Ammonia nitrogen detection system and application method thereof

Abstract

The invention discloses an ammonia nitrogen detection system and an application method thereof, and ammonia nitrogen detection test paper, the ammonia nitrogen detection system is prepared by the following steps: step SA1) preparing a dipping mixed solution, the dipping mixed solution comprises: a potassium sodium tartrate solution with a concentration of 3-60 g / L; a sodium salicylate solution with a concentration of 20-320 g / L; the concentration of the sodium nitroprusside solution is 0.1 to 0.8 g / L; and deionized water. On the basis of the principle of salicylic acid-pypocholoride spectrophotometry, the impregnated test paper, the reagent tube and the standard colorimetric card are combined, and the rapid ammonia nitrogen detection system special for medium-concentration sewage detection is successfully developed. The toxicity problem of mercury iodide in a Nessler reagent method and the toxicity problem of phenol in a phenol-pypocholoride spectrophotometric method are avoided, main reagents are non-toxic and harmless to a human body, interference of metal ions in a water sample can be effectively eliminated by adopting sodium potassium tartrate tetrahydrate as a chelating agent, and the detection stability and accuracy are improved.

Description

Technical Field

[0001] The present invention relates to the field of water quality detection, and in particular to an ammonia nitrogen detection system and an application method thereof. Background Art

[0002] As one of the basic elements of cell composition, nitrogen is generally distributed evenly in nature, and the nitrogen cycle continues stably. However, due to the influence of some human behaviors, the balanced nitrogen distribution in water bodies has been broken and the nitrogen cycle has changed. Globally, sewage generated by life, agriculture and some industrial activities (including food processing, papermaking and printing and dyeing industries, etc.) contains a large amount of nitrogen derivatives, such as ammonia nitrogen (NH4 + -N), nitrite nitrogen (NO2 - -N) and nitrate nitrogen (NO3 - -N) and so on. These untreated or only partially treated sewage is discharged into natural water bodies, especially the ammonia nitrogen in the water will stimulate the acceleration of eutrophication of water bodies, leading to the rapid and massive reproduction of algae in the water. The large-scale growth of algae will cause environmental pollution phenomena such as algal blooms and red tides, thereby affecting the biodiversity of aquatic organisms in water bodies. At the same time, the deterioration of water quality in natural water bodies will also seriously endanger the safety of surrounding life forms. Many data show that the eutrophication problem of water bodies in my country is still a key environmental problem that needs to be solved urgently, and it is particularly important to detect the concentration of ammonia nitrogen in water bodies.

[0003] Among the main methods for measuring ammonia nitrogen at present, spectrophotometry is the most widely used, most practical and most accurate method, and among the spectrophotometry methods, Nessler's reagent method, salicylic acid method and indophenol blue method are the most used. For the existing technical solutions, it can be mainly divided into two categories: laboratory detection and on-site rapid detection. Laboratory detection refers to the sealing of water samples after sampling and sending them to the laboratory for detection by professionals. The main methods for detecting ammonia nitrogen in the laboratory are Nessler's reagent spectrophotometry and salicylic acid-hypochlorite photometry. Although laboratory detection has the advantages of high accuracy, strong stability and high safety, it still has some disadvantages, especially in the transportation of water samples, it may be affected by various environmental conditions, resulting in changes in pollutants in the water samples, thereby affecting the accuracy of the experimental results. In order to improve the efficiency of on-site detection, it is currently more common to use rapid kit detection methods. The use of rapid detection kits can achieve on-site rapid detection, no professional personnel are required for detection, and the detection accuracy is high.

[0004] However, the main problems existing in the prior art are: 1) the mercuric iodide in the Nessler reagent method is highly toxic and is also interfered by various metal ion factors, which affects the stability and accuracy of its use; 2) the phenol in the phenol-hypochlorite photometric method is also toxic, which limits its use; 3) in the traditional ammonia nitrogen determination, the sampling personnel need to quickly send the water samples taken on site to the laboratory for testing by professional laboratory personnel. The testing time is relatively long (about one hour) and there is a hysteresis, especially for flowing water bodies (rivers, lakes, etc.), the hysteresis is stronger; 4) the existing rapid test kit has strict requirements on the concentration gradient of ammonia nitrogen during use, and can only detect water samples with a smaller ammonia nitrogen concentration range.

[0005] Therefore, there is an urgent need to develop a rapid ammonia nitrogen detection system that is safe, non-toxic, easy to operate, fast to detect and applicable to a wide concentration range to meet the actual needs of water quality monitoring. Summary of the invention

[0006] The purpose of the present invention is to provide an ammonia nitrogen detection system and an application method thereof, so as to solve the problems existing in the prior art in the detection of ammonia nitrogen content in water quality.

[0007] To achieve the above object, the present invention provides the following technical solution, an ammonia nitrogen detection test paper, comprising the following preparation steps:

[0008] Step SA1) preparing a mixed solution for impregnation, wherein the mixed solution for impregnation comprises:

[0009] Potassium sodium tartrate solution, concentration 3-60g / L;

[0010] Sodium salicylate solution, concentration 20-320g / L;

[0011] Sodium nitrosoferricyanide solution, concentration 0.1-0.8g / L;

[0012] Deionized water;

[0013] Wherein, the potassium sodium tartrate solution is used as a chelating agent, the sodium salicylate solution is used as a color developer, the sodium nitrosoferrocyanide solution is used as a catalyst, and the deionized water is used as a solvent;

[0014] Step SA2) placing the fixed-speed filter paper in the impregnation mixed solution for shaking and soaking;

[0015] Step SA3) Hang the soaked fixed-speed filter paper in the air to dry in the dark for 12-18 hours;

[0016] Step SA4) Cut the dried filter paper into test paper and store it at low temperature and away from light.

[0017] Preferably, in step SA2, the shaking and soaking time is 120-240 minutes.

[0018] Preferably, in step SA3, the drying temperature is 15-35°C.

[0019] Preferably, before step SA1, a pretreatment step is also included, and the pretreatment step includes:

[0020] Step SA01) pre-soaking the fixed-speed filter paper in deionized water for 30-60 minutes;

[0021] Step SA02) placing the soaked filter paper in a drying oven and pre-drying at 50-60° C. for 1-2 hours;

[0022] Step SA03) cutting the pre-dried filter paper into required sizes for later use;

[0023] The impregnation mixed solution prepared in step SA04) is ultrasonically treated for 15-30 minutes before use.

[0024] An ammonia nitrogen detection test paper reagent tube comprises the following preparation steps:

[0025] Step SB1) Preparation of oxidant

[0026] The oxidant is sodium hypochlorite solution, in which the effective chlorine concentration is 3.5g / L, and the free OH - The concentration is 0.75 mol / L (in terms of NaOH);

[0027] Step SB2) Prepare reagent tube

[0028] Add 0.8-2 ml of the oxidant into a centrifuge tube with a cap.

[0029] A standard colorimetric card comprises the following preparation steps:

[0030] Step SC1) preparing ammonium chloride standard solutions with ammonia nitrogen concentration gradient, the concentrations of which are 2.0 mg / L, 5.0 mg / L, 8.0 mg / L, 10.0 mg / L, 15.0 mg / L, 20.0 mg / L, and 50.0 mg / L;

[0031] Step SC2) adding each gradient ammonia nitrogen standard solution into the ammonia nitrogen test paper reagent tube respectively;

[0032] Step SC3) Add 2 ammonia nitrogen test strips to each reagent tube;

[0033] Step SC4) Shake to mix, and let stand until the color is stable;

[0034] Step SC5) preparing a standard color block according to the color development result;

[0035] Step SC6) Arrange the standard color blocks in order according to the concentration of the ammonia nitrogen standard solution to obtain a standard colorimetric card.

[0036] An ammonia nitrogen detection system comprises the ammonia nitrogen detection test paper, an ammonia nitrogen detection test paper reagent tube and a standard colorimetric card.

[0037] An application method of an ammonia nitrogen detection system, the application method is based on the ammonia nitrogen detection system, and the application method comprises the following steps:

[0038] Step SD1) Take a water sample with ammonia nitrogen concentration to be tested and add it to the ammonia nitrogen test paper reagent tube, and shake it for 3-5 seconds;

[0039] Step SD2) Add 2 pieces of ammonia nitrogen test paper into the ammonia nitrogen test paper reagent tube and shake for 3-5 seconds;

[0040] Step SD3) let the solution stand until the color is stable, and compare the color result with the standard colorimetric card to obtain the ammonia nitrogen content in the water sample to be tested.

[0041] Preferably, the application method further comprises a water sample pretreatment step:

[0042] Step SD01) Check the turbidity of the water sample and filter it if necessary;

[0043] Step SD02) detects whether the ammonia nitrogen content in the water sample to be tested is within the range of 2.0-50.0 mg / L. If it exceeds the detection range, the water sample is appropriately diluted to within the detection range.

[0044] Step SD03) If dilution is performed, the measurement result needs to be multiplied by the corresponding dilution factor.

[0045] Preferably, parallel sample measurements are performed during the detection process, and a reagent blank control should be set for each detection.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1) Based on the principle of salicylic acid-hypochlorite photometry, the present application successfully developed an ammonia nitrogen rapid detection system specifically for medium-concentration sewage detection by combining an immersion test paper, a reagent tube and a standard colorimetric card. The system uses salicylic acid instead of phenol, avoiding the toxicity problem of mercuric iodide in the Nessler reagent method and the toxicity problem of phenol in the phenol-hypochlorite photometry. The main reagents are non-toxic and harmless to the human body. Among them, the use of potassium sodium tartrate as a chelating agent can effectively eliminate the interference of metal ions in water samples, improve the stability and accuracy of detection, and introduce sodium nitrosoferrocyanide as a catalyst to accelerate the color development reaction speed and ensure the detection efficiency. The reliability of the detection results is ensured through a specific test paper preparation process and pretreatment steps;

[0048] 2) The ammonia nitrogen test paper of the present application has the characteristics of small size and simple preparation process. By strictly controlling the ratio range of each component in the impregnation mixed solution, combined with a specific immersion time and drying temperature, the test paper has good color development performance. The prepared oxidant controls the effective chlorine concentration and free OH - Concentration ensures the smooth progress of the reaction. The standard colorimetric card is prepared with standard solutions of multiple concentration gradients to meet the detection needs of different water samples. The detection range of the system is 2.0-50.0 mg / L, which is particularly suitable for the detection of medium-concentration sewage.

[0049] 3) The detection method provided in this application is simple and fast to operate. No other instruments and accessories are required during use, and no professional personnel are required to operate. The system integrates test strips, reagent tubes and colorimetric cards, which is convenient for rapid on-site detection. The test strip configuration process and on-site detection operation process are simple. The detection can be completed by simple steps such as shaking, adding test strips, standing for color development and colorimetry. The comprehensive cost of the system is lower than that of laboratory detection methods, which is about one percent of the test cost. The test strip area is small, which reduces the material cost;

[0050] 4) The detection system and method of the present application are applicable to the detection of ammonia nitrogen content in various types of water bodies, including municipal sewage, rural domestic sewage, food processing industry wastewater, papermaking industry wastewater, printing and dyeing industry wastewater, surface water, groundwater, etc. By setting up water sample pretreatment steps and quality control measures, the reliability of the detection results is further guaranteed. The system overcomes the technical barriers existing in the prior art and provides a safe, fast, economical and accurate solution for detecting ammonia nitrogen content in water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The present invention is a flow chart for preparing the ammonia nitrogen test paper;

[0052] Figure 2 It is a flow chart of the pretreatment steps of the ammonia nitrogen detection test paper of the present invention;

[0053] Figure 3 The present invention is a flow chart for preparing the ammonia nitrogen detection test paper reagent tube;

[0054] Figure 4 The present invention is a flow chart of the preparation of the standard colorimetric card;

[0055] Figure 5 It is a flow chart of the application method of the ammonia nitrogen detection system of the present invention;

[0056] Figure 6 The present invention is a flowchart of the water sample pretreatment steps of the application method of the present invention. DETAILED DESCRIPTION

[0057] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] In the description of the invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0059] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] In the description of the invention, it should be noted that the execution order of the steps is not limited by the serial numbers, and the order of some steps can be changed, the steps can be executed simultaneously, the steps can be executed separately, etc., all of which are within the protection scope of this application.

[0061] See also Figure 1 The present invention provides an ammonia nitrogen detection test paper, comprising the following preparation steps:

[0062] Step SA1) preparing a mixed solution for impregnation, wherein the mixed solution for impregnation comprises:

[0063] Potassium sodium tartrate solution, concentration 3-60g / L;

[0064] Sodium salicylate solution, concentration 20-320g / L;

[0065] Sodium nitrosoferricyanide solution, concentration 0.1-0.8g / L;

[0066] Deionized water;

[0067] Wherein, the potassium sodium tartrate solution is used as a chelating agent, the sodium salicylate solution is used as a color developer, the sodium nitrosoferrocyanide solution is used as a catalyst, and the deionized water is used as a solvent;

[0068] Step SA2) placing the fixed-speed filter paper in the impregnation mixed solution for shaking and soaking;

[0069] Step SA3) Hang the soaked fixed-speed filter paper in the air to dry in the dark for 12-18 hours;

[0070] Step SA4) Cut the dried filter paper into test paper and store it at low temperature and away from light.

[0071] Specifically, in the ammonia nitrogen test paper preparation method provided by the present application, a combination formula of three core reagents is used, wherein potassium sodium tartrate can form a stable complex with the metal ions in the water sample as a chelating agent, effectively avoiding the interference of metal ions on the test results; sodium salicylate is used as a color developer, and the monochloramine generated by reacting with ammonia in the water sample under alkaline conditions undergoes a color reaction, and 5-aminosalicylic acid and quinone imine are sequentially generated, and finally condensed into a blue product with salicylic acid, and the color development effect is stable and highly sensitive; sodium nitrosoferricyanide can significantly improve the color development reaction rate as a catalyst. This formula not only avoids the toxic reagents (such as mercuric iodide, phenol) used in the traditional method, but also ensures the accuracy and stability of the detection by the synergistic effect of the three reagents. In addition, using fixed-speed filter paper as a carrier, the reagent can be evenly distributed on the filter paper after soaking, drying and other process preparations, and the repeatability of the detection is improved.

[0072] As an additional explanation, the current water quality testing methods can be mainly divided into laboratory testing and on-site rapid testing. Laboratory testing refers to the sealing of water samples after sampling and sending them to the laboratory for testing by professionals. The main methods for detecting ammonia nitrogen in water in the laboratory are Nessler's reagent spectrophotometry and salicylic acid-hypochlorite photometry. The advantages of laboratory testing are: high accuracy, strong stability, and high safety, but there are still some disadvantages, especially during the transportation of water samples, it may be affected by various environmental conditions, causing changes in pollutants in the water samples, thereby affecting the accuracy of the experimental results; at the same time, a lot of manpower and material resources will be consumed during transportation and testing, resulting in high inspection costs. In order to improve the efficiency of on-site testing, the rapid test kit detection method is currently more common. The use of rapid test kits can achieve rapid on-site testing, without the need for professional personnel to conduct testing, and the detection accuracy is high.

[0073] As an additional note, ammonia nitrogen exists in water in the form of free ammonia or ammonium salts. The main sources of ammonia nitrogen in water include nitrogen-containing organic matter in human production and life, as well as nitrates and nitrites present in groundwater, which produce a large amount of ammonia nitrogen under the action of aerobic / anaerobic microorganisms. Ammonia nitrogen is one of the important water quality indicators, and its detection is crucial. The current determination methods mainly include Nessler's reagent spectrophotometry, phenol salt photometry, and salicylic acid-hypochlorite photometry. The spectrophotometric method for determining the concentration of ammonia nitrogen in water has the characteristics of high accuracy and strong stability. It is widely used and is also the main detection method of national standards. However, the determination of ammonia nitrogen concentration in water samples by spectrophotometry needs to be completed by professional laboratory personnel in the laboratory, which cannot meet the needs of rapid detection of flowing water bodies on site and water quality detection in remote areas. At present, scholars at home and abroad have developed ammonia nitrogen rapid detection kits for on-site field detection. The reaction principles of various kits are different, the detection ranges are different, and the performance is different.

[0074] As an additional explanation, the principle of the rapid test kit using Nessler's colorimetric method is to use Nessler's reagent (alkaline solution of HgI2 and KI) to react with free ammonia / ammonium salt in water to form a yellow-brown complex, and the ammonia nitrogen concentration is judged by color. The result is reflected in the NH4 + The concentration of the reagent kit is low, and the kit is greatly affected by metal ions during use. Although the effect can be eliminated by adding potassium sodium tartrate, the overall stability is poor. At the same time, mercuric iodide is toxic and requires strict protection during preparation. In addition, rubber gloves should be worn as much as possible during use to avoid contact with the skin or direct contact with food after contact, which may cause poisoning.

[0075] As an additional explanation, the reaction principle of phenol-hypochlorite photometry is: under alkaline conditions (usually considered to be between pH: 10-12), ammonia in water reacts with hypochlorite in the added reagent to generate monochloramine, and monochloramine reacts with phenol (using sodium nitrosoferrocyanide as a catalyst) to generate indophenol blue, and the ammonia nitrogen concentration is determined by color. Compared with Nessler's reagent method, this rapid test kit avoids the problem of mercury pollution, but it has its disadvantages: the added phenol is highly toxic and has a certain volatility, which is extremely harmful to the human body.

[0076] Therefore, the mercuric iodide in the Nessler reagent method is highly toxic and is interfered by various metal ion factors, which affects the stability and accuracy of its use. The phenol in the phenol-hypochlorite photometry is also toxic, which limits its use. The salicylic acid-hypochlorite photometry principle adopted in this application is similar to the phenol-hypochlorite photometry. It is also based on the reaction of ammonia in water with hypochlorite in the solution to generate monochloramine, and salicylic acid is used instead of phenol. The reaction generates 5-aminosalicylic acid, quinone imine, and quinone imine in sequence, and then condenses with salicylic acid to form phenol blue. The ammonia nitrogen concentration is judged by color. This detection method is safe and non-toxic and suitable for large-scale daily use.

[0077] In certain embodiments, in step SA2, the oscillation soaking time is 120-240 minutes. Specifically, the oscillation soaking process is a key step for the reagent to fully contact and combine with the filter paper. If the time is too short, the reagent will not be fully impregnated, affecting the color development effect; if the time is too long, the reagent may be wasted and the filter paper strength may decrease. The immersion time of 120-240 minutes determined by experimental optimization can ensure that the reagent is fully impregnated into the filter paper fiber, maintain the physical strength of the filter paper, and improve the efficiency of test paper preparation.

[0078] In some embodiments, in step SA3, the drying temperature is 15-35°C. Specifically, the selection of this temperature range fully considers the stability requirements of the reagents. Too high a temperature will cause the reagents to decompose or deteriorate, especially sodium salicylate and sodium nitrosoferrocyanide are more sensitive to temperature; too low a temperature will prolong the drying time and affect production efficiency. The temperature range of 15-35°C can not only ensure the chemical stability of the reagents, but also complete the drying process within a reasonable time. At the same time, this temperature range is easy to control, which is conducive to industrial production.

[0079] See also Figure 2 In some embodiments, before step SA1, a pre-processing step is also included, and the pre-processing step includes:

[0080] Step SA01) pre-soaking the fixed-speed filter paper in deionized water for 30-60 minutes;

[0081] Step SA02) placing the soaked filter paper in a drying oven and pre-drying at 50-60° C. for 1-2 hours;

[0082] Step SA03) cutting the pre-dried filter paper into required sizes for later use;

[0083] The impregnation mixed solution prepared in step SA04) is ultrasonically treated for 15-30 minutes before use.

[0084] Specifically, the pretreatment step significantly improves the preparation quality of the test paper. Pre-soaking in deionized water can remove impurities that may exist in the filter paper to prevent impurities from interfering with the color development reaction; pre-drying at 50-60°C can remove residual moisture in the filter paper to prepare for subsequent impregnation; ultrasonic treatment of the impregnation solution can improve the uniformity of the solution and prevent reagent precipitation or stratification. The setting of these pretreatment steps greatly improves the quality stability of the final product.

[0085] See also Figure 3 According to another aspect of the present application, there is also provided an ammonia nitrogen detection test paper reagent tube, comprising the following preparation steps:

[0086] Step SB1) Preparation of oxidant

[0087] The oxidant is sodium hypochlorite solution, in which the effective chlorine concentration is 3.5g / L, and the free OH - The concentration is 0.75 mol / L (in terms of NaOH);

[0088] Step SB2) Prepare reagent tube

[0089] Add 0.8-2 ml of the oxidant into a centrifuge tube with a cap.

[0090] Specifically, the effective chlorine concentration of 3.5 g / L can ensure that it reacts with ammonia in the water sample to produce an appropriate amount of monochloramine, while free OH - The concentration of 0.75 mol / L ensures that the reaction is carried out in a suitable alkaline environment. The synergistic effect of these two parameters can ensure the complete color development reaction. The use of centrifuge tubes with caps can prevent the oxidant from volatilizing and contaminating, and is also convenient for shaking operations.

[0091] See also Figure 4 According to another aspect of the present application, a standard colorimetric card is also provided, comprising the following preparation steps:

[0092] Step SC1) preparing ammonium chloride standard solutions with ammonia nitrogen concentration gradient, the concentrations of which are 2.0 mg / L, 5.0 mg / L, 8.0 mg / L, 10.0 mg / L, 15.0 mg / L, 20.0 mg / L, and 50.0 mg / L;

[0093] Step SC2) adding each gradient ammonia nitrogen standard solution into the ammonia nitrogen test paper reagent tube respectively;

[0094] Step SC3) Add 2 pieces of ammonia nitrogen test paper to each reagent tube;

[0095] Step SC4) Shake to mix, and let stand until the color is stable;

[0096] Step SC5) preparing a standard color block according to the color development result;

[0097] Step SC6) Arrange the standard color blocks in order according to the concentration of the ammonia nitrogen standard solution to obtain a standard colorimetric card.

[0098] Specifically, the standard colorimetric card preparation method selects seven concentration gradients from 2.0 mg / L to 50.0 mg / L. The low concentration points (2.0, 5.0, 8.0 mg / L) can meet the detection needs of cleaner water bodies, the medium concentration points (10.0, 15.0, 20.0 mg / L) are suitable for general sewage detection, and the high concentration point (50.0 mg / L) can be used for the detection of heavily polluted water bodies. Through this reasonable concentration gradient design, combined with the preparation of standard color blocks, accurate detection of different types of water bodies can be achieved.

[0099] According to another aspect of the present application, an ammonia nitrogen detection system is also provided, which includes an ammonia nitrogen detection test paper, an ammonia nitrogen detection test paper reagent tube, and a standard colorimetric card.

[0100] See also Figure 5 According to another aspect of the present application, an application method of an ammonia nitrogen detection system is also provided. The application method is based on the use of the ammonia nitrogen detection system, and the application method includes the following steps:

[0101] Step SD1) Take a water sample with ammonia nitrogen concentration to be tested and add it to the ammonia nitrogen test paper reagent tube, and shake it for 3-5 seconds;

[0102] Step SD2) Add 2 pieces of ammonia nitrogen test paper into the ammonia nitrogen test paper reagent tube and shake for 3-5 seconds;

[0103] Step SD3) Let the solution stand until the color is stable, and compare the color result with the standard colorimetric card to obtain the ammonia nitrogen content in the water sample to be tested.

[0104] Specifically, the shaking operation ensures that the sample and the reagent are fully mixed. The time control of the two shakings (3-5 seconds) can ensure sufficient mixing without causing damage to the test paper. The entire detection process is simple and fast, which greatly improves the detection efficiency.

[0105] See also Figure 6 In some embodiments, the application method further comprises a water sample pretreatment step:

[0106] Step SD01) Check the turbidity of the water sample and filter it if necessary;

[0107] Step SD02) detects whether the ammonia nitrogen content in the water sample to be tested is within the range of 2.0-50.0 mg / L. If it exceeds the detection range, the water sample is appropriately diluted to within the detection range.

[0108] Step SD03) If dilution is performed, the measurement result needs to be multiplied by the corresponding dilution factor.

[0109] Specifically, turbidity control can prevent suspended matter from interfering with the color development reaction; concentration range check and dilution operations ensure that the measurement results fall within the linear range of the method; accurate test results can be obtained by multiplying the dilution factor.

[0110] In some embodiments, parallel sample measurements are performed during the detection process, and a reagent blank control should be set for each detection.

[0111] Specifically, parallel sample measurements can evaluate the precision of the method, and setting up blank controls can eliminate interference from the reagent background. The implementation of these quality control measures makes the test results more scientific and reliable, meeting the needs of practical applications.

[0112] Example 1

[0113] 1. Preparation of ammonia nitrogen test paper

[0114] Preprocessing steps:

[0115] (1) Soak the fixed-rate filter paper in deionized water for 45 minutes;

[0116] (2) Place the soaked filter paper in a drying oven and pre-dry at 55°C for 1.5 hours;

[0117] (3) Cut the pre-dried filter paper into strips of 10 mm × 50 mm for later use;

[0118] (4) The prepared impregnation mixed solution was ultrasonically treated for 20 minutes before use.

[0119] Preparation steps:

[0120] (1) Preparation of impregnation mixed solution:

[0121] Potassium sodium tartrate solution, concentration 30g / L;

[0122] Sodium salicylate solution, concentration 160g / L;

[0123] Sodium nitrosoferricyanide solution, concentration 0.5g / L;

[0124] The solvent is deionized water.

[0125] (2) placing the pretreated fixed-rate filter paper in the impregnation mixed solution and shaking and soaking it at 25° C. for 180 minutes;

[0126] (3) Hang the soaked filter paper in the dark at 25°C to dry for 15 hours;

[0127] (4) Cut the dried filter paper into 5 mm × 5 mm test papers and store them at 4°C away from light.

[0128] 2. Preparation of Reagent Tubes

[0129] (1) Prepare sodium hypochlorite solution, adjust the effective chlorine concentration to 3.5 g / L, and the free OH- concentration to 0.75 mol / L;

[0130] (2) Take a centrifuge tube with a lid and add 1.5 ml of the prepared sodium hypochlorite solution.

[0131] 3. Preparation of standard colorimetric cards

[0132] (1) Prepare standard ammonium chloride solutions with concentrations of 2.0, 5.0, 8.0, 10.0, 15.0, 20.0, and 50.0 mg / L respectively;

[0133] (2) Add each standard solution into the reagent tube respectively;

[0134] (3) Add 2 test strips to each reagent tube;

[0135] (4) Shake for 15 seconds and let stand for 5 minutes until the color is stable;

[0136] (5) Record the color corresponding to each concentration and make a standard colorimetric card.

[0137] 4. Application Method

[0138] The influent of a sewage treatment plant was used as the test sample to detect the ammonia nitrogen content:

[0139] (1) Water sample pretreatment:

[0140] The turbidity of the water sample was detected to be 45 NTU, which required filtration treatment;

[0141] Filtered with 0.45 μm membrane;

[0142] The filtrate was taken for testing.

[0143] (2) Detection steps:

[0144] Take the pretreated water sample and add it to the reagent tube, and shake it for 4 seconds;

[0145] Add 2 ammonia nitrogen test strips and shake for 4 seconds;

[0146] Let it stand for 5 minutes until the color is stable, and compare it with the standard color chart.

[0147] (3) Result analysis:

[0148] The color is dark blue, and the concentration is about 15.0 mg / L according to the colorimetric card;

[0149] The result determined by the standard method (Nessler's reagent spectrophotometry) was 15.3 mg / L; the relative error was 2.0%.

[0150] 5. Verification of test results

[0151] Test different types of water samples separately:

[0152] (1) Municipal sewage (n = 10):

[0153] Ammonia nitrogen concentration range: 8.5-25.6 mg / L

[0154] Average recovery rate: 97.5%

[0155] Relative standard deviation: 2.3%

[0156] (2) Rural domestic sewage (n = 10):

[0157] Ammonia nitrogen concentration range: 12.3-35.8mg / L

[0158] Average recovery rate: 98.2%

[0159] Relative standard deviation: 2.5%

[0160] (3) Food processing wastewater (n=10):

[0161] Ammonia nitrogen concentration range: 18.5-45.6 mg / L

[0162] Average recovery rate: 97.8%

[0163] Relative standard deviation: 2.4%

[0164] Example 2

[0165] This example is based on Example 1, but the reagent concentration and preparation conditions are changed. 1. Changes in reagent concentration:

[0166] The concentration of potassium sodium tartrate solution increased to 45g / L

[0167] The concentration of sodium salicylate solution was increased to 240 g / L

[0168] The concentration of sodium nitrosoferricyanide solution increased to 0.6g / L

[0169] 2. Changes in preparation conditions:

[0170] The immersion temperature was increased to 30°C

[0171] The shaking soaking time is extended to 200 minutes and the drying time is extended to 16 hours.

[0172] 3. Application method

[0173] Take the wastewater from a paper mill as the test sample:

[0174] (1) Water sample pretreatment:

[0175] The original turbidity is 68NTU, which requires filtration treatment;

[0176] Filter with multiple layers of filter paper;

[0177] Take the filtrate for testing.

[0178] (2) Test results:

[0179] The measured value of this method: 32.5mg / L

[0180] Standard method determination value: 33.1mg / L

[0181] Relative error: 1.8%

[0182] 4. Performance evaluation:

[0183] Detection sensitivity increased by about 15%

[0184] Color development time shortened to 3 minutes

[0185] But the reagent cost increases by about 50%

[0186] The preparation cycle is extended by about 20%

[0187] Example 3

[0188] This example explores the effect of different pH conditions on the detection effect.

[0189] 1. Preparation conditions are the same as in Example 1

[0190] 2. pH influence study:

[0191] Adjust the pH of the 10.0 mg / L standard solution to: pH = 6.0 pH = 7.0 pH = 8.0 pH = 9.0 pH = 10.0

[0192] 3. Test results:

[0193] (1) pH = 6.0:

[0194] Average measured value: 9.2mg / L Relative error: 8.0%

[0195] Color development time: 8 minutes

[0196] (2) pH = 7.0:

[0197] Average measured value: 9.6mg / L Relative error: 4.0%

[0198] Color development time: 6 minutes

[0199] (3) pH = 8.0:

[0200] Average measured value: 9.8mg / L Relative error: 2.0%

[0201] Color development time: 5 minutes

[0202] (4) pH = 9.0:

[0203] Average measured value: 9.9 mg / L Relative error: 1.0%

[0204] Color development time: 5 minutes

[0205] (5) pH = 10.0:

[0206] Average measured value: 9.7mg / L Relative error: 3.0%

[0207] Color development time: 5 minutes

[0208] 4. Conclusion:

[0209] The detection effect is best when the pH is in the range of 8.0-9.0.

[0210] Example 4

[0211] This embodiment studies the influence of different temperatures on the detection effect.

[0212] 1. Preparation conditions are the same as in Example 1

[0213] 2. Test at 5℃, 15℃, 25℃, 35℃ and 45℃ respectively. 3. Test results (10.0mg / L standard solution):

[0214] (1) 5℃:

[0215] Average measured value: 9.3 mg / L

[0216] Color development time: 12 minutes

[0217] Relative error: 7.0%

[0218] (2) 15℃:

[0219] Average measured value: 9.7 mg / L

[0220] Color development time: 8 minutes

[0221] Relative error: 3.0%

[0222] (3) 25℃:

[0223] Average measured value: 9.9 mg / L

[0224] Color development time: 5 minutes

[0225] Relative error: 1.0%

[0226] (4) 35℃:

[0227] Average measured value: 9.8 mg / L

[0228] Color development time: 4 minutes

[0229] Relative error: 2.0%

[0230] (5) 45℃:

[0231] Average measured value: 9.5 mg / L

[0232] Color development time: 3 minutes

[0233] Relative error: 5.0%

[0234] 4. Conclusion:

[0235] The optimum detection temperature is 20-30℃.

[0236] Comparative Example 1

[0237] This comparative example did not carry out a pretreatment step, and the necessity of pretreatment was studied.

[0238] 1. Preparation method:

[0239] Direct use of fixed-rate filter paper without pretreatment

[0240] Other conditions are the same as in Example 1

[0241] 2. Test results:

[0242] (1) Test paper performance: uneven color development, large differences between batches, and poor storage stability.

[0243] (2) Determination of standard solution (10.0 mg / L):

[0244] Average measured value: 8.9 mg / L; relative standard deviation: 5.6%; average recovery rate: 89%.

[0245] 3. Actual water sample test (n=10):

[0246] Relative error range: 8.5-15.6%;

[0247] Coefficient of variation between batches: 8.2%;

[0248] The color development time is unstable: 5-12 minutes.

[0249] Comparative Example 2

[0250] This comparative example adopts the traditional Nessler's reagent method to prepare the test paper.

[0251] 1. Reagent formula:

[0252] Mercuric iodide: 20g / L

[0253] Potassium iodide: 40g / L

[0254] Sodium hydroxide: 160g / L

[0255] 2. Preparation conditions are the same as in Example 1

[0256] 3. Test results:

[0257] (1) Standard solution test:

[0258] Detection limit: 0.8mg / L

[0259] Linear range: 2-40mg / L

[0260] Relative standard deviation: 3.8%

[0261] (2) Interference experiment:

[0262] Add different concentrations of metal ions: Cu 2+ (1.0mg / L): Measurement value deviation + 12% Fe 3+ (1.0mg / L): Measurement value deviation + 15% Zn 2+ (1.0mg / L): Measurement value deviation +8%

[0263] (3) Stability study:

[0264] Store at room temperature for 30 days:

[0265] Color sensitivity decreased by 20%

[0266] Detection accuracy decreased by 15%

[0267] Increased batch-to-batch variability

[0268] 4. Problems:

[0269] The reagent is highly toxic

[0270] Susceptible to interference from metal ions

[0271] Poor storage stability

[0272] Operators need protection

[0273] Comparative Example 3

[0274] This comparative example adopts phenol-hypochlorite photometric method to prepare the test paper. 1. Reagent formula:

[0275] Phenol: 150g / L

[0276] Sodium nitrosoferrocyanide: 0.5g / L

[0277] Other conditions are the same as in Example 1

[0278] 2. Detection performance:

[0279] (1) Determination of standard solution (10.0 mg / L):

[0280] Average measured value: 9.6 mg / L

[0281] Relative standard deviation: 3.2%

[0282] Average recovery rate: 96%

[0283] (2) Method characteristics:

[0284] Detection limit: 1.0mg / L

[0285] Linear range: 2-45mg / L

[0286] Color development time: 4-6 minutes

[0287] 3. Environmental impact study:

[0288] (1) Temperature influence:

[0289] For every 5°C increase in temperature, the volatile loss increases by 8%

[0290] Color is unstable above 35℃

[0291] (2) Influence of light:

[0292] After 7 days of exposure to sunlight, the color rendering ability decreased by 25%

[0293] After 14 days of storage away from light, the color development ability decreased by 10%

[0294] 4. Problems:

[0295] Phenol is highly volatile

[0296] Toxic to operators

[0297] Ventilation conditions required

[0298] High risk of environmental pollution

[0299] Comparative Example 4

[0300] This comparative example studies the influence of different substrate materials on the detection effect.

[0301] 1. Test materials:

[0302] (1) Filter paper type:

[0303] Quantitative filter paper (used in Example 1)

[0304] Qualitative filter paper

[0305] Mixed cellulose filter paper

[0306] Glass fiber filter paper

[0307] 2. Preparation conditions:

[0308] The reagent formula is the same as in Example 1, and other conditions remain unchanged. 3. Comparison of test results:

[0309] (1) Qualitative filter paper:

[0310] Uneven color rendering

[0311] Poor water absorption

[0312] Relative error: 8.5%

[0313] (2) Mixed cellulose filter paper:

[0314] Low mechanical strength

[0315] Fragile

[0316] Relative error: 6.2%

[0317] (3) Glass fiber filter paper:

[0318] High cost

[0319] Slow color development

[0320] Relative error: 5.8%

[0321] 4. Conclusion:

[0322] Quantitative filter paper has the best overall performance.

[0323] The following conclusions can be drawn from the above embodiments and comparative examples:

[0324] 1. The best preparation conditions are as in Example 1:

[0325] Reagent concentration: potassium sodium tartrate 30g / L, sodium salicylate 160g / L, sodium nitrosoferrocyanide 0.5g / L;

[0326] Soaking conditions: Soak for 180 minutes at 25°C with shaking;

[0327] Drying conditions: dry in the dark at 25℃ for 15 hours;

[0328] 2. Optimal testing conditions:

[0329] Temperature range: 20-30℃

[0330] pH range: 8.0-9.0

[0331] Color development time: 5 minutes

[0332] Detection range: 2.0-50.0mg / L

[0333] 3. Method advantages:

[0334] The pretreatment step significantly improves the detection accuracy and repeatability. The quantitative filter paper has the best performance as the base material. Compared with the traditional method, it avoids the use of toxic reagents. The detection results are stable and reliable, and are less affected by environmental factors.

[0335] The physical and chemical index comparison table of each embodiment and comparative example is as follows:

[0336]

[0337]

[0338]

[0339] Note:

[0340] 1. All recovery and error data are based on repeated determination of 10.0 mg / L standard solution (n=10)

[0341] 2. Color development time refers to the time required to achieve stable color development;

[0342] 3. The reagent cost is compared with Example 1 as the benchmark value (100%);

[0343] 4. The relative standard deviation reflects the precision of the method. The smaller the value, the better the repeatability.

[0344] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ammonia nitrogen test paper, characterized in that, The method comprises the following preparation steps: Step SA1) preparing a mixed solution for impregnation, wherein the mixed solution for impregnation comprises: Potassium sodium tartrate solution, concentration 3-60g / L; Sodium salicylate solution, concentration 20-320g / L; Sodium nitrosoferricyanide solution, concentration 0.1-0.8g / L; Deionized water; Wherein, the potassium sodium tartrate solution is used as a chelating agent, the sodium salicylate solution is used as a color developer, the sodium nitrosoferrocyanide solution is used as a catalyst, and the deionized water is used as a solvent; Step SA2) placing the fixed-speed filter paper in the impregnation mixed solution for shaking and soaking; Step SA3) Hang the soaked fixed-speed filter paper in the air to dry in the dark for 12-18 hours; Step SA4) Cut the dried filter paper into test paper and store it at low temperature and away from light.

2. The ammonia nitrogen test paper according to claim 1, characterized in that In the step SA2, the shaking and soaking time is 120-240 minutes.

3. The ammonia nitrogen test paper according to claim 1, characterized in that In the step SA3, the drying temperature is 15-35°C.

4. The ammonia nitrogen test paper according to claim 1, characterized in that Before step SA1, a pre-processing step is also included, and the pre-processing step includes: Step SA01) pre-soaking the fixed-speed filter paper in deionized water for 30-60 minutes; Step SA02) placing the soaked filter paper in a drying oven and pre-drying at 50-60° C. for 1-2 hours; Step SA03) cutting the pre-dried filter paper into required sizes for later use; The impregnation mixed solution prepared in step SA04) is ultrasonically treated for 15-30 minutes before use.

5. An ammonia nitrogen test paper reagent tube, characterized in that: The method comprises the following preparation steps: Step SB1) Preparation of oxidant The oxidant is sodium hypochlorite solution, in which the effective chlorine concentration is 3.5g / L, and the free OH - The concentration is 0.75 mol / L (in terms of NaOH); Step SB2) Prepare reagent tube Add 0.8-2 ml of the oxidant into a centrifuge tube with a cap.

6. A standard colorimetric card, characterized in that: The method comprises the following preparation steps: Step SC1) preparing ammonium chloride standard solutions with ammonia nitrogen concentration gradient, the concentrations of which are 2.0 mg / L, 5.0 mg / L, 8.0 mg / L, 10.0 mg / L, 15.0 mg / L, 20.0 mg / L, and 50.0 mg / L; Step SC2) adding each gradient ammonia nitrogen standard solution into the ammonia nitrogen test paper reagent tube respectively; Step SC3) Add 2 pieces of ammonia nitrogen test paper to each reagent tube; Step SC4) Shake to mix, and let stand until the color is stable; Step SC5) preparing a standard color block according to the color development result; Step SC6) Arrange the standard color blocks in order according to the concentration of the ammonia nitrogen standard solution to obtain a standard colorimetric card.

7. An ammonia nitrogen detection system, characterized in that: The system comprises the ammonia nitrogen detection test paper, the ammonia nitrogen detection test paper reagent tube and the standard colorimetric card as described in any one of claims 1 to 6.

8. An application method of an ammonia nitrogen detection system, characterized in that: The application method is based on the ammonia nitrogen detection system according to claim 7, and the application method comprises the following steps: Step SD1) Take a water sample with ammonia nitrogen concentration to be tested and add it to the ammonia nitrogen test paper reagent tube, and shake it for 3-5 seconds; Step SD2) Add 2 pieces of ammonia nitrogen test paper into the ammonia nitrogen test paper reagent tube and shake for 3-5 seconds; Step SD3) Let the solution stand until the color is stable, and compare the color result with the standard colorimetric card to obtain the ammonia nitrogen content in the water sample to be tested.

9. The application method of the ammonia nitrogen detection system according to claim 8, characterized in that: The application method also includes a water sample pretreatment step: Step SD01) Check the turbidity of the water sample and filter it if necessary; Step SD02) detects whether the ammonia nitrogen content in the water sample to be tested is within the range of 2.0-50.0 mg / L. If it exceeds the detection range, the water sample is appropriately diluted to within the detection range. Step SD03) If dilution is performed, the measurement result needs to be multiplied by the corresponding dilution factor.

10. The application method of the ammonia nitrogen detection system according to claim 8, characterized in that: Parallel sample measurements should be performed during the test process, and a reagent blank control should be set up for each test.

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