A method for detecting nitrate nitrogen on site, a water sampler and an analysis and detection device

Abstract

The present application relates to a kind of nitrate nitrogen on-site detection method, water sampler and analytical detection device, belong to water quality detection and monitoring technical field, the scheme of the present application includes a kind of water sampler, comprising: sampler tube, and the push-pull rod that can be moved along its axial direction is arranged in the sampler tube;The sampler tube includes the opening end for the push-pull rod insertion, and when the push-pull rod is pushed and pulled, water sample can be discharged and suction into the sampler tube, the inlet-outlet sample end is equipped with inlet tube and outlet tube;The inlet tube and the outlet tube are all equipped with check valve.Detection method includes wavelength selection→standard curve drawing→sample removal→sample color reaction→on-site detection→result calculation.The water sampler and detection method of the present application are high in precision, good in accuracy, and can be used for the on-site rapid quantitative detection of nitrate nitrogen concentration in water.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water quality detection and monitoring, and particularly relates to a nitrate nitrogen on-site detection method, a water sample sampler and an analysis and detection device. BACKGROUND

[0002] Nitrate nitrogen is an important water quality component in water bodies, and human activities such as agricultural fertilization, sewage irrigation, industrial wastewater and domestic wastewater discharge can all lead to an increase in the concentration of nitrate nitrogen in water bodies. High concentration of nitrate nitrogen in surface water can cause water eutrophication, and excessive concentration of nitrate nitrogen in drinking water can cause harm to the human body.

[0003] Conventional water quality analysis requires water samples to be transported to a laboratory for testing. During the process of water sample collection, preservation and transportation, nitrate nitrogen, nitrite nitrogen and ammonia nitrogen in the water body are mutually converted under nitrification or denitrification, thereby affecting the accurate determination of the concentration of nitrate nitrogen in the water.

[0004] Liquid reagents used in laboratory testing are not easy to store and need to be prepared regularly, and the reagent consumption is large. Sample collection, preservation and transportation require sample bottles, preservatives, transportation costs and other related costs. Large-scale analytical instruments are required during the testing process, and the comprehensive cost of laboratory testing is high.

[0005] In addition, existing on-site detection technologies mainly include test paper visual colorimetric method and sensor in-situ online monitoring method. The test paper visual colorimetric method uses the color scale of standard test paper and the naked eye to subjectively judge the concentration of nitrate nitrogen, which has a large error and low sensitivity. In the process of in-situ online monitoring by the sensor, with the extension of the monitoring time, organic matter and some slightly soluble and easily precipitated substances in the water are easily deposited on the sensor probe, affecting the stability and accuracy of the detection results. SUMMARY

[0006] In view of the above analysis, the present application aims to provide a nitrate nitrogen on-site detection method, a water sample sampler and an analysis and detection device to solve the problems of single function of the existing sampler, long laboratory detection water sample transfer period, large in-situ detection error and low stability.

[0007] The main purpose of the present application is achieved by the following technical solutions:

[0008] On the one hand, the present application provides a water sample sampler, which comprises a sampler tube and a push-pull rod arranged in the sampler tube and capable of moving along the axial direction thereof; the sampler tube comprises an open end for inserting the push-pull rod and an inlet and outlet end capable of discharging and sucking water samples into the sampler tube when the push-pull rod is pushed and pulled, the inlet and outlet end is provided with an inlet tube and an outlet tube; the inlet tube and the outlet tube are both provided with a one-way valve.

[0009] Optionally, the length of the sample outlet tube is not more than half of the length of the sample inlet tube.

[0010] 3. The water sampler according to claim 1 or 2, wherein the one-way valve is arranged on the outer port of the sample inlet tube.

[0011] Optionally, the one-way valve is arranged on the inner and outer ports of the sample outlet tube respectively.

[0012] Optionally, the sample inlet tube is filled with filter material.

[0013] Optionally, the length of the push-pull rod is greater than the length of the sampler tube.

[0014] In another aspect, the present application also provides an analysis and detection device, comprising the water sampler, a cuvette and a spectrophotometer, wherein the cuvette is used to hold the water sample collected by the water sampler, and the known component content is detected by the spectrophotometer.

[0015] In addition, the present application also provides a method for detecting nitrate nitrogen on site, comprising the following steps:

[0016] The water sample to be tested is collected by the water sampler, filtered, and mixed with an indicator after filtration, and then a color reaction is performed; during the color reaction process, concentrated sulfuric acid, deionized water, and a sodium hydroxide solution with a mass concentration of 30-35% are sequentially added and mixed with the water sample to be tested; after the above steps are completed, the absorbance value is measured, and the mass concentration of nitrate nitrogen in the water sample to be tested is calculated by a standard linear equation.

[0017] Optionally, the absorption wavelength used in the process of measuring the absorbance value is 390 nm.

[0018] Optionally, the mass concentration of nitrate nitrogen in the actual water sample is calculated by the mass concentration of nitrate nitrogen in the water sample to be tested, and the specific calculation formula is: ρ = f × C.

[0019] In the formula, ρ is the mass concentration of nitrate nitrogen in the actual water sample, mg / L;

[0020] f is the dilution multiple of the water sample;

[0021] C is the mass concentration of nitrate nitrogen in the water sample to be tested, mg / L.

[0022] Optionally, the sample outlet tube is preloaded with an indicator, and the indicator is 2-isopropyl-5-methylphenol.

[0023] Optionally, the one-way valve comprises a fixed valve plate and a movable valve plate which are staggered and overlapped; the fixed valve plate on the sample inlet is arranged outside the movable valve plate, and the movable valve plate on the sample outlet is arranged outside the fixed valve plate.

[0024] Optionally, the fixed valve plate is connected in the radial direction of the sample inlet tube or the sample outlet tube, and at least a part of the movable valve plate can be overlapped and fitted with the fixed valve plate to cut off the flow channel of the water sample in the sample inlet tube or the sample outlet tube.

[0025] Optionally, the filtering material is prepared by the following method:

[0026] 5-7% of the total reagent mass of ethylene glycol polyoxyethylene ether is added to acetyldimethylamine, stirred uniformly, 4-6% of the total reagent mass of polysulfonated phenyl ether sulfone and 14-16% of the total reagent mass of polyphenylene sulfone are added, heated to 40-70℃, stirred uniformly, and vacuum degassing for more than 24 hours.

[0027] Optionally, the mixing method of the filtered test sample and the indicator is that the filtered test sample carries the indicator into the colorimetric tube during the process of being pushed out from the water sample sampler.

[0028] Optionally, the method for establishing the standard linear equation comprises:

[0029] A series of nitrate nitrogen standard solutions are prepared first, and then the nitrate nitrogen standard solution is mixed with an indicator to perform a color reaction;

[0030] In the color reaction process, concentrated sulfuric acid, deionized water, a 30-35% mass concentration sodium hydroxide solution and the nitrate nitrogen standard solution are sequentially added and mixed;

[0031] After the above steps are completed, a series of absorbance value determinations of the nitrate nitrogen standard solution are performed, a standard curve is drawn, and a standard linear equation is simulated.

[0032] The present application can achieve at least one of the following beneficial effects:

[0033] (1) The sampler pipe of the prior art has only one port, and the water sample enters and exits through the same port, and the application sets separate sample inlet and sample outlet ports, and different materials can be filled in the sample inlet pipe and the sample outlet pipe according to the purposes of sample inlet and sample outlet, thereby playing different roles. Specifically, the sample inlet pipe is filled with filter material to filter solid impurities in the water sample; and the sample outlet pipe is preloaded with an indicator, so that the water sample will inject the preloaded indicator in the sample outlet pipe into the colorimetric tube during injection, without the need for a separate step of adding an indicator, thereby reducing the operation steps and improving the detection efficiency. The sampler of the application not only has a sampling function, but also has a function of carrying an indicator into the colorimetric tube, thereby enriching the functions of the sampler.

[0034] (2) The length of the sample inlet pipe is set to be longer than that of the sample outlet pipe, so that the water sample is conveniently collected, and the port of the sample outlet pipe is prevented from contacting the water sample during the collection of the water sample, thereby preventing the original water sample from contaminating the sample outlet port.

[0035] (3) The sample inlet port and the sample outlet port of the sampling pipe are both provided with a one-way valve, thereby ensuring the one-way inlet and outlet effects and preventing mutual influence.

[0036] (4) In order to strengthen the effect of the one-way valve, each one-way valve is designed in a mode that a fixed valve plate and a movable valve plate are alternately overlapped and matched, so that the movable valve plate and the fixed valve plate form a gap during pushing and pulling, thereby ensuring the effect of smooth passage of liquid.

[0037] (5) The valve plates of the sample inlet port and the sample outlet port are uniquely arranged, so that the movable valve plate on the sample inlet port can only move towards the inside of the sampler pipe during suction of the water sample; and the sample outlet port can only be tightly sucked and attached to the fixed valve plate under the action of suction, thereby preventing the vacuum degree in the sampler pipe from being destroyed by suction, and preventing the water sample from entering the sampler pipe through the sample outlet port, thereby forming the only-in and not-out effect of the water sample sampler during the pulling and suction of the push-pull rod.

[0038] (6) The water sample sampler of the application can be mass-produced as disposable supplies, the indicator preloaded in the sample outlet port is a solid medicament, and the water sample sampler has the advantages of simple structure, convenient operation and suitability for popularization and application in the field of water environment on-site monitoring.

[0039] (7) During on-site detection, through the selection of a specific combination of reagents added in a color development reaction (i.e., the combined use of concentrated sulfuric acid and a 30-35% mass concentration sodium hydroxide solution), the detection method of the application has a wide detection range. The existing on-site detection method can only detect water samples with a target substance concentration of 0.3-30 mg / L, while the detection method of the application can detect water samples with a target substance concentration of 0.2-40.0 mg / L.

[0040] (8) The detection method of the present invention can be used for on-site detection without the need for water sample collection and protection (adding protective agent), storage and transportation. It effectively avoids the mutual conversion of ammonia nitrogen, nitrate nitrogen and nitrite nitrogen in water during the sampling, preservation and transportation process. Therefore, the detection method of the present invention has high accuracy, good stability and small error, and can detect water samples quickly and efficiently.

[0041] (9) The on-site detection and analysis of this invention only takes 9-10 minutes per sample, while collecting, storing and transporting water samples to the laboratory, and then completing the steps of sample reception, sample distribution and analysis and detection in the laboratory takes at least 1-2 days. In comparison, the detection method of this invention is very time-efficient.

[0042] (10) The detection method of the present invention only requires the injection of 1.5-2ml of water sample on site, which requires a very small amount. There is no need to collect a large number of samples and add protective agents. There are no storage or transportation costs, and no need to use large laboratory analytical instruments. Overall, the testing cost is very low.

[0043] (11) In order to ensure the cleanliness of the water sample drawn into the sampler tube, a filter layer is provided in the sample inlet tube. The pore size of the filter material is 0.4 to 0.5 micrometers. The structure of the present invention can achieve a better filtration effect than a complicated filtration device. Moreover, by selecting specific materials for preparation, it can achieve a good filtration effect on the test sample. While obtaining a good filtration effect, it can simplify the filling process and make it less complicated.

[0044] (12) The on-site detection method of the present invention detects concentrations in the range of 0.2 to 40.0 mg / L, and the correlation coefficient (R) of the linear equation is [missing value]. 2 The α value was 0.9995, the recovery rate of spiked samples at different concentrations was 95.00% to 104.00%, and the relative standard deviation (RSD) was 0.88% to 2.97%. The method of this invention has high precision and good accuracy, and can be used for rapid on-site quantitative detection of nitrate nitrogen concentration in water.

[0045] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0046] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0047] Figure 1 This is a schematic diagram of the structure of the water sampler provided by the present invention;

[0048] Figure 2 This is a schematic diagram of the structure of the colorimetric tube provided by the present invention;

[0049] Figure 3 This is a schematic diagram of the spectrophotometer provided by the present invention;

[0050] Figure 4 The spectral scanning curve provided for this invention.

[0051] Figure label:

[0052] 1-Sampling tube; 10-Sampling tube body; 11-Open end; 12-Inlet / outlet end; 13-Inlet; 14-Inlet tube; 15-Outlet; 16-Outlet tube; 17-Filter layer; 18-Indicator layer;

[0053] 2-Push-pull rod;

[0054] 3-One-way valve; 31-Fixed valve plate; 32-Moving valve plate. Detailed Implementation

[0055] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0056] Example

[0057] This embodiment provides a method for on-site detection of nitrate nitrogen, which includes the following steps:

[0058] ① Wavelength selection: Using a standard nitrate nitrogen solution of a certain concentration as the test sample, absorbance wavelength scanning was performed in a spectrophotometer (see details). Figure 4 The maximum absorption wavelength is 390 nm, and therefore the absorption wavelength selected by the method of this invention is 390 nm.

[0059] ② Standard Curve Plotting: Step 1, Standard Solution Preparation: Prepare a series of standard solutions (0.0, 0.5, 2.0, 5.0, 10.0, 20.0, 40.0 mg / L) by serially diluting a certified nitrate nitrogen standard solution. Step 2, Standard Solution Transfer: Accurately transfer 2.0 ml of each standard solution (to the 2.0 ml mark) using a water sampler and inject it into a colorimetric tube through the sample outlet (the pre-filled indicator reagent in the outlet will be injected into the colorimetric tube along with the standard solution). Step 3, Colorimetric Reaction: Add 1.5 ml of concentrated sulfuric acid to the colorimetric tube containing the standard solution, mix well, and let stand for 4-5 minutes; then add 6.5 ml of deionized water and mix well; finally, add 32% sodium hydroxide solution to the 20 ml mark of the colorimetric tube, shake 5-6 times, and let stand for 2-3 minutes to allow the colorimetric reaction to occur. Step 4, On-site Testing: After the colorimetric reaction is complete, select the single-wavelength detection mode in the portable spectrophotometer, with a detection wavelength of 390 nm. Use a 0.0 mg / L blank sample as a reference solution to zero the instrument. Then, place a series of standard solution samples of 0.0, 0.5, 2.0, 5.0, 10.0, 20.0, and 40.0 mg / L into the colorimetric wells for absorbance measurement. After the absorbance test, plot a standard curve with the absorbance of the series of standard solutions as the abscissa and the nitrate nitrogen concentration as the ordinate. Calculate the linear equation and complete the standard curve plotting. The simulated linear equation is shown in Table 1 below.

[0060] Table 1 Simulation Results

[0061]

[0062] ③ Sample Transfer: Accurately transfer 2.0 ml of the water sample to be tested (to the 2.0 ml mark on the sampler. When the water sample is drawn through the inlet, solid impurities in the water sample will be automatically filtered out to ensure the accuracy of subsequent test results). Then, inject the 2.0 ml water sample into the colorimetric tube (during the water sample injection process, the pre-filled indicator reagent in the outlet will also be injected into the colorimetric tube). Figure 2 As shown.

[0063] When injecting the water sample from the sampler into the colorimetric tube, the injection speed should not be too fast, and it is necessary to ensure that all the pre-filled indicator enters the colorimetric tube. For example, when injecting 2.0 ml of water sample, the injection time is 30-60 seconds.

[0064] The methods for preparing the filter materials used in the filtration process include:

[0065] Add 5-7% (by weight of total reagents) of ethylene glycol polyoxyethylene ether to acetylated dimethylamine and stir until homogeneous. Then add 4-6% (by weight of total reagents) of polysulfonated phenylene ether sulfone and 14-16% (by weight of total reagents) of polyphenylene sulfone. Heat to 40-70°C, stir until homogeneous, and degas under vacuum for at least 24 hours. The total reagents include the reactants and solvent. The reactants include ethylene glycol polyoxyethylene ether, polysulfonated phenylene ether sulfone, and polyphenylene sulfone, and the solvent includes acetylated dimethylamine.

[0066] Then, at room temperature, the material is placed in several glass molds that match the sampler inlet, and placed in deionized water at 20-25℃. After solidification for 20-30 hours, it is taken out, thoroughly washed with deionized water to obtain the filter material, and then installed in the sampler inlet tube.

[0067] In a preferred embodiment, 7% (by mass) of ethylene glycol polyoxyethylene ether is added to acetylated dimethylamine and stirred until homogeneous. Then, 5% (by mass) of polysulfonated phenylene ether sulfone and 15% (by mass) of polyphenylene sulfone are added. The mixture is heated to 60°C, stirred until homogeneous, and then vacuum degassed for 24 hours. The filter material prepared in this embodiment has a pore size of 0.4–0.5 micrometers, which can effectively filter solid impurities in water samples. Multiple tests were performed on the same actual spiked water sample before and after filtration using this detection method. The results showed that the test results of the sample filtered using the prepared filter layer were more accurate and reliable. The test results are shown in Table 2 below.

[0068] Table 2. Detection results (mg / L) of actual spiked samples before and after filtration.

[0069]

[0070] This invention optimizes the raw materials and their content for the preparation of filter materials, and through combined optimization of the preparation process and control of specific process parameters, the resulting filter materials can effectively filter solid impurities in water samples and are relatively simple to fill. Furthermore, the resulting test results are more accurate and reliable.

[0071] In order for the filter material to be successfully filled into the injection tube, the size of the glass mold needs to match the diameter of the injection tube, so as to ensure that the prepared filter material can be successfully filled into the injection tube.

[0072] ④ Sample colorimetric reaction: Add 1.5 ml of concentrated sulfuric acid to a colorimetric tube containing 2.0 ml of water sample via the sampler, mix well, and let stand for 4-5 minutes; then add 6.5 ml of deionized water and mix well; finally, add 32% sodium hydroxide solution to the 20 ml mark of the colorimetric tube, shake 5-6 times, and let stand for 2-3 minutes to carry out the colorimetric reaction.

[0073] ⑤ On-site testing: After the sample colorimetric reaction is complete, select the single-wavelength detection mode in the portable spectrophotometer, such as... Figure 3 As shown. The detection wavelength was 390 nm. The instrument was zeroed using a 0.0 mg / L blank sample as a reference solution. Then, the water sample after the colorimetric reaction was completed was placed in the colorimetric well for absorbance measurement, and the absorbance value was read.

[0074] ⑥ Result calculation: Based on the absorbance value of the sample, the nitrate nitrogen mass concentration (mg / L) in the test sample is calculated using a linear equation.

[0075] The formula for calculating the nitrate nitrogen mass concentration in a water sample is: ρ = f × C;

[0076] In the formula:

[0077] ρ—Nitrate nitrogen concentration in the water sample, mg / L;

[0078] f—dilution factor of the water sample;

[0079] C — Nitrate nitrogen concentration in the test sample, mg / L.

[0080] The measurement results are shown in Table 3 below.

[0081] Table 3. Results of spiked recovery tests (each sample was measured in parallel 5 times).

[0082]

[0083] In the above embodiments, the water sample to be tested can also be transferred in 1.5ml, 1.6ml, 1.7ml, 1.8ml, etc., as long as the transfer is accurate.

[0084] In the above embodiments, the mass concentration of sodium hydroxide added during the colorimetric reaction can also be selected as 30%, 31%, 33%, 34%, 35%, etc.

[0085] In addition, for this embodiment, the present invention also discloses a water sampler for use in taking water samples, including: a sampler tube 1, and a push-pull rod 2 disposed in the sampler tube 1 and capable of moving along its axial direction.

[0086] The sampler tube 1 includes an open end 11 for inserting the push-pull rod 2, and an inlet / outlet end 12 that allows water samples to be discharged and drawn into the sampler tube 1 when the push-pull rod 2 is pushed or pulled. The inlet / outlet end 12 is connected to an inlet port 13 and an outlet port 15. Figure 1 As shown.

[0087] Existing samplers have only one inlet, with the same inlet for both water sample entry and exit. This invention, by providing separate inlet and outlet ports, allows for the filling of different materials into the inlet and outlet tubes to achieve different functions depending on the purpose of sampling. Specifically, a filter material is filled into the inlet tube to filter solid impurities from the water sample; an indicator is pre-filled in the outlet tube, ensuring that the indicator is injected into the colorimetric tube along with the water sample during injection, eliminating the need for a separate indicator addition step, reducing operational steps, and improving detection efficiency.

[0088] After the water sample is drawn into sampler tube 1, it is pushed into a colorimetric tube. The colorimetric tube containing the water sample is then placed in a spectrophotometer. The concentration of nitrate nitrogen in the water sample is determined by combining the pre-obtained standard curve data with the absorbance detected by the spectrophotometer.

[0089] Specifically, in this embodiment, a one-way valve 3 is provided on the inlet 13 and outlet 15 of the sampler tube 1 sampler end 12, which enables the water sampler to only enter and not exit when the push-pull rod 2 is pulled back to draw liquid, and to only exit and not enter when the push-pull rod 2 is pushed to discharge liquid.

[0090] To ensure the above effect, each one-way valve 3 includes a fixed valve plate 31 and a movable valve plate 32 that are staggered and overlapped. The movable valve plate 32 can move along with the push-pull rod 2. During the push-pull process of the push-pull rod 2, the movable valve plate 32 can be moved according to the suction force or the injection force, thereby forming a gap between the fixed valve plate 31 and the movable valve plate 32.

[0091] The fixed valve plate 31 on the inlet 13 is located outside the movable valve plate 32, and the movable valve plate 32 on the outlet 15 is located outside the fixed valve plate 31. This arrangement ensures that the movable valve plate 32 on the inlet 13 can only move towards the inside of the sampler tube 1 when drawing water samples. The movable valve plate 32, after moving, forms a water sample inlet channel with the relatively fixed valve plate 31. Since the movable valve plate 32 on the outlet 15 is located outside the fixed valve plate 31, it can only be firmly adhered to the fixed valve plate 31 under suction force. This prevents the vacuum in the sampler tube 1 created by suction force from being disrupted, and also prevents water samples from entering the sampler tube 1 through the outlet 15, thus ensuring that the water sampler only draws in water and does not draw out water when the push-pull rod 2 is pulled back to draw liquid.

[0092] Correspondingly, when the push-pull rod 2 pushes the liquid out, the movable valve plate 32 on the inlet 13 will be firmly attached to the inner side of the movable valve plate 32 under the action of the pushing force, so that the inlet 13 is closed when the liquid is pushed; while the movable valve plate 32 on the outlet 15 will tilt outward under the action of the pushing force, so that a gap for liquid outflow is formed between the movable valve plate 32 and the fixed valve plate 31 on the outlet 15, so that the water sampler can only outflow and not inflow when the push-pull rod 2 pushes the liquid out.

[0093] In this embodiment, the inlet 13 includes an inlet tube 14 connected to the inlet / outlet end 12, and the inlet tube 14 is connected to the sampler tube 1. The one-way valve 3 on the inlet 13, namely the fixed valve plate 31 and the movable valve plate 32 on the inlet 13, are both set on the outer port of the inlet tube 14. In order to ensure the cleanliness of the water sample drawn into the sampler tube 1, a filter layer 17 is provided in the inlet tube 14. The filter layer 17 is specifically a filter material filled in the inlet tube 14, which can filter out solid impurities in the water sample and prevent solid impurities from interfering with subsequent detection.

[0094] It should be noted that, as needed, one-way valves 3 can also be installed on the inner and outer sides of the inlet of the sample inlet tube 14.

[0095] The sample outlet 15 includes a sample outlet tube 16 connected to the inlet / outlet end 12 and communicating with the sampler tube 1. Two one-way valves 3 are connected to the sample outlet 15, respectively located on the inner and outer sides of the sample outlet tube 16. An indicator layer 18 is pre-installed between the two one-way valves 3. In this embodiment, the indicator layer 18 is a pre-installed indicator used for detecting nitrate nitrogen content in water samples. The indicator is 0.001g of pre-installed 2-isopropyl-5-methylphenol. The pre-installed indicator simplifies the detection process, allowing the indicator to be incorporated into the water sample during transfer to the colorimetric tube, eliminating the need for an additional indicator addition step and effectively improving the speed and efficiency of the detection.

[0096] To reduce the risk of the original water sample adhering to the outlet 15 during water sampling and thus contaminating it, the length of the inlet tube 14 in this embodiment is greater than the length of the outlet tube 16. Specifically, the length of the outlet tube 16 does not exceed half the length of the inlet tube 14. This arrangement allows the inlet tube 14 to effectively extend into the water sample and maintains a certain distance between the outlet tube 16 and the water sample, thus preventing the original water sample from contaminating the outlet tube 16.

[0097] To improve the smoothness of suction and drainage, both the inlet tube 14 and the outlet tube 16 are straight tubes connected to the inlet and outlet ends 12 of the sampler tube 1, and the inlet tube 14 and the outlet tube 16 are integral with the sampler tube 1. This integral structure facilitates the processing and manufacturing of the water sampler and avoids affecting the overall sealing performance during the connection of components.

[0098] The fixed valve plate 31 is connected in the radial direction of the inlet pipe 14 or the outlet pipe 16. At least a portion of the movable valve plate 32 can overlap and fit with the fixed valve plate 31 to cut off the flow channel of the water sample in the inlet pipe 14 or the outlet pipe 16. Based on the operating principle of the fixed valve plate 31 and the movable valve plate 32 described above, in this embodiment, both the fixed valve plate 31 and the movable valve plate 32 are connected in the radial direction of the inlet pipe 14 or the outlet pipe 16. Furthermore, both the fixed valve plate 31 and the movable valve plate 32 are approximately semi-circular plate structures, and their straight edges protrude beyond the diameter line of the inlet pipe 14 or the outlet pipe 16, achieving good overlap and cutting off the flow channel of the water sample in the inlet pipe 14 or the outlet pipe 16, ensuring a tight seal during suction and injection.

[0099] It should be noted that, in order to ensure a good sealing effect during suction, a sealing element is provided at the joint between the fixed valve plate 31 and the movable valve plate 32.

[0100] To more intuitively observe the state of the water sample in the sampler tube 1, the sampler tube 1 in this embodiment includes a transparent sampler tube body 10. Volume scales are provided on the sampler tube body 10, allowing for intuitive adjustment of the water sample intake and improving detection accuracy. The sampler tube body 10 can be made of glass or plastic.

[0101] In this embodiment, the fixed valve plate 31 can be made of hard glass or plastic, the same material as the sampler tube, and the movable valve plate 32 can be a soft rubber sheet connected to the main structure, allowing the movable valve plate 32 to move freely.

[0102] In this embodiment, the length of the push-pull rod 2 is greater than the length of the sampler tube 10. In its original state, one end of the push-pull rod 2 is attached to the inner end face of the sample inlet / outlet end 12 of the sampler tube 1, and the other end of the push-pull rod 2 protrudes from the open end 11 of the sampler tube 1, which facilitates the operation of the push-pull rod 2. It should be noted that, in order to further ensure the airtightness of the water sample during suction and discharge in the sampler tube 1, a rubber head can also be provided on the end of the push-pull rod 2 located inside the sampler tube 10 to achieve smooth operation. This will not be elaborated further here.

[0103] The water sampler of this invention can effectively ensure the smoothness of sampling and water sample transfer, effectively simplify the detection steps, and importantly, avoid mutual interference caused by the sharing of channels when water samples are extracted and discharged, thus fundamentally improving the accuracy of detection.

[0104] Based on the detection process in this invention, this embodiment also provides an analytical detection device, including the above-mentioned water sampler, colorimetric tube, and spectrophotometer. The colorimetric tube is used to hold the water sample collected by the water sampler and to detect the content of known components by the spectrophotometer.

[0105] The analytical detection device in this invention can realize in-situ detection of water samples, avoiding the component transformation that is very likely to occur when water samples are transported from the sampling site to the laboratory, and can ensure the accuracy of analysis and testing and reduce errors.

[0106] Of course, there are many alternative solutions to the present invention. For example, during on-site testing, a portable spectrophotometer can be omitted, and standard colorimetric cards or standard colorimetric reagent tubes can be used instead. That is, a series of standard solutions are subjected to a colorimetric reaction, and then the concentrations and color intensities of the standard solutions are made into standard colorimetric cards or standard colorimetric reagent tubes. The concentration of nitrate nitrogen in the water is then determined on-site by visual colorimetry. However, the above method has lower sensitivity and accuracy compared to a spectrophotometer, and the error in determining the concentration of nitrate nitrogen in the water sample by visual colorimetry is relatively large.

[0107] Alternatively, the sampler of this invention can be omitted during on-site sampling. A regular syringe and needle filter can be used to transfer water samples, and an indicator can be added on-site for testing. The disadvantage is that a balance and a 0.001g electronic balance cannot be carried on-site, making it impossible to accurately weigh 0.001g of indicator, which affects the color development of the water sample and the accuracy of the test results.

[0108] The water sample testing method of the present invention can be well applied in the following fields:

[0109] ① In the field of water environment monitoring: The monitoring of surface water and groundwater quality and the research on water environment assessment often require accurate measurement of nitrate nitrogen content in water to assess the evolution of water chemistry, water environment and water pollution status. This invention can provide rapid and accurate on-site detection and monitoring data for this field.

[0110] ② In the field of water environment remediation and treatment: High-frequency, long-term monitoring of nitrate nitrogen content in surface water and groundwater is necessary during the remediation of nitrate pollution to assess the degree of nitrate pollution and the effectiveness of remediation. This invention can detect nitrate nitrogen concentration in the aquatic environment in real time on-site, providing real-time monitoring data for water environment monitoring and remediation processes in the field.

[0111] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A water sampler for real-time field monitoring of water samples, characterized in that, Includes: a sampler tube, and a push-pull rod disposed in the sampler tube that is movable along its axial direction; The sampler tube includes an open end for inserting the push-pull rod, and an inlet / outlet end for discharging and drawing water samples into the sampler tube when the push-pull rod is pushed or pulled. The inlet / outlet end is provided with an inlet tube and an outlet tube. Both the inlet tube and the outlet tube are equipped with one-way valves; The inlet tube is filled with filter material, and the outlet tube is pre-loaded with indicator; The one-way valve includes a fixed valve plate and a movable valve plate that are staggered and overlapped; the fixed valve plate on the inlet is located outside the movable valve plate, and the movable valve plate on the outlet is located outside the fixed valve plate. The fixed valve plate is connected in the radial direction of the inlet pipe or the outlet pipe, and at least a portion of the movable valve plate can overlap and fit with the fixed valve plate to cut off the flow channel of the water sample in the inlet pipe or the outlet pipe. The filter material was prepared using the following method: Add 5-7% of the total reagent mass of ethylene glycol polyoxyethylene ether to acetylated dimethylamine, stir evenly, then add 4-6% of the total reagent mass of polysulfonated phenyl ether sulfone and 14-16% of the total reagent mass of polyphenylene sulfone, heat to 40-70℃, stir evenly, and vacuum degas for more than 24 hours. Then, at room temperature, the material is placed in several glass molds that match the sampler inlet, and placed in deionized water at 20-25℃. After solidification for 20-30 hours, it is taken out and thoroughly washed with deionized water to obtain the filter material.

2. The water sampler according to claim 1, characterized in that, The length of the sample outlet tube shall not exceed one-half the length of the sample inlet tube.

3. The water sampler according to claim 1 or 2, characterized in that, The one-way valve is provided on the outer port of the injection tube.

4. The water sampler according to claim 3, characterized in that, The one-way valve is provided on the inlet and outlet of the sample tube on both the inside and outside.

5. The water sampler according to claim 3, characterized in that, The length of the push-pull rod is greater than the length of the sampler tube.

6. An analytical and detection device, characterized in that, The invention includes a water sampler, a colorimetric tube, and a spectrophotometer as described in any one of claims 1-5, wherein the colorimetric tube is used to hold the water sample collected by the water sampler and to detect the content of known components by the spectrophotometer.

7. A method for on-site detection of nitrate nitrogen, characterized in that, Includes the following steps: The water sampler according to any one of claims 1-5 is used to collect the test sample, which is then filtered. The filtered test sample is mixed with an indicator and subjected to a colorimetric reaction. During the colorimetric reaction, concentrated sulfuric acid, deionized water, and sodium hydroxide solution with a mass concentration of 30-35% are added sequentially and mixed with the sample to be tested. After the above steps are completed, the absorbance value is measured, and the nitrate nitrogen mass concentration in the test sample is calculated using a standard linear equation.

8. The method for on-site detection of nitrate nitrogen according to claim 7, characterized in that, The absorption wavelength used in the absorbance measurement was 390 nm.

9. The method for on-site detection of nitrate nitrogen according to claim 7, characterized in that, The nitrate nitrogen concentration in the actual water sample is calculated using the nitrate nitrogen concentration in the test sample. The specific calculation formula is as follows: ρ = f ×C; In the formula, ρ —The mass concentration of nitrate nitrogen in the actual water sample, in mg / L; f —Water sample dilution factor; C—The mass concentration of nitrate nitrogen in the test sample, mg / L.

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