CN115979978A - A method for measuring ammonia nitrogen content in seawater aquaculture water - Google Patents

Abstract

The invention discloses a method for measuring the ammonia nitrogen content of seawater aquaculture water, which comprises the steps of taking the seawater aquaculture water as a sample to be tested, filtering and measuring the salinity of the sample to be tested; preparing ammonia nitrogen stock solution, blank solution, standard solution, sample solution and reagent A-C, draw a standard curve with the absorbance value as the ordinate and the ammonia nitrogen concentration as the abscissa, fit the standard curve equation, pipette the same volume of sample solution to measure the absorbance, and obtain the ammonia nitrogen concentration in the mariculture pond according to the standard curve equation. The present invention increases the pH of the reaction system by adding sodium hydroxide solution, shields the interference of calcium, magnesium, iron, manganese and other ions in seawater samples, and realizes ammonia in the complex water body with mercuric potassium iodide solution in seawater and brackish water with a salinity below 30. Color, the ammonia nitrogen content is determined by spectrophotometer colorimetry, the required amount of reagents is small, the reaction stability time is long, the application range is wide, the accuracy and repeatability are good, and it is suitable for various marine aquaculture water bodies.

Description

A method for measuring ammonia nitrogen content in seawater aquaculture water

technical field

The invention relates to the field of environmental detection and analysis, in particular to a method for measuring ammonia nitrogen content in seawater aquaculture water.

Background technique

Ammonia nitrogen is a common pollutant in aquaculture water, and it is the main product of protein catabolism, residual bait and feces decomposition of marine aquaculture objects, and it will accumulate in water during the aquaculture process. Excessive ammonia nitrogen in the water body will negatively affect the growth, survival, and health of the cultured objects, and cause economic losses. Therefore, in the production of mariculture, it is of great significance to be able to measure the ammonia nitrogen content of mariculture ponds conveniently, quickly and universally.

The method for determining ammonia nitrogen in seawater is the sodium hypobromite oxidation method commonly used. The principle is that under alkaline conditions, sodium hypobromite oxidizes ammonia in seawater to nitrite, and the diazo-azo spectrophotometric method is used to The total amount of nitrite nitrogen is measured, and the original nitrite content is deducted to obtain the concentration of nitrogen and ammonia. In this method, the requirements for experimental reagents are relatively high, and sodium hypobromite solution is easy to decompose under natural conditions, and it is not easy to preserve, and the method involves many reagents, complicated steps, and is inconvenient for direct use in production. In samples containing more pollutants, organic matter and nitrite, such as mariculture pond water, this method often results in poor repeatability and accuracy due to the interference of various pollutants. In addition, indophenol blue spectrophotometry can also be used to measure ammonia nitrogen in seawater. The principle is that under the action of hypochlorous acid, ammonia is oxidized to form chloramine, and chloramine reacts with phenol to form indophenol blue complex, which is detected by spectrophotometer. The absorbance of the complex at 640nm, but this method has low sensitivity, takes a long time, requires complex reagents, and has a small linear range, and is also not suitable for the determination of ammonia nitrogen in water in mariculture sites.

The determination of ammonia nitrogen by Nessler's reagent spectrophotometry is a good method for the determination of ammonia nitrogen in fresh water. In an alkaline environment, ammonia can react with mercury potassium iodide solution to form a reddish-brown colloidal compound. This color is strongly absorbed in a wider wavelength, and the The absorbance of the complex is directly proportional to the content of ammonia nitrogen, and the wavelength used for measurement is usually 410-425nm. However, when the calcium and magnesium ions in the water sample are too high, they will react with the reagents to produce turbidity or precipitation and interfere with the measurement. Usually, it cannot be measured in seawater or water samples containing high calcium, magnesium, iron, manganese and other ions. For example, Chinese patent application (CN202111190348) discloses a method for measuring ammonia nitrogen content in seawater by Nessler's reagent spectrophotometry, but in this method, the consumption of potassium sodium tartrate solution and Nessler's reagent is large, and the total amount reaches the concentration of the sample to be tested. 90%, and the concentration of potassium sodium tartrate solution required for the reaction needs to be adjusted according to the salinity, which cannot be used directly in production, and the actual operation is cumbersome, and is not suitable for mariculture.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for measuring the ammonia nitrogen content in mariculture water, with less reagent consumption, suitable for aquaculture water with various salinities, convenient operation, and suitable for direct use in mariculture.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The invention provides a method for measuring ammonia nitrogen content in seawater aquaculture water, comprising the following steps:

Step 1: Sample pretreatment;

Take the mariculture water body as the sample to be tested, filter it through a needle filter of 0.45 μm and place it in the Erlenmeyer flask, and measure the salinity of the sample to be tested;

Step 2: Reagent preparation, including:

1g/L ammonia nitrogen stock solution: place ammonium chloride (AR) in an oven at 105°C for more than 2 hours, weigh 3.819g, dissolve it in deionized water and set the volume to 1L;

Blank solution: ammonia-free seawater with the same salinity as the sample to be tested;

Standard solution: use the blank solution as the diluent to dilute the ammonia nitrogen stock solution into ammonia nitrogen standard solutions of different concentrations;

Sample solution: pretreated sample solution, if the concentration of ammonia nitrogen in the sample is too high, it can be diluted with blank solution;

Reagent A: sodium potassium tartrate solution;

Reagent B: sodium hydroxide solution;

Reagent C: potassium mercury iodide solution;

Step 3: Standard curve drawing, including

(3a) Take a certain volume of the standard solution respectively, and place in different test tubes or colorimetric tubes;

(3b) Taking the volume of the standard solution as a reference, add reagent A with a volume ratio of 5:0.1-0.2 and mix immediately, then immediately add reagent B with a volume ratio of 5:0.1-0.2 and mix immediately;

(3c) Taking the volume of the standard solution as a reference, add reagent C with a volume ratio of 5:0.1-0.2, mix well, and let stand for 10 minutes until the color is stable;

(3d) Use a spectrophotometer at a wavelength of 420nm, take a 1cm cuvette, zero it with deionized water, and measure the absorbance;

(3e) take the absorbance value as the ordinate, and the ammonia nitrogen concentration (mg/L) as the abscissa, draw a standard curve, and obtain the standard curve equation through fitting;

Step 4: Sample determination, including:

With reference to the standard curve solution, pipette an equal volume of sample solution and place it in a test tube; measure the absorbance of the sample solution according to (3b)-(3e) in step 3;

Step 5: Compare the sample tube with the standard curve equation to obtain the ammonia nitrogen concentration in the mariculture pond.

As a preference, the concentration of the reagent A is 0.25-0.5 g/mL, 25-50 g of potassium sodium tartrate is dissolved in deionized water and fixed to 100 mL.

As a preference, the concentration of the reagent B is 0.4-0.5 g/mL, 40-50 g of sodium hydroxide is dissolved in deionized water and fixed to 100 mL.

Preferably, the preparation method of the reagent C is as follows: take 7 g of potassium iodide and dissolve it in deionized water, continue to weigh 10 g of mercury iodide and dissolve it in the potassium iodide solution, and set the volume to 100 mL.

Preferably, the ammonia nitrogen concentration of the standard solution is 0-2 mg/L, and at least 5 standard solutions with different ammonia nitrogen concentrations are prepared by using the blank solution and the ammonia nitrogen stock solution.

Preferably, the minimum detection limit is 0.05mg/L.

Preferably, the sample to be tested is selected from seawater samples with a salinity not exceeding 30‰.

Compared with prior art, the beneficial effect of the present invention is:

(1) the present invention measures the method for the ammonia nitrogen content of mariculture water body by adding sodium hydroxide solution in reaction system, improves reaction system pH, strengthens the shielding ability of potassium sodium tartrate, can shield calcium, magnesium, iron, manganese in seawater sample Plasma interference, realize the color development of ammonia in the complex water body with mercuric potassium iodide solution in 0-30‰ seawater, and measure the ammonia nitrogen content in seawater aquaculture water by spectrophotometer colorimetry, with long reaction stability time and wide application range Wide range, good accuracy and repeatability.

(2) The type of reagent used in the present invention is simple, and the amount of reagent used is only 2%-4% of the volume of the liquid to be tested, which reduces pollution, saves costs, and is simple to operate. It can be simplified as a rapid detection kit, and is suitable for rapid use in production practice by colorimetric spectrophotometer.

Description of drawings

Fig. 1 is the ammonia nitrogen standard curve under salinity 30‰ in the embodiment.

Fig. 2 is the ammonia nitrogen standard curve under salinity 20‰ in the embodiment.

Fig. 3 is the ammonia nitrogen standard curve under salinity 10‰ in the embodiment.

Fig. 4 is the ammonia nitrogen standard curve under salinity 5‰ in the embodiment.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the drawings of the embodiments of the present invention. Apparently, the described embodiments are some, not all, embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative effort fall within the protection scope of the present invention.

Example 1

For the determination of the ammonia nitrogen concentration of the water body samples in the mariculture ponds with a salinity of 30‰, prepare the following reagents or solutions:

Ammonia-free seawater: use ammonia-free brine with a salinity of 90‰ (filtered through a needle filter), and dilute it with ammonia-free deionized water to a salinity of 30‰.

1g/L ammonia nitrogen stock solution: place ammonium chloride in an oven at 105°C for more than 2 hours, weigh 3.819g and dissolve it in deionized water to make up to 1L.

Samples to be tested: Prepared with ammonia-free seawater and 1g/L ammonia nitrogen stock solution, the samples to be tested with a salinity of 30‰ and ammonia nitrogen content of 0.3, 0.5, 0.8 mg/L.

Standard solution: prepared from ammonia-free seawater and 1g/L ammonia nitrogen stock solution, with a salinity of 30‰, standard solutions with ammonia nitrogen contents of 0, 0.1, 0.2, 0.4, 0.6, 1.0, 1.5, 2.0mg/L.

Reagent A: Weigh 25g of potassium sodium tartrate and heat it to dissolve with deionized water, after cooling, dilute to 100mL, and prepare 0.25g/mL potassium sodium tartrate solution.

Reagent B: Weigh 40g of sodium hydroxide and dissolve it in deionized water. After cooling, dilute to 100mL to prepare a 0.4g/mL sodium hydroxide solution.

Reagent C: Weigh 7g of potassium iodide and dissolve it in deionized water, continue to weigh 10g of mercury iodide and dissolve it in the potassium iodide solution, set the volume to 100mL, and prepare a 0.17g/mL potassium mercury iodide solution.

Determination steps:

1) Standard curve drawing

Take 5mL standard solutions of different ammonia nitrogen concentrations in 15mL test tubes, add 150μL reagent A to each test tube in turn, mix immediately, add 150μL reagent B, mix immediately, add 150μL reagent C, mix well, wait for 10 minutes, Use a spectrophotometer to measure the absorbance at a wavelength of 420 nm with deionized water as a reference. Take the absorbance as the ordinate and the ammonia nitrogen concentration as the abscissa to draw a standard curve (Fig. 1).

2) Sample determination

Take 5mL of the sample to be tested in a 15mL test tube, add 150μL of reagent A to the test tube, mix immediately, add 150μL of reagent B, mix immediately, add 150μL of reagent C, mix, wait for 10 minutes, and use a spectrophotometer at a wavelength of 420nm Next, deionized water was used as a reference to measure the absorbance value, and the measured value was calculated according to the standard curve, and each sample was measured in triplicate.

As shown in Figure 1, the standard curve is y=0.183x+0.0461, R ² =0.9994, showing good linearity in the range of 0-2mg/L.

The measurement results are shown in Table 1, and the measurement results are basically consistent with the actual values, and the coefficient of variation is less than 5%, with good accuracy and repeatability.

Table 1: Determination of samples in seawater with a salinity of 30‰

Example 2

For the determination of the ammonia nitrogen concentration of the sample at a salinity of 20‰, prepare the following reagents or solutions:

Ammonia-free seawater: use ammonia-free brine with a salinity of 90‰ (filtered through a needle filter), and dilute it with ammonia-free deionized water to a salinity of 20‰.

1g/L ammonia nitrogen stock solution: place ammonium chloride in an oven at 105°C for more than 2 hours, weigh 3.819g and dissolve it in deionized water to make up to 1L.

Sample to be tested: Prepared with ammonia-free seawater and 1g/L ammonia nitrogen stock solution, with a salinity of 20‰, samples to be tested with ammonia nitrogen content of 0.3, 0.5, and 0.8 mg/L.

Standard solution: prepared from ammonia-free seawater and 1g/L ammonia nitrogen stock solution, with a salinity of 20‰, standard solutions with ammonia nitrogen contents of 0, 0.1, 0.2, 0.4, 0.6, 1.0, 1.5, and 2.0 mg/L.

Reagent A: Weigh 25g of potassium sodium tartrate and heat to dissolve with deionized water, after cooling, make the volume to 100mL, and prepare 0.25g/mL potassium sodium tartrate solution.

Reagent B: Weigh 40g of sodium hydroxide and dissolve it in deionized water. After cooling, dilute to 100mL to prepare a 0.4g/mL sodium hydroxide solution.

Reagent C: Weigh 7g of potassium iodide and dissolve it in deionized water, continue to weigh 10g of mercury iodide and dissolve it in the potassium iodide solution, dilute to 100mL, and prepare a 0.17g/mL potassium mercury iodide solution.

Determination steps:

1) Standard curve drawing

Take 5mL standard solutions of different ammonia nitrogen concentrations in 15mL test tubes, add 150μL reagent A to each test tube in turn, mix immediately, add 150μL reagent B, mix immediately, add 150μL reagent C, mix well, wait for 10 minutes, Use a spectrophotometer to measure the absorbance at a wavelength of 420 nm with deionized water as a reference. Take the absorbance as the ordinate and the ammonia nitrogen concentration as the abscissa to draw a standard curve (Fig. 2).

2) Sample determination

Take 5mL of the sample to be tested in a 15mL test tube, add 150μL of reagent A to the test tube, mix immediately, add 150μL of reagent B, mix immediately, add 150μL of reagent C, mix, wait for 10 minutes, and use a spectrophotometer at a wavelength of 420nm Next, deionized water was used as a reference to measure the absorbance value, and the measured value was calculated according to the standard curve, and each sample was measured in triplicate.

As shown in Figure 2, the standard curve is y=0.2082x+0.0592, R ² =0.9991, which shows good linearity in the range of 0-2 mg/L.

The measurement results are shown in Table 2, the measurement results are basically consistent with the actual values, and the coefficient of variation is less than 5%, with good accuracy and repeatability.

Table 2: Determination of samples in seawater with a salinity of 20‰

Sample (mg/mL) Mean (mg/mL) Standard deviation (mg/mL) Coefficient of variation (%) Recovery rate(%) 0.3 0.30 0.01 3.8 97-105 0.5 0.49 0.02 3.9 94-102 0.8 0.81 0.01 1.8 99-102

Example 3

For the determination of the ammonia nitrogen concentration of the sample at a salinity of 10‰, prepare the following reagents or solutions:

Ammonia-free seawater: Use ammonia-free brine with a salinity of 90‰ (filtered through a needle filter) and dilute it with ammonia-free deionized water to a salinity of 10‰.

1g/L ammonia nitrogen stock solution: place ammonium chloride in an oven at 105°C for more than 2 hours, weigh 3.819g and dissolve it in deionized water to make up to 1L.

Sample to be tested: Prepared with ammonia-free seawater and 1g/L ammonia nitrogen stock solution, with a salinity of 10‰, samples to be tested with ammonia nitrogen content of 0.3, 0.5, and 0.8mg/L.

Standard solution: Ammonia-free seawater and 1g/L ammonia nitrogen stock solution are prepared, and the salinity is 10‰ standard solution with ammonia nitrogen content of 0, 0.1, 0.2, 0.4, 0.6, 1.0, 1.5, 2.0mg/L respectively.

Reagent A: Weigh 25g of potassium sodium tartrate and heat to dissolve with deionized water, after cooling, make the volume to 100mL, and prepare 0.25g/mL potassium sodium tartrate solution.

Reagent B: Weigh 40g of sodium hydroxide and dissolve it in deionized water. After cooling, dilute to 100mL to prepare a 0.4g/mL sodium hydroxide solution.

Reagent C: Weigh 7g of potassium iodide and dissolve it in deionized water, continue to weigh 10g of mercury iodide and dissolve it in the potassium iodide solution, dilute to 100mL, and prepare a 0.17g/mL potassium mercury iodide solution.

Determination steps:

1) Standard curve drawing

Take 5mL standard solutions of different ammonia nitrogen concentrations in 15mL test tubes, add 150μL reagent A to each test tube in turn, mix immediately, add 150μL reagent B, mix immediately, add 150μL reagent C, mix well, wait for 10 minutes, Use a spectrophotometer to measure the absorbance at a wavelength of 420 nm with deionized water as a reference. Take the absorbance as the ordinate and the ammonia nitrogen concentration as the abscissa to draw a standard curve (Fig. 2).

2) Sample determination

Take 5mL of the sample to be tested in a 15mL test tube, add 150μL of reagent A to the test tube, mix immediately, add 150μL of reagent B, mix immediately, add 150μL of reagent C, mix, wait for 10 minutes, and use a spectrophotometer at a wavelength of 420nm Next, deionized water was used as a reference to measure the absorbance value, and the measured value was calculated according to the standard curve, and each sample was measured in triplicate.

As shown in Fig. 3, the standard curve is y=0.2201x+0.0253, R ² =0.9988, showing good linearity in the range of 0-2 mg/L.

The measurement results are shown in Table 3, the measurement results are basically consistent with the actual values, and the coefficient of variation is less than 5%, with good accuracy and repeatability.

Table 3: Determination of samples in seawater with a salinity of 10‰

Sample (mg/mL) Mean (mg/mL) Standard deviation (mg/mL) Coefficient of variation (%) Recovery rate(%) 0.3 0.30 0.01 3.0 96-104 0.5 0.51 0.02 3.1 98-105 0.8 0.80 0.03 3.6 96-104

Example 4

For the determination of the ammonia nitrogen concentration of the sample at a salinity of 5‰, prepare the following reagents or solutions:

Ammonia-free seawater: Use ammonia-free brine with a salinity of 90‰ (filtered through a needle filter) and dilute it with ammonia-free deionized water to a salinity of 5‰.

1g/L ammonia nitrogen stock solution: place ammonium chloride in an oven at 105°C for more than 2 hours, weigh 3.819g and dissolve it in deionized water to make up to 1L.

Samples to be tested: Prepared with ammonia-free seawater and 1g/L ammonia nitrogen stock solution, with a salinity of 5‰, samples to be tested with ammonia nitrogen content of 0.3, 0.5, and 0.8mg/L.

Standard solution: prepared from ammonia-free seawater and 1g/L ammonia nitrogen stock solution, with a salinity of 5‰, standard solutions with ammonia nitrogen contents of 0, 0.1, 0.2, 0.4, 0.6, 1.0, 1.5, 2.0mg/L.

Reagent A: Weigh 25g of potassium sodium tartrate and heat to dissolve with deionized water, after cooling, make the volume to 100mL, and prepare 0.25g/mL potassium sodium tartrate solution.

Reagent B: Weigh 40g of sodium hydroxide and dissolve it in deionized water. After cooling, dilute to 100mL to prepare a 0.4g/mL sodium hydroxide solution.

Reagent C: Weigh 7g of potassium iodide and dissolve it in deionized water, continue to weigh 10g of mercury iodide and dissolve it in the potassium iodide solution, dilute to 100mL, and prepare a 0.17g/mL potassium mercury iodide solution.

Determination steps:

1) Standard curve drawing

Take 5mL standard solutions of different ammonia nitrogen concentrations in 15mL test tubes, add 150μL reagent A to each test tube in turn, mix immediately, add 150μL reagent B, mix immediately, add 150μL reagent C, mix well, wait for 10 minutes, Use a spectrophotometer to measure the absorbance at a wavelength of 420 nm with deionized water as a reference. Take the absorbance value as the ordinate and the ammonia nitrogen concentration as the abscissa to draw a standard curve (Fig. 4).

2) Sample determination

Take 5mL of the sample to be tested in a 15mL test tube, add 150 μL of reagent A to the test tube, mix immediately, add 150 μL of reagent B, mix immediately, add 150 μL of reagent C, mix well, wait for 10 minutes, and use a spectrophotometer at a wavelength of 420nm Next, deionized water was used as a reference to measure the absorbance value, and the measured value was calculated according to the standard curve, and each sample was measured in triplicate.

As shown in Fig. 4, the standard curve is y=0.189x+0.0311, R ² =0.9995, showing good linearity in the range of 0-2 mg/L.

The measurement results are shown in Table 4, the measurement results are basically consistent with the actual values, and the coefficient of variation is less than 5%, with good accuracy and repeatability.

Table 4: Determination of samples in seawater with a salinity of 5‰

The above description of the embodiments is for those of ordinary skill in the art to understand and use the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art according to the principle of the present invention without departing from the scope of the present invention shall fall within the protection scope of the present invention.

Claims (7)

1. A method for measuring the ammonia nitrogen content of seawater aquaculture water, is characterized in that, the method may further comprise the steps: Step 1: Sample pretreatment; Take the mariculture water body as the sample to be tested, filter it through a needle filter of 0.45 μm and place it in the Erlenmeyer flask, and measure the salinity of the sample to be tested; Step 2: Reagent preparation, including: 1g/L ammonia nitrogen stock solution: place ammonium chloride in an oven at 105°C for more than 2 hours, weigh 3.819g, dissolve with deionized water and make up to 1L; Blank solution: ammonia-free seawater with the same salinity as the sample to be tested; Standard solution: use the blank solution as the diluent to dilute the ammonia nitrogen stock solution into ammonia nitrogen standard solutions of different concentrations; Sample solution: pretreated sample solution, if the concentration of ammonia nitrogen in the sample is too high, it can be diluted with blank solution; Reagent A: sodium potassium tartrate solution; Reagent B: sodium hydroxide solution; Reagent C: potassium mercury iodide solution; Step 3: Standard curve drawing, including: (3a) Take a certain volume of the standard solution respectively, and place in different test tubes or colorimetric tubes; (3b) Taking the volume of the standard solution as a reference, add reagent A with a volume ratio of 5:0.1-0.2, mix immediately, then immediately add reagent B with a volume ratio of 5:0.1-0.2, and mix immediately; (3c) Taking the volume of the standard solution as a reference, add reagent C with a volume ratio of 5:0.1-0.2, mix well, and let stand for 10 minutes until the color is stable; (3d) Use a spectrophotometer at a wavelength of 420nm, take a 1cm cuvette, zero it with deionized water, and measure the absorbance; (3e) take the absorbance value as the ordinate, and the ammonia nitrogen concentration (mg/L) as the abscissa, draw a standard curve, and obtain the standard curve equation through fitting; Step 4: Sample determination, including: With reference to the standard curve solution, pipette an equal volume of sample solution and place it in a test tube; measure the absorbance of the sample solution according to (3b)-(3e) in step 3; Step 5: Compare the sample tube with the standard curve equation to obtain the ammonia nitrogen concentration in the mariculture pond. 2. according to claim 1, measure the method for the ammonia-nitrogen content of mariculture water body, it is characterized in that, the concentration of described reagent A is 0.25-0.5g/mL, gets 25-50g potassium sodium tartrate and dissolves and settles in deionized water 100mL. 3. according to claim 1, measure the method for mariculture water body ammonia nitrogen content, it is characterized in that, the concentration of described reagent B is 0.4-0.5g/mL, gets 40-50g sodium hydroxide and dissolves and settles in deionized water 100mL. 4. according to claim 1, measure the method for mariculture water body ammonia nitrogen content, it is characterized in that, the preparation method of described reagent C is: get 7g potassium iodide and dissolve with deionized water, continue to take by weighing 10g mercuric iodide and be dissolved in potassium iodide solution In, set the volume at 100mL. 5. according to claim 1, measure the method for ammonia nitrogen content in mariculture water body, it is characterized in that, the ammonia nitrogen concentration of described standard solution is 0-2mg/L, adopt described blank solution and ammonia nitrogen reserve solution to prepare at least 5 different ammonia nitrogen concentrations of standard solutions. 6. The method for measuring the ammonia nitrogen content in seawater aquaculture water according to claim 1, wherein the minimum detection limit is 0.05 mg/L. 7. The method for measuring ammonia nitrogen content in seawater aquaculture water according to claim 1, wherein the sample to be tested is selected from seawater samples with a salinity of no more than 30‰.

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