, and high cost (the multi-position selective rotary switching valve used in the sequential injection analysis technology also has this problem). In comparison, the sequential injection analysis technology solves the problem of continuous flow of reagents, thereby having the advantage of saving reagents, but its single-flow design allows the "sample plug" and many "reagent plugs" to converge only in a sequential chase manner, and the physical mixing degree of the reagent and sample in this state is low (relying only on dispersion), thereby reducing the detection sensitivity of the sample to be tested. In addition, there is an important hidden danger in the flow analysis method. When dissolved bubbles in the solution precipitate or bubbles are introduced into the flow, they will be adsorbed on the inner wall of the flow cuvette, and then the bubbles need to be manually driven away. Therefore, in this type of method, it is usually recommended to degas all solutions, which greatly limits its application as a monitoring instrument in unattended scenarios.

[0007] In order to solve the above problems, the present invention combines the basic schemes of flow injection analysis technology and sequential injection analysis technology to develop a new flow analysis system, and designs an ammonia nitrogen analysis flow path according to the salicylic acid reaction system, thereby realizing automatic and rapid analysis of ammonia nitrogen in water quality samples. Summary of the invention

[0008] In the present invention, firstly, in order to solve the problems and application limitations existing in many current flow analysis technologies, a new flow analysis system is developed. In the flow analysis system, a micro double plunger pump is used as a fluid power transmission unit to realize the one-touch start of the chemical analysis process, and no preheating, no additional manual operation, no need to replace consumables are required during use, and its liquid flow rate can always remain consistent; a three-way solenoid valve group and a fixed length of polytetrafluoroethylene pipeline connected therebetween are used as the volume quantitative unit of the sample solution and the reagent solution, and the scheme has the advantages of low cost, fast flow path switching response speed, and high flexibility of building block assembly; a single wavelength optical detection module designed with a monochromatic LED lamp as a light source has the characteristics of no need for preheating, fast response speed, long service life, and small size; a coil-type reaction thermostat unit designed and developed in conjunction with the supporting design provides a stable temperature for the chemical reaction, further improves the reaction rate, and accelerates the analysis speed; in addition, the control and interactive software developed based on the STM32 single-chip microcontroller realizes the integrated design of the analytical instrument. Secondly, on this basis, a dedicated analysis flow path was designed specifically for the salicylic acid reaction system involving ammonia nitrogen (sodium hypochlorite / sodium nitrosoferricyanide dihydrate / sodium salicylate), and the various system parameters and reaction conditions involved were optimized to achieve automatic, rapid and accurate quantitative analysis of ammonia nitrogen in various water quality samples.

[0009] The technical solution of the present invention is composed of an analytical flow path system and corresponding analytical instruments.

[0010] The ammonia nitrogen automated analysis system of the present invention comprises two micro plunger pumps (1, 2), ten three-way solenoid valves (3-12), sample and reagent quantitative loops (14-17), a sample storage coil (13), a reaction coil (18), a coil-type thermostatic controller (19), a single wavelength (700 nm) photometer (20) equipped with a flow cuvette, a touch screen (with built-in control and interactive software developed based on an STM32 single-chip microcomputer) (21), and a polytetrafluoroethylene pipe connecting various components and serving as a fluid channel.

[0011] The implementation process of several measurement procedures and functions involved in the present invention is described as follows.

[0012] 1. The system baseline procedure and flow path cleaning process are as follows: In the first step, the solenoid valves (3) and (8) are energized, and the others remain in the de-energized state. Under the suction action of the plunger pumps (1) and (2), the carrier solution (22) passes through (3c) → (3a) and (8c) → (8a) respectively to enter the respective pump chambers; In the second step, the solenoid valves (6) and (9) are energized, and the others remain in the de-energized state. Under the driving action of the solenoid valves (6) and (9), part of the carrier solution in the chamber of the plunger pump (1) passes through (3a) → (3b) to enter the tee. At the same time, under the driving action of the plunger pump (2), part of the carrier solution in the chamber passes through (8a) → (8b), (9a) → (9c), the sample storage coil (13), (4a) → (4b) to enter the tee. After the two carrier solutions merge, they flow through the sample quantitative loop (14), (6a) → (6c) and are discharged from the waste liquid 1 (25); In the third step, all solenoid valves are kept in the off-state. The remaining carrier solution in the chambers of the two plunger pumps (1, 2) flows through (3a) → (3b), the sample quantitative loop (14), (6a) → (6b), the reagent quantitative loop (15), (7a) → (7b) and (8a) → (8b), (9a) → (9b), the second reagent quantitative loop (16), (10a) → (10b), the third reagent quantitative loop (17), (11a) → (11b), and then merges at the tee and enters the reaction coil (18) and the flow detector (20). At this time, a stable blank baseline is recorded on the screen. At the same time, the program completes the cleaning process of the analytical flow path and ensures that the pipeline is full of carrier solution. Finally, the carrier solution flows through (12a) → (12b) and is discharged from the waste liquid 2 (29).

[0013] 2. The process of establishing the ammonia nitrogen standard curve is as follows: the solenoid valves (3) and (8) are energized, and the others remain de-energized. Under the suction action of the plunger pumps (1) and (2), the carrier solution (22) passes through (3c) → (3a) and (8c) → (8a) respectively and enters the respective pump chambers;

[0014] The solenoid valves (7) and (11) are energized, and the others remain de-energized. Under the suction action of the plunger pump (1), the reagent 1 (26) passes through (7c) → (7a) and enters and fills the reagent measuring ring (15). At the same time, under the suction action of the plunger pump (2), the reagent 3 (28) passes through (11c) → (11a) and enters and fills the reagent 3 measuring ring (17).

[0015] The solenoid valve (10) is energized, while the others remain de-energized. Under the suction action of the plunger pump (2), the reagent 2 (27) passes through (10c) → (10a) and enters and fills the reagent 2 quantitative loop (16);

[0016] The solenoid valves (4), (5), and (9) are energized, and the others remain de-energized. Under the suction action of the plunger pump (2), the standard solution (24) passes through (5c) → (5a), (4c) → (4a) and enters the sample storage coil (13);

[0017] The solenoid valves (6) and (9) are energized, while the others remain de-energized. Under the driving force of the plunger pump (2), the standard solution in the sample storage coil (13) passes through (4a) → (4b), the sample quantitative loop (14), (6a) → (6c), and is discharged from the waste liquid 1 (25). At this time, the sample quantitative loop (14) is filled with the standard solution, and the loading process of the sample and the reagent is completed.

[0018] All solenoid valves are kept in the off state. Under the driving action of the respective plunger pumps, the carrier solutions in the cavities of the two plunger pumps (1, 2) sequentially push the standard solution in the sample quantitative loop (14), the reagent one solution in the reagent quantitative loop (15), the reagent two solution in the reagent two quantitative loop (16), and the reagent three solution in the reagent three quantitative loop (17) to be combined at the three-way joint. When the mixed sample flows through the reaction coil (18), a color reaction occurs. Then, the mixed sample enters the flow-through detector (20) to obtain an absorbance response signal peak. The absorbance at the top of the peak (or the peak area) is used as the quantitative signal. Finally, the solution is discharged from the waste liquid 2 (29). At this point, the sample / reagent injection and chemical analysis process is completed.

[0019] The solenoid valves (6) and (9) are energized, while the others remain in an energized state. The carrier solution discharges the excess standard solution in the sample storage coil (13) from the waste liquid one (25). The solenoid valve (12) is energized, while the others remain in an energized state. The air (30) enters the flow cuvette (20) and the reaction coil (18) through (12c) → (12a) under the suction action of the plunger pump (1) or (2). Subsequently, all the solenoid valves remain in an energized state, and the two carrier solutions flow through (3a) → (3b) and the sample quantification tube, respectively. After the reagent ring (14), (6a) → (6b), the reagent quantitative ring (15), (7a) → (7b) and (8a) → (8b), (9a) → (9b), the reagent second quantitative ring (16), (10a) → (10b), and the reagent third quantitative ring (17), (11a) → (11b), they converge at the tee and enter the reaction coil (18), the flow detector (20), and finally are discharged from the waste liquid second (29), thus completing the process of cleaning the flow path and eliminating the residual bubbles on the inner wall of the flow cuvette.

[0020] During the process of injecting the sample and the reagent and causing the chemical reaction, the standard solution (24) can be replaced with other concentrations to prepare for the next sample loading and analysis. By cycling the above process, the absorbance corresponding to a series of standard solutions of different concentrations can be obtained, thereby obtaining an ammonia nitrogen standard curve.

[0021] In addition, it should be noted that in this analysis system, after the reaction reagent is replaced for the first time, the above process should be repeated several times (estimated to be 4 to 6 times) to ensure that all reagent liquid guide tubes connected to the solenoid valves (7c), (10c), and (11c) are filled with their corresponding reagent solutions before the calibration curve can be established or the water sample analyzed.

[0022] 3. The only difference between the determination process of ammonia nitrogen samples and the process of establishing the standard curve is that when the sample is loaded, the solenoid valves (4) and (9) are energized, while the others remain de-energized. At this time, the actual water sample (23) will pass through (5b) → (5a), (4c) → (4a) and enter the sample storage coil (13). The remaining steps are consistent with the above process.

[0023] 4. Standard solution verification process: When the instrument is running for a long time, in order to verify the stability of the analysis system, standard curve and reaction reagents, the "water sample measurement program" can be automatically switched to the "standard solution verification program" at regular intervals (set the interval yourself, or manually select to execute the program). At this time, the fixed concentration standard solution (24) will enter the sample storage coil (13) from (5c) → (5a), (4c) → (4a), and it will be used as a standard water sample for measurement. Finally, the obtained concentration value is compared with its theoretical concentration value to determine the accuracy of the measurement. If the relative deviation exceeds the tolerance range (usually >5%), the standard curve can be updated or replaced by the "single point" or "two-point calibration method".

[0024] 5. In the analysis system, the automatic establishment process of the standard curve is as follows: after the standard solution at the upper limit of the detection range enters the sample storage coil (13), the plunger pump (1) and the plunger pump (2) push out the carrier solution in their respective cavities at different pump speed ratios (e.g., 9+1, 8+2, 6+4, 4+6, 2+8, 0+10), so that the standard solution in the sample storage coil (13) passes through (4a)→(4b) and then merges with another carrier solution at the tee according to the corresponding flow ratio to fill the sample quantitative loop (14), and then passes through (6a)→(6c) and is discharged from the waste liquid one (25). At this time, standard solutions of different concentrations (e.g., 10%, 20%, 40%, 60%, 80%, 100%) will appear in the sample quantitative loop (14). Then, under the driving action of the plunger pump (1), the standard solution in the sample quantitative loop (14) is injected into the analysis system, participates in the chemical reaction, and obtains the corresponding absorbance signal, thereby realizing the establishment of a standard curve by automatically diluting a standard solution of a concentration through the system online.

[0025] 6. For the establishment and determination of ammonia nitrogen standard curves in different detection ranges, in addition to changing the reaction temperature (changing the reaction sensitivity) and changing the injection flow rate (changing the reaction time) in the conventional flow analysis method, in the present analysis system, before the plunger pump (1) pushes the sample solution in the sample quantitative loop (14) to participate in the reaction, the solenoid valve (6) is energized. At this time, the plunger pump (1) will push the sample solution in the sample quantitative loop (14) through (6a) → (6c) and then be discharged from the waste liquid (25). When only the tail end of the sample plug is retained, it is injected into the analysis system to participate in the reaction. Then, by changing the sample waste discharge volume in the above process, the establishment of standard curves and sample determination in different detection ranges can be achieved.

[0026] The advantages and positive effects of the present invention are: a new type of flow analysis system is designed and established, which inherits the advantages of traditional flow analysis technology (including continuous flow analysis, flow injection analysis, and sequential injection analysis) and solves the problems and limitations of these technologies; an ammonia nitrogen flow analysis flow path is designed for ammonia nitrogen / sodium hypochlorite / sodium nitrosoferricyanide dihydrate / sodium salicylate, and automatic, rapid, and accurate quantitative analysis of ammonia nitrogen in multiple ranges in different water samples is achieved, and the method effectively saves reagents and samples and is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the automated ammonia nitrogen analysis system

[0028] In the figure, (1) to (2) micro plunger pump, (3) to (12) three-way solenoid valve group, (3a) to (12a) common end (COM) of the three-way solenoid valve, (3b) to (12b) power-off connection end (NO, i.e. closed after power on) of the three-way solenoid valve, (3c) to (12c) power-off connection end (NC, i.e. connected after power on) of the three-way solenoid valve, (13) sample storage coil, (14) sample quantitative loop, (15) reagent quantitative loop, (16) Reagent 2 quantitative loop, (17) reagent 3 quantitative loop, (18) reaction coil, (19) coil-type constant temperature controller, (20) single wavelength photometer (700nm), (21) touch screen and built-in STM32 single chip microcomputer control / interactive software, (22) carrier solution, (23) actual water sample, (24) standard solution, (25) waste liquid 1, (26) reagent 1, (27) reagent 2, (28) reagent 3, (29) waste liquid 2, (30) air.

[0029] Figure 2 . Example 1 Response signal curve obtained after multiple parallel measurements of ammonia nitrogen standard solution.

[0030] Figure 3 Example 2 Response signal curve and its fitting standard curve when establishing the ammonia nitrogen standard curve.

[0031] Figure 4 . Example 3 Effect of reaction temperature on ammonia nitrogen standard curve.

[0032] Figure 5 . Example 4 Ammonia nitrogen standard curves with different detection ranges. DETAILED DESCRIPTION

[0033] The embodiments of the present invention are further described in conjunction with the accompanying drawings.

[0034] Example 1

[0035] Utilize the ammonia nitrogen analysis system of the present invention (see Figure 1 ), and the system parameters involved (volume of sample and reagent quantitative loop, storage coil length, reaction coil length, speed and duration of loading reagents and samples, injection speed of reagents and samples) and reaction conditions (concentration of all reagents, reaction pH, reaction temperature) were optimized. 5 mg / L ammonia nitrogen standard solution was used as a water sample for 11 cycles of measurement. The response signal curve obtained is shown in the figure below. Figure 2 As shown, it can be seen that the analytical system has good precision (the relative standard deviation of the absorbance detection is 1.27%).

[0036] Example 2

[0037] A series of ammonia nitrogen standard solutions with different concentrations (0.5, 1.0, 2.0, 3.0, 4.0, 5.0 mg / L) were injected into the analysis system to obtain the response signal curve (A) and the linear relationship between concentration and absorbance (B). Figure 3 As shown, this is the standard curve for the detection range of 0~5mg / L ammonia nitrogen.

[0038] Example 3

[0039] By changing the set temperature of the coil temperature controller, the ammonia nitrogen standard curve was established and the influence was obtained. Figure 4 shown.

[0040] Example 4

[0041] According to the method of changing the detection range designed in the analysis system, standard curves with different ammonia nitrogen detection ranges (0-5 mg / L, 0-50 mg / L, 0-200 mg / L) were obtained. Figure 5 shown.

Claims

1. A fluid analysis method for an ammonia nitrogen automated analysis instrument, characterized in that: The ammonia nitrogen automatic analysis instrument comprises a micro dual-plunger pump (1, 2) as a fluid power transmission unit, the micro dual-plunger pump (1, 2) comprises a first plunger pump (1) and a second plunger pump (2), and also comprises ten three-way solenoid valves (3-12), sample and reagent quantitative rings (14-17), a sample storage coil (13), a reaction coil (18), a coil-type constant temperature controller (19), a single-wavelength photometer (20) equipped with a flow cuvette, a touch screen (21), and a polytetrafluoroethylene pipeline as a fluid channel, the three-way solenoid valve group and the polytetrafluoroethylene pipeline constitute a sample quantitative and converging flow path, the wavelength of the single-wavelength photometer is 700nm, and the touch screen is built-in with control and interactive software developed based on an STM32 single-chip microcomputer; The fluid analysis method comprises: a system baseline procedure and a flow path cleaning process. In the first step, the first three-way solenoid valve (3) and the sixth three-way solenoid valve (8) are energized, and the rest remain in an off-state. Under the suction action of the first plunger pump (1) and the second plunger pump (2), the carrier solution (22) passes through the first three-way solenoid valve 3c end, 3a end and the sixth three-way solenoid valve 8c end, 8a end, respectively, and enters the respective pump cavities. In the second step, the fourth three-way solenoid valve (6) and the seventh three-way solenoid valve (9) are energized, and the rest remain in an off-state. Under the driving action of the first plunger pump (1), part of the carrier solution in the cavity of the first plunger pump (1) passes through the first three-way solenoid valve 3a end, 3b end, and at the same time, under the driving action of the second plunger pump (2), part of the carrier solution in the cavity of the second plunger pump (2) passes through the sixth three-way solenoid valve 8c end, 8a end. The two carrier solutions merge at the three-way point and flow through the sample quantitative loop (14), the fourth three-way solenoid valve 6a and the fourth three-way solenoid valve 6c, and finally are discharged from the sample waste outlet 1 (25). In the third step, all the solenoid valves are kept in the off state. Under the driving action of the first plunger pump (1), the remaining carrier solution in the cavity of the first plunger pump (1) flows through the first three-way solenoid valve 3a and the first three-way solenoid valve 3b, the sample quantitative loop (14), the fourth three-way solenoid valve 6a and the fourth three-way solenoid valve 6c, the reagent quantitative loop (15), the fifth three-way solenoid valve 6a and the fourth three-way solenoid valve 6c, and finally are discharged from the sample waste outlet 1 (25). In the third step, all the solenoid valves are kept in the off state. Under the driving action of the first plunger pump (1), the remaining carrier solution in the cavity of the first plunger pump (1) flows through the first three-way solenoid valve 3a and the first three-way solenoid valve 3b, the sample quantitative loop (14), the fourth three-way solenoid valve 6a and the fourth three-way solenoid valve 6b, the reagent quantitative loop (15), the fifth three-way solenoid valve 6a and the fourth three-way solenoid valve 6c, and finally are discharged from the sample waste outlet 1 (25). The remaining carrier solution in the cavity of the second plunger pump (2) flows through the end of the three-way solenoid valve 7a and the end of the fifth three-way solenoid valve 7b, and flows through the end of the sixth three-way solenoid valve 8a, the end of the sixth three-way solenoid valve 8b, the end of the seventh three-way solenoid valve 9a, the end of the seventh three-way solenoid valve 9b, the second reagent quantitative ring (16), the end of the eighth three-way solenoid valve 10a, the end of the eighth three-way solenoid valve 10b, the third reagent quantitative ring (17), the end of the ninth three-way solenoid valve 11a, and the end of the ninth three-way solenoid valve 11b. Then, the two carrier solutions merge at the three-way point and enter the reaction coil (18) and the single wavelength photometer (20). At this time, a stable blank baseline is recorded on the screen. At the same time, the program completes the cleaning process of the analysis flow path and ensures that the pipeline is filled with the carrier solution.Finally, the carrier solution flows through the thirteenth solenoid valve 12a end and the thirteenth solenoid valve 12b end and is discharged from the second waste outlet (29); the process of establishing the ammonia nitrogen standard curve, the first step, the first three-way solenoid valve (3) and the sixth three-way solenoid valve (8) are energized, and the rest remain in the off state. The carrier solution (22) passes through the first three-way solenoid valve 3c end, 3a end and the sixth three-way solenoid valve 8c end, 8a end respectively under the suction action of the first plunger pump (1) and the second plunger pump (2), and enters the respective pump chambers; the second step, the fifth three-way solenoid valve (7) and the ninth three-way solenoid valve (11) are energized, and the rest remain in the off state. Reagent 1 (26) enters through the fifth three-way solenoid valve 7c end, 7a end under the suction action of the first plunger pump (1). In step 3, the eighth three-way solenoid valve (10) is energized, and the rest remain in an off-state. Reagent two (27) enters and fills the reagent two quantitative ring (16) through the eighth three-way solenoid valve 10c end and 10a end under the suction action of the second plunger pump (2). In step 4, the second three-way solenoid valve (4), the third three-way solenoid valve (5), and the seventh three-way solenoid valve (9) are energized, and the rest remain in an off-state. The standard solution (24) enters and fills the reagent two quantitative ring (16) through the third three-way solenoid valve 5c end and the third three-way solenoid valve 5a end under the suction action of the second plunger pump (2). The three-way solenoid valve 5a end, the second three-way solenoid valve 4c end, and the second three-way solenoid valve 4a end enter the sample storage coil (13). In the fifth step, the fourth three-way solenoid valve (6) and the seventh three-way solenoid valve (9) are energized, and the rest remain in the de-energized state. Under the driving action of the second plunger pump (2), the standard solution in the sample storage coil (13) passes through the second three-way solenoid valve 4a end, the second three-way solenoid valve 4b end, the sample quantitative loop (14), the fourth three-way solenoid valve 6a end, and the fourth three-way solenoid valve 6c end, and is discharged from the sample waste outlet 1 (25). At this time, the sample quantitative loop (14) is filled with the standard solution. At this point, the sample and reagent loading process is completed. In the sixth step, all solenoid valves remain in the de-energized state. The first plunger pump (1) and the second Under the driving action of each plunger pump, the carrier solution in the cavity of the plunger pump (2) sequentially pushes the standard solution in the sample quantitative ring (14), the reagent one solution in the reagent quantitative ring (15), the reagent two solution in the reagent two quantitative ring (16), and the reagent three solution in the reagent three quantitative ring (17) to be combined at the three-way point. Then, the mixed sample band undergoes a color reaction when flowing through the reaction coil (18). Subsequently, when it enters the single wavelength photometer (20), an absorbance response signal peak is obtained, and the absorbance at the top of the peak is used as a quantitative signal. Finally, the solution is discharged from the second waste outlet (29). At this point, the sample / reagent injection and chemical analysis process is completed. In the seventh step, the fourth three-way solenoid valve (6) and the seventh three-way solenoid valve (9) are energized, and the rest remain in a de-energized state.The carrier solution discharges the excess standard solution in the sample storage coil (13) from the sample waste outlet (25). In the eighth step, the thirteenth solenoid valve (12) is energized, and the others remain in a de-energized state. The air (30) enters the single wavelength photometer (20) and the reaction coil (18) through the thirteenth solenoid valve 12c end and 12a end under the suction action of the first plunger pump (1) or the second plunger pump (2). In the ninth step, all solenoid valves remain in a de-energized state. The carrier solution in the cavity of the first plunger pump (1) flows through the first three-way solenoid valve 3a end, the first three-way solenoid valve 3b end, the sample quantitative loop (14), the fourth three-way solenoid valve 6a end, the fourth three-way solenoid valve 6b end, the reagent quantitative loop (15 ), the fifth three-way solenoid valve 7a end, the fifth three-way solenoid valve 7b end, the carrier solution in the second plunger pump (2) cavity flows through the sixth three-way solenoid valve 8a end, the sixth three-way solenoid valve 8b end, the seventh three-way solenoid valve 9a end, the seventh three-way solenoid valve 9b end, the second reagent quantitative ring (16), the eighth three-way solenoid valve 10a end, the eighth three-way solenoid valve 10b end, the third reagent quantitative ring (17), the ninth three-way solenoid valve 11a end, the ninth three-way solenoid valve 11b end, the two paths of carrier solution merge at the three-way point and enter the reaction coil (18), the single wavelength photometer (20), and finally discharged from the second waste outlet (29), thus completing the process of cleaning the flow path and eliminating the residual bubbles on the inner wall of the flow cuvette.

2. The fluid analysis method of the ammonia nitrogen automated analysis instrument according to claim 1, characterized in that: In the process of establishing a standard curve, when the standard solution of the upper limit concentration of the detection range is sucked into the storage coil (13) by the second plunger pump (2), and then flows through the sample quantitative loop (14) and the waste outlet (25) under the push of the second plunger pump (2), the first plunger pump (1) can be set to be pushed out synchronously at a certain speed. Then, when the first plunger pump (1) and the second plunger pump (2) are set to different speed ratios at this time, the standard solution filling the sample quantitative loop (14) will be the standard solution diluted according to the corresponding ratio. As a series of standard solutions of different concentrations enter the analysis system and obtain the corresponding absorbance, the function of establishing a standard curve by automatically diluting a standard solution of one concentration through the system is realized.

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