Method and equipment for detecting nitrogen content of water body based on ultraviolet spectrophotometry and medium

Abstract

The invention relates to the technical field of water body detection, in particular to a water body nitrogen content detection method and device based on ultraviolet spectrophotometry and a medium. The method comprises the steps that a target water body area is set, and water samples are extracted from multiple positions of the target water body area and mixed; weighing potassium persulfate, adding a potassium persulfate solution into the water sample, heating to a preset temperature, keeping for a preset time, after the water sample is cooled, adding a quantitative prepared hydrochloric acid solution and ammonia-free water into the digested water sample, slowly dropwise adding and stirring, so that the diluted water sample is fully and uniformly mixed; preheating an ultraviolet spectrophotometer to a stable state, setting a first wavelength and a second wavelength, placing the ultraviolet spectrophotometer into the ultraviolet spectrophotometer for determination, and obtaining first absorbance and second absorbance under the first wavelength and the second wavelength; a correction equation is formulated, the first absorbance and the second absorbance are converted into corresponding nitrogen concentrations, and the accuracy of nitrogen content detection in the water body can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of water body detection, and more specifically to a method, equipment and medium for detecting nitrogen content in water body based on ultraviolet spectrophotometry. Background Art

[0002] The discharge of nitrogen pollutants into water bodies can lead to eutrophication problems. How to effectively detect the nitrogen content in water bodies has become a concern for researchers. When determining the total nitrogen concentration, the potassium persulfate-oxidized nitrite colorimetric method is usually used to determine the total nitrogen concentration. The chemical oxidation method is used to determine the total nitrogen concentration, but the accuracy is difficult to control. Therefore, a method that can quickly and accurately determine the nitrogen content in water is needed. Summary of the invention

[0003] In order to overcome the problem that the determination of total nitrogen in the prior art takes too long, the present invention provides a method for detecting nitrogen content in water based on ultraviolet spectrophotometry, which can improve the accuracy of nitrogen content detection and can be applied to the detection of total nitrogen in various water bodies.

[0004] A method for detecting nitrogen content in water based on ultraviolet spectrophotometry comprises preparing an ultraviolet spectrophotometer needle, potassium persulfate, hydrochloric acid solution, ammonia-free water, glassware and a filter membrane with a fine pore size, and performing the following steps:

[0005] Step S1: setting a target water body area, extracting water samples from multiple locations in the target water body area and mixing them, oscillating and incubating them in a closed container for a preset time to convert nitrate nitrogen in the water samples into nitrite, and using the filter membrane with a fine pore size to remove suspended matter and microbial impurities in the water samples when the concentration of the nitrite reaches a maximum value;

[0006] Step S2: based on the volume of the water sample, potassium persulfate is weighed in a preset ratio, and the potassium persulfate is dissolved in an appropriate amount of water to form a potassium persulfate liquid, and then the potassium persulfate liquid is added to the water sample, and heated to a preset temperature, and maintained for a preset time;

[0007] Step S3: After the water sample is cooled, a predetermined amount of hydrochloric acid solution and ammonia-free water are added to the digested water sample, and when the hydrochloric acid solution is added, it is slowly added dropwise and stirred to make the diluted water sample fully mixed;

[0008] Step S4: preheating the ultraviolet spectrophotometer to a stable state, and setting a first wavelength and a second wavelength, pouring the diluted water sample into a cuvette, and placing it in the ultraviolet spectrophotometer for measurement, and obtaining a first absorbance and a second absorbance of the water sample at the first wavelength and the second wavelength respectively;

[0009] Step S5: formulating a correction equation based on experimental conditions and the characteristics of the water sample, converting the first absorbance and the second absorbance into corresponding nitrogen concentrations based on the correction equation, and calculating an average value of the nitrogen concentrations as the total nitrogen concentration.

[0010] As a preferred technical solution of the present invention, the step S5 further includes:

[0011] If the first absorbance is not within the valid range of the calibration equation, then search for the absorbance closest to the first absorbance within the valid range of the calibration equation as a reference absorbance, obtain the concentration corresponding to the reference absorbance to determine the dilution factor of the water sample, dilute the water sample based on the dilution factor, and re-measure the third absorbance and the fourth absorbance of the diluted water sample at the first wavelength and the second wavelength, respectively, calculate the total nitrogen concentration of the diluted water sample based on the third absorbance and the fourth absorbance, and multiply the total nitrogen concentration after dilution by the total number of dilutions to obtain the total nitrogen concentration of the original water sample.

[0012] As a preferred technical solution of the present invention, formulating the correction equation includes:

[0013] Record the absorbance data and the corresponding known concentration data measured under all relevant experimental conditions, and organize them into a table, divide the absorbance data and the corresponding known concentration data into fitting data and verification data, and draw a scatter plot with the concentration data as the abscissa and the absorbance data as the ordinate;

[0014] quantifying the strength of the linear relationship between the concentration data and the absorbance data using statistical software; if the correlation coefficient between the concentration data and the absorbance data is close to 1 or -1, it indicates that there is a strong linear relationship between the concentration data and the absorbance data; if the correlation coefficient between the concentration data and the absorbance data is low, it indicates that there is a nonlinear relationship between the concentration data and the absorbance data;

[0015] If the scatter plot shows a linear trend and the correlation coefficient is close to 1 or -1, a linear equation is used as a correction equation, represented by y=ax+b, wherein y represents the absorbance, x represents the concentration, and a and b are constants. If the scatter plot shows a nonlinear trend or the correlation coefficient is low, a nonlinear equation is used as a correction equation, and the form of the nonlinear equation is determined based on the trend of the scatter plot and a known mathematical model;

[0016] Using statistical software to perform regression analysis, during the regression analysis process, the form of the correction equation is also specified, and the fitting data is input for fitting, the goodness of the fitting equation is evaluated by statistical indicators, and the constant term and coefficient in the correction equation are determined according to the fitting result;

[0017] The absorbance value in the verification data is substituted into the correction equation, and the concentration value is calculated as the calculated concentration value, the calculated concentration value is compared with the known concentration value, and the error between the calculated concentration value and the known concentration value is calculated, and when the error is greater than or equal to a preset threshold, the correction equation is re-regressed until the error between the calculated concentration value and the known concentration value is less than the preset threshold.

[0018] As a preferred technical solution of the present invention, before extracting the water sample, the method includes:

[0019] First, rinse the glassware with water in the target water area, and then take an appropriate amount of water as a water sample. The water sample should be kept away from direct sunlight, and analyzed as soon as possible after taking out the water sample to avoid chemical reactions with air.

[0020] As a preferred technical solution of the present invention, dissolving the potassium persulfate in an appropriate amount of water to form a potassium persulfate solution comprises:

[0021] The potassium persulfate solution should be prepared before use, and the ground stopper should be quickly plugged after the water sample is added with the potassium persulfate solution to prevent the escape of gas generated during the digestion process.

[0022] As a preferred technical solution of the present invention, after the potassium persulfate solution is added to the water sample:

[0023] Put the water sample into a high pressure steam sterilizer and heat it to the preset temperature and keep it for a preset time, wherein the preset temperature is within the range of 120 to 124 degrees and the preset time is 30 to 60 minutes;

[0024] The pressure and temperature of the autoclave should be checked periodically during the heating of the water sample to ensure that the temperature and time are within the preset range;

[0025] After digestion is completed, the water sample should be cooled naturally to room temperature, and rapid cooling is prohibited.

[0026] As a preferred technical solution of the present invention, before being placed in the ultraviolet spectrophotometer for measurement, the following steps are included:

[0027] First, the cuvette is cleaned with ammonia-free water and dried. Meanwhile, when measuring the absorbance, it is ensured that the water sample in the cuvette is free of bubbles and suspended matter.

[0028] As a preferred technical solution of the present invention, after formulating the correction equation, it also includes:

[0029] When converting absorbance to concentration, the units of measurement should be standardized and the calibration equations should be verified and updated regularly.

[0030] The present invention also provides a computing device, the device comprising:

[0031] Memory and processor;

[0032] The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the above-mentioned method for detecting nitrogen content in water based on ultraviolet spectrophotometry is implemented.

[0033] The present invention also provides a storage medium, wherein the storage medium stores computer executable instructions, and when the computer executable instructions are executed by a processor, the above-mentioned method for detecting nitrogen content in water based on ultraviolet spectrophotometry is implemented.

[0034] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0035] The technical solution of the present invention sets a target water body area, extracts water samples from multiple locations in the target water body area and mixes them to reflect the average nitrogen content of the entire target water body area, and oscillates and cultivates the preset time in a closed container to convert the nitrate nitrogen in the water sample into nitrite. When the concentration of nitrite reaches the maximum value, a filter membrane with a fine pore size is used to remove suspended matter and microbial impurities in the water sample, thereby reducing the influence of suspended matter and microorganisms on the test results. Based on the volume of the water sample, potassium persulfate is weighed according to a preset ratio, and potassium persulfate is dissolved in an appropriate amount of water to form a potassium persulfate liquid, and then the potassium persulfate liquid is added to the water sample, and heated to a preset temperature, and maintained for a preset time, to ensure the adequacy of digestion. After the water sample is cooled, a quantitative hydrochloric acid solution and ammonia-free water are prepared and added to the water sample after digestion. At the same time, when the hydrochloric acid solution is added, it is slowly dripped and stirred so that the diluted water sample is fully mixed and evenly mixed, thereby improving the accuracy of the test results. Preheat the ultraviolet spectrophotometer to a stable state, and set the first wavelength and the second wavelength. Pour the diluted water sample into a cuvette and place it in the ultraviolet spectrophotometer for measurement to obtain the first absorbance and the second absorbance of the water sample at the first wavelength and the second wavelength, respectively. A correction equation is formulated based on the experimental conditions and the characteristics of the water sample. Based on the correction equation, the first absorbance and the second absorbance are respectively converted into corresponding nitrogen concentrations, and the average value of the nitrogen concentration is calculated as the total nitrogen concentration. The correction equation takes into account the influence of the experimental conditions and the characteristics of the water sample, and improves the accuracy of the test results. By averaging, the error is further reduced, and a reliable total nitrogen concentration value is obtained. Through the coordination between the above steps, the present invention realizes the accurate detection of nitrogen content in water bodies, and has the advantages of high sensitivity and good accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1 The present invention is a flow chart of the steps of the method for detecting nitrogen content in water based on ultraviolet spectrophotometry. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but unless otherwise specified, these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first xx script may be referred to as a second xx script, and similarly, a second xx script may be referred to as a first xx script.

[0040] When determining the total nitrogen concentration, the potassium persulfate-oxidation nitrite colorimetric method is usually used to determine the total nitrogen concentration. The chemical oxidation method for determining the total nitrogen concentration has better accuracy, but the process is time-consuming.

[0041] In view of the above technical problems, the present invention proposes Figure 1 A method for detecting nitrogen content in water based on ultraviolet spectrophotometry is shown, wherein an ultraviolet spectrophotometer needle, potassium persulfate, hydrochloric acid solution, ammonia-free water, glassware and a filter membrane with a fine pore size are prepared, and the method is implemented by performing the following steps:

[0042] Step S1: Set a target water area, extract water samples from multiple locations in the target water area and mix them, oscillate and incubate them in a closed container for a preset time to convert nitrate nitrogen in the water samples into nitrite, and when the concentration of nitrite reaches a maximum value, use a fine-pore filter membrane to remove suspended matter and microbial impurities in the water samples.

[0043] Specifically, a target water area is set, such as a river, lake or reservoir, and water samples are collected at multiple representative locations based on the fluidity and uniformity of the water body. The collected water samples are mixed evenly to reflect the average nitrogen content of the entire target water area. The mixed water sample is placed in a closed container and incubated with shaking for a period of time (such as 24 hours) to allow the nitrate nitrogen to be fully converted into nitrite. When the nitrite concentration reaches the maximum value (which can be determined experimentally), a fine-pore filter membrane (such as a pore size of 0.45 μm) is used to filter the water sample to remove suspended matter and microbial impurities, thereby reducing the impact of suspended matter and microorganisms on the test results.

[0044] Step S2: Based on the volume of the water sample, potassium persulfate is weighed according to a preset ratio, and the potassium persulfate is dissolved in an appropriate amount of water to form a potassium persulfate liquid, and then the potassium persulfate liquid is added to the water sample, and heated to a preset temperature and maintained for a preset time.

[0045] Specifically, potassium persulfate is weighed according to the volume of the water sample at a preset ratio (such as adding 5g of potassium persulfate per 100mL of water sample). Potassium persulfate is dissolved in an appropriate amount of ammonia-free water to form a potassium persulfate solution. The potassium persulfate solution is added to the water sample and heated to a preset temperature (such as 120-124°C) and maintained for a period of time (such as 30 minutes) to oxidize and decompose the organic matter and release nitrogen. Potassium persulfate digestion converts the nitrogen element in the organic matter into inorganic nitrogen, which is convenient for subsequent detection. Heating and maintaining for a certain period of time is to ensure the adequacy of digestion.

[0046] Step S3: After the water sample is cooled, a certain amount of hydrochloric acid solution and ammonia-free water are added to the digested water sample. When adding the hydrochloric acid solution, slowly add it dropwise and stir it to make the diluted water sample fully mixed.

[0047] Specifically, after the water sample is cooled to room temperature, a certain amount of hydrochloric acid solution and ammonia-free water are added to the digested water sample for dilution. When the hydrochloric acid solution is added, it is slowly dripped and stirred to fully mix the diluted water sample. The dilution process reduces the nitrogen concentration of the water sample, making it suitable for the measurement range of the ultraviolet spectrophotometer. The slow dripping and stirring ensure that the diluted water sample is mixed evenly, thereby improving the accuracy of the test results.

[0048] Step S4: preheat the ultraviolet spectrophotometer to a stable state, and set the first wavelength and the second wavelength, pour the diluted water sample into a cuvette, and put it into the ultraviolet spectrophotometer for measurement, and obtain the first absorbance and the second absorbance of the water sample at the first wavelength and the second wavelength respectively.

[0049] Specifically, the ultraviolet spectrophotometer is preheated to a stable state, and a first wavelength (such as 220 nm) and a second wavelength (such as 275 nm) are set. Setting two wavelengths can eliminate background interference and improve the accuracy of the test results. The diluted water sample is poured into a cuvette and placed in an ultraviolet spectrophotometer for measurement. The first absorbance and the second absorbance of the water sample at the first wavelength and the second wavelength are measured and recorded. Among them, ultraviolet spectrophotometry is a sensitive and accurate detection method that can measure the nitrogen concentration in the water sample.

[0050] Step S5: A correction equation is formulated based on the experimental conditions and the characteristics of the water sample. Based on the correction equation, the first absorbance and the second absorbance are respectively converted into corresponding nitrogen concentrations, and the average value of the nitrogen concentrations is calculated as the total nitrogen concentration.

[0051] Specifically, a correction equation is formulated based on the experimental conditions and the characteristics of the water sample. The correction equation can be obtained by fitting the experimental data and is used to convert the absorbance into the nitrogen concentration. The first absorbance and the second absorbance are respectively substituted into the correction equation to calculate the corresponding nitrogen concentration, and the average of the two nitrogen concentrations is calculated as the total nitrogen concentration. The correction equation takes into account the influence of the experimental conditions and the characteristics of the water sample, and improves the accuracy of the test results. By averaging, the error is further reduced, and a reliable total nitrogen concentration value is obtained.

[0052] Through the coordination of the above steps, the present invention realizes accurate detection of nitrogen content in water, and has the advantages of high sensitivity, good accuracy, etc.

[0053] Furthermore, after the above step S5, the following steps are further included:

[0054] If the first absorbance is not within the valid range of the calibration equation, the absorbance closest to the first absorbance is searched within the valid range of the calibration equation as a reference absorbance, the concentration corresponding to the reference absorbance is obtained to determine the dilution multiple of the water sample, the water sample is diluted based on the dilution multiple, and the third absorbance and the fourth absorbance of the diluted water sample at the first wavelength and the second wavelength respectively are re-measured, the total nitrogen concentration of the diluted water sample is calculated based on the third absorbance and the fourth absorbance, and the total nitrogen concentration of the diluted water sample is multiplied by the total number of dilutions to obtain the total nitrogen concentration of the original water sample.

[0055] Specifically, in step S5, if it is calculated that the first absorbance (A220, i.e., the absorbance at a wavelength of 220 nm) is not within the effective range of the pre-established calibration equation, special processing is required. Within the effective absorbance range of the calibration equation, find the absorbance value closest to the first absorbance, which is recorded as the reference absorbance (A_ref). Obtain the reference concentration and determine the dilution factor: According to the calibration equation, obtain the nitrogen concentration corresponding to the reference absorbance (A_ref), which is recorded as the reference concentration (C_ref). According to the difference between the first absorbance (A220) and the reference absorbance (A_ref), and the slope of the calibration equation, estimate the initial concentration range of the water sample. Based on the concentration range and the volume of the water sample, determine a suitable dilution factor to ensure that the first absorbance of the diluted water sample falls within the effective range of the calibration equation. Dilution and re-measurement: Use ammonia-free water or other appropriate diluent to dilute the water sample according to the determined dilution factor. After dilution, the method of step S4 is used to measure again, and the third absorbance (A220_diluted) and the fourth absorbance (A275_diluted) of the diluted water sample at the first wavelength (220nm) and the second wavelength (275nm) are obtained. Calculate the total nitrogen concentration after dilution and the original concentration: Substitute the third absorbance (A220_diluted) and the fourth absorbance (A275_diluted) into the calibration equation to calculate the total nitrogen concentration (C_diluted) of the diluted water sample. Multiply the total nitrogen concentration (C_diluted) after dilution by the dilution factor to obtain the total nitrogen concentration (C_original) of the original water sample.

[0056] By finding the reference absorbance and the corresponding concentration, and estimating the dilution factor, it is ensured that even if the first absorbance exceeds the effective range of the calibration equation, the total nitrogen concentration of the original water sample can be accurately calculated by dilution and re-measurement. This method improves the flexibility and scope of application of the test, making it applicable to a wider range of water nitrogen content detection scenarios.

[0057] Through the steps after step S5, when processing the first absorbance that exceeds the effective range of the calibration equation, the method can also take reasonable measures to ensure the accuracy and reliability of the detection result.

[0058] Further, the correction equation is formulated including:

[0059] Record the absorbance data and corresponding known concentration data measured under all relevant experimental conditions, and organize them into a table. Divide the absorbance data and corresponding known concentration data into fitting data and verification data, and draw a scatter plot with concentration data as the horizontal axis and absorbance data as the vertical axis;

[0060] Statistical software was used to quantify the strength of the linear relationship between the concentration data and the absorbance data. If the correlation coefficient between the concentration data and the absorbance data was close to 1 or -1, it indicated that there was a strong linear relationship between the concentration data and the absorbance data. If the correlation coefficient between the concentration data and the absorbance data was low, it indicated that there was a nonlinear relationship between the concentration data and the absorbance data.

[0061] If the scatter plot shows a linear trend and the correlation coefficient is close to 1 or -1, a linear equation is used as the correction equation, expressed as y=ax+b, where y represents absorbance, x represents concentration, and a and b are constants. If the scatter plot shows a nonlinear trend or the correlation coefficient is low, a nonlinear equation is used as the correction equation, and the form of the nonlinear equation is determined based on the trend of the scatter plot and the known mathematical model;

[0062] Statistical software is used to perform regression analysis. During the regression analysis, the form of the correction equation is specified, and fitting data is input for fitting. The goodness of the fitting equation is evaluated by statistical indicators, and the constant term and coefficient in the correction equation are determined based on the fitting results.

[0063] Substitute the absorbance value in the verification data into the calibration equation, and calculate the concentration value as the calculated concentration value, compare the calculated concentration value with the known concentration value, and calculate the error between the concentration value and the known concentration value. When the error is greater than or equal to a preset threshold, regress the calibration equation until the error between the calculated concentration value and the known concentration value is less than the preset threshold.

[0064] Further, before extracting the water sample, the following steps are included:

[0065] First, rinse the glassware with water from the target water area, and then take an appropriate amount of water as the water sample. The water sample should be kept away from direct sunlight, and analyzed as soon as possible after taking out the water sample to avoid chemical reactions with air.

[0066] Further, dissolving potassium persulfate in an appropriate amount of water to form a potassium persulfate solution comprises:

[0067] Potassium persulfate solution should be prepared before use, and the ground-mouth stopper should be quickly plugged after the potassium persulfate solution is added to the water sample to prevent the escape of gas generated during the digestion process.

[0068] Furthermore, after potassium persulfate solution was added to the water sample:

[0069] Place the water sample in a high pressure steam sterilizer and heat it to a preset temperature and maintain it for a preset time, wherein the preset temperature is within a range of 120 to 124 degrees and the preset time is 30 to 60 minutes;

[0070] The pressure and temperature of the autoclave should be checked periodically during the heating of the water sample to ensure that the temperature and time are within the preset range;

[0071] After digestion is completed, the water sample should be cooled naturally to room temperature. Rapid cooling is prohibited.

[0072] Further, before being placed in an ultraviolet spectrophotometer for measurement, the method includes:

[0073] First, clean the cuvette with ammonia-free water and dry it. At the same time, when measuring the absorbance, make sure that there are no bubbles or suspended matter in the water sample in the cuvette.

[0074] Furthermore, after formulating the correction equation, it also includes:

[0075] When converting absorbance to concentration, the units of measurement should be standardized and the calibration equations should be verified and updated regularly.

[0076] The present invention also provides a computing device, the device comprising:

[0077] Memory and processor;

[0078] The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the above-mentioned method for detecting nitrogen content in water based on ultraviolet spectrophotometry is implemented.

[0079] The present invention also provides a computer storage medium, which stores program instructions. When the program instructions are executed, the device where the computer storage medium is located is controlled to execute the above-mentioned method for detecting nitrogen content in water based on ultraviolet spectrophotometry.

[0080] In summary, by setting the target water area, extracting water samples from multiple locations in the target water area and mixing them to reflect the average nitrogen content of the entire target water area, oscillating and cultivating them in a closed container for a preset time, the nitrate nitrogen in the water sample is converted into nitrite. When the concentration of nitrite reaches the maximum value, a fine-pore filter membrane is used to remove suspended matter and microbial impurities in the water sample, thereby reducing the influence of suspended matter and microorganisms on the test results. Based on the volume of the water sample, potassium persulfate is weighed according to a preset ratio, and potassium persulfate is dissolved in an appropriate amount of water to form a potassium persulfate solution. The potassium persulfate solution is then added to the water sample, heated to a preset temperature, and maintained for a preset time to ensure the adequacy of the digestion. After the water sample is cooled, a quantitative hydrochloric acid solution and ammonia-free water are prepared and added to the digested water sample. At the same time, when the hydrochloric acid solution is added, it is slowly dripped and stirred so that the diluted water sample is fully mixed and evenly mixed, thereby improving the accuracy of the test results. Preheat the ultraviolet spectrophotometer to a stable state, and set the first wavelength and the second wavelength. Pour the diluted water sample into a cuvette and place it in the ultraviolet spectrophotometer for measurement to obtain the first absorbance and the second absorbance of the water sample at the first wavelength and the second wavelength, respectively. A correction equation is formulated based on the experimental conditions and the characteristics of the water sample. Based on the correction equation, the first absorbance and the second absorbance are respectively converted into corresponding nitrogen concentrations, and the average value of the nitrogen concentration is calculated as the total nitrogen concentration. The correction equation takes into account the influence of the experimental conditions and the characteristics of the water sample, and improves the accuracy of the test results. By averaging, the error is further reduced, and a reliable total nitrogen concentration value is obtained. Through the coordination between the above steps, the present invention realizes the accurate detection of nitrogen content in water bodies, and has the advantages of high sensitivity and good accuracy.

[0081] It should be understood that, although the various steps in the flowchart of each embodiment of the present invention are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in each embodiment may include a plurality of sub-steps or a plurality of stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0082] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

[0084] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting nitrogen content in water based on ultraviolet spectrophotometry, comprising preparing an ultraviolet spectrophotometer needle, potassium persulfate, hydrochloric acid solution, ammonia-free water, glassware and a filter membrane with a fine pore size, characterized in that: The method comprises the following steps: Step S1: setting a target water body area, extracting water samples from multiple locations in the target water body area and mixing them, oscillating and incubating them in a closed container for a preset time to convert nitrate nitrogen in the water samples into nitrite, and using the filter membrane with a fine pore size to remove suspended matter and microbial impurities in the water samples when the concentration of the nitrite reaches a maximum value; Step S2: based on the volume of the water sample, potassium persulfate is weighed in a preset ratio, and the potassium persulfate is dissolved in an appropriate amount of water to form a potassium persulfate liquid, and then the potassium persulfate liquid is added to the water sample, and heated to a preset temperature, and maintained for a preset time; Step S3: After the water sample is cooled, a predetermined amount of hydrochloric acid solution and ammonia-free water are added to the digested water sample, and when the hydrochloric acid solution is added, it is slowly added dropwise and stirred to make the diluted water sample fully mixed; Step S4: preheating the ultraviolet spectrophotometer to a stable state, and setting a first wavelength and a second wavelength, pouring the diluted water sample into a cuvette, and placing it in the ultraviolet spectrophotometer for measurement, and obtaining a first absorbance and a second absorbance of the water sample at the first wavelength and the second wavelength respectively; Step S5: formulating a correction equation based on experimental conditions and the characteristics of the water sample, converting the first absorbance and the second absorbance into corresponding nitrogen concentrations based on the correction equation, and calculating an average value of the nitrogen concentrations as the total nitrogen concentration.

2. The method according to claim 1, characterized in that After step S5, the following steps are also included: If the first absorbance is not within the valid range of the calibration equation, then search for the absorbance closest to the first absorbance within the valid range of the calibration equation as a reference absorbance, obtain the concentration corresponding to the reference absorbance to determine the dilution factor of the water sample, dilute the water sample based on the dilution factor, and re-measure the third absorbance and the fourth absorbance of the diluted water sample at the first wavelength and the second wavelength, respectively, calculate the total nitrogen concentration of the diluted water sample based on the third absorbance and the fourth absorbance, and multiply the total nitrogen concentration after dilution by the total number of dilutions to obtain the total nitrogen concentration of the original water sample.

3. The method according to claim 1, characterized in that Formulating the correction equation includes: Record the absorbance data and the corresponding known concentration data measured under all relevant experimental conditions, and organize them into a table, divide the absorbance data and the corresponding known concentration data into fitting data and verification data, and draw a scatter plot with the concentration data as the abscissa and the absorbance data as the ordinate; quantifying the strength of the linear relationship between the concentration data and the absorbance data using statistical software; if the correlation coefficient between the concentration data and the absorbance data is close to 1 or -1, it indicates that there is a strong linear relationship between the concentration data and the absorbance data; if the correlation coefficient between the concentration data and the absorbance data is low, it indicates that there is a nonlinear relationship between the concentration data and the absorbance data; If the scatter plot shows a linear trend and the correlation coefficient is close to 1 or -1, a linear equation is used as a correction equation, represented by y=ax+b, wherein y represents the absorbance, x represents the concentration, and a and b are constants. If the scatter plot shows a nonlinear trend or the correlation coefficient is low, a nonlinear equation is used as a correction equation, and the form of the nonlinear equation is determined based on the trend of the scatter plot and a known mathematical model; Using statistical software to perform regression analysis, during the regression analysis process, the form of the correction equation is also specified, and the fitting data is input for fitting, the goodness of the fitting equation is evaluated by statistical indicators, and the constant term and coefficient in the correction equation are determined according to the fitting result; The absorbance value in the verification data is substituted into the correction equation, and the concentration value is calculated as the calculated concentration value, the calculated concentration value is compared with the known concentration value, and the error between the calculated concentration value and the known concentration value is calculated, and when the error is greater than or equal to a preset threshold, the correction equation is re-regressed until the error between the calculated concentration value and the known concentration value is less than the preset threshold.

4. The method according to claim 1, characterized in that: Before taking water samples include: First, rinse the glassware with water in the target water area, and then take an appropriate amount of water as a water sample. The water sample should be kept away from direct sunlight, and analyzed as soon as possible after taking out the water sample to avoid chemical reactions with air.

5. The method according to claim 1, characterized in that Dissolving the potassium persulfate in an appropriate amount of water to form a potassium persulfate solution comprises: The potassium persulfate solution should be prepared before use, and the ground stopper should be quickly plugged after the water sample is added with the potassium persulfate solution to prevent the escape of gas generated during the digestion process.

6. The method according to claim 1, characterized in that After the potassium persulfate solution is added to the water sample: Put the water sample into a high pressure steam sterilizer and heat it to the preset temperature and keep it for a preset time, wherein the preset temperature is within the range of 120 to 124 degrees and the preset time is 30 to 60 minutes; The pressure and temperature of the autoclave should be checked periodically during the heating of the water sample to ensure that the temperature and time are within the preset range; After digestion is completed, the water sample should be cooled naturally to room temperature, and rapid cooling is prohibited.

7. The method according to claim 1, characterized in that Before being placed in the ultraviolet spectrophotometer for measurement, the method comprises: First, the cuvette is cleaned with ammonia-free water and dried. Meanwhile, when measuring the absorbance, it is ensured that the water sample in the cuvette is free of bubbles and suspended matter.

8. The method according to claim 3, characterized in that After developing the correction equation, also include: When converting absorbance to concentration, the units of measurement should be standardized and the calibration equations should be verified and updated regularly.

9. A computing device, characterized in that: The device comprises: Memory and processor; The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the method for detecting nitrogen content in water based on ultraviolet spectrophotometry described in any one of claims 1 to 8 is implemented.

10. A computer storage medium, characterized in that: The storage medium stores program instructions, wherein when the program instructions are executed, the device where the storage medium is located is controlled to execute the method for detecting nitrogen content in water based on ultraviolet spectrophotometry according to any one of claims 1 to 8.

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