CN116297297B - Method and sensor for detecting total nitrogen in water based on array spectrum and ion selection method - Google Patents
Method and sensor for detecting total nitrogen in water based on array spectrum and ion selection method Download PDFInfo
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 283
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 164
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 141
- 238000000034 method Methods 0.000 title claims abstract description 81
- 238000001228 spectrum Methods 0.000 title claims abstract description 42
- 238000010187 selection method Methods 0.000 title claims abstract description 24
- 125000001477 organic nitrogen group Chemical group 0.000 claims abstract description 88
- 238000001514 detection method Methods 0.000 claims abstract description 80
- 238000006243 chemical reaction Methods 0.000 claims abstract description 21
- 150000002500 ions Chemical class 0.000 claims description 154
- 239000000126 substance Substances 0.000 claims description 34
- 239000000243 solution Substances 0.000 claims description 32
- 238000002835 absorbance Methods 0.000 claims description 31
- 239000012528 membrane Substances 0.000 claims description 20
- 238000004364 calculation method Methods 0.000 claims description 18
- 230000004044 response Effects 0.000 claims description 12
- 239000012086 standard solution Substances 0.000 claims description 10
- 238000012937 correction Methods 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 8
- 238000005259 measurement Methods 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 7
- 238000012360 testing method Methods 0.000 claims description 7
- 238000002329 infrared spectrum Methods 0.000 claims description 5
- 238000010521 absorption reaction Methods 0.000 claims description 4
- 230000031700 light absorption Effects 0.000 claims description 4
- 239000005416 organic matter Substances 0.000 claims description 4
- 238000010276 construction Methods 0.000 claims description 3
- 238000004445 quantitative analysis Methods 0.000 claims description 3
- 235000013405 beer Nutrition 0.000 claims description 2
- 230000005540 biological transmission Effects 0.000 claims description 2
- 238000013507 mapping Methods 0.000 claims description 2
- 238000002834 transmittance Methods 0.000 claims description 2
- 238000004611 spectroscopical analysis Methods 0.000 claims 3
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 10
- 150000001412 amines Chemical class 0.000 description 8
- -1 ammonium ions Chemical class 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 6
- 229910001414 potassium ion Inorganic materials 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 5
- 229910002651 NO3 Inorganic materials 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 5
- 230000002452 interceptive effect Effects 0.000 description 4
- 229920000642 polymer Polymers 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- NPYPAHLBTDXSSS-UHFFFAOYSA-N Potassium ion Chemical compound [K+] NPYPAHLBTDXSSS-UHFFFAOYSA-N 0.000 description 3
- MMDJDBSEMBIJBB-UHFFFAOYSA-N [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] Chemical compound [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] MMDJDBSEMBIJBB-UHFFFAOYSA-N 0.000 description 3
- 150000001413 amino acids Chemical class 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 125000000018 nitroso group Chemical group N(=O)* 0.000 description 3
- 235000015097 nutrients Nutrition 0.000 description 3
- 229920000915 polyvinyl chloride Polymers 0.000 description 3
- 239000004800 polyvinyl chloride Substances 0.000 description 3
- 102000004169 proteins and genes Human genes 0.000 description 3
- 108090000623 proteins and genes Proteins 0.000 description 3
- 239000013543 active substance Substances 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000012851 eutrophication Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 2
- 239000010865 sewage Substances 0.000 description 2
- 239000012085 test solution Substances 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- HFVIYAZBVIGNAN-UHFFFAOYSA-N 1,1-dibromodecane Chemical compound CCCCCCCCCC(Br)Br HFVIYAZBVIGNAN-UHFFFAOYSA-N 0.000 description 1
- GEYOCULIXLDCMW-UHFFFAOYSA-N 1,2-phenylenediamine Chemical compound NC1=CC=CC=C1N GEYOCULIXLDCMW-UHFFFAOYSA-N 0.000 description 1
- XMGWNAIPGOPSNX-UHFFFAOYSA-N 1,5-diaminotetrazole Chemical compound NC1=NN=NN1N XMGWNAIPGOPSNX-UHFFFAOYSA-N 0.000 description 1
- LSZQMSSIUQNTDX-UHFFFAOYSA-N 1,5-dimethylpyrazole Chemical compound CC1=CC=NN1C LSZQMSSIUQNTDX-UHFFFAOYSA-N 0.000 description 1
- CMCBDXRRFKYBDG-UHFFFAOYSA-N 1-dodecoxydodecane Chemical compound CCCCCCCCCCCCOCCCCCCCCCCCC CMCBDXRRFKYBDG-UHFFFAOYSA-N 0.000 description 1
- OSSNTDFYBPYIEC-UHFFFAOYSA-N 1-ethenylimidazole Chemical compound C=CN1C=CN=C1 OSSNTDFYBPYIEC-UHFFFAOYSA-N 0.000 description 1
- XEZNGIUYQVAUSS-UHFFFAOYSA-N 18-crown-6 Chemical compound C1COCCOCCOCCOCCOCCO1 XEZNGIUYQVAUSS-UHFFFAOYSA-N 0.000 description 1
- KGIGUEBEKRSTEW-UHFFFAOYSA-N 2-vinylpyridine Chemical compound C=CC1=CC=CC=N1 KGIGUEBEKRSTEW-UHFFFAOYSA-N 0.000 description 1
- RISOHYOEPYWKOB-UHFFFAOYSA-N 4-bromo-3,5-dimethyl-1h-pyrazole Chemical compound CC1=NNC(C)=C1Br RISOHYOEPYWKOB-UHFFFAOYSA-N 0.000 description 1
- 241000894006 Bacteria Species 0.000 description 1
- 241000192710 Microcystis aeruginosa Species 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 1
- QALQXPDXOWOWLD-UHFFFAOYSA-N [N][N+]([O-])=O Chemical compound [N][N+]([O-])=O QALQXPDXOWOWLD-UHFFFAOYSA-N 0.000 description 1
- 239000011358 absorbing material Substances 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007405 data analysis Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 150000004985 diamines Chemical class 0.000 description 1
- VJHINFRRDQUWOJ-UHFFFAOYSA-N dioctyl sebacate Chemical compound CCCCC(CC)COC(=O)CCCCCCCCC(=O)OCC(CC)CCCC VJHINFRRDQUWOJ-UHFFFAOYSA-N 0.000 description 1
- 235000020774 essential nutrients Nutrition 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000002466 imines Chemical class 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000010842 industrial wastewater Substances 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- XAEFZNCEHLXOMS-UHFFFAOYSA-M potassium benzoate Chemical compound [K+].[O-]C(=O)C1=CC=CC=C1 XAEFZNCEHLXOMS-UHFFFAOYSA-M 0.000 description 1
- 150000003141 primary amines Chemical class 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 150000003242 quaternary ammonium salts Chemical class 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
- SWZDQOUHBYYPJD-UHFFFAOYSA-N tridodecylamine Chemical compound CCCCCCCCCCCCN(CCCCCCCCCCCC)CCCCCCCCCCCC SWZDQOUHBYYPJD-UHFFFAOYSA-N 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 238000003911 water pollution Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3577—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing liquids, e.g. polluted water
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/333—Ion-selective electrodes or membranes
- G01N27/3335—Ion-selective electrodes or membranes the membrane containing at least one organic component
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/20—Controlling water pollution; Waste water treatment
Abstract
The invention discloses a method and a sensor for detecting total nitrogen in water based on an array spectrum and an ion selection method, which comprise the steps of obtaining the measured concentration of different types of organic nitrogen in a water body to be detected and a TN conversion coefficient corresponding to the measured concentration; calculating the content of all kinds of organic nitrogen in the water body to be measured based on the measured concentration of the different kinds of organic nitrogen and the TN conversion coefficient corresponding to the measured concentration; obtaining the measured concentration of different kinds of inorganic nitrogen in the water body to be measured and the corresponding potential selection coefficient thereof; calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentrations of the different kinds of inorganic nitrogen and the corresponding potential selection coefficients thereof; and determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected. The organic nitrogen content and the inorganic nitrogen content in the water body to be detected are detected respectively by adopting an array spectrum and an ion selection method, so that the direct continuous on-line detection of the total nitrogen in the water body to be detected is realized, and the detection efficiency is improved.
Description
Technical Field
The invention relates to the technical field of detection of total nitrogen content in water, in particular to a detection method and a sensor of total nitrogen in water based on an array spectrum and an ion selection method.
Background
Total Nitrogen (TN) refers to the sum of nitrogen in ammonia nitrogen, nitrate, nitrite, organic nitrogen and other compounds in the water body. Comprising NO 3 - 、NO 2 - And NH 4 + Inorganic nitrogen and organic nitrogen such as protein, amino acid and organic amine, calculated as milligrams of nitrogen per liter of water. Are often used to represent the degree to which a body of water is contaminated with nutrients.
The total nitrogen in the sewage mainly comes from domestic sewage, industrial wastewater and discharged water after agricultural and landscaping fertilizers are applied. Nitrogen is an essential nutrient for biological growth, but the water contains excessive nitrogen, which can cause eutrophication of the water. In recent years, red tide and water bloom phenomena at the report ends are water eutrophication caused by too high content of nutrient substances such as nitrogen in the sea and lakes.
Nitrogen is an important control index in the treatment of water pollution. The existing total nitrogen detection is carried out by an analysis instrument, belongs to a chemical method, and can detect results after a water sample is collected once in a plurality of hours, so that the total nitrogen at a certain time point can be detected only, and the direct continuous on-line detection of the total nitrogen of the water quality can not be realized.
The national requirement on the environment is increased, the traditional water quality analysis instrument cannot meet the continuous detection of total nitrogen in water quality, the existing total nitrogen detection single-group data analysis time is long, the intermittent disconnection is avoided, and the sporadic property and the randomness of the detection cannot be solved. At present, direct continuous detection of total nitrogen cannot be realized in global total nitrogen detection equipment.
In summary, the conventional detection of total nitrogen in water has the problems that the direct continuous online detection cannot be realized, and the detection and analysis efficiency is low.
Disclosure of Invention
In view of the above, the invention provides a method and a sensor for detecting total nitrogen in water based on an array spectrum and an ion selection method, which aim to solve the problems that the traditional method for detecting total nitrogen in water cannot directly and continuously detect on line and has low detection and analysis efficiency.
In order to solve the technical problems, the technical scheme of the invention is that the method for detecting total nitrogen in water based on an array spectrum and an ion selection method is adopted and comprises the steps of obtaining the measured concentration of different types of organic nitrogen in a water body to be detected and the TN conversion coefficient corresponding to the measured concentration;
calculating the content of all kinds of organic nitrogen in the water body to be measured based on the measured concentration of the different kinds of organic nitrogen and the TN conversion coefficient corresponding to the measured concentration;
Obtaining the measured concentration of different kinds of inorganic nitrogen in the water body to be measured and the corresponding potential selection coefficient thereof;
calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentrations of the different kinds of inorganic nitrogen and the corresponding potential selection coefficients thereof;
and determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected.
The method for obtaining the measured concentration of different types of organic nitrogen in the water body to be measured comprises the following steps:
calibrating molar absorptivity of different types of organic nitrogen under infrared light with different wavelengths;
constructing standard calculation equations of total absorbance when infrared light with different wavelengths transmits all kinds of organic matters;
the method comprises the steps of projecting incident light intensity and emergent light intensity of infrared light with each wavelength obtained when a water body to be measured is projected through an array spectrum, and calculating actual total absorbance of the infrared light with each wavelength;
and obtaining the measured concentration of different types of organic nitrogen based on the standard calculation equation of the total absorbance and the actual total absorbance of the infrared light with each wavelength.
Optionally, the method for determining the potential selectivity coefficient of different kinds of inorganic nitrogen comprises the following steps:
generating an ion selective electrode cell based on the ion selective electrode and the reference electrode;
Obtaining a first standard solution and a second standard solution;
determining a response curve of an ion selective electrode by mapping potential readings of the first standard solution and the second standard solution on a semi-logarithmic curve paper;
and based on the response curve, obtaining a potential selection coefficient by adopting a graphic method.
Optionally, the method for obtaining the measured concentration of different kinds of inorganic nitrogen in the water body to be measured includes:
when determining that the ion selective electrode battery is put into a water body to be detected, the sensitive membranes with different ion selective electrodes selectively respond to the specific ions corresponding to the sensitive membranes, wherein the different types of inorganic nitrogen contain the specific ions;
acquiring an electrode acquisition signal of the specific ion, and calculating an electromotive force of the specific ion based on the electrode acquisition signal of the specific ion;
calculating the measured concentration of the specific ion in the water body to be measured based on the electromotive force of the specific ion;
and obtaining the measured concentration of all specific ions contained in the different types of inorganic nitrogen in the water body to be measured, and taking the measured concentration as the measured concentration of the different types of inorganic nitrogen.
Optionally, after obtaining the measured concentrations of different types of organic nitrogen or inorganic nitrogen in the water body to be measured, the method further includes:
Constructing a calibration equation based on a background sample calibration method;
calibrating the measured concentration of the different kinds of organic nitrogen or inorganic nitrogen using the calibration equation;
constructing a temperature correction equation;
correcting the calibrated measured concentration of the different kinds of organic nitrogen or inorganic nitrogen based on the temperature correction equation.
Optionally, the method for pre-constructing the calibration equation based on the background sample calibration method comprises the following steps:
dividing a water body to be measured into a first sample and a second sample;
measuring the concentration of substances to be calibrated of different types of organic nitrogen or inorganic nitrogen of the first sample through the array spectrum or ion selective electrode;
removing the water of the second sample through a background sample concentration device, and measuring substance concentration samples of different types of organic nitrogen or inorganic nitrogen;
construction of calibration equationWherein->For regression coefficient->For the intercept->For the calibrated measurement, +.>And obtaining the regression coefficient and the intercept based on the substance concentration to be calibrated and the substance concentration sample as measured values.
Optionally, the temperature correction equation is specifically:and (2) andwherein->For the compensated TN value, +.>For the compensated TN value, +.>For the current test liquid temperature, +. >Is the expansion coefficient of water.
Optionally, the array spectrum is configured to include at least: four groups of fixed combined detection light paths for detecting organic nitrogen, in particular,
the first set of detection light paths includes at least: 2.8 μm, 2.94 μm, 3.05 μm;
the second set of detection light paths includes at least: 5.56 μm, 6.06 μm, 6.12 μm, 6.25 μm, 6.37 μm, 6.54 μm, 6.67 μm;
the third set of detection light paths includes at least: 8.50 μm, 8.80 μm, 9.20 μm;
the fourth set of detection light paths includes at least: 12.58 μm, 13.7 μm;
further comprises: 365nm and 550nm differential light sources for eliminating turbidity of water body to be measured and interference of other material light sources, in particular,
adopting 365nm differential light source to eliminate turbidity influence of the first group, the second group and the third group of detection light paths;
and a 550nm differential light source is adopted to eliminate the turbidity influence of the fourth group of detection light paths.
Accordingly, the invention provides a sensor applied to the method for detecting total nitrogen in water based on the array spectrum and the ion selection method, which comprises the following steps:
the array spectrum consists of a light source and a light detector and is used for acquiring the incident light intensity and the emergent light intensity of infrared light with various wavelengths contained in the array spectrum;
The ion selective electrode battery consists of an ion selective electrode and a reference electrode and is used for acquiring an electrode acquisition signal of the specific ion;
the organic nitrogen detection unit is used for obtaining the measured concentration of different types of organic nitrogen in the water body to be detected and the TN conversion coefficient corresponding to the measured concentration; calculating the content of all kinds of organic nitrogen in the water body to be measured based on the measured concentration of the different kinds of organic nitrogen and the TN conversion coefficient corresponding to the measured concentration;
the inorganic nitrogen detection unit is used for obtaining the measured concentration of different types of inorganic nitrogen in the water body to be detected and the corresponding potential selection coefficient thereof; calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentration of the different kinds of inorganic nitrogen and the corresponding potential selection coefficient;
the total nitrogen detection unit is used for determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected.
Optionally, the array spectrum is configured to include at least: four groups of fixed combined detection light paths for detecting organic nitrogen, in particular,
the first set of detection light paths includes at least: 2.8 μm, 2.94 μm, 3.05 μm;
the second set of detection light paths includes at least: 5.56 μm, 6.06 μm, 6.12 μm, 6.25 μm, 6.37 μm, 6.54 μm, 6.67 μm;
The third set of detection light paths includes at least: 8.50 μm, 8.80 μm, 9.20 μm;
the fourth set of detection light paths includes at least: 12.58 μm, 13.7 μm;
further comprises: 365nm and 550nm differential light sources for eliminating turbidity of water body to be measured and interference of other material light sources, in particular,
adopting 365nm differential light source to eliminate turbidity influence of the first group, the second group and the third group of detection light paths;
and a 550nm differential light source is adopted to eliminate the turbidity influence of the fourth group of detection light paths.
The primary improvement of the invention is to provide a method and a sensor for detecting total nitrogen in water based on an array spectrum and an ion selection method, which are characterized in that the measured concentration of different types of organic nitrogen in a water body to be detected and the corresponding TN conversion coefficient are obtained; calculating the content of all kinds of organic nitrogen in the water body to be measured based on the measured concentration of the different kinds of organic nitrogen and the TN conversion coefficient corresponding to the measured concentration; obtaining the measured concentration of different kinds of inorganic nitrogen in the water body to be measured and the corresponding potential selection coefficient thereof; calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentrations of the different kinds of inorganic nitrogen and the corresponding potential selection coefficients thereof; and determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected. The method has the advantages that the array spectrum is adopted to detect the organic nitrogen content in the water body to be detected, and the ion selection method is adopted to detect the inorganic nitrogen content in the water body to be detected, so that the direct continuous online detection of the total nitrogen in the water body to be detected is realized, the accuracy and the comprehensiveness of the total nitrogen detection of the water body to be detected are further improved by utilizing the background sample calibration method and constructing the temperature correction coefficient, and the problems that the direct continuous online detection cannot be realized and the detection analysis efficiency is low in the traditional total nitrogen detection in water are solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a method for detecting total nitrogen in water based on an array spectrum and an ion selection method according to an embodiment of the application;
FIG. 2 is a flow chart of a method for obtaining measured concentrations of different types of organic nitrogen in a water body to be measured according to an embodiment of the present application;
FIG. 3 is a flow chart of a method for obtaining measured concentrations of different types of inorganic nitrogen in a water body to be measured according to an embodiment of the present application;
FIG. 4 is a simplified schematic diagram of a sensor according to an embodiment of the present application;
fig. 5 is a simplified schematic structural diagram of a detection unit according to an embodiment of the present application.
Detailed Description
In order that those skilled in the art will better understand the embodiments of the present application, a technical solution in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Total nitrogen, called TN for short, is one of the important indexes for measuring the water quality. The definition of total nitrogen is the total amount of inorganic and organic nitrogen of various forms in water. Comprising NO 3 - 、NO 2 - And NH 4 + Inorganic nitrogen and organic nitrogen such as protein, amino acid and organic amine, calculated as milligrams of nitrogen per liter of water. Are often used to represent the degree to which a body of water is contaminated with nutrients.
The measurement of total nitrogen can be classified into inorganic nitrogen and organic nitrogen. Correspondingly, inorganic nitrogen is measured by adopting an ion selective electrode method, and organic nitrogen is measured by adopting an infrared spectrum.
First, ion selective electrodes and infrared spectra are described:
ion Selective Electrodes (ISEs) are electrochemical sensors based on a sensitive membrane, which is the element that makes the electrode selectively responsive to specific ions. Ion selective electrodes can be divided into 4 types according to the materials of the membrane: glass film (e.g. Na + Or pH) solid film (e.g. Pb 2+ ) Polymeric films (e.g. K + ) Gas permeable membranes (e.g. CO 2 ) When the electrodes are placed in solution, a potential difference is formed across the membrane. When the concentration of the ions to be measured in the sample changes, the change in the potential difference can be measured by using the ion-selective electrode together with an internal or external reference electrode. (wherein the specific ions comprise the measured ions and interfering ions relative to the measured ions, for example, the specific ions required by inorganic nitrogen comprise ammonia nitrogen, the ammonia nitrogen comprises the measured ions of ammonium ions and the interfering ions of potassium ions relative to the measured ions, and in a conventional water body, the potassium ions interfere with the ammonium ions). It can be understood that the number of the interference ions of the same measured ion in different water bodies can be a plurality, and the ion selection electrode of the corresponding interference ion can be selected according to the interference conditions of different measured water bodies.
Infrared spectra, when the sample is irradiated with infrared light, the radiation is insufficient to cause a transition in the electron energy level in the molecule, but can be absorbed by the molecule causing a transition in the vibration and rotation energy levels.
Fig. 1 is a schematic flow chart of a method for detecting total nitrogen in water based on an array spectrum and an ion selection method according to an embodiment of the invention.
S11, obtaining the measured concentration of different types of organic nitrogen in the water body to be measured and the TN conversion coefficient corresponding to the measured concentration.
The detection of the content of different types of organic nitrogen in the water body to be detected is carried out by adopting an array spectrum, specifically, the measured concentration of the different types of organic nitrogen in the water body to be detected is firstly obtained, and reference is made to fig. 2.
S111, calibrating the molar absorptivity of different types of organic nitrogen under the infrared light of different wavelengths.
Organic nitrogen in surface water mainly comprises organic nitrogen such as protein, amino acid, organic amine and the like, wherein the organic nitrogen mainly comprises amine, nitro, nitroso and other functional groups.
Wherein the amine mainly exists in the form of primary amine, imine, diamine, free amine and other functional groups, and the wave number range of the infrared light mainly absorbed by the amine is 3250-3350, 2400-2600, 1490-1650 and 700-750; the corresponding wavelength ranges are: 2.82 μm-3.08 μm, 3.85-4.15 μm, 6.06 μm-6.71 μm, 13.33 μm-14.29 μm.
Wherein the nitro, nitroso groups are mainly-C-NO 2 Aliphatic R-NO 2 、C=C-NO 2 、、/>， R-O-NO 2 ， R-N-NO 2 The method comprises the steps of carrying out a first treatment on the surface of the The wave number range of the infrared light mainly absorbed by the infrared light is as follows: 1500-1575, 1570-1580, 1500-1550, 1650-1530, 1500-1430; the corresponding wavelength ranges are: 6.35 μm-6.67 μm,6.25 μm-6.37 μm,6.45 μm-6.67 μm,6.06 μm-6.54 μm,6.67 μm-6.69 μm.
Further, based on the above-mentioned wave number range and corresponding wavelength range of the infrared light, the array spectrum is configured to divide the detection light paths into four groups, and the first group of detection light paths includes at least: 2.8 μm, 2.94 μm, 3.05 μm; the second set of detection light paths includes at least: 5.56 μm,6.06 μm, 6.12 μm,6.25 μm, 6.37 μm, 6.54 μm,6.67 μm; the third set of detection light paths includes at least: 8.50 μm, 8.80 μm, 9.20 μm; the fourth set of detection light paths includes at least: 12.58 μm, 13.7 μm.
Further, the method can further comprise 365nm and 550nm differential light sources for eliminating turbidity of the water body to be detected and interference of light sources of other substances, turbidity compensation light intensity is calculated based on the two differential light sources under the condition that an array spectrum comprises the 365nm and 550nm differential light sources, turbidity compensation light intensity is introduced to compensate influence of turbidity on measured total absorbance when measured total absorbance of ultraviolet light with each wavelength is calculated based on incident light intensity and emergent light intensity, specifically, the 365nm differential light sources are adopted to eliminate turbidity influence of a first group, a second group and a third group of detection light paths, and the 550nm differential light sources are adopted to eliminate turbidity influence of a fourth group of detection light paths.
Further, a table lookup method is adopted to search the molar absorptivity of amine and nitroso in pharmacopoeia at the corresponding selected wavelength, and the molar absorptivity is set as a default molar absorptivity.
Further, these organics were quantitatively formulated to a concentration C using laboratory calibration to obtain A, C and d values by experimental use, which were substituted into the formula: ɛ =a/dc. Where A is the amount of light of a particular wavelength absorbed by the sample, ɛ is the molar absorption coefficient, d is the distance of light passing through the solution, and c is the concentration of the absorbing material per unit volume. Multiplying d by c, and dividing A by the product of the products to obtain the molar absorptivity of the corresponding wavelength.
S112, constructing a standard calculation equation of total absorbance when infrared light with different wavelengths transmits all kinds of organic matters.
The standard calculation equation for absorbance is:in the formula, A n For each organic matter A 1 、A 2 、A 3 The sum of the absorbance of … … and other organic substances, < >>And->The intensities of the incident light and the transmitted light are indicated, respectively. When the incident light is totally absorbed +.>When the incident light is not absorbed, the incident light is +.>=/>Then->=0. n=1, 2,3 … …,17 corresponds to the first, second, third and fourth group of wavelengths.
S113, calculating the actual total absorbance of the infrared light with each wavelength according to the incident light intensity and the emergent light intensity of the infrared light with each wavelength obtained when the water body to be measured is projected through the array spectrum.
Quantitative analysis of infrared spectrum is based on absorption lawWherein A is absorbance, T is light transmittance, and is +.>Intensity of incident light, < >>The light intensity is the light intensity, a is the light absorption coefficient, c is the concentration of the solution of the substance to be detected, and d is the light transmission distance of the solution.
According to the relationship between the absorption intensity of the lambert beer law substance to light with a certain wavelength and the concentration of the light absorbing substance and the liquid layer thickness thereof:，/>. The output result A is the actual absorbance of different organic matters under the projection of infrared light. Output result->Is the concentration of the substances of different organic matters under the actual absorbance.
S114, obtaining the measurement concentration of different types of organic nitrogen based on a standard calculation equation of total absorbance and the actual total absorbance of infrared light with each wavelength.
S12, calculating the content of all kinds of organic nitrogen in the water body to be measured based on the measured concentration of the organic nitrogen of different kinds and the TN conversion coefficient corresponding to the measured concentration.
Based on the measured concentration of different types of organic nitrogen and TN conversion coefficients corresponding to the measured concentration, the content of all types of organic nitrogen in the water body to be measured is calculated, and a formula is adoptedWherein->Conversion coefficient for TN of different substances, < >>Organic matter concentration.
S13, obtaining the measured concentration of different kinds of inorganic nitrogen in the water body to be measured and the corresponding potential selection coefficient.
The detection of the content of different inorganic nitrogen in the water body to be detected is carried out by adopting an ion selection method, specifically, the measured concentration of the different inorganic nitrogen in the water body to be detected is firstly obtained, and reference is made to fig. 3.
Wherein, for inorganic nitrogen in the water body to be measured, when the ion electrode is generally selected, the method at least comprises the following steps: an ammonia ion electrode; a cation interference electrode; nitrate ion electrode, anion interference electrode; a PH electrode.
The ammonia ion electrode, namely the ammonia ion single electrode and the composite electrode are ion selective electrodes of a PVC membrane, are used for testing free ammonia ions in water, and the ion selective membrane adopts a specially customized polymer sensitive membrane and can be used for detecting ammonia nitrogen concentration in water by an ion selective method. The main raw materials of the mold are formed by polymerizing a plurality of parts of polymer base materials, a plurality of parts of plasticizers, a plurality of parts of active substances, a plurality of parts of ion exchangers and the like through a special process, wherein the active substances comprise substances such as aseptic bacteria, ammonium phosphotungstate, 18-crown ether-6, o-phenylenediamine, 4-bromo-3, 5-dimethylpyrazole, 2, 3-dimethylpyrazole, trilaurylamine, tetrazole-1, 5-diamine, triamide, heterocrown ether derivatives and the like.
Cation-interfering electrodes, i.e. K + The single electrode and the composite electrode are ion selective electrodes of a PVC film,for testing free ammonium ions, K in water + The ion selective mould adopts a specially customized polymer sensitive film, and the main components of the ion selective mould are potassium salt, di (2-ethylhexyl) sebacate, polyvinyl chloride and a cation exchanger.
The nitrate electrode and the reference electrode form a working battery. The measurement is realized by the different potential responses of the inert film on the electrode head to nitrate ions with different concentrations in the solution,the ion selective membrane adopts a specially customized polymer sensitive membrane, and the main components of the ion selective membrane are nitrate, vinyl imidazole, dibromodecane, vinyl pyridine poly or quaternary ammonium salt o-Dan Jiben dodecyl ether liquid membrane.
The ion selective electrode is suitable for water quality samples with low concentration, and the method has the advantages of high accuracy and precision, high sensitivity, high measuring speed, simple operation, low cost and the like. The ion detector can selectively identify ions to be detected in the solution and generate corresponding membrane potential, and the size of the membrane potential is determined by the distribution of charged substances at a membrane/water interface.
Further, based on the selected ion selective electrode, the corresponding potential selection coefficient is measured, specifically, the potential selection coefficient is measured for the ion selective electrode to which the fixed interference method and the solution method are applied.
Fixed interference method: in the presence of fixed activity a B In the solution of interfering ion B, the activity a of main ion A is changed A And the battery is formed by the ion-selective electrode A and the reference electrode A. The electromotive force E of the cell is plotted against the logarithm of the main ion activity a. The linear part of the graph is extrapolated to the value of a at the horizontal intersection point, and the value is used to formulateAnd calculating a potential selection coefficient. Wherein, the liquid crystal display device comprises a liquid crystal display device,for the degree of interference of B ions in solution A, i.e.the potential selectivity coefficient, +.>Charge number of A ion, +.>Is the charge number of the B ion.
The solution method is divided into a solution isoactivity method and a solution equipotential method:
solution equivalent activity method: the ion selective electrode and the reference electrode are respectively used for preparing the active a containing only the ion A (without containing the ion B), the other active a containing only the ion B B =a A The solution (without ion A) forms cells, and the electromotive force of the corresponding cells is measured as E A And E is B . The potential selection coefficient is calculated by the value, and the specific formula is as follows: 、、/>. When->=/>When in use, then->、. Wherein (1)>To the extent of interference of B ions in solution A, i.e. electricallyBit select coefficient, +.>Charge number of A ion, +.>Is the charge number of B ions, R is the molar gas constant, T is the thermodynamic temperature, F is the Faraday constant,>to indicate the standard potential of the electrode, S is a process variable, and has no specific meaning (all S parameters present in the following are process variables and will not be described in detail).
Solution isoelectric method: the selective electrode and the reference electrode are respectively connected with an activity containing only ion AThe solution (without ion B) constitutes a battery; another activity of ion B only +.>The solution (without ion a) constitutes the cell. The solution concentrations of the two cells were adjusted to equalize the measured potentials. From any pair of measured equal potentials, the activity is +.>And->To calculate the interference factor. When E is A =E B When get +.>。
Further, the potential selection coefficient may be obtained by a solution method or a solution method.
S131, when the ion selective electrode battery is thrown into the water body to be detected, the sensitive membranes with different ion selective electrodes selectively respond to the corresponding specific ions, and different types of inorganic nitrogen contain the specific ions.
An ion selective electrode and a reference electrode are connected by a wire to form an ion selective electrode cell, which can be written generally as: external reference electrode |test solution |membrane|internal reference electrode|external reference electrode|test solution|ion selective electrode.
S132, acquiring an electrode acquisition signal of the specific ion, and calculating the electromotive force of the specific ion based on the electrode acquisition signal of the specific ion.
Further, for electrode data acquisition, the sensor system is used for acquiring different electrode signals to obtain voltage values, and the voltage values are specific:
respectively collecting the voltages of the ammonia nitrogen ion electrodesInterfering ion electrode voltage->PH electrode voltage->Nitrate ion electrode voltage->Chloride electrode voltage->Wherein, the method comprises the steps of, wherein,for the voltage value acquired by the sensor system, < >>For the magnification of the electrical signal, +.>、/>、/>、/>、The electromotive forces generated by the concentrations of the ions in the solution, respectively.
Further, the method comprises the steps of firstly adding a standard solutionIn measuring battery electromotive force +.>Then in the test solution->In measuring battery electromotive force->From the electromotive force measured twice:>、/>、、/>、/>。
furthermore, the method requires that the concentration of the detected ions is in the linear range of the response of the electrode, the slope of the electrode is consistent with the theoretical value, and a double standard method can be adopted for reducing the measurement error，//>) Even if the concentration of the measured ions is higher than that of the two standard solutionsBetween the degrees, then the electromotive force of the battery is measured, +.>If getThen: />Wherein- >May be the concentration of the measured ions; />To measure the potential of the ions.
S133, calculating the measured concentration of the specific ion in the water body to be measured based on the electromotive force of the specific ion.
S134, obtaining the measured concentration of all specific ions contained in different types of inorganic nitrogen in the water body to be measured, and taking the measured concentration as the measured concentration of the different types of inorganic nitrogen.
C) confirming electromotive force of calibration point of interfering ion by using standard substance liquid to perform two-point calibration of standard liquid s1 ，c s2 Calibrating the concentrations of the points at the second point, E 1 ，E 2 The calibration point potentials at the second points of the first points, respectively.
Potassium ion concentration: if c S2 =10c S1 The potassium ion calculated concentration is:if c S2 ≠10c S1 The potassium ion calculated concentration is: />。
Correspondingly, the ammonia ion concentration, the nitrate ion concentration and the chloride ion calculated concentration: because ofThe electrode expression of (2) is、/>The method comprises the steps of carrying out a first treatment on the surface of the The expression of the actual water sample test is +.>、。
S14, calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentration of the different kinds of inorganic nitrogen and the corresponding potential selection coefficient.
And combining the calculated concentration of potassium ions and the calculated concentration of ammonia ions to obtain a calculation formula of ammonia nitrogen:wherein->Measuring the concentration of ammonia nitrogen; />Is->An interference coefficient; / >Is thatMeasuring the concentration; />Is->An interference coefficient; />Is->Measuring the concentration; />Is->Ion concentration; />Is an ammonia nitrogen conversion coefficient.
Further, the calculated concentration of nitrate ions and the calculated concentration of chloride ions are combined to obtain a calculation formula of nitrate nitrogen:wherein->Measuring the concentration for the nitrate nitrogen; />Is->An interference coefficient; />Is->Measuring the concentration; />Is the pH interference coefficient; />Is->Measuring the concentration; />Is->Ion concentration; />Is an ammonia nitrogen conversion coefficient.
S15, determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected.
Further, based on the obtained organic nitrogen information and inorganic nitrogen information, a calculation formula of total nitrogen is obtained as follows:wherein->Is the total nitrogen content; />Measuring error coefficients for infrared organic nitrogen; />Measuring the concentration for infrared organic nitrogen; />The error coefficient is measured for ammonia nitrogen; />Measuring the concentration of ammonia nitrogen; />Measuring an error coefficient for nitrate nitrogen; />The concentration was measured for nitronitrogen.
It should be noted that after obtaining the measured concentrations of different types of organic nitrogen or inorganic nitrogen in the water body to be measured, a calibration equation can be constructed based on a background sample calibration method, including: dividing a water body to be measured into a first sample and a second sample; measuring the concentration of substances to be calibrated of different types of organic nitrogen or inorganic nitrogen of the first sample by an array spectrum or ion selection method; removing water from the second sample by a background sample concentration device After removal, measuring a substance concentration sample of different types of organic nitrogen or inorganic nitrogen; construction of calibration equationWherein->For regression coefficient->For the intercept->As a result of the measurement after the calibration,for the measured values, regression coefficients and intercepts are determined on the basis of the substance concentration to be calibrated and the substance concentration samples.
Further, the method for obtaining the regression coefficient and the intercept based on the substance concentration to be calibrated and the substance concentration sample comprises the following steps: order the、/>There is->、/>、Wherein->、/>、/>、/>And->Are all process variables, are not defined by special parameters, < ->The substance concentration to be calibrated for different kinds of organic matters or inorganic matters comprises: />，/>Samples of substance concentration for different kinds of organic or inorganic substances, including +.>S is the number of organic or inorganic substances, and regression coefficients and intercepts can be calculated by the following formulas respectively>、/>. At the same time (I)>And->The degree of closeness of the linear relationship is measured by the correlation coefficient R (precision): />。
Further, after calibrating the measured concentration of the different types of organic nitrogen or inorganic matters by using the calibration equation, a temperature correction coefficient may be further constructed, and correcting the calibrated measured concentration of the different types of organic nitrogen or inorganic matters based on the temperature correction coefficient includes: the calculation formula is adopted: ，/>Wherein->For the current test liquid temperature, +.>Is the expansion coefficient of water, +.>For the compensated TN value, +.>Is the compensated TN value.
It can be understood that the components mentioned in this embodiment are only representative and structurally stable components, and other components with relatively weak influence or unknown components are also included in the total nitrogen, so that the above-mentioned background sample calibration method can be adopted, and the related calibration coefficients, that is, the regression coefficients and the intercept, of the components mentioned in this embodiment are successfully determined, and then the other components with relatively weak influence or unknown components are carried into the sample to calculate, so that the accuracy and the comprehensiveness of the total nitrogen content calculation are improved.
Similarly, the background sample calibration method can be used for verifying and calculating the known components in the solution to be detected in the embodiment, so that the accuracy of total nitrogen detection is further improved.
Based on the measured concentration of different types of organic nitrogen and the TN conversion coefficient corresponding to the measured concentration, the method calculates the content of all types of organic nitrogen in the water body to be measured; obtaining the measured concentration of different kinds of inorganic nitrogen in the water body to be measured and the corresponding potential selection coefficient thereof; calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentrations of the different kinds of inorganic nitrogen and the corresponding potential selection coefficients thereof; and determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected. The organic nitrogen content in the water body to be detected is detected by adopting the array spectrum, and the inorganic nitrogen content in the water body to be detected is detected by adopting the ion selection method, so that the direct continuous on-line detection of the total nitrogen in the water body to be detected is realized, and the detection efficiency is improved. In addition, the background sample calibration method is adopted to carry out supplementary calculation on other components which are not mentioned in the solution to be detected in the embodiment, and verification calculation is carried out on the other components which are mentioned in the solution to be detected in the embodiment, so that the accuracy and the comprehensiveness of total nitrogen detection are further improved.
Accordingly, as shown in fig. 4, a simplified schematic structural diagram of a sensor according to an embodiment of the present invention is applied to the method for detecting total nitrogen in water based on array spectrum and ion selection method, which includes: the array spectrum consists of a light source and a light detector and is used for acquiring the incident light intensity and the emergent light intensity of infrared light with various wavelengths contained in the array spectrum; the ion selective electrode battery consists of an ion selective electrode and a reference electrode, and is used for acquiring an electrode acquisition signal of the specific ion and a detection unit.
Further, as shown in fig. 5, the detection unit specifically includes:
the organic nitrogen detection unit is used for obtaining the measured concentration of different types of organic nitrogen in the water body to be detected and the TN conversion coefficient corresponding to the measured concentration; and calculating the content of all kinds of organic nitrogen in the water body to be measured based on the measured concentrations of the different kinds of organic nitrogen and the TN conversion coefficients corresponding to the measured concentrations.
The inorganic nitrogen detection unit is used for obtaining the measured concentration of different types of inorganic nitrogen in the water body to be detected and the corresponding potential selection coefficient thereof; and calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentrations of the different kinds of inorganic nitrogen and the corresponding potential selection coefficients.
The total nitrogen detection unit is used for determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected.
Further, the array spectrum is configured to include at least: four groups of fixed combined detection light paths for detecting organic nitrogen, in particular,
the first set of detection light paths includes at least: 2.8 μm, 2.94 μm, 3.05 μm;
the second set of detection light paths includes at least: 5.56 μm, 6.06 μm, 6.12 μm, 6.25 μm, 6.37 μm, 6.54 μm, 6.67 μm;
the third set of detection light paths includes at least: 8.50 μm, 8.80 μm, 9.20 μm;
the fourth set of detection light paths includes at least: 12.58 μm, 13.7 μm.
May further include: 365nm and 550nm differential light sources for eliminating turbidity of water body to be measured and interference of other material light sources, in particular,
adopting 365nm differential light source to eliminate turbidity influence of the first group, the second group and the third group of detection light paths;
and a 550nm differential light source is adopted to eliminate the turbidity influence of the fourth group of detection light paths.
The method and the sensor for detecting total nitrogen in water based on the array spectrum and the ion selection method provided by the embodiment of the invention. In the description, each embodiment is described in a progressive manner, and each embodiment is mainly described by the differences from other embodiments, so that the same similar parts among the embodiments are mutually referred. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
Claims (10)
1. The method for detecting total nitrogen in water based on array spectrum and ion selection method is characterized by comprising the following steps:
Calibrating molar absorptivity of different types of organic nitrogen under infrared light with different wavelengths, and acquiring TN conversion coefficients corresponding to the different types of organic nitrogen;
constructing standard calculation equations of total absorbance when infrared light with different wavelengths transmits all kinds of organic matters;
the method comprises the steps of projecting incident light intensity and emergent light intensity of infrared light with each wavelength obtained when a water body to be measured is projected through an array spectrum, and calculating actual total absorbance of the infrared light with each wavelength;
based on the standard calculation equation of the total absorbance and the actual total absorbance of the infrared light with each wavelength, obtaining the measured concentration of different types of organic nitrogen in the water body to be measured;
calculating the content of all kinds of organic nitrogen in the water body to be measured based on the measured concentration of the different kinds of organic nitrogen and the TN conversion coefficient corresponding to the measured concentration;
generating an ion selective electrode cell based on the ion selective electrode and the reference electrode;
when the ion selective electrode battery is thrown into a water body to be detected, the different sensitive membranes of the ion selective electrode selectively respond to the corresponding specific ions, wherein the specific ions comprise detected ions and interference ions relative to the detected ions;
acquiring electrode acquisition signals of the specific ions, and determining electromotive force of the specific ions based on the electrode acquisition signals, so as to obtain the measured concentration of different inorganic nitrogen in the water body to be measured;
Obtaining a response curve of the ion selective electrode by adopting a solution method, and obtaining a potential selection coefficient by adopting a graphic method based on the response curve;
calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentrations of the different kinds of inorganic nitrogen and the corresponding potential selection coefficients thereof;
and determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected.
2. The method for detecting total nitrogen in water based on array spectrum and ion selection method according to claim 1, wherein the standard calculation equation based on the total absorbance and the actual total absorbance of each wavelength infrared light obtain the measured concentration of different kinds of organic nitrogen in the water to be detected, comprising:
the standard calculation equation of the total absorbance adopts the formula:wherein A is n For each organic matter A 1 、A 2 、A 3 Sum of absorbance of … … and other organic matter, I n0 And I nt Respectively representing the intensities of the incident light and the transmitted light;
based on the quantitative analysis of infrared spectrum and lambert beer law, the actual total absorbance of the infrared light with each wavelength is calculated, in particular,
by law of absorptionQuantitative analysis is carried out, wherein A is absorbance, T is light transmittance, and I 0 Intensity of incident light, I t The light intensity is the light intensity, a is the light absorption coefficient, c is the concentration of the solution of the substance to be detected, and d is the light transmission distance of the solution;
according to lambert's law, a substance is specific to a certain wavelengthRelationship between intensity of light absorption and concentration of light absorbing substance and liquid layer thickness thereof:the output result A is the actual absorbance of different organic matters under the projection of infrared light, and the output result c x Is the concentration of the substances of different organic matters under the actual absorbance.
3. The method for detecting total nitrogen in water based on array spectrum and ion selection method according to claim 1, wherein obtaining a response curve of the ion selective electrode by using a standard solution method and obtaining a potential selection coefficient by using a graph method based on the response curve comprises:
obtaining a first standard solution and a second standard solution;
determining a response curve of an ion selective electrode by mapping potential readings of the first standard solution and the second standard solution on a semi-logarithmic curve paper;
and based on the response curve, obtaining a potential selection coefficient by adopting a graphic method.
4. The method for detecting total nitrogen in water based on array spectrum and ion selection method according to claim 3, wherein the steps of obtaining electrode collection signals of the specific ions, determining electromotive force of the specific ions based on the electrode collection signals, and further obtaining measured concentrations of the different kinds of inorganic nitrogen in the water to be detected comprise:
Collecting different kinds of electrode signals by using a sensor system to obtain voltage values;
determining an electromotive force of the specific ion based on the voltage value;
based on the obtained electromotive force, the formula is adoptedCalculating the measured concentration of the specific ions in the water body to be measured, wherein c x Can be the concentration of measured ionsA degree; e (E) x To measure the potential of ions, E s1 For the first calibration point potential E s2 Is a second calibration point potential;
and obtaining the measured concentration of all specific ions contained in the different types of inorganic nitrogen in the water body to be measured, and taking the measured concentration as the measured concentration of the different types of inorganic nitrogen.
5. The method for detecting total nitrogen in water based on array spectrum and ion selection method according to claim 1, wherein after obtaining the measured concentration of different kinds of organic nitrogen or inorganic nitrogen in the water to be detected, further comprising:
constructing a calibration equation based on a background sample calibration method;
calibrating the measured concentration of the different kinds of organic nitrogen or inorganic nitrogen using the calibration equation;
constructing a temperature correction equation;
correcting the calibrated measured concentration of the different kinds of organic nitrogen or inorganic nitrogen based on the temperature correction equation.
6. The method for detecting total nitrogen in water based on array spectrum and ion selection method according to claim 5, wherein the method for pre-constructing calibration equation based on background sample calibration method comprises the following steps:
Dividing a water body to be measured into a first sample and a second sample;
measuring the concentration of substances to be calibrated of different types of organic nitrogen or inorganic nitrogen of the first sample through the array spectrum or ion selective electrode;
removing the water of the second sample through a background sample concentration device, and measuring substance concentration samples of different types of organic nitrogen or inorganic nitrogen;
construction of the calibration equation c' TN ＝kc TN +b, where k is the regression coefficient, b is the intercept, c' TN C as a calibrated measurement TN And obtaining the regression coefficient and the intercept based on the substance concentration to be calibrated and the substance concentration sample as measured values.
7. The method for detecting total nitrogen in water based on array spectrum and ion selection method according to claim 5, wherein the temperature correction equation is specifically:and is also provided withWherein c' TN For the compensated TN value, C is the compensated TN value, t is the current test liquid temperature, and α is the expansion coefficient of water.
8. The method of detecting total nitrogen in water based on array spectroscopy and ion selection as claimed in claim 2, wherein the array spectroscopy is configured to include at least: four groups of fixed combined detection light paths for detecting organic nitrogen, in particular,
The first set of detection light paths includes at least: 2.8 μm, 2.94 μm, 3.05 μm;
the second set of detection light paths includes at least: 5.56 μm, 6.06 μm, 6.12 μm, 6.25 μm, 6.37 μm, 6.54 μm, 6.67 μm;
the third set of detection light paths includes at least: 8.50 μm, 8.80 μm, 9.20 μm;
the fourth set of detection light paths includes at least: 12.58 μm, 13.7 μm;
further comprises: 365nm and 550nm differential light sources for eliminating turbidity of water body to be measured and interference of other material light sources, in particular,
adopting 365nm differential light source to eliminate turbidity influence of the first group, the second group and the third group of detection light paths;
and a 550nm differential light source is adopted to eliminate the turbidity influence of the fourth group of detection light paths.
9. A sensor for use in the method for detecting total nitrogen in water based on array spectroscopy and ion selection as claimed in any one of claims 1 to 8, comprising:
the array spectrum consists of a light source and a light detector and is used for acquiring the incident light intensity and the emergent light intensity of infrared light with various wavelengths contained in the array spectrum;
the ion selective electrode battery consists of an ion selective electrode and a reference electrode and is used for acquiring an electrode acquisition signal of the specific ion;
the organic nitrogen detection unit is used for calibrating molar light absorption coefficients of different types of organic nitrogen under infrared light with different wavelengths and obtaining TN conversion coefficients corresponding to the different types of organic nitrogen; constructing standard calculation equations of total absorbance when infrared light with different wavelengths transmits all kinds of organic matters; the method comprises the steps of projecting incident light intensity and emergent light intensity of infrared light with each wavelength obtained when a water body to be measured is projected through an array spectrum, and calculating actual total absorbance of the infrared light with each wavelength; based on the standard calculation equation of the total absorbance and the actual total absorbance of the infrared light with each wavelength, obtaining the measured concentration of different types of organic nitrogen in the water body to be measured; calculating the content of all kinds of organic nitrogen in the water body to be measured based on the measured concentration of the different kinds of organic nitrogen and the TN conversion coefficient corresponding to the measured concentration;
An inorganic nitrogen detection unit for generating an ion selective electrode cell based on the ion selective electrode and the reference electrode; when the ion selective electrode battery is thrown into a water body to be detected, the different sensitive membranes of the ion selective electrode selectively respond to the corresponding specific ions, wherein the specific ions comprise detected ions and interference ions relative to the detected ions; acquiring electrode acquisition signals of the specific ions, determining electromotive force of the specific ions based on the electrode acquisition signals, and further obtaining measurement concentration of the different kinds of inorganic nitrogen in the water body to be measured; obtaining a response curve of the ion selective electrode by adopting a solution method, and obtaining a potential selection coefficient by adopting a graphic method based on the response curve; calculating the content of all kinds of inorganic nitrogen in the water body to be measured based on the measured concentrations of the different kinds of inorganic nitrogen and the corresponding potential selection coefficients thereof;
the total nitrogen detection unit is used for determining the total nitrogen content in the water body to be detected according to the organic nitrogen content in the water body to be detected and the inorganic nitrogen content in the water body to be detected.
10. A sensor according to claim 9, wherein the array spectrum is configured to include at least: four groups of fixed combined detection light paths for detecting organic nitrogen, in particular,
The first set of detection light paths includes at least: 2.8 μm, 2.94 μm, 3.05 μm;
the second set of detection light paths includes at least: 5.56 μm, 6.06 μm, 6.12 μm, 6.25 μm, 6.37 μm, 6.54 μm, 6.67 μm;
the third set of detection light paths includes at least: 8.50 μm, 8.80 μm, 9.20 μm;
the fourth set of detection light paths includes at least: 12.58 μm, 13.7 μm;
further comprises: 365nm and 550nm differential light sources for eliminating turbidity of water body to be measured and interference of other material light sources, in particular,
adopting 365nm differential light source to eliminate turbidity influence of the first group, the second group and the third group of detection light paths;
and a 550nm differential light source is adopted to eliminate the turbidity influence of the fourth group of detection light paths.
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