CN116008202A

CN116008202A - Improved seawater ammonia nitrogen detection device and method based on salicylic acid spectrophotometry

Info

Publication number: CN116008202A
Application number: CN202310020562.1A
Authority: CN
Inventors: 沈洋洋; 林方; 颜静佳; 周海亮
Original assignee: Hangzhou Ruili Marine Equipment Co ltd
Current assignee: Hangzhou Ruili Marine Equipment Co ltd
Priority date: 2023-01-06
Filing date: 2023-01-06
Publication date: 2023-04-25

Abstract

The invention discloses a salicylic acid spectrophotometry-based improved seawater ammonia nitrogen detection device and a salicylic acid spectrophotometry-based improved seawater ammonia nitrogen detection method. The device comprises a measuring column, a peristaltic pump, a multi-channel switching electromagnetic valve and a photoelectric colorimetric unit; the bottom of the measuring column is connected with a normally open port of the three-way electromagnetic valve; the inlet of the three-way electromagnetic valve is connected with the normally open port of the three-way electromagnetic valve; the normally closed port of the three-way electromagnetic valve is connected with the waste liquid barrel; the inlet of the three-way electromagnetic valve is connected with the peristaltic pump; the other side of the peristaltic pump is connected with the middle main port of the multi-channel switching electromagnetic valve; 7 sub-ports of the multi-channel switching electromagnetic valve are respectively connected with a first reagent storage bottle, a second reagent storage bottle, an ammonia nitrogen standard solution storage bottle, a waste liquid barrel, a pure water barrel, a photoelectric colorimetric unit and a water sample cup; the photoelectric colorimetric unit is connected with the two-way electromagnetic valve; the other end of the two-way electromagnetic valve is communicated with air. The masking agent in the reagent can mask calcium and magnesium ions in a water sample, avoids precipitation to influence color comparison, has small error, and can be used for on-line monitoring of ammonia nitrogen concentration in ocean water quality.

Description

Improved seawater ammonia nitrogen detection device and method based on salicylic acid spectrophotometry

Technical Field

The invention belongs to the field of water quality monitoring equipment, and particularly relates to a salicylic acid spectrophotometry-based improved seawater ammonia nitrogen detection device and method.

Background

Ammonia nitrogen is an important water quality parameter in marine environmental monitoring, and is one of the indispensable nutrients for phytoplankton in the ocean. Meanwhile, ammonia nitrogen is also an important component of nitrogen circulation in the marine ecosystem. The real-time online monitoring of the ammonia nitrogen in the seawater can provide real-time data support for marine ecological environment research, marine fishery development, marine water pollution early warning and the like, and has important practical significance.

According to GB17378.4-2007, marine monitoring Specification section 4: the standard analysis methods of seawater ammonia nitrogen are hypobromite oxidation method and indophenol blue spectrophotometry. The hypobromite oxidation method has the advantages that partial reagents need to be prepared and used at present, the requirements on the testing environment are high, and the measurement is easily influenced by environmental factors; the indophenol blue spectrophotometry method is simple and convenient, has low blank value and good reproducibility, but has slow reaction (the color reaction time of the seawater sample is more than 6 hours). Therefore, both standard methods are not suitable for online monitoring of seawater ammonia nitrogen. The methods adopted by the ammonia nitrogen on-line monitoring equipment generally used for ocean water quality at present mainly comprise a phenol colorimetric method and an OPA fluorescent method. The phenol colorimetric method is an improved method of the indophenol blue spectrophotometry, shortens the color development time in the reaction process by changing part of reagent formulas, and can be better applied to online monitoring of seawater ammonia nitrogen. However, the phenol colorimetric method has the defects that the quality guarantee period of the reagent is short (phenol is easy to oxidize when contacting with air), and the reagent contains pollutants which are not friendly to the environment (phenol is a toxic substance); the OPA fluorescence method has advantages of low detection limit, but its principle is different from that of the standard analysis method, and the result is poor in alignment, and its method stability is poor, which is related to instability of fluorescent substances generated after the reaction.

Disclosure of Invention

The invention aims to solve the problem that the concentration of seawater ammonia nitrogen is difficult to accurately measure by a salicylic acid spectrophotometry in the prior art, and provides an improved seawater ammonia nitrogen detection device and method based on the salicylic acid spectrophotometry.

The specific technical scheme adopted by the invention is as follows:

in a first aspect, the invention provides a salicylic acid spectrophotometry-based improved seawater ammonia nitrogen detection device, which comprises a measuring column, a first three-way electromagnetic valve, a second three-way electromagnetic valve, a peristaltic pump, a multi-channel switching electromagnetic valve and a photoelectric colorimetric unit; the first three-way electromagnetic valve and the second three-way electromagnetic valve are two three-way electromagnetic valves of one inlet and two outlets; the peristaltic pump can switch between forward rotation and reverse rotation; the liquid inlet and outlet of the metering column are connected with the normally open port of the first three-way electromagnetic valve, the normally closed port of the first three-way electromagnetic valve is connected with the atmosphere, and the inlet of the first three-way electromagnetic valve is connected with the normally open port of the second three-way electromagnetic valve; the inlet of the second three-way electromagnetic valve is connected with one opening of the peristaltic pump, the other opening of the peristaltic pump is connected with the main opening of the multi-channel switching electromagnetic valve, 7 sub-openings capable of being independently switched and communicated with the main opening are arranged on the multi-channel switching electromagnetic valve, and the 7 sub-openings are respectively connected with the first reagent storage bottle, the second reagent storage bottle, the ammonia nitrogen standard solution storage bottle, the waste liquid barrel, the pure water barrel, the photoelectric colorimetric unit and the water sample cup in a selected mode; the upper part of the photoelectric colorimetric unit is connected with two electromagnetic valves, and the other ends of the two electromagnetic valves are communicated with the atmosphere; the metering column and the peristaltic pump can be switched by valves, and the solution to be measured, the first reagent and the second reagent are respectively quantitatively pumped into a reactor in the photoelectric colorimetric unit for color reaction, wherein the solution to be measured is one of pure water, ammonia nitrogen standard solution and a seawater sample; the photoelectric colorimetric unit can be used for carrying out colorimetric comparison on the internal chromogenic reaction solution to obtain absorbance positively correlated with the ammonia nitrogen concentration in the solution to be detected.

Preferably, the photoelectric colorimetric unit comprises a reactor, a temperature control system, a colorimetric light source and a photoelectric detector, wherein the solution to be detected, the first reagent and the second reagent enter the transparent reactor to be mixed to form a chromogenic reaction liquid, the temperature control system is used for adjusting the reaction temperature in the reactor, the colorimetric light source is used for applying light with a specified wavelength to the reactor, and the photoelectric detector is used for measuring the transmitted light intensity passing through the reactor and the internal chromogenic reaction liquid.

Preferably, the reactor is made of quartz glass.

Preferably, the colorimetric light source adopts a 660nm wavelength light source.

Preferably, the two-way solenoid valve is a normally closed two-way solenoid valve.

Preferably, the first reagent adopts a mixed solution of sodium salicylate, sodium citrate, sodium nitrosoferricyanide and disodium ethylenediamine tetraacetate; preferably, the preparation method of the first reagent comprises the following steps: 20+/-0.1 g of disodium ethylenediamine tetraacetate is weighed and dissolved in 300mL of purified water, then 65+/-0.1 g of sodium citrate and 65+/-0.1 g of sodium salicylate are weighed and dissolved in the solution, then 0.5+/-0.01 g of sodium nitrosoferricyanide is added, and after all the sodium disodium ethylenediamine tetraacetate is dissolved, the solution is subjected to constant volume to 500mL by water and is uniformly shaken.

Preferably, the second reagent adopts sodium hydroxide-sodium dichloroisocyanurate mixed solution; preferably, the preparation method of the second reagent comprises the following steps: 10.0+/-0.1 g of sodium hydroxide is dissolved in 150mL of purified water and cooled to room temperature, 1.0+/-0.01 g of sodium dichloroisocyanurate is dissolved in sodium hydroxide solution cooled to room temperature, and then water is used for constant volume to 250mL, and shaking is carried out uniformly.

In a second aspect, the present invention provides a seawater ammonia nitrogen detecting method using the seawater ammonia nitrogen detecting apparatus according to any one of the first aspect, comprising:

sequentially taking pure water, an ammonia nitrogen standard solution and a seawater sample as solutions to be measured, executing an ammonia nitrogen concentration measuring process by combining valve switching operation, and obtaining absorbance positively correlated with the ammonia nitrogen concentration in the three solutions to be measured through a photoelectric colorimetric unit; forming a working curve according to the absorbance and the ammonia nitrogen concentration corresponding to the pure ammonia nitrogen standard solution, and then converting the concentration of ammonia nitrogen in the seawater sample based on the working curve and the absorbance corresponding to the seawater sample;

the method for executing the ammonia nitrogen concentration measuring process by combining the valve switching operation comprises the following steps:

s1, initializing a reactor inner cavity of a photoelectric colorimetric unit to be in a state of empty and no solution residue, and enabling a valve and a pipeline in a detection device to be in an initial standby state through valve switching operation;

In the standby state, the inlet of the first three-way electromagnetic valve is communicated with the normally open port, the inlet of the second three-way electromagnetic valve is communicated with the normally open port, the main port of the multi-channel switching electromagnetic method is empty, and the two-way electromagnetic valve is closed;

s2, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the current solution to be measured, controlling the peristaltic pump to reversely rotate to quantitatively pump the current solution to be measured into the measuring column, switching the valves of the multi-channel switching electromagnetic valve again to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the waste liquid barrel, and controlling the peristaltic pump to reversely rotate to discharge the residual current solution to be measured in the pipeline into the waste liquid barrel; then, valve switching is carried out on the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the photoelectric colorimetric unit, the inlet of the first three-way electromagnetic valve is kept to be communicated with the normally open port, after the two-way electromagnetic valve is controlled to be communicated, the peristaltic pump is controlled to positively rotate, and all the current solution to be measured in the measuring column is pumped into the reactor of the photoelectric colorimetric unit; finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

s3, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the first reagent storage bottle, controlling the peristaltic pump to reversely rotate to pump the first reagent into the metering column quantitatively, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the waste liquid barrel, and controlling the peristaltic pump to reversely rotate to discharge the first reagent remained in the pipeline into the waste liquid barrel; then, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the photoelectric colorimetric unit, keeping the inlet of the first three-way electromagnetic valve communicated with the normally open port, and controlling the peristaltic pump to positively rotate to pump all the first reagent in the measuring column into the reactor of the photoelectric colorimetric unit after controlling the two-way electromagnetic valve to be communicated; finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

S4, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the corresponding sub-port of the pure water barrel, controlling the peristaltic pump to reversely rotate to pump pure water into the measuring column quantitatively, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the corresponding sub-port of the waste water barrel again, controlling the peristaltic pump to positively rotate to drain the residual pure water in the measuring column and the pipeline into the waste water barrel, and completing cleaning of the measuring column and the pipeline; finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

s5, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the second reagent storage bottle, controlling the peristaltic pump to reversely rotate to quantitatively pump the second reagent into the metering column, switching the valves of the multi-channel switching electromagnetic valve again to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the waste liquid barrel, and controlling the peristaltic pump to reversely rotate to discharge the second reagent remained in the pipeline into the waste liquid barrel; then, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the photoelectric colorimetric unit, keeping the inlet of the first three-way electromagnetic valve communicated with the normally open port, and controlling the peristaltic pump to positively rotate to pump all the second reagent in the measuring column into the reactor of the photoelectric colorimetric unit after controlling the two-way electromagnetic valve to be communicated; finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

S6, after the current solution to be detected, the first reagent and the second reagent are all pumped into a reactor of a photoelectric colorimetric unit, controlling the temperature in the reactor to be maintained at the temperature required by the color development reaction, applying light with characteristic absorption wavelength required by ammonia nitrogen determination to the reactor through a colorimetric light source after the color development reaction is completed, and then measuring the transmitted light intensity passing through the reactor and the internal color development reaction solution through a photoelectric detector to obtain the absorbance of the current solution to be detected after the color development reaction; then, the main port of the multi-channel switching electromagnetic valve is kept to be communicated with the sub port corresponding to the photoelectric colorimetric unit, the inlet of the second three-way electromagnetic valve is controlled to be normally closed, the two-way electromagnetic valve is controlled to be communicated, and the peristaltic pump is controlled to reversely rotate so as to completely discharge the color reaction liquid in the photoelectric colorimetric unit into the waste liquid barrel; finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

s7, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the pure water barrel, controlling the peristaltic pump to reversely rotate to pump pure water into the metering column quantitatively, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the photoelectric colorimetric unit again, and controlling the peristaltic pump to positively rotate to pump all the pure water in the metering column into the reactor of the photoelectric colorimetric unit to clean the inner cavity of the reactor; controlling the inlet connection of the second three-way electromagnetic valve to be normally closed, controlling the two-way electromagnetic valve to be conducted, and controlling the peristaltic pump to reversely rotate so as to discharge all the cleaned solution in the photoelectric colorimetric unit into the waste liquid barrel; finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

S8, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the pure water barrel, controlling the peristaltic pump to reversely rotate to pump pure water into the metering column quantitatively, switching the valves of the multi-channel switching electromagnetic valve to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the photoelectric colorimetric unit again, and controlling the peristaltic pump to positively rotate to pump all the pure water in the metering column into the reactor of the photoelectric colorimetric unit to fill the inner cavity of the reactor; and finally, the valve and the pipeline in the detection device are restored to a standby state by the valve switching operation again, and the next measurement is waited.

Preferably, the volume ratio of the current solution to be tested, the first reagent and the second reagent pumped into the reactor is 10:1:1.2; the first reagent adopts a mixed solution of sodium salicylate, sodium citrate, sodium nitrosoferricyanide and disodium ethylenediamine tetraacetate, and the preparation method of the first reagent comprises the following steps: dissolving 20+/-0.1 g of disodium ethylenediamine tetraacetate in 300mL of purified water, then dissolving 65+/-0.1 g of sodium citrate and 65+/-0.1 g of sodium salicylate in the solution, adding 0.5+/-0.01 g of sodium nitrosoferricyanide, and shaking uniformly after the disodium ethylenediamine tetraacetate and the sodium salicylate are completely dissolved, and using water to fix the volume to 500 mL; the second reagent adopts sodium hydroxide-sodium dichloroisocyanurate mixed solution, and the preparation method of the second reagent comprises the following steps: dissolving 10.0+/-0.1 g of sodium hydroxide in 150mL of purified water and cooling to room temperature, dissolving 1.0+/-0.01 g of sodium dichloroisocyanurate in sodium hydroxide solution cooled to room temperature, then fixing the volume to 250mL by using water, and shaking uniformly; the temperature required by the color reaction is 45 ℃, the color reaction time is 10min, and the characteristic absorption wavelength required by the determination of ammonia nitrogen is 660nm.

Preferably, the working curve is periodically re-measured and drawn once, during which only the absorbance of the seawater sample needs to be directly measured and the latest working curve is called for only ammonia nitrogen concentration conversion.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, through the improvement of the reagent formula, the used reagent has better stability and short color reaction time; the masking agent in the reagent can mask calcium and magnesium ions in the water sample, and avoids precipitation caused by the reaction of the calcium and magnesium ions and salicylate in the reagent to affect color comparison. The detection device has reasonable pipeline arrangement, high automation degree and smaller error of the actual water sample test result compared with the laboratory standard method, and can be used for on-line monitoring of ammonia nitrogen concentration in ocean water quality.

Drawings

FIG. 1 is a schematic general construction of the present invention;

in the figure: the device comprises a metering column 1, a three-way electromagnetic valve 2, a three-way electromagnetic valve 3, a peristaltic pump 4, a multi-channel switching electromagnetic valve 5, a first reagent storage bottle 6, a second reagent storage bottle 7, an ammonia nitrogen standard liquid storage bottle 8, a waste liquid barrel 9, a pure water barrel 10, a photoelectric colorimetric unit 11, a water sample cup 12 and a two-way electromagnetic valve 13.

Detailed Description

In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the invention, whereby the invention is not limited to the specific embodiments disclosed below. The technical features of the embodiments of the invention can be combined correspondingly on the premise of no mutual conflict.

In the description of the present invention, it will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or be indirectly connected with intervening elements present. In contrast, when an element is referred to as being "directly connected" to another element, there are no intervening elements present.

In the description of the present invention, it should be understood that the terms "first" and "second" are used solely for the purpose of distinguishing between the descriptions and not necessarily for the purpose of indicating or implying a relative importance or implicitly indicating the number of features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature.

The invention provides an improved salicylic acid spectrophotometry for measuring ammonia nitrogen concentration of a sample, which comprises the following steps:

and quantitatively adding a first reagent and a second reagent into the solution to be detected, mixing, performing color development reaction, performing color comparison on the color development reaction liquid by a spectrophotometry after the reaction is finished, measuring the absorbance of the color development reaction liquid, and converting the ammonia nitrogen concentration in the solution to be detected by a working curve.

Among these, the parameters in the above measurement method are preferably as follows: the volume ratio of the solution to be tested, the first reagent and the second reagent pumped into the reactor is 10:1:1.2. The first reagent adopts a mixed solution of sodium salicylate, sodium citrate, sodium nitrosoferricyanide and disodium ethylenediamine tetraacetate. The preparation method of the first reagent R1 serving as a color developing agent comprises the following steps: weighing (20+/-0.1) g of disodium ethylenediamine tetraacetate, dissolving in 300mL of purified water, then weighing (65+/-0.1) g of sodium citrate and (65+/-0.1) g of sodium salicylate, dissolving in the solution, adding (0.5+/-0.01) g of sodium nitrosoferricyanide, transferring to a 500mL volumetric flask after all the sodium nitrosoferricyanide is dissolved, diluting to a marked line by purified water, and shaking uniformly. Compared with a mixed solution of salicylic acid and potassium tartrate as a color developing agent in HJ 536-2009 'determination of water quality ammonia nitrogen spectrophotometry', the reagent is more stable, and disodium ethylenediamine tetraacetate can be complexed with calcium and magnesium ions in a water sample, so that the reaction of the calcium and magnesium ions and sodium salicylate is avoided to generate white precipitation to influence color comparison.

The second reagent adopts sodium hydroxide-sodium dichloroisocyanurate mixed solution. The second reagent R2 is used as an oxidant, and the preparation method is as follows: accurately weighing (10.0+/-0.1) g of sodium hydroxide, dissolving in 150mL of purified water, and cooling for later use. Weighing (1.0+/-0.01) g of sodium dichloroisocyanurate, dissolving in sodium hydroxide solution cooled to room temperature, transferring into a 250mL volumetric flask, diluting to marked line with purified water, and shaking uniformly. Compared with a sodium hypochlorite solution of a color reagent in HJ 536-2009 'determination of water quality ammonia nitrogen and salicylic acid spectrophotometry', the reagent is more stable, and compared with the preparation of the sodium hypochlorite solution, the preparation operation of the solution is very simple. In the detection method, the temperature required by the color reaction is 45 ℃, the color reaction time is 10min, the characteristic absorption wavelength required by the determination of ammonia nitrogen is 660nm, namely the absorbance of the color reaction liquid is determined under a 660nm light source.

In a preferred embodiment of the present invention, as shown in fig. 1, in order to implement the improved salicylic acid spectrophotometry for measuring ammonia nitrogen concentration of a sample, an improved seawater ammonia nitrogen detection device based on salicylic acid spectrophotometry is provided, which comprises a measuring column 1, a first three-way electromagnetic valve 2, a second three-way electromagnetic valve 3, a peristaltic pump 4, a multi-channel switching electromagnetic valve 5, a photoelectric colorimetric unit 11 and other constituent units. The first three-way electromagnetic valve 2 and the second three-way electromagnetic valve 3 are two three-way electromagnetic valves, each of which comprises an inlet and two outlets, and the two outlets are respectively a normal opening and a normal closing. The peristaltic pump 4 can realize free switching between forward rotation and reverse rotation under the control of a control system. The metering column 1 has a metering function, can accurately quantitatively meter the volume of liquid pumped by the peristaltic pump, and has a liquid inlet and a liquid outlet at the bottom. The multi-channel switching electromagnetic valve 5 is provided with a main port in the middle and 7 sub-ports distributed around, wherein the main port can be communicated with any one sub-port, and can be in a emptying state under a standby state and is not communicated with any one sub-port. The specific structure of each component and the corresponding connection coordination relationship are described in detail below.

The metering column 1 can meter the liquid such as the reagent, the water sample, the pure water, the standard liquid and the like taken in the reaction. The liquid inlet and outlet of the metering column 1 is connected with the normally open port of the first three-way electromagnetic valve 2, and the normally closed port of the first three-way electromagnetic valve 2 is connected with the atmosphere for discharging redundant liquid in a pipeline after metering reagent, water sample, pure water, standard liquid and the like are completed, so that the volume of the liquid finally entering the photoelectric colorimetric unit is more accurate. The inlet of the first three-way electromagnetic valve 2 is connected with the normally open port of the second three-way electromagnetic valve 3. And a normally closed port of the second three-way electromagnetic valve 3 is connected to the waste liquid barrel 9 and is used for discharging the final liquid in the photoelectric colorimetric unit into the waste liquid barrel 9 after the test is completed. The inlet of the second three-way electromagnetic valve 3 is connected with one opening of the peristaltic pump 4, and the other opening of the peristaltic pump 4 is connected with the main opening of the multi-channel switching electromagnetic valve 5. The peristaltic pump 4 adopts a small peristaltic pump capable of being switched in forward and reverse directions, and is mainly used for extracting reagents, seawater samples, pure water and discharged waste liquid. Be equipped with 7 sub-mouthfuls that can independently switch the main mouthful of intercommunication on the multichannel switching solenoid valve 5, 7 sub-mouthfuls select one with first reagent storage bottle 6, second reagent storage bottle 7, ammonia nitrogen standard solution storage bottle 8, waste liquid bucket 9, pure water bucket 10, photoelectricity colorimetric unit 11, water sample cup 12 respectively, and every sub-mouthfuls connect and just connect one in first reagent storage bottle 6, second reagent storage bottle 7, ammonia nitrogen standard solution storage bottle 8, waste liquid bucket 9, pure water bucket 10, photoelectricity colorimetric unit 11, the water sample cup 12. The first reagent storage bottle 6, the second reagent storage bottle 7, the ammonia nitrogen standard solution storage bottle 8, the waste liquid barrel 9, the pure water barrel 10 and the water sample cup 12 are respectively used for storing the first reagent, the second reagent, the ammonia nitrogen standard solution, the waste liquid, the pure water and the seawater sample. The first reagent and the second reagent are respectively reagents which are added in the improved salicylic acid spectrophotometry and are needed to be added for measuring the ammonia nitrogen concentration of the sample, and the pumping is needed to be carried out through the switching operation of each valve and the power provided by the peristaltic pump 4. The ammonia nitrogen standard solution is used for calibration as the standard solution in the working curve, while the pure water is used for blank calibration in the working curve, and in addition, the pure water can be used as cleaning agent for each component and pipeline. Seawater samples in the water sample cup 12 come from monitoring points to be detected, and can be automatically sampled by manpower or other instruments and equipment and then injected into the water sample cup 12. The waste liquid barrel is used for collecting waste liquid in the testing process, so that the waste liquid can be conveniently and uniformly recycled, and the waste liquid is prevented from being discharged and polluting the environment.

The upper part of the photoelectric colorimetric unit 11 is connected with a two-way electromagnetic valve 13, and the other end of the two-way electromagnetic valve 13 is communicated with the atmosphere. When the two-way electromagnetic valve 13 is closed, the reactor inside the photoelectric colorimetric unit 11 is closed and is not communicated with the atmosphere, and when the two-way electromagnetic valve 13 is conducted, the reactor inside the photoelectric colorimetric unit 11 is communicated with the atmosphere.

The metering column 1 and the peristaltic pump 4 can be operated by valve switching to quantitatively pump the solution to be measured, the first reagent and the second reagent into the reactor in the photoelectric colorimetric unit 11 respectively for color reaction. The solution to be measured is one of pure water, ammonia nitrogen standard solution and seawater sample, and the pure water and the ammonia nitrogen standard solution are required to be used as the solution to be measured to construct a working curve before the seawater sample is measured. The specific manner in which the working curve is constructed and the measurement process will be described in detail later.

The photoelectric colorimetric unit 11 is capable of colorimetrically comparing the internal chromogenic reaction solution to obtain absorbance positively correlated with the ammonia nitrogen concentration in the solution to be detected. In the embodiment of the present invention, the photoelectric colorimetric unit 11 comprises a reactor, a temperature control system, a colorimetric light source and a photoelectric detector, wherein the solution to be measured, the first reagent and the second reagent enter the transparent reactor and are mixed to form a chromogenic reaction solution, the temperature control system is used for adjusting the reaction temperature in the reactor, the colorimetric light source is used for applying light with a specified wavelength to the reactor, and the photoelectric detector is used for measuring the transmitted light intensity passing through the reactor and the internal chromogenic reaction solution. The reactor is made of quartz glass, can resist high temperature and high pressure and corrosion, and does not influence the light transmittance of the light source during color comparison. The colorimetric light source adopts a 660nm wavelength light source.

It should be noted that the photoelectric colorimeter 11 may also be a conventional device such as a photoelectric colorimeter.

Based on the seawater ammonia nitrogen detection device shown in fig. 1, the invention provides a seawater ammonia nitrogen detection method, which comprises the following steps:

sequentially taking pure water, an ammonia nitrogen standard solution and a seawater sample as solutions to be measured, executing an ammonia nitrogen concentration measurement process by combining valve switching operation, and obtaining absorbance positively correlated with the ammonia nitrogen concentration in the three solutions to be measured through a photoelectric colorimetric unit 11; and forming a working curve according to the absorbance and the ammonia nitrogen concentration corresponding to the pure ammonia nitrogen standard solution, and then converting the concentration of the ammonia nitrogen in the seawater sample based on the working curve and the absorbance corresponding to the seawater sample.

s1, initializing a reactor inner cavity of the photoelectric colorimetric unit 11 to be in a state of empty and no solution residue, and enabling a valve and a pipeline in the detection device to be in an initial standby state through valve switching operation.

In the standby state, the inlet of the first three-way electromagnetic valve 2 is communicated with the normally open port, the inlet of the second three-way electromagnetic valve 3 is communicated with the normally open port, the main port of the multi-channel switching electromagnetic method 5 is empty, and the two-way electromagnetic valve 13 is closed.

S2, switching valves of the multi-channel switching electromagnetic valve 5 to enable a main port of the multi-channel switching electromagnetic valve 5 to be communicated with a sub-port corresponding to the current solution to be measured, controlling the peristaltic pump 4 to reversely rotate to quantitatively pump the current solution to be measured into the measuring column 1, switching the valves of the multi-channel switching electromagnetic valve 5 again to enable the main port of the multi-channel switching electromagnetic valve 5 to be communicated with the sub-port corresponding to the waste liquid barrel 9, and controlling the peristaltic pump 4 to reversely rotate to discharge the residual current solution to be measured in the pipeline into the waste liquid barrel 9; then, valve switching is carried out on the multi-channel switching electromagnetic valve 5 to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the photoelectric colorimetric unit 11, the inlet of the first three-way electromagnetic valve 2 is kept to be communicated with the normally open port, after the two-way electromagnetic valve 13 is controlled to be conducted, the peristaltic pump 4 is controlled to rotate forwards, and all the current solution to be measured in the measuring column 1 is pumped into the reactor of the photoelectric colorimetric unit 11; and finally, the valve and the pipeline in the detection device are restored to the standby state by the valve switching operation again.

S3, switching valves of the multi-channel switching electromagnetic valve 5 to enable a main port of the multi-channel switching electromagnetic valve 5 to be communicated with a sub-port corresponding to the first reagent storage bottle 6, controlling the peristaltic pump 4 to reversely rotate to pump the first reagent into the metering column 1 quantitatively, switching the valves of the multi-channel switching electromagnetic valve 5 again to enable the main port of the multi-channel switching electromagnetic valve 5 to be communicated with the sub-port corresponding to the waste liquid barrel 9, and controlling the peristaltic pump 4 to reversely rotate to discharge the first reagent remained in the pipeline into the waste liquid barrel 9; then, the multi-channel switching electromagnetic valve 5 is subjected to valve switching to enable the main port of the multi-channel switching electromagnetic valve 5 to be communicated with the sub port corresponding to the photoelectric colorimetric unit 11, the inlet of the first three-way electromagnetic valve 2 is kept to be communicated with the normally open port, after the two-way electromagnetic valve 13 is controlled to be conducted, the peristaltic pump 4 is controlled to rotate forwards, and all the first reagent in the metering column 1 is pumped into the reactor of the photoelectric colorimetric unit 11; and finally, the valve and the pipeline in the detection device are restored to the standby state by the valve switching operation again.

S4, switching valves of the multi-channel switching electromagnetic valve 5 to enable the main opening of the multi-channel switching electromagnetic valve 5 to be communicated with the sub opening corresponding to the pure water barrel 10, controlling the peristaltic pump 4 to reversely rotate to pump pure water into the metering column 1 quantitatively, switching the valves of the multi-channel switching electromagnetic valve 5 again to enable the main opening of the multi-channel switching electromagnetic valve 5 to be communicated with the sub opening corresponding to the waste liquid barrel 9, controlling the peristaltic pump 4 to positively rotate to drain the residual pure water in the metering column 1 and the pipeline into the waste liquid barrel 9, and completing cleaning of the metering column 1 and the pipeline; and finally, the valve and the pipeline in the detection device are restored to the standby state by the valve switching operation again.

S5, switching valves of the multi-channel switching electromagnetic valve 5 to enable the main port of the multi-channel switching electromagnetic valve 5 to be communicated with the sub-port corresponding to the second reagent storage bottle 7, controlling the peristaltic pump 4 to reversely rotate to pump the second reagent into the metering column 1 quantitatively, switching the valves of the multi-channel switching electromagnetic valve 5 again to enable the main port of the multi-channel switching electromagnetic valve 5 to be communicated with the sub-port corresponding to the waste liquid barrel 9, and controlling the peristaltic pump 4 to reversely rotate to discharge the second reagent remained in the pipeline into the waste liquid barrel 9; then, the multi-channel switching electromagnetic valve 5 is subjected to valve switching to enable the main port of the multi-channel switching electromagnetic valve 5 to be communicated with the sub port corresponding to the photoelectric colorimetric unit 11, the inlet of the first three-way electromagnetic valve 2 is kept to be communicated with the normally open port, after the two-way electromagnetic valve 13 is controlled to be conducted, the peristaltic pump 4 is controlled to rotate forwards, and all second reagents in the metering column 1 are pumped into the reactor of the photoelectric colorimetric unit 11; and finally, the valve and the pipeline in the detection device are restored to the standby state by the valve switching operation again.

S6, after the current solution to be detected, the first reagent and the second reagent are all pumped into the reactor of the photoelectric colorimetric unit 11, controlling the temperature in the reactor to be maintained at the temperature required by the color development reaction, applying light with characteristic absorption wavelength required by ammonia nitrogen determination to the reactor through a colorimetric light source after the color development reaction is completed, and then measuring the transmitted light intensity passing through the reactor and the internal color development reaction solution through a photoelectric detector to obtain the absorbance of the current solution to be detected after the color development reaction; then, the main port of the multi-channel switching electromagnetic valve 5 is kept to be communicated with the sub-port corresponding to the photoelectric colorimetric unit 11, the inlet of the second three-way electromagnetic valve 3 is controlled to be normally closed, the two-way electromagnetic valve 13 is controlled to be communicated, and the peristaltic pump 4 is controlled to reversely rotate so as to discharge all the color developing reaction liquid in the photoelectric colorimetric unit 11 into the waste liquid barrel 9; and finally, the valve and the pipeline in the detection device are restored to the standby state by the valve switching operation again.

S7, switching the valves of the multi-channel switching electromagnetic valve 5 to enable the main opening of the multi-channel switching electromagnetic valve 5 to be communicated with the sub opening corresponding to the pure water barrel 10, controlling the peristaltic pump 4 to reversely rotate to pump pure water into the metering column 1 quantitatively, switching the valves of the multi-channel switching electromagnetic valve 5 again to enable the main opening of the multi-channel switching electromagnetic valve 5 to be communicated with the sub opening corresponding to the photoelectric colorimetric unit 11, and controlling the peristaltic pump 4 to positively rotate to pump all pure water in the metering column 1 into the reactor of the photoelectric colorimetric unit 11 to clean the inner cavity of the reactor; the inlet of the second three-way electromagnetic valve 3 is controlled to be normally closed, the two-way electromagnetic valve 13 is controlled to be conducted, and the peristaltic pump 4 is controlled to reversely rotate so as to discharge all the solution after cleaning in the photoelectric colorimetric unit 11 into the waste liquid barrel 9; and finally, the valve and the pipeline in the detection device are restored to the standby state by the valve switching operation again.

S8, switching the valves of the multi-channel switching electromagnetic valve 5 to enable the main opening of the multi-channel switching electromagnetic valve 5 to be communicated with the sub opening corresponding to the pure water barrel 10, controlling the peristaltic pump 4 to reversely rotate to pump pure water into the metering column 1 quantitatively, switching the valves of the multi-channel switching electromagnetic valve 5 again to enable the main opening of the multi-channel switching electromagnetic valve 5 to be communicated with the sub opening corresponding to the photoelectric colorimetric unit 11, and controlling the peristaltic pump 4 to positively rotate to pump all pure water in the metering column 1 into the reactor of the photoelectric colorimetric unit 11 to fill the inner cavity of the reactor; and finally, the valve and the pipeline in the detection device are restored to a standby state by the valve switching operation again, and the next measurement is waited.

As described above, the volume ratio of the current solution to be tested, the first reagent and the second reagent pumped into the reactor is 10:1:1.2, and the first reagent is a mixed solution of sodium salicylate, sodium citrate, sodium nitrosoferricyanide and disodium ethylenediamine tetraacetate, and the preparation method is as described above. The second reagent adopts sodium hydroxide-sodium dichloroisocyanurate mixed solution, and the preparation method is as described above. The temperature required by the color reaction is 45 ℃, the color reaction time is 10min, and the characteristic absorption wavelength required by the determination of ammonia nitrogen is 660nm.

In addition, it should be noted that the first three-way electromagnetic valve 2, the second three-way electromagnetic valve 3, the two-way electromagnetic valve 13, etc. may also be directly implemented by using an existing valve model, the first three-way electromagnetic valve 2 and the second three-way electromagnetic valve 3 may be in a valve form in which an inlet is connected with a normally open port when the power is off and an inlet is connected with a normally closed port when the power is on, and the two-way electromagnetic valve 13 may be a normally closed two-way electromagnetic valve, and is closed when the power is off and is on when the power is on. Therefore, based on such valve selection, in an embodiment of the present invention, the detection device works as follows:

1. Blank calibration flow:

a. the three-way electromagnetic valve 3 is powered on, and the inlet of the three-way electromagnetic valve is connected with the normally closed port; the multi-channel switching electromagnetic valve 5 is powered on to switch the main port of the multi-channel switching electromagnetic valve to the photoelectric colorimetric unit 11; the two solenoid valves 13 are powered on to enable the reactor in the photoelectric colorimetric unit 11 to be communicated with air; the peristaltic pump 4 is powered on to reverse the direction for 20s, and all the pure water stored in the reactor in the standby state is discharged into the waste liquid barrel. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

b. The multi-channel switching electromagnetic valve 5 is powered on to switch the main port of the multi-channel switching electromagnetic valve to the pure water barrel 10; the peristaltic pump 4 is powered on to enable the peristaltic pump 4 to reversely rotate, pure water is pumped into the measuring column to 10mL, the peristaltic pump 4 stops powering on, and the main port of the multichannel switching electromagnetic method 5 is switched to the waste liquid barrel 9; the three-way electromagnetic valve 2 is powered on, the peristaltic pump is powered on to enable the peristaltic pump to reverse for 5 seconds, and the residual pure water in the pipeline is discharged into the waste liquid barrel 9; the peristaltic pump 4 is powered off; the multi-channel switching electromagnetic valve 5 is switched to the photoelectric colorimetric unit 11, the three-way electromagnetic valve 2 is powered off, the two-way electromagnetic valve 13 is powered on, the peristaltic pump 4 is powered on to rotate forward for 15s, and 10mL of pure water in the measuring column is pumped into the reactor of the photoelectric colorimetric unit 11. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

c. The multi-channel switching electromagnetic valve 5 is powered on to switch the main port of the multi-channel switching electromagnetic valve to the reagent R1 storage bottle 6; the peristaltic pump 4 is powered up to reverse, the reagent R1 is pumped into the measuring column to 1mL, the peristaltic pump 4 stops powering up, and the main port of the multi-channel switching electromagnetic method 5 is switched to the waste liquid barrel 9; the three-way electromagnetic valve 2 is powered on, the peristaltic pump is powered on to enable the peristaltic pump to reverse for 5 seconds, and the residual reagent R1 in the pipeline is discharged into the waste liquid barrel 9. The peristaltic pump 4 is powered off; the multi-channel switching electromagnetic valve 5 is switched to the photoelectric colorimetric unit 11, the three-way electromagnetic valve 2 is powered off, the two-way electromagnetic valve 13 is powered on, the peristaltic pump 4 is powered on to rotate forward for 15s, and 1mL of reagent R1 in the measuring column is pumped into the reactor of the photoelectric colorimetric unit 11. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

d. The multi-channel switching electromagnetic valve 5 is powered on to switch the main port of the multi-channel switching electromagnetic valve to the pure water barrel 10; the peristaltic pump 4 is powered up to reverse, pure water is pumped into the measuring column to 5mL, the peristaltic pump 4 stops powering up, and the main port of the multichannel switching electromagnetic method 5 is switched to the waste liquid barrel 9; the peristaltic pump is powered up to rotate forward for 15s, all liquid in the measuring column and the pipeline is discharged into the waste liquid barrel 9, and the cleaning of the measuring column and the pipeline is completed. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

e. The multi-channel switching electromagnetic valve 5 is powered on to switch the main port of the multi-channel switching electromagnetic valve to the reagent R2 storage bottle 7; the peristaltic pump 4 is powered up to reverse, the reagent R2 is pumped into the measuring column to 1.2mL, the peristaltic pump 4 stops powering up, and the main port of the multi-channel switching electromagnetic method 5 is switched to the waste liquid barrel 9; the three-way electromagnetic valve 2 is powered on, the peristaltic pump is reversed for 5 seconds, and the residual reagent R2 in the pipeline is discharged into the waste liquid barrel 9. The peristaltic pump 4 is powered off; the multi-channel switching electromagnetic valve 5 is switched to the photoelectric colorimetric unit 11, the three-way electromagnetic valve 2 is powered off, the two-way electromagnetic valve 13 is powered on, the peristaltic pump 4 is powered on to rotate forward for 15s, and 1.2mL of reagent R2 in the measuring column is pumped into the reactor of the photoelectric colorimetric unit 11. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

f. After the reagent in the reactor of the photoelectric colorimetric unit 11 is mixed with pure water, a temperature control system is started to work, the temperature in the reactor is controlled at about 45 ℃, the color development reaction is started, the color development reaction is kept for 10 minutes, a colorimetric light source is powered on, and the absorbance of liquid after the color development reaction is read; the three-way electromagnetic valve 3 is powered on, the main port of the multi-channel switching electromagnetic method 5 is switched to the photoelectric colorimetric unit 11, the two power-on valves 13 are powered on, the peristaltic pump is powered on and inverted for 20s, and all liquid in the reactor of the photoelectric colorimetric unit 11 is discharged into the waste liquid barrel 9. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

g. The multi-channel switching electromagnetic valve 5 is powered on to switch the main port of the multi-channel switching electromagnetic valve to the pure water barrel 10; the peristaltic pump 4 is powered on and reversely rotates, pure water is pumped into the measuring column to 15mL, the peristaltic pump 4 stops powering on, the main port of the multi-channel switching electromagnetic valve 5 is switched to the photoelectric colorimetric unit 11, the two electromagnetic valves 13 are powered on, the peristaltic pump is powered on and rotates forward for 20s, and all the pure water in the measuring column 1 is pumped into the reactor of the photoelectric colorimetric unit 11; the peristaltic pump 4 is powered off, the three-way electromagnetic valve 3 is powered on, the peristaltic pump 4 is powered on and is reversed for 20s, and all liquid in the reactor of the photoelectric colorimetric unit 11 is discharged into the waste liquid barrel 9. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored. And (5) finishing the cleaning of the system flow path.

h. The multi-channel switching electromagnetic valve 5 is powered on to switch the main port of the multi-channel switching electromagnetic valve to the pure water barrel 10; the peristaltic pump 4 is powered on and reversely rotates, pure water is pumped into the measuring column to 10mL, the peristaltic pump 4 stops powering on, the main port of the multi-channel switching electromagnetic valve 5 is switched to the photoelectric colorimetric unit 11, the two electromagnetic valves 13 are powered on, the peristaltic pump is powered on and rotates forward for 20s, and all pure water in the measuring column 1 is pumped into the reactor of the photoelectric colorimetric unit 11. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

And (3) completing a blank calibration flow to obtain absorbance after the blank solution is reacted.

2. Standard solution calibration procedure:

a. the step a is the same as the step a in the blank calibration flow.

b. The multi-channel switching electromagnetic valve 5 is powered on to switch the main port of the multi-channel switching electromagnetic valve to the ammonia nitrogen standard liquid storage bottle 8; the peristaltic pump 4 is powered up to enable the peristaltic pump 4 to reversely rotate, ammonia nitrogen standard liquid is pumped into the metering column to 10mL, the peristaltic pump 4 stops powering up, and the main port of the multichannel switching electromagnetic method 5 is switched to the waste liquid barrel 9; the three-way electromagnetic valve 2 is powered on, the peristaltic pump is powered on to enable the peristaltic pump to reverse for 5 seconds, and the ammonia nitrogen standard solution remained in the pipeline is discharged into the waste liquid barrel 9; the peristaltic pump 4 is powered off; the multi-channel switching electromagnetic valve 5 is switched to the photoelectric colorimetric unit 11, the three-way electromagnetic valve 2 is powered off, the two-way electromagnetic valve 13 is powered on, the peristaltic pump 4 is powered on to rotate forward for 15s, and 10mL of ammonia nitrogen standard solution in the measuring column is pumped into the reactor of the photoelectric colorimetric unit 11. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

The following steps are the same as steps c-h in the blank calibration flow. And (3) completing the standard solution calibration flow to obtain the absorbance of the standard solution after the reaction.

3. The seawater sample measurement flow comprises the following steps:

a. the step a is the same as the step a in the blank calibration flow.

b. The multi-channel switching electromagnetic valve 5 is powered on, so that the main port of the multi-channel switching electromagnetic valve is switched to the ammonia nitrogen standard liquid sample cup 12; the peristaltic pump 4 is powered up to reverse, the seawater sample is pumped into the metering column to 10mL, the peristaltic pump 4 stops powering up, and the main port of the multichannel switching electromagnetic method 5 is switched to the waste liquid barrel 9; the three-way electromagnetic valve 2 is powered on, the peristaltic pump is powered on to enable the peristaltic pump to reverse for 5 seconds, and the residual seawater sample in the pipeline is discharged into the waste liquid barrel 9; the peristaltic pump 4 is powered off; the multi-channel switching electromagnetic valve 5 is switched to the photoelectric colorimetric unit 11, the three-way electromagnetic valve 2 is powered off, the two-way electromagnetic valve 13 is powered on, the peristaltic pump 4 is powered on to rotate forward for 15s, and 10mL of seawater sample in the measuring column is pumped into the reactor of the photoelectric colorimetric unit 11. The solenoid valves and the peristaltic pumps are powered off, and the standby state is restored.

The following steps are the same as steps c-h in the blank calibration flow. And (3) completing the seawater sample measurement flow to obtain absorbance after the seawater sample is reacted.

And drawing a working curve according to the absorbance calibrated by the blank and the absorbance calibrated by the standard solution, and the concentration of ammonia nitrogen in the seawater sample can be converted through the absorbance and the working curve measured by the seawater sample. In practical application, the blank calibration and the standard solution calibration can be performed once a month (i.e. the working curve of each time can be used for about one month), and only the seawater sample test flow is needed in the continuous online measurement process.

In order to prove the accuracy of the detection method, the result of the detection device is compared with a laboratory manual analysis method, and the result is as follows:

the detection device and the laboratory manual analysis are adopted to carry out actual collected seawater sample comparison analysis at a river inlet (station 1), a river inlet (station 2) and a sewage outlet (station 3) of a sewage treatment plant respectively, and the reference laboratory manual analysis method is a hypobromite oxidation method in ocean monitoring Specification (GB 17318.4-2007). Meanwhile, referring to a management method (trial run) of a real-time monitoring system of ocean water quality buoy in Zhejiang province, the actual seawater sample test result of the device is compared by adopting absolute error or relative error. The real-time monitoring system management method (trial) of ocean water quality buoy in Zhejiang province is as follows: when the actual sampling comparison error of seawater ammonia nitrogen is calculated to be less than or equal to 20 mug/L, the absolute error is adopted for evaluation, and the evaluation standard is less than or equal to +/-10 mug/L; when the background value is more than or equal to 20 mug/L, the relative error is adopted for evaluation, and the evaluation standard is less than or equal to +/-30 percent.

The manual analysis result of the device and the laboratory is as follows:

the method is based on the principle of testing ammonia nitrogen in the salicylic acid spectrophotometry for measuring water ammonia nitrogen of HJ 536-2009, and the stability of the used reagent is better and the color reaction time is short by improving the reagent formula; the masking agent in the reagent can mask calcium and magnesium ions in the water sample, and avoids precipitation caused by the reaction of the calcium and magnesium ions and salicylate in the reagent to affect color comparison. The pipeline is reasonable in arrangement, high in automation degree, small in error compared with a laboratory standard method in an actual water sample test result, and capable of being used for on-line monitoring of ammonia nitrogen concentration in ocean water quality.

The above embodiment is only a preferred embodiment of the present invention, but it is not intended to limit the present invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, all the technical schemes obtained by adopting the equivalent substitution or equivalent transformation are within the protection scope of the invention.

Claims

1. The improved seawater ammonia nitrogen detection device based on the salicylic acid spectrophotometry is characterized by comprising a metering column (1), a first three-way electromagnetic valve (2), a second three-way electromagnetic valve (3), a peristaltic pump (4), a multi-channel switching electromagnetic valve (5) and a photoelectric colorimetric unit (11); the first three-way electromagnetic valve (2) and the second three-way electromagnetic valve (3) are two three-way electromagnetic valves of one inlet and two outlets; the peristaltic pump (4) can switch between forward rotation and reverse rotation; the liquid inlet and outlet of the metering column (1) are connected with the normally open port of the first three-way electromagnetic valve (2), the normally closed port of the first three-way electromagnetic valve (2) is connected with the atmosphere, and the inlet of the first three-way electromagnetic valve (2) is connected with the normally open port of the second three-way electromagnetic valve (3); the inlet of the second three-way electromagnetic valve (3) is connected with one opening of the peristaltic pump (4), the other opening of the peristaltic pump (4) is connected with the main opening of the multi-channel switching electromagnetic valve (5), 7 sub-openings which can be independently switched and communicated with the main opening are arranged on the multi-channel switching electromagnetic valve (5), and the 7 sub-openings are respectively connected with one of the first reagent storage bottle (6), the second reagent storage bottle (7), the ammonia nitrogen standard solution storage bottle (8), the waste liquid barrel (9), the pure water barrel (10), the photoelectric colorimetric unit (11) and the water sample cup (12); the upper part of the photoelectric colorimetric unit (11) is connected with a two-way electromagnetic valve (13), and the other end of the two-way electromagnetic valve (13) is communicated with the atmosphere; the metering column (1) and the peristaltic pump (4) can be switched by valves to pump a solution to be measured, a first reagent and a second reagent into a reactor in the photoelectric colorimetric unit (11) quantitatively for color reaction, wherein the solution to be measured is one of pure water, an ammonia nitrogen standard solution and a seawater sample; the photoelectric colorimetric unit (11) can be used for carrying out colorimetric comparison on the internal chromogenic reaction liquid to obtain absorbance positively related to the ammonia nitrogen concentration in the solution to be detected.

2. The improved seawater ammonia nitrogen detecting device based on salicylic acid spectrophotometry according to claim 1, wherein the photoelectric colorimetric unit (11) comprises a reactor, a temperature control system, a colorimetric light source and a photoelectric detector, the solution to be detected, the first reagent and the second reagent enter the transparent reactor to be mixed to form a chromogenic reaction solution, the temperature control system is used for adjusting the reaction temperature in the reactor, the colorimetric light source is used for applying light with a specified wavelength to the reactor, and the photoelectric detector is used for measuring the transmitted light intensity passing through the reactor and the internal chromogenic reaction solution.

3. The improved seawater ammonia nitrogen detecting device based on salicylic acid spectrophotometry according to claim 2, wherein the reactor is made of quartz glass.

4. The improved seawater ammonia nitrogen detecting device based on salicylic acid spectrophotometry according to claim 2, wherein the colorimetric light source is a 660nm wavelength light source.

5. The improved seawater ammonia nitrogen detecting device based on salicylic acid spectrophotometry according to claim 1, wherein the two-way electromagnetic valve (13) is a normally closed two-way electromagnetic valve.

6. The improved seawater ammonia nitrogen detecting device based on salicylic acid spectrophotometry according to claim 1, wherein the first reagent is a mixed solution of sodium salicylate, sodium citrate, sodium nitrosoferricyanide and disodium ethylenediamine tetraacetate; preferably, the preparation method of the first reagent comprises the following steps: 20+/-0.1 g of disodium ethylenediamine tetraacetate is weighed and dissolved in 300mL of purified water, then 65+/-0.1 g of sodium citrate and 65+/-0.1 g of sodium salicylate are weighed and dissolved in the solution, then 0.5+/-0.01 g of sodium nitrosoferricyanide is added, and after all the sodium disodium ethylenediamine tetraacetate is dissolved, the solution is subjected to constant volume to 500mL by water and is uniformly shaken.

7. The improved seawater ammonia nitrogen detecting device based on salicylic acid spectrophotometry according to claim 1, wherein the second reagent is sodium hydroxide-dichloro sodium isocyanurate mixed solution; preferably, the preparation method of the second reagent comprises the following steps: 10.0+/-0.1 g of sodium hydroxide is dissolved in 150mL of purified water and cooled to room temperature, 1.0+/-0.01 g of sodium dichloroisocyanurate is dissolved in sodium hydroxide solution cooled to room temperature, and then water is used for constant volume to 250mL, and shaking is carried out uniformly.

8. A seawater ammonia nitrogen detecting method using the seawater ammonia nitrogen detecting apparatus as defined in any one of claims 1 to 7, comprising:

Sequentially taking pure water, an ammonia nitrogen standard solution and a seawater sample as solutions to be measured, executing an ammonia nitrogen concentration measurement process by combining valve switching operation, and obtaining absorbance positively correlated with the ammonia nitrogen concentration in the three solutions to be measured through a photoelectric colorimetric unit (11); forming a working curve according to the absorbance and the ammonia nitrogen concentration corresponding to the pure ammonia nitrogen standard solution, and then converting the concentration of ammonia nitrogen in the seawater sample based on the working curve and the absorbance corresponding to the seawater sample;

s1, initializing a reactor inner cavity of a photoelectric colorimetric unit (11) to be in a state of empty and no solution residue, and enabling a valve and a pipeline in a detection device to be in an initial standby state through valve switching operation;

in the standby state, the inlet of the first three-way electromagnetic valve (2) is communicated with the normally open port, the inlet of the second three-way electromagnetic valve (3) is communicated with the normally open port, the main port of the multi-channel switching electromagnetic method (5) is empty, and the two-way electromagnetic valve (13) is closed;

s2, switching valves of the multi-channel switching electromagnetic valve (5) to enable a main port of the multi-channel switching electromagnetic valve to be communicated with a sub-port corresponding to the current solution to be measured, controlling the peristaltic pump (4) to reversely rotate to quantitatively pump the current solution to be measured into the measuring column (1), switching the valves of the multi-channel switching electromagnetic valve (5) again to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the waste liquid barrel (9), and controlling the peristaltic pump (4) to reversely rotate to discharge the residual current solution to be measured in the pipeline into the waste liquid barrel (9); then, valve switching is carried out on the multi-channel switching electromagnetic valve (5) to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the photoelectric colorimetric unit (11), the inlet of the first three-way electromagnetic valve (2) is kept to be communicated with the normally open port, after the two-way electromagnetic valve (13) is controlled to be conducted, the peristaltic pump (4) is controlled to rotate forwards, and all the current solution to be measured in the measuring column (1) is pumped into the reactor of the photoelectric colorimetric unit (11); finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

S3, switching valves of the multi-channel switching electromagnetic valve (5) to enable a main port of the multi-channel switching electromagnetic valve to be communicated with a sub port corresponding to the first reagent storage bottle (6), controlling the peristaltic pump (4) to reversely rotate to quantitatively pump the first reagent into the metering column (1), switching the valves of the multi-channel switching electromagnetic valve (5) again to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the waste liquid barrel (9), and controlling the peristaltic pump (4) to reversely rotate to discharge the first reagent remained in the pipeline into the waste liquid barrel (9); then, valve switching is carried out on the multi-channel switching electromagnetic valve (5) to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the photoelectric colorimetric unit (11), the inlet of the first three-way electromagnetic valve (2) is kept to be communicated with the normally open port, after the two-way electromagnetic valve (13) is controlled to be conducted, the peristaltic pump (4) is controlled to rotate forwards, and all first reagents in the metering column (1) are pumped into the reactor of the photoelectric colorimetric unit (11); finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

s4, switching valves of the multi-channel switching electromagnetic valve (5) to enable a main port of the multi-channel switching electromagnetic valve to be communicated with a sub-port corresponding to the pure water barrel (10), controlling the peristaltic pump (4) to reversely pump pure water into the metering column (1) quantitatively, switching the valves of the multi-channel switching electromagnetic valve (5) again to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the waste liquid barrel (9), controlling the peristaltic pump (4) to positively rotate to drain the residual pure water in the metering column (1) and the pipeline into the waste liquid barrel (9), and completing cleaning of the metering column (1) and the pipeline; finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

S5, switching valves of the multi-channel switching electromagnetic valve (5) to enable a main port of the multi-channel switching electromagnetic valve to be communicated with a sub port corresponding to a second reagent storage bottle (7), controlling the peristaltic pump (4) to reversely rotate to quantitatively pump a second reagent into the metering column (1), switching the valves of the multi-channel switching electromagnetic valve (5) again to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the waste liquid barrel (9), and controlling the peristaltic pump (4) to reversely rotate to discharge the second reagent remained in the pipeline into the waste liquid barrel (9); then, valve switching is carried out on the multi-channel switching electromagnetic valve (5) to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub port corresponding to the photoelectric colorimetric unit (11), the inlet of the first three-way electromagnetic valve (2) is kept to be communicated with the normally open port, after the two-way electromagnetic valve (13) is controlled to be conducted, the peristaltic pump (4) is controlled to rotate forwards, and all second reagents in the metering column (1) are pumped into the reactor of the photoelectric colorimetric unit (11); finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

s6, after the current solution to be detected, the first reagent and the second reagent are all pumped into a reactor of a photoelectric colorimetric unit (11), controlling the temperature in the reactor to be maintained at the temperature required by the color development reaction, applying light with characteristic absorption wavelength required by ammonia nitrogen determination to the reactor through a colorimetric light source after the color development reaction is completed, and then measuring the transmitted light intensity passing through the reactor and the internal color development reaction solution through a photoelectric detector to obtain the absorbance of the current solution to be detected after the color development reaction; then, the main port of the multi-channel switching electromagnetic valve (5) is kept to be communicated with the sub port corresponding to the photoelectric colorimetric unit (11), the inlet connection of the second three-way electromagnetic valve (3) is controlled to be normally closed, the two-way electromagnetic valve (13) is controlled to be conducted, and the peristaltic pump (4) is controlled to reversely rotate so as to discharge all the color reaction liquid in the photoelectric colorimetric unit (11) into the waste liquid barrel (9); finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

S7, switching valves of the multi-channel switching electromagnetic valve (5) to enable a main port of the multi-channel switching electromagnetic valve to be communicated with a sub-port corresponding to the pure water barrel (10), controlling the peristaltic pump (4) to reversely pump pure water into the metering column (1) quantitatively, switching the valves of the multi-channel switching electromagnetic valve (5) again to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the photoelectric colorimetric unit (11), and controlling the peristaltic pump (4) to positively rotate to pump all pure water in the metering column (1) into a reactor of the photoelectric colorimetric unit (11) to clean an inner cavity of the reactor; the inlet of the second three-way electromagnetic valve (3) is controlled to be normally closed, the two-way electromagnetic valve (13) is controlled to be conducted, and the peristaltic pump (4) is controlled to reversely rotate so as to discharge all the solution after cleaning in the photoelectric colorimetric unit (11) into the waste liquid barrel (9); finally, the valve and the pipeline in the detection device are restored to the standby state through valve switching operation again;

s8, switching valves of the multi-channel switching electromagnetic valve (5) to enable a main port of the multi-channel switching electromagnetic valve to be communicated with a sub-port corresponding to the pure water barrel (10), controlling the peristaltic pump (4) to reversely pump pure water into the metering column (1) quantitatively, switching the valves of the multi-channel switching electromagnetic valve (5) again to enable the main port of the multi-channel switching electromagnetic valve to be communicated with the sub-port corresponding to the photoelectric colorimetric unit (11), controlling the peristaltic pump (4) to positively rotate to pump all pure water in the metering column (1) into a reactor of the photoelectric colorimetric unit (11) to fill an inner cavity of the reactor; and finally, the valve and the pipeline in the detection device are restored to a standby state by the valve switching operation again, and the next measurement is waited.

9. The method for detecting ammonia nitrogen in seawater according to claim 8, wherein the volume ratio of the current solution to be detected, the first reagent and the second reagent pumped into the reactor is 10:1:1.2; the first reagent adopts a mixed solution of sodium salicylate, sodium citrate, sodium nitrosoferricyanide and disodium ethylenediamine tetraacetate, and the preparation method of the first reagent comprises the following steps: dissolving 20+/-0.1 g of disodium ethylenediamine tetraacetate in 300mL of purified water, then dissolving 65+/-0.1 g of sodium citrate and 65+/-0.1 g of sodium salicylate in the solution, adding 0.5+/-0.01 g of sodium nitrosoferricyanide, and shaking uniformly after the disodium ethylenediamine tetraacetate and the sodium salicylate are completely dissolved, and using water to fix the volume to 500 mL; the second reagent adopts sodium hydroxide-sodium dichloroisocyanurate mixed solution, and the preparation method of the second reagent comprises the following steps: dissolving 10.0+/-0.1 g of sodium hydroxide in 150mL of purified water and cooling to room temperature, dissolving 1.0+/-0.01 g of sodium dichloroisocyanurate in sodium hydroxide solution cooled to room temperature, then fixing the volume to 250mL by using water, and shaking uniformly; the temperature required by the color reaction is 45 ℃, the color reaction time is 10min, and the characteristic absorption wavelength required by the determination of ammonia nitrogen is 660nm.

10. The method for detecting ammonia nitrogen in seawater according to claim 8, wherein the working curve is periodically re-measured and plotted once, during which only the absorbance of the seawater sample is directly measured and the latest working curve is called for only the conversion of ammonia nitrogen concentration.