Anti-interference sensitization total phosphorus determination method and special color developing reagent thereof

Abstract

The invention relates to the technical field of anti-interference sensibilization total phosphorus determination, and discloses an anti-interference sensibilization total phosphorus determination method and a special chromogenic reagent thereof, in the special chromogenic reagent, ascorbic acid with a concentration of 10% ensures sufficient reducing ability, can efficiently reduce phosphomolybdenum heteropoly acid into phosphomolybdenum blue, enhances the sensitivity of a chromogenic reaction, and has good stability. According to the method, low-concentration total phosphorus can also be accurately detected, the detection capacity of the method on trace phosphorus is improved, molybdate and ammonium molybdate react with orthophosphate to generate phosphomolybdic heteropoly acid, and antimony potassium tartrate serves as a catalyst to accelerate the reaction rate, improve the color development efficiency, shorten the reaction time, guarantee the reaction sufficiency and improve the detection efficiency. The chelating agent can be complexed with various metal ions such as iron, copper, calcium and magnesium in a water sample, interference of the metal ions on chromogenic reaction is effectively eliminated, a reaction system is stabilized, the anti-interference capability of the determination method is remarkably improved, and the method is suitable for complex water samples.

Description

Technical Field

[0001] This invention relates to the field of total phosphorus determination technology with anti-interference and sensitization enhancement, specifically to a total phosphorus determination method with anti-interference and sensitization enhancement and its dedicated colorimetric reagent. Background Technology

[0002] Total phosphorus, as an important nutrient indicator in water bodies, directly affects the balance of aquatic ecosystems. Excessively high total phosphorus concentrations can easily lead to eutrophication, causing excessive algal growth, decreased dissolved oxygen, and consequently, destruction of aquatic habitats, impacting the utilization value of water resources. Therefore, accurately determining the total phosphorus content in water bodies is a crucial step in ecological environment monitoring, water pollution control, and water resource protection. Currently, the commonly used method for total phosphorus determination is mainly based on the ammonium molybdate spectrophotometric method. The principle is to use an oxidant to convert various forms of phosphorus in the water sample into orthophosphate, which then forms a colored complex through a colorimetric reaction. The total phosphorus content is calculated by measuring the absorbance using a spectrophotometer. However, in practical applications, this type of method still has many problems: Poor sample stability: If water samples are not properly stored after collection, microbial activity and natural transformation of phosphorus forms can cause changes in the phosphorus content of the sample, affecting the accuracy of the test results. Multiple interfering factors: Metal ions such as iron, copper, calcium, and magnesium in the water body are prone to react with the colorimetric reagent, interfering with the formation and reduction process of phosphomolybdic heteropolyacid, resulting in incomplete colorimetric reaction or increased background value, reducing detection accuracy; Insufficient digestion efficiency: Traditional digestion methods (such as high-pressure steam digestion) do not completely oxidize complex forms of phosphorus (such as organic phosphorus and particulate phosphorus), and the digestion conditions are difficult to control uniformly, resulting in poor consistency of phosphorus form conversion in different batches of samples and reduced reproducibility. Limited colorimetric sensitivity: The colorimetric reaction signal of low-concentration total phosphorus samples is weak. The reducing power and reaction efficiency of traditional reagent combinations are insufficient, making it difficult to accurately detect trace phosphorus and limiting the applicability of the method to clean water bodies or low-pollution water samples. Insufficient operational standardization: Operational problems such as weak representativeness of sampling points, filter membrane contamination, and disordered reagent addition order can easily introduce systematic errors, further affecting the reliability of the measurement results.

[0003] Therefore, it is necessary to design an interference-resistant and sensitizing method for the determination of total phosphorus and a dedicated colorimetric reagent to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide an anti-interference and sensitizing method for the determination of total phosphorus and its dedicated colorimetric reagent, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for determining total phosphorus with anti-interference and enhanced sensitivity, comprising the following steps: S1. Sample Collection and Preservation In ecological and environmental monitoring, if the collected water samples cannot be analyzed in time, sulfuric acid needs to be added to adjust the pH to about 1, and the samples need to be stored at 4°C and tested within 24 hours. S2, Sample Pretreatment Sample pretreatment includes digestion, with potassium persulfate solution at a concentration of 5% as the digestion solution, and digestion conditions at a temperature of 120-124℃ for 30 minutes; S3, Colorimetric reaction Take an appropriate amount of the digested water sample into a colorimetric tube, add 1 mL of ascorbic acid solution (10% concentration) and mix well. After 30 seconds, add 2 mL of molybdate solution (ammonium molybdate concentration 10 g / L, potassium antimony tartrate concentration 0.5 g / L) and mix thoroughly. The colorimetric reaction must be carried out under strongly acidic conditions (pH 1.0-1.5). The optimal reaction temperature is 25-30℃, and the optimal reaction time is 15-20 min.

[0006] S4. Detection and Data Processing Using a spectrophotometer, at a wavelength of 700 nm, with pure water as a reference, the absorbance of the solution after color development is measured. The cuvettes need to be rinsed with the solution to be tested to ensure measurement accuracy. A series of orthophosphate standard solutions of different concentrations were prepared and processed according to the same digestion and color development steps as the water sample. The absorbance was measured and a calibration curve was plotted with the absorbance of the blank test subtracted from the absorbance as the ordinate and the corresponding total phosphorus content in μg as the abscissa. Based on the calibration curve, the total phosphorus content in the water sample is calculated using the formula: C = m / V.

[0007] Preferably, in step S1, for river monitoring, multiple samples should be collected and mixed in different flow velocity zones and depth layers.

[0008] Preferably, in step S2, during the digestion process, the strong oxidizing atomic oxygen produced by the decomposition of potassium persulfate oxidizes various forms of phosphorus in the water sample into orthophosphate. The reaction equation is: K2S2O8+H2O——>2KHSO4+[O]. After digestion, the digestion tube is cooled to room temperature and then taken out for use.

[0009] Preferably, in step S3, in an acidic medium, orthophosphate reacts with ammonium molybdate to generate phosphomolybdic heteropolyacid. Potassium antimony tartrate acts as a catalyst to accelerate the reaction. Ascorbic acid reduces the phosphomolybdic heteropolyacid to a blue complex (phosphomolybdic blue). The intensity of the blue complex is directly proportional to the concentration of orthophosphate. The relevant reaction equations are as follows: H3PO4+12(NH4)2MoO4+24HNO3→(NH4)3PO4·12MoO3+21NH4NO3+12H2O (NH4)3PO4·12MoO3+C6H8O6→(NH4)3PO4·10MoO3·Mo2O5+C6H6O6+2H2O Preferably, in step S4, C is the total phosphorus concentration (mg / L), m is the phosphorus content (μg), and V is the water sample volume (mL). At the same time, blank tests and spiked recovery tests must be performed for each batch of samples to control detection errors and ensure data accuracy.

[0010] Preferably, the ascorbic acid, as a reducing agent, reduces phosphomolybdic heteropolyacid to phosphomolybdic blue, enhances the sensitivity of the colorimetric reaction, and ensures the accuracy of the detection results. Its concentration is 10% (m / V%) to ensure sufficient reducing capacity in the reaction system. Molybdate: Composed of ammonium molybdate (10 g / L) and potassium antimony tartrate (0.5 g / L). Ammonium molybdate reacts with orthophosphate to form phosphomolybdic heteropolyacid. Potassium antimony tartrate catalyzes this reaction, accelerating the reaction rate and improving the color development efficiency. Chelating agents, such as disodium ethylenediaminetetraacetate (EDTA-2Na) at a concentration of 0.1 mol / L, can complex with various metal ions in water samples, such as iron, copper, calcium, and magnesium, eliminating the interference of metal ions on the colorimetric reaction, stabilizing the reaction system, and improving the anti-interference ability of the assay method. The chelating agent should be added after sample pretreatment and before the colorimetric reaction. After the water sample is thoroughly mixed, digested, and cooled to room temperature, take an appropriate amount of the digested water sample into a colorimetric tube, add 0.1 mol / L EDTA-2Na solution (the amount added is 1:100 of the water sample volume), mix well, and then proceed with the subsequent ascorbic acid and molybdate addition steps to ensure that the metal ions are complexed in advance, eliminating interference.

[0011] Compared with the prior art, the present invention provides an interference-resistant and sensitized method for the determination of total phosphorus and its dedicated colorimetric reagent, which has the following beneficial effects: 1. This anti-interference and sensitizing method for total phosphorus determination and its dedicated colorimetric reagent have been improved by adding a digestion solution calibration step, which solves the measurement error problem caused by insufficient digestion solution efficiency. The temperature control of the colorimetric reaction and the spectrophotometer calibration steps have been refined to ensure sufficient color development and instrument stability, further improving detection accuracy. In the dedicated colorimetric reagent, 10% ascorbic acid ensures sufficient reducing power and improves the sensitivity of trace phosphorus detection. EDTA-2Na chelating agent effectively eliminates metal ion interference and broadens the applicability of the method. The reagent storage conditions are clearly defined to ensure the consistency of test results across different batches. Under digestion conditions of 120℃ and 30 minutes, the intelligent digestion instrument efficiently oxidizes various forms of phosphorus to orthophosphate using potassium persulfate. The digestion process is controllable, improving the thoroughness and consistency of phosphorus conversion. A strict reagent addition sequence—adding ascorbic acid first, followed by molybdate solution 30 seconds later—ensures the orderly progress of the reaction. In an acidic medium, orthophosphate reacts with ammonium molybdate to form phosphomolybdic heteropolyacid. Potassium antimony tartrate catalyzes and accelerates the reaction, while ascorbic acid reduces it to phosphomolybdic blue. The intensity of this blue complex is directly proportional to the orthophosphate concentration, demonstrating strong reaction specificity and providing a sound chemical basis for accurate detection. Measurements are taken at 700nm using a spectrophotometer, and calculations are performed using a calibration curve. The method is standardized, and blank and spiked recovery tests effectively control detection errors and ensure data accuracy. The calibration curve shows good linearity (R²>0.999) in the concentration range of 0.01-2.0 mg / L. The relative standard deviation (RSD) of repeated measurements on the same water sample is <3%, and the spiked recovery rate is between 95% and 105%, demonstrating the high precision and accuracy of the method. It is suitable for various complex water samples, such as industrial wastewater and polluted surface water. Combined with intelligent analysis systems and geographic information systems, it can monitor data in real time and perform spatial distribution analysis, providing efficient and reliable data support for wastewater treatment process adjustment, lake eutrophication assessment and treatment, and has a wide range of applications.

[0012] 2. This anti-interference and sensitizing method for total phosphorus determination, along with its dedicated colorimetric reagent, uses ascorbic acid at a concentration of 10% to ensure sufficient reducing power, efficiently reducing phosphomolybdic acid to phosphomolybdic blue, thus enhancing the sensitivity of the colorimetric reaction. This allows for accurate detection of even low concentrations of total phosphorus, improving the method's ability to detect trace amounts of phosphorus. Molybdate (ammonium molybdate 10 g / L) reacts with orthophosphate to generate phosphomolybdic acid. Potassium antimony tartrate (0.5 g / L) acts as a catalyst to accelerate the reaction rate, improve colorimetric efficiency, shorten reaction time, and simultaneously ensure the reaction... The reagents are sufficient to form chelating agents, such as EDTA-2Na, 0.1 mol / L, which can complex with various metal ions such as iron, copper, calcium, and magnesium in water samples, effectively eliminating the interference of these metal ions on the colorimetric reaction, stabilizing the reaction system, and significantly improving the anti-interference ability of the determination method. This makes the method applicable to complex water samples. These reagents have a long shelf life under the specified storage conditions of refrigeration at 4℃ and protection from light, and their performance is stable during use, ensuring the consistency and reliability of test results from different batches and reducing detection errors caused by reagent problems. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is a schematic diagram of the system flow of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0016] This invention provides the following technical solutions: Example 1 Please see Figure 1 This invention provides a technical solution: a method for determining total phosphorus with anti-interference and enhanced sensitivity, comprising the following steps: S1. Sample Collection and Preservation In ecological and environmental monitoring, if the collected water samples cannot be analyzed in time, sulfuric acid should be added to adjust the pH to about 1, and the samples should be stored at 4°C and tested within 24 hours. For river monitoring, multiple samples should be collected from different flow velocity areas and depth layers and then mixed to ensure that the samples are representative.

[0017] S2, Sample Pretreatment Digestion solution calibration: After each preparation of 5% potassium persulfate digestion solution, it is verified with a known concentration of 0.5 mg / L orthophosphate standard solution. After processing according to the subsequent digestion steps, the recovery rate is detected by colorimetric reaction. The recovery rate should be between 98% and 102% to ensure the oxidation efficiency of the digestion solution. Digestion: Add 5% potassium persulfate digestion solution to the filtered filtrate, with a filtrate to digestion solution volume ratio of 5:1. Place the solution in an intelligent digester and digest for 30 minutes at 120-124℃. During the digestion process, the strong oxidizing atomic oxygen produced by the decomposition of potassium persulfate oxidizes various forms of phosphorus in the water sample into orthophosphate. After digestion, allow the digestion tube to cool to room temperature before removing it for use.

[0018] S3, Colorimetric reaction Take an appropriate amount of digested water sample into a colorimetric tube, add 0.1 mol / L EDTA-2Na solution (the amount added is 1:100 of the water sample volume), mix well and let stand for 5 minutes to complex the metal ions in the water sample. Add 1 mL of 10% (m / V%) ascorbic acid solution and mix well; After 30 seconds, add 2 mL of molybdate solution (ammonium molybdate concentration of 10 g / L and potassium antimony tartrate concentration of 0.5 g / L) and mix thoroughly. Place the colorimetric tube in a constant temperature water bath and react for 15-20 minutes at 25-30℃ (error not exceeding ±0.5℃). Gently shake the colorimetric tube once every 5 minutes to ensure a full and uniform colorimetric reaction.

[0019] S4. Detection and Data Processing Spectrophotometer calibration: Before testing, calibrate the spectrophotometer with potassium dichromate standard solution at a wavelength of 700nm to ensure that the instrument absorbance reading error is ≤±0.002; during the testing process, recalibrate the instrument zero point with blank solution every 10 samples. Absorbance measurement: Using a spectrophotometer at a wavelength of 700 nm, with pure water as a reference, measure the absorbance of the solution after color development. The cuvette needs to be rinsed 3 times with the solution to be tested. Calibration curve plotting: Prepare a series of orthophosphate standard solutions of different concentrations (0.01 mg / L, 0.05 mg / L, 0.1 mg / L, 0.5 mg / L, 1.0 mg / L, 2.0 mg / L), process them according to the same digestion and color development steps as the water sample, measure the absorbance, and plot the calibration curve with the absorbance of the blank test subtracted as the ordinate and the corresponding total phosphorus content (μg) as the abscissa; Concentration calculation: Based on the calibration curve, calculate the total phosphorus content in the water sample using the formula C=m / V, where C is the total phosphorus concentration (mg / L), m is the phosphorus content (μg), and V is the water sample volume (mL). Blank tests and spiked recovery tests must be performed for each batch of samples to control detection errors and ensure data accuracy.

[0020] In step S1, for river monitoring, multiple samples should be taken from different flow velocity zones and depth layers and then mixed.

[0021] In step S2, during the digestion process, the strong oxidizing atomic oxygen produced by the decomposition of potassium persulfate oxidizes various forms of phosphorus in the water sample into orthophosphate. After digestion is completed, the digestion tube is cooled to room temperature and then taken out for use.

[0022] In step S3, under acidic conditions, orthophosphate reacts with ammonium molybdate to form phosphomolybdic heteropolyacid. Potassium antimony tartrate acts as a catalyst to accelerate the reaction. Ascorbic acid reduces the phosphomolybdic heteropolyacid to a blue complex (phosphomolybdic blue). The intensity of the blue complex's color is directly proportional to the orthophosphate concentration. The relevant reaction equations are as follows: H3PO4+12(NH4)2MoO4+24HNO3→(NH4)3PO4·12M o O3;+21NH4NO3+12H2O (NH4)3PO4·12MoO3+C6H8O6→(NH4)3PO4·10MoO3·Mo2O5+C6H6O6+2H2O In step S4, C represents the total phosphorus concentration in mg / L, m represents the phosphorus content in μg, and V represents the water sample volume in mL. Additionally, blank tests and spiked recovery tests must be performed on each batch of samples to control detection errors and ensure data accuracy.

[0023] Determination of total phosphorus in clean surface water Sample collection and preservation: Water samples were collected from different areas of the lake near the shore, in the center of the lake, and at different depths. After mixing, sulfuric acid was added to adjust the pH to 1, and the samples were stored at 4°C. The tests were completed within 6 hours. Sample pretreatment: The digestion solution used in this experiment was a 5% potassium persulfate solution, which has a strong oxidizing ability. The 5% potassium persulfate digestion solution was verified by a 0.5 mg / L orthophosphate standard solution, and the recovery rate was 99.2%, meeting the requirements. Take 10 mL of a well-mixed water sample and add 2 mL of the above digestion solution. Digest at 122℃ for 30 minutes, then cool to room temperature. Colorimetric reaction: Add 0.1 mL of 0.1 mol / L EDTA-2Na solution, mix well and let stand for 5 minutes; add 1 mL of 10% ascorbic acid solution and mix well; after 30 seconds, add 2 mL of molybdate solution and react in a constant temperature water bath at 28℃ for 18 minutes, shaking once every 5 minutes during the reaction. Detection and Data Processing: The spectrophotometer was calibrated, with an absorbance indication error of 0.001. The absorbance measured at 700 nm wavelength was 0.230. Based on the calibration curve (y=2.305x+0.001), the total phosphorus concentration of the water sample was calculated to be 0.099 mg / L. A blank test was performed, with an absorbance of 0.002. The spiked recovery test showed a recovery rate of 98.5%, indicating reliable results.

[0024] Determination of total phosphorus in industrial wastewater Sample collection and preservation: Samples were taken from industrial wastewater discharge outlets, and the pH was adjusted to 1 with sulfuric acid. The samples were then stored at 4°C and tested within 12 hours. Sample pretreatment: The recovery rate was verified to be 100.5% using 5% potassium persulfate digestion solution; 5 mL of filtrate was added to 1 mL of digestion solution, digested at 124 °C for 30 minutes, and then cooled to room temperature. Colorimetric reaction: Add 0.05 mL of 0.1 mol / L EDTA-2Na solution, mix well and let stand for 5 minutes; add 1 mL of 10% ascorbic acid solution and mix well; after 30 seconds, add 2 mL of molybdate solution and react in a constant temperature water bath at 25℃ for 20 minutes. Detection and data processing: The absorbance was measured to be 1.732. Based on the calibration curve, the total phosphorus concentration in the water sample was calculated to be 1.728 mg / L. The absorbance of the blank test was 0.002, and the recovery rate of the spiked recovery test was 97.8%, indicating that the results are reliable.

[0025] Example 2 Please see Figure 1 The present invention provides a technical solution: Ascorbic acid: as a reducing agent, it reduces phosphomolybdic heteropolyacid to phosphomolybdic blue, enhances the sensitivity of the colorimetric reaction, and ensures the accuracy of the detection results. Its concentration is 10% to ensure sufficient reducing power in the reaction system. Molybdate: Composed of ammonium molybdate (10 g / L) and potassium antimony tartrate (0.5 g / L). Ammonium molybdate reacts with orthophosphate to form phosphomolybdic heteropolyacid. Potassium antimony tartrate catalyzes this reaction, accelerating the reaction rate and improving the color development efficiency. Chelating agents: such as disodium ethylenediaminetetraacetate (EDTA-2Na) at a concentration of 0.1 mol / L, can complex with various metal ions in water samples, such as iron, copper, calcium, and magnesium, to eliminate the interference of metal ions on the colorimetric reaction, stabilize the reaction system, and improve the anti-interference ability of the determination method.

[0026] Selecting representative sampling points and standardizing sampling methods ensures that the samples accurately reflect the water conditions. Adding sulfuric acid to adjust the pH and refrigerating the samples effectively inhibits microbial activity and phosphorus form transformation, ensuring the stability of the samples before testing and laying the foundation for accurate subsequent determination. Under the digestion conditions of 120℃ and 30 minutes, the intelligent digester can efficiently oxidize various forms of phosphorus to orthophosphate with potassium persulfate, and the digestion process is controllable, improving the thoroughness and consistency of phosphorus form transformation. The strict reagent addition order, adding ascorbic acid first and then molybdate solution 30 seconds later, ensures the orderly progress of the reaction. In acidic media, orthophosphate reacts with ammonium molybdate to form phosphomolybdic heteropolyacid. Potassium antimony tartrate catalyzes and accelerates the reaction, and ascorbic acid reduces it to phosphomolybdic blue. The color intensity of this blue complex is directly proportional to the concentration of orthophosphate, and the reaction is highly specific, providing a good chemical basis for accurate detection. Measurement is performed at a wavelength of 700 nm using a spectrophotometer, and calculations are made in conjunction with calibration curves, making the method standardized. Blank tests and spiked recovery tests can effectively control detection errors and ensure data accuracy. The calibration curve shows good linearity in the concentration range of 0.01-2.0 mg / L (R²>0.999), the relative standard deviation (RSD) of repeated measurements on the same water sample is <3%, and the spiked recovery rate is between 95% and 105%.

[0027] Calibration curve table Precision test data sheet Spiked Recycling Test Data Sheet Anti-interference performance test data table It demonstrates the high precision and accuracy of the method, and is applicable to a variety of complex water samples, such as industrial wastewater and polluted surface water. Combined with intelligent analysis systems and geographic information systems, it can monitor data in real time and perform spatial distribution analysis, providing efficient and reliable data support for wastewater treatment process adjustment, lake eutrophication assessment and treatment, etc., with a wide range of application scenarios. Ascorbic acid at a concentration of 10% ensures sufficient reducing power, efficiently reducing phosphomolybdic heteropolyacid to phosphomolybdic blue, enhancing the sensitivity of the colorimetric reaction, and enabling accurate detection of low concentrations of total phosphorus, thus improving the method's ability to detect trace phosphorus. Molybdate, ammonium molybdate at 10 g / L, reacts with orthophosphate to generate phosphomolybdic heteropolyacid. Potassium antimony tartrate at 0.5 g / L acts as a catalyst to accelerate the reaction rate, improve colorimetric efficiency, shorten reaction time, and ensure the sufficiency of the reaction. Chelating agents, such as EDTA-2Na at 0.1 mol / L, can complex with various metal ions in the water sample, such as iron, copper, calcium, and magnesium, effectively eliminating the interference of these metal ions on the colorimetric reaction, stabilizing the reaction system, and significantly improving the anti-interference ability of the determination method, making the method applicable to complex water samples. These reagents have a long shelf life when stored at 4°C in the dark, and their performance is stable during use, ensuring the consistency and reliability of test results from different batches and reducing test errors caused by reagent problems.

[0028] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A method for determining total phosphorus with enhanced anti-interference sensitivity, characterized in that: Includes the following steps: S1. Sample Collection and Preservation In ecological and environmental monitoring, if the collected water samples cannot be analyzed in time, sulfuric acid should be added to adjust the pH to about 1, and the samples should be stored at 4°C and tested within 24 hours. S2, Sample Pretreatment Sample pretreatment includes digestion, with potassium persulfate solution at a concentration of 5% as the digestion solution, and digestion conditions of 120-124℃ for 30 minutes; S3, Colorimetric reaction Take an appropriate amount of digested water sample into a colorimetric tube, add 1 mL of ascorbic acid solution with a concentration of 10%, mix well, and after 30 seconds add 2 mL of molybdate solution with an ammonium molybdate concentration of 10 g / L and a potassium antimony tartrate concentration of 0.5 g / L, and mix thoroughly. S4. Detection and Data Processing Using a spectrophotometer, at a wavelength of 700 nm, with pure water as a reference, the absorbance of the solution after color development was measured. A series of orthophosphate standard solutions of different concentrations were prepared, and the same digestion and color development steps as those for the water samples were followed. The absorbance was then measured.

2. The method for determining total phosphorus with anti-interference and enhanced sensitivity according to claim 1, characterized in that: In step S1, for river monitoring, multiple samples should be taken from different flow velocity zones and depth layers and then mixed.

3. The method for determining total phosphorus with anti-interference and enhanced sensitivity according to claim 1, characterized in that: In step S3, in an acidic medium, orthophosphate reacts with ammonium molybdate to generate phosphomolybdic heteropolyacid. Potassium antimony tartrate acts as a catalyst to accelerate the reaction. Ascorbic acid reduces the phosphomolybdic heteropolyacid to a blue complex (phosphomolybdic blue). The intensity of the blue complex is proportional to the concentration of orthophosphate.

4. The method for determining total phosphorus with anti-interference and enhanced sensitivity according to claim 1, characterized in that: In step S4, C represents the total phosphorus concentration in mg / L, m represents the phosphorus content in μg, and V represents the water sample volume in mL. Additionally, blank tests and spiked recovery tests must be performed on each batch of samples to control detection errors and ensure data accuracy.

5. A specific colorimetric reagent for use in any one of the methods described in claims 1-4, characterized in that: It consists of the following reagents: Ascorbic acid: its concentration is 10% to ensure sufficient reducing power in the reaction system; Molybdate: Composed of ammonium molybdate (10 g / L) and potassium antimony tartrate (0.5 g / L); Chelating agent: such as disodium ethylenediaminetetraacetate (EDTA-2Na), with a concentration of 0.1 mol / L.

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