CN103063816B - Method for simultaneously detecting nitrogen and phosphorus indexes of water quality - Google Patents

Abstract

A method for simultaneously detecting nitrogen and phosphorus indexes of water quality comprises the following steps: (1) through integrating and improving a sample injector and two flow analyzers, enabling a sample to pass through the sample injector and then shunting the sample to the two flow analyzers through a tee-joint, and respectively detecting the nitrogen and phosphorus indexes of the sample; (2) using ammonium nitrogen, nitrate nitrogen, nitrite nitrogen and phosphate as working mother liquors; respectively absorbing the working mother liquors into 6 volumetric flasks; metering the volumes of the volumetric flasks and preparing a mixed standard solution, wherein the concentration of the nitrate nitrogen is the concentration sum of the nitrite nitrogen and the nitrate nitrogen; the total concentration of the nitrogen is the concentration sum of the ammonium nitrogen, the nitrite nitrogen and the nitrate nitrogen; and the total concentration of the phosphorus is equal to the concentration of the phosphate; and (3) detecting an environment water quality sample by using an integrated instrument according to a standard curve method. According to the invention, the defect that the larger error problem is caused by non-simultaneous detection when the nitrogen and phosphorus indexes in the water quality sample are detected by the traditional instrument and technology is overcome; and in particular, simultaneous detection of the nitrogen and phosphorus indexes in the water quality sample with small volume is satisfied.

Description

A Method for Simultaneously Determining Water Quality Nitrogen and Phosphorus

technical field

The invention belongs to the technical field of water quality monitoring, in particular to a method for measuring nitrogen and phosphorus indexes.

Background technique

Agricultural non-point source pollution has seriously affected industrial and agricultural production. A large amount of nutrient salts and pollutants are discharged into rivers and lakes. Surface water in some areas is seriously polluted, and even directly affects agricultural irrigation and rural drinking water sources. Farmland fertilization, livestock and poultry manure, crop straw, and phosphate in washing powder have become the main sources of non-point source pollution in rural areas in my country, and the harm to the environment and human health has attracted much attention. Therefore, it is very important to measure the nitrogen and phosphorus indicators of water quality in time and quickly.

The continuous flow analyzer uses a peristaltic pump to compress pump tubes of different diameters according to the continuous flow method, and injects the reaction reagent and the sample to be tested in proportion to a closed continuous flow carrier, and the color development occurs in the chemical reaction unit. Reaction, its signal value is measured in the detector, and a detection instrument is used to determine the concentration of the sample to be tested according to the standard curve method. Commonly used in water quality analysis in the field of environmental monitoring.

When environmental water samples are collected and analyzed in the laboratory for nitrogen and phosphorus indicators, if a single indicator is tested separately, after one or several items are determined, nitrogen and phosphorus are easily converted between different forms, making nitrogen in a certain form There will be an obvious error between the sum of each form and the total amount in the results of element and phosphorus. For example, ammonia volatilization may occur after the ammonium nitrogen in the environmental water sample is determined. After that, nitrification may occur. At this time, the concentration of nitrate nitrogen has obviously become larger, which is not the concentration of nitrate nitrogen when measuring ammonium nitrogen, which is easy to mislead the scientific research results. In order to avoid such problems, it is necessary to have an analytical method capable of simultaneously determining nitrogen and phosphorus indicators in water quality samples.

In the soil column leaching scientific research experiment, since the volume of the collected leaching solution is relatively small in a certain period of time, in order to investigate the changes of nitrogen and phosphorus in the leaching solution in different time periods, it is necessary to have a An analysis method that can meet the simultaneous determination of nitrogen and phosphorus indicators in water quality samples with small volumes.

Contents of the invention

Technical issues solved:

The purpose of the present invention is to provide a method for simultaneously measuring nitrogen and phosphorus indicators in water quality, which solves the defect that large errors are introduced due to non-simultaneous measurement when the existing instruments and technologies measure nitrogen and phosphorus indicators in water quality samples, especially to meet the volume Simultaneous determination of nitrogen and phosphorus indicators in a small amount of water quality samples.

Technical solution: a method for simultaneous determination of water quality nitrogen and phosphorus indicators, through the connection of one sample injector and two parallel flow analyzers, respectively measure the inorganic state concentration and total concentration of nitrogen and phosphorus indicators, the specific steps are: with 200.0 mg/L ammonium nitrogen (NH ₄ Cl-N), 100.0mg/L nitrate nitrogen (KNO ₃ -N), 4.0mg/L nitrite nitrogen (NaNO ₂ -N), 20.0mg/L phosphate ( KH ₂ PO ₄ -P) is the working mother solution, absorb 0.00, 1.00, 2.00, 3.00, 4.00, 5.00mL respectively into six 100.0mL volumetric flasks, and prepare mixed standard solution with pure water; the sampling time is 50s, the cleaning time is 100s, and the sample injection detection at the same time is obtained:

The standard curve linear equation of ammonium nitrogen 0.32mL/min injection flow rate is Y=43.5+387.5X;

The linear equation of the standard curve for the injection flow of nitrite nitrogen at 0.42mL/min is Y=16.8+15664.0X;

The linear equation of the standard curve for the injection flow rate of nitrate nitrogen 0.16mL/min is Y=13.24+306.8X;

The linear equation of the standard curve for the injection flow rate of 0.42mL/min total nitrogen is Y=-71.9+332.3X;

The linear equation of the standard curve for phosphate 0.80mL/min injection flow rate is Y=-30309.5+1140024.2X;

The linear equation of the standard curve for the injection flow rate of 0.42mL/min of total phosphorus is Y=-17313.4+398251.2X;

Among them: X is the concentration, the unit is mg/L; Y is the signal value reading of the flow analyzer;

Then, the injection volume of the sample to be tested is consistent with the standard curve, its corresponding signal value is measured, and its concentration is calculated according to the standard curve method.

Various nitrogen and phosphorus indicators were calculated through the standard curve equation, where:

The reaction reagents required for the determination of ammonium nitrogen are: NH ₄ ⁺ -A is a mixed solution containing 33g/L potassium sodium tartrate and 24g/L trisodium citrate, pH=5.2, and the two flow rates are 1mL/min and 0.8 mL/min; NH ₄ ⁺ -B is a mixed solution containing 80g/L sodium salicylate and 25g/L sodium hydroxide, with a flow rate of 0.32mL/min; NH ₄ ⁺ -C is sodium nitroferricyanide 1g/L, the flow rate is 0.16mL/min; NH ₄ ⁺ -D is sodium dichloroisocyanurate 2g/L, the flow rate is 0.32mL/min;

The reaction reagents required for the determination of nitrate nitrogen are: NO ₃ ^- -A is a mixed solution containing potassium sodium tartrate 33g/L, trisodium citrate 24g/L, and the flow rate is 0.8mL/min; NO ₃ ^- -B is hydrogen Sodium oxide 6g/L, the flow rate is 1mL/min; NO ₃ ^- -C is a mixed solution, containing hydrazine sulfate 2g/L, copper sulfate 18mg/L, the flow rate is 0.42mL/min; NO ₃ ^- -D is a mixed solution , containing N-(1-naphthyl)ethylenediamine dihydrochloride 0.5g/L, sulfonamide 10g/L, phosphoric acid 169g/L, the flow rate is 0.42mL/min;

The reaction reagents required for the determination of nitrite nitrogen are: NO ₂ ^- -A is pure water, resistivity: 18.3MΩ·cm, flow rate is 1mL/min; NO ₂ ^- -B is a mixed solution containing (N-(1 -Naphthyl) ethylenediamine dihydrochloride 0.5g/L, sulfonamide 10g/L, phosphoric acid 253.5g/L, flow rate is 0.32mL/min;

The reaction reagents required for the determination of total nitrogen are: TN-A is a mixed solution containing potassium persulfate 40g/L, sodium hydroxide 12g/L, and the flow rate is 0.42mL/min; TN-B is boric acid 24g/L, and the flow rate is 0.42mL/min; TN-C is ammonium chloride 50g/L, pH=8.2, the two flow rates are 1mL/min and 0.8mL/min respectively; TN-D is a mixed solution containing N-(1-naphthyl ) Ethylenediamine dihydrochloride 0.5g/L, sulfonamide 10g/L, hydrochloric acid 118g/L, the flow rate is 0.23mL/min;

The reaction reagents required for the determination of phosphate are: PO ₄ ^3- -A is a mixed solution containing 4.8g/L ammonium molybdate and 73.6g/L sulfuric acid, and the flow rate is 0.42mL/min; PO ₄ ^3- -B is a mixed solution Solution, containing ascorbic acid 18g/L, antimony potassium tartrate 6mg/L, the flow rate is 0.42mL/min;

The reaction reagents required for the determination of total phosphorus are: TP-A is a mixed solution containing potassium persulfate 9.9g/L, sulfuric acid 156.4g/L, and the flow rate is 0.23mL/min; TP-B is sulfuric acid 294.4g/L, the flow rate TP-C is sodium hydroxide 210g/L, the flow rate is 0.32mL/min; TP-D is a mixed solution containing 4.8g/L ammonium molybdate and sulfuric acid 73.6g/L, and the flow rate is 0.42 mL/min; TP-E is a mixed solution containing 18g/L ascorbic acid and 6mg/L antimony potassium tartrate, with a flow rate of 0.42mL/min.

In the present invention, through the integration and improvement of one sample injector and two flow analyzers, the sample passes through the sample injector and then is shunted to two flow analyzers through a tee to measure the inorganic state concentration and total amount of nitrogen and phosphorus indicators respectively. concentration. A mixed standard curve (mixed standard) was prepared using ammonium nitrogen (NH ₄ Cl), nitrate nitrogen (KNO ₃ ), nitrite nitrogen (NaNO ₂ ), and phosphate (KH ₂ PO ₄ ) as the mother liquor. In the mixed standard, the concentration of nitrate nitrogen is the sum of the concentrations of nitrite nitrogen and nitrate nitrogen; the concentration of total nitrogen is the sum of the concentrations of ammonium nitrogen, nitrite nitrogen and nitrate nitrogen; the concentration of total phosphorus equal to the concentration of phosphate. As well as the modification of the measurement project pipeline and the adjustment of the experimental conditions to ensure the simultaneous determination of water quality ammonium nitrogen NH ₄ ⁺ -N, nitrate nitrogen (NO ₃ ^- +NO ₂ ^- )-N, nitrite nitrogen NO ₂ ^- -N, total nitrogen TN-N, phosphate PO ₄ ^3- -P, total phosphorus TP-P six items.

Beneficial effect:

Through the improvement of instrument integration and the use of mixed standard solutions, the simultaneous analysis of nitrogen and phosphorus indicators in water quality can be achieved. This not only reduces the amount of sample required for analysis, (such as: soil column leaching experiment, in order to investigate the changes of nitrogen and phosphorus in the leachate in different time periods, the volume of the collected leach solution is very small, only 3mL shower solution), and ensure that all items are measured at the same time (if not measured at the same time, nitrogen and phosphorus are easily transformed between different forms during this time period, so that there will be a clear gap between the sum of each form and the total amount) error). To achieve timely, rapid and accurate analysis of water quality nitrogen and phosphorus indicators. The measured environmental standard samples were all within the guaranteed value, the recovery rate of standard addition was between 96.3% and 107.6%, and the relative standard deviation was between 0.54% and 2.85%. The method can be widely used in the field of environmental monitoring to quickly analyze a large number of nitrogen and phosphorus indicators of water quality samples, and is especially suitable for simultaneous determination of nitrogen and phosphorus indicators in water quality samples with small volumes.

Description of drawings

Fig. 1 is the measurement pipeline connection schematic diagram of the present invention;

Fig. 2 is a schematic diagram of the combination of the modules of the present invention.

Detailed ways

The following specific embodiments do not limit the technical solutions of the present invention in any form, and all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Example 1

As shown in Figure 1, through the integration and improvement of one sampler and two flow analyzers, the sample is divided into two flow analyzers after passing through the sampler, and the inorganic state of nitrogen and phosphorus indicators are determined respectively. concentration and total concentration. A mixed standard curve (mixed standard) was prepared using ammonium nitrogen (NH ₄ Cl), nitrate nitrogen (KNO ₃ ), nitrite nitrogen (NaNO ₂ ), and phosphate (KH ₂ PO ₄ ) as the mother liquor. In the mixed standard, the concentration of nitrate nitrogen is the sum of the concentrations of nitrite nitrogen and nitrate nitrogen; the concentration of total nitrogen is the sum of the concentrations of ammonium nitrogen, nitrite nitrogen and nitrate nitrogen; the concentration of total phosphorus equal to the concentration of phosphate. As well as the modification of the measurement project pipeline and the adjustment of the experimental conditions to ensure the simultaneous determination of water quality ammonium nitrogen NH ₄ ⁺ -N, nitrate nitrogen (NO ₃ ^- +NO ₂ ^- )-N, nitrite nitrogen NO ₂ ^- -N, total nitrogen TN-N, phosphate PO ₄ ^3- -P, total phosphorus TP-P six items.

Instruments and reagents:

Two flow analyzers (Sakar San ⁺⁺ System, Netherlands); one auto sampler (Auto sampler1075); ultrapure water machine (Chongqing AJY-6000-U).

Sodium potassium tartrate, trisodium citrate, sodium nitroferricyanide, sodium dichloroisocyanurate, hydrazine sulfate, copper sulfate, N-(1-naphthyl)ethylenediamine dihydrochloride, sulfonamide, chloride Ammonium, ammonium molybdate, ascorbic acid, and potassium antimony tartrate were all analytically pure and purchased from Sinopharm Chemical Reagent Co., Ltd.; sodium salicylate, sodium hydroxide, boric acid, phosphoric acid, hydrochloric acid, and sulfuric acid were analytically pure and were purchased from Nanjing Chemical Reagent Co., Ltd. Company; potassium persulfate was analytically pure, purchased from Fluka Reagent Co., Ltd.; experimental water was ultrapure water (resistivity: 18.23 ΜΩ·cm).

Instrument integration and its parameter settings:

Through the integration and improvement of one sampler and two flow analyzers, the sample passes through the sampler and then splits to two flow analyzers through a tee, and the inorganic state concentration and total concentration of nitrogen and phosphorus indicators are determined respectively. The organic species concentration is the total minus the inorganic species fraction. The schematic diagram of instrument integration and measurement process is shown in Figure 1. At the same time as the instrument integration, the pipeline of the measurement project was also modified (including: adjusting part of the semi-permeable membrane filter bed, changing the flow rate of the reagent, changing the concentration of the reagent, etc.). given in the schematic. The refitting of the instrument and the selection of appropriate reagent conditions can achieve the purpose of taking into account the linear range and sensitivity of the determination of environmental water quality samples. Other main analytical parameters of the instrument are shown in Table 1.

Table 1: Analysis parameters of the flow analyzer

Note: - indicates that this item does not need to be set

The concentration of the reaction reagent solution used:

The reaction reagents required for the determination of ammonium nitrogen are: NH ₄ ⁺ -A is a mixed solution containing 33g/L potassium sodium tartrate and 24g/L trisodium citrate, pH=5.2, and the two flow rates are 1mL/min and 0.8 mL/min; NH ₄ ⁺ -B is a mixed solution containing 80g/L sodium salicylate and 25g/L sodium hydroxide, with a flow rate of 0.32mL/min; NH ₄ ⁺ -C is sodium nitroferricyanide 1g/L, the flow rate is 0.16mL/min; NH ₄ ⁺ -D is sodium dichloroisocyanurate 2g/L, the flow rate is 0.32mL/min;

The reaction reagents required for the determination of nitrate nitrogen are: NO ₃ ^- -A is a mixed solution containing potassium sodium tartrate 33g/L, trisodium citrate 24g/L, and the flow rate is 0.8mL/min; NO ₃ ^- -B is hydrogen Sodium oxide 6g/L, the flow rate is 1mL/min; NO ₃ ^- -C is a mixed solution, containing hydrazine sulfate 2g/L, copper sulfate 18mg/L, the flow rate is 0.42mL/min; NO ₃ ^- -D is a mixed solution , containing N-(1-naphthyl)ethylenediamine dihydrochloride 0.5g/L, sulfonamide 10g/L, phosphoric acid 169g/L, the flow rate is 0.42mL/min;

The reaction reagents required for the determination of nitrite nitrogen are: NO ₂ ^- -A is pure water, resistivity: 18.3MΩ·cm, flow rate is 1mL/min; NO ₂ ^- -B is a mixed solution containing (N-(1 -Naphthyl) ethylenediamine dihydrochloride 0.5g/L, sulfonamide 10g/L, phosphoric acid 253.5g/L, flow rate is 0.32mL/min;

The reaction reagents required for the determination of total nitrogen are: TN-A is a mixed solution containing potassium persulfate 40g/L, sodium hydroxide 12g/L, and the flow rate is 0.42mL/min; TN-B is boric acid 24g/L, and the flow rate is 0.42mL/min; TN-C is ammonium chloride 50g/L, pH=8.2, the two flow rates are 1mL/min and 0.8mL/min respectively; TN-D is a mixed solution containing N-(1-naphthyl ) Ethylenediamine dihydrochloride 0.5g/L, sulfonamide 10g/L, hydrochloric acid 118g/L, the flow rate is 0.23mL/min;

The reaction reagents required for the determination of phosphate are: PO ₄ ^3- -A is a mixed solution containing 4.8g/L ammonium molybdate and 73.6g/L sulfuric acid, and the flow rate is 0.42mL/min; PO ₄ ^3- -B is a mixed solution Solution, containing ascorbic acid 18g/L, antimony potassium tartrate 6mg/L, the flow rate is 0.42mL/min;

The reaction reagents required for the determination of total phosphorus are: TP-A is a mixed solution containing potassium persulfate 9.9g/L, sulfuric acid 156.4g/L, and the flow rate is 0.23mL/min; TP-B is sulfuric acid 294.4g/L, the flow rate TP-C is sodium hydroxide 210g/L, the flow rate is 0.32mL/min; TP-D is a mixed solution containing 4.8g/L ammonium molybdate and sulfuric acid 73.6g/L, and the flow rate is 0.42 mL/min; TP-E is a mixed solution containing 18g/L ascorbic acid and 6mg/L antimony potassium tartrate, with a flow rate of 0.42mL/min.

Preparation of standard curve:

With 200.0mg/L ammonium nitrogen (NH ₄ Cl-N), 100.0mg/L nitrate nitrogen (KNO ₃ -N), 4.0mg/L nitrite nitrogen (NaNO ₂ -N), 20.0mg/L phosphoric acid Salt (KH ₂ PO ₄ -P) is the working mother solution. The above concentrations represent the concentrations of N and P elements. They are marked with -N and -P, respectively absorb 0.00, 1.00, 2.00, 3.00, 4.00, 5.00mL to 6 pieces of 100.0 In a mL volumetric flask, dilute to volume with pure water to prepare a mixed standard solution. In the mixed standard, the concentration of nitrate nitrogen is the sum of the concentrations of nitrite nitrogen and nitrate nitrogen; the concentration of total nitrogen is the sum of the concentrations of ammonium nitrogen, nitrite nitrogen and nitrate nitrogen; the concentration of total phosphorus equal to the concentration of phosphate. The injection time is 50s and the cleaning time is 100s. See Table 2 for the concentrations, linear equations, linear coefficients and detection limits of each component of the mixed solution of the standard solution of the 6 indicators.

Table 2: Linear coefficients and detection limits of the method

Note: X is the concentration of the sample in mg/L; Y is the signal value reading of the flow analyzer

Determination of samples:

The environmental standard sample is analyzed and measured by the method of the invention. Environmental standard samples were purchased from the Environmental Standard Sample Research Institute of the Ministry of Environmental Protection. From the test results, the measured value is within the guaranteed value range, which proves the accuracy of this method for determining nitrogen and phosphorus indicators. The results are shown in Table 3.

Table 3: Accuracy tests of the method

Example 2

The combination of instruments alone cannot meet the detection range of each index and cover the common concentrations of environmental water quality samples, and the modules and reagents need to be optimized. Now compare the optimized modules and reagents with those without optimization. In order to meet the detection range of each index can cover the common concentration of environmental water quality samples, according to the standard curve preparation method of embodiment 1, nitrate nitrogen concentration is 0.00, 1.04, 2.08, 3.12, 4.16, 5.20mg/L; Phosphate and total The concentration of phosphorus is 0.00, 0.20, 0.40, 0.60, 0.80, 1.00 mg/L, and the measured data are shown in Table 4.

The variation range of nitrate nitrogen concentration in environmental water quality samples is relatively large, basically in the range of 0.5 to 5 mg/L. When the injection volume was 0.42 mg/L, the highest point of the standard curve was close to saturation, which made the standard curve curved and the linear coefficient deteriorated. If the injection volume is changed to 0.16mg/L, the standard curve becomes better obviously, which can meet the requirement of large variation range of nitrate nitrogen concentration.

The phosphorus concentration of environmental water quality samples is low. In order to improve the sensitivity of phosphorus determination, as shown in the phosphate and total phosphorus modules in Fig. Reaction, improve sensitivity, and at the same time, the concentration of the reagent NaOH should be reduced to 210g/L due to the removal of the membrane, so as to ensure the pH of molybdenum antimony anti-color development. After removing the filter membrane, the slope of the standard curve of phosphate and total phosphorus becomes larger obviously, and the sensitivity becomes higher, which meets the determination of low concentration of phosphorus.

In short, the combined instrument, after optimization of the modules and reagents, is significantly superior to the unoptimized measurement effect. The detection range that can meet the various indicators can cover the common concentrations of environmental water quality samples, and meets the analysis needs of daily environmental water quality samples.

Table 4: Comparison test of module and reagent optimization or not

Note: X is the concentration of the sample in mg/L; Y is the signal value reading of the flow analyzer

Example 3

The method of the content of the invention is used to analyze and measure the water quality samples in the field. Instrument connection and experimental conditions are the same as in Example 1. The runoff water sample was collected from a rice field in Dapu Town, Yixing City (31°16′32″N, 119°53′32″E) after sowing and flooding with basal fertilizer, and it belongs to the non-point source pollution monitoring water sample in the Taihu Lake Basin. Its pH value is 6.70; COD _Cr (Chemical Oxygen Demand) is 68.0mg/L. The nitrogen and phosphorus indexes were measured repeatedly, and the calculated relative standard deviation (RSD) was between 0.54% and 2.85% (n=11). The environmental water quality sample was divided into five groups to carry out standard addition recovery test, absorbing 40.0, 30.0, 25.0, 20.0, 10.0mL of the environmental water quality sample respectively, adding the corresponding amount of standard solution, constant volume to 50.0mL, measuring its concentration, and its recovery The rate was between 96.3% and 107.6% (n=5). See Table 5 for the data.

Table 5: Precision and Spike Recovery of Environmental Water Quality Samples

Example 4

Adopt the method of the present invention to analyze and measure the soil column leaching solution, and the collected forest solution volume is 3mL. Instrument connection and experimental conditions are the same as in Example 1. The concentrations of ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen, phosphate, and total phosphorus were measured to be 4.02mg/L, 0.015mg/L, 2.07mg/L, 6.80mg/L, and 0.212mg/L respectively. , 0.245mg/L. Existing equipment and methods cannot analyze the nitrogen and phosphorus indicators in the leachate (including: ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen, phosphate, and total phosphorus), because each indicator needs to be analyzed separately. The volume of the sample is far from enough, and there is no way to investigate the change relationship of nitrogen and phosphorus throughout the leaching process, and the present invention just solves the problem of simultaneous determination of nitrogen and phosphorus indicators in water quality samples with a small volume .

Claims (1)

1. A method for simultaneously measuring water quality nitrogen and phosphorus indicators is characterized in that it is connected with two parallel Sakar San ⁺⁺ System flow analyzers through an Auto sampler 1075, and simultaneously removes phosphate and total The filter membrane of the phosphorus module measures the inorganic state concentration and the total concentration of nitrogen and phosphorus indicators respectively. The specific steps are: 200.0 mg/L ammonium nitrogen (NH ₄ Cl-N), 100.0 mg/L nitrate nitrogen (KNO ₃ -N), 4.0 mg/L nitrite nitrogen (NaNO ₂ -N), 20.0 mg/L phosphate (KH ₂ PO ₄ -P) as the working mother solution, absorb 0.00, 1.00, 2.00, 3.00, 4.00, Put 5.00 mL into six 100.0 mL volumetric flasks, dilute to volume with pure water, and prepare a mixed standard solution; the injection time is 50 s, and the cleaning time is 100 s. Simultaneously inject and detect: The linear equation of the standard curve for the injection flow rate of ammonium nitrogen at 0.32 mL/min is Y=43.5+387.5X; The linear equation of the standard curve of 0.42 mL/min injection flow rate of nitrite nitrogen is Y=16.8+15664.0X; The linear equation of the standard curve for 0.16 mL/min injection flow rate of nitrate nitrogen is Y=13.24+306.8X; The linear equation of the standard curve for the injection flow rate of 0.42 mL/min of total nitrogen is Y=-71.9+332.3X; The linear equation of the standard curve for 0.80 mL/min injection flow rate of phosphate is Y=-30309.5+1140024.2X; The linear equation of the standard curve for the injection flow rate of 0.42 mL/min of total phosphorus is Y=-17313.4+398251.2X; Among them: X is the concentration, the unit is mg/L; Y is the signal value reading of the flow analyzer; Then the injection volume of the sample to be tested is consistent with the standard curve, and its corresponding signal value reading is measured, and its concentration is calculated according to the standard curve method; Various nitrogen and phosphorus indicators were calculated through the standard curve equation, where: The reaction reagents required for the determination of ammonium nitrogen are: NH ₄ ⁺ -A is a mixed solution containing 33 g/L potassium sodium tartrate and 24 g/L trisodium citrate, pH=5.2, and the two flow rates are 1 mL/L respectively. min and 0.8 mL/min; NH ₄ ⁺ -B is a mixed solution containing 80 g/L sodium salicylate and 25 g/L sodium hydroxide, and the flow rate is 0.32 mL/min; NH ₄ ⁺ -C is nitrous Sodium ferricyanide 1 g/L, the flow rate is 0.16 mL/min; NH ₄ ⁺ -D is sodium dichloroisocyanurate 2 g/L, the flow rate is 0.32 mL/min; The reaction reagents required for the determination of nitrate nitrogen are: NO ₃ ^- -A is a mixed solution containing potassium sodium tartrate 33 g/L, trisodium citrate 24 g/L, and the flow rate is 0.8 mL/min; NO ₃ ^- -B Sodium hydroxide 6 g/L, the flow rate is 1 mL/min; NO ₃ ^- -C is a mixed solution, containing hydrazine sulfate 2 g/L, copper sulfate 18 mg/L, the flow rate is 0.42 mL/min; NO ₃ ^- -D is a mixed solution containing 0.5 g/L of N-(1-naphthyl)ethylenediamine dihydrochloride, 10 g/L of sulfonamide, and 169 g/L of phosphoric acid, with a flow rate of 0.42 mL/min; The reaction reagents required for the determination of nitrite nitrogen are: NO ₂ ^- -A is pure water, resistivity: 18.3 ΜΩ·cm, flow rate is 1 mL/min; NO ₂ ^- -B is a mixed solution containing (N-( 1-naphthyl) ethylenediamine dihydrochloride 0.5 g/L, sulfonamide 10 g/L, phosphoric acid 253.5 g/L, the flow rate is 0.32 mL/min; The reaction reagents required for the determination of total nitrogen are: TN-A is a mixed solution containing potassium persulfate 40 g/L, sodium hydroxide 12 g/L, and the flow rate is 0.42 mL/min; TN-B is boric acid 24 g/L , the flow rate is 0.42 mL/min; TN-C is ammonium chloride 50 g/L, pH= 8.2, the two flow rates are 1 mL/min and 0.8 mL/min respectively; TN-D is a mixed solution containing N- (1-naphthyl)ethylenediamine dihydrochloride 0.5 g/L, sulfonamide 10 g/L, hydrochloric acid 118 g/L, the flow rate is 0.23 mL/min; The reaction reagents required for the determination of phosphate are: PO ₄ ^3- -A is a mixed solution containing 4.8 g/L ammonium molybdate and 73.6 g/L sulfuric acid, and the flow rate is 0.42 mL/min; PO ₄ ^3- -B is a mixed solution Solution, containing ascorbic acid 18 g/L, antimony potassium tartrate 6 mg/L, the flow rate is 0.42 mL/min; The reaction reagents required for the determination of total phosphorus are: TP-A is a mixed solution containing potassium persulfate 9.9 g/L, sulfuric acid 156.4 g/L, and the flow rate is 0.23 mL/min; TP-B is sulfuric acid 294.4 g/L, the flow rate TP-C is sodium hydroxide 210 g/L, the flow rate is 0.32 mL/min; TP-D is a mixed solution containing 4.8 g/L ammonium molybdate and sulfuric acid 73.6 g/L, and the flow rate is 0.32 mL/min. 0.42 mL/min; TP-E is a mixed solution containing 18 g/L ascorbic acid and 6 mg/L antimony potassium tartrate, and the flow rate is 0.42 mL/min.