CN111912814B - Method for measuring total nitrogen content in water - Google Patents
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- CN111912814B CN111912814B CN201911302641.1A CN201911302641A CN111912814B CN 111912814 B CN111912814 B CN 111912814B CN 201911302641 A CN201911302641 A CN 201911302641A CN 111912814 B CN111912814 B CN 111912814B
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 51
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 48
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 24
- 238000000034 method Methods 0.000 title claims abstract description 20
- 229910002651 NO3 Inorganic materials 0.000 claims abstract description 27
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims abstract description 27
- 238000002835 absorbance Methods 0.000 claims abstract description 20
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 8
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 8
- 230000003647 oxidation Effects 0.000 claims abstract description 6
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 6
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 12
- 238000010521 absorption reaction Methods 0.000 claims description 8
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims description 6
- 230000003595 spectral effect Effects 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims 1
- 150000003839 salts Chemical class 0.000 claims 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 abstract description 5
- 238000005259 measurement Methods 0.000 abstract description 5
- 230000001590 oxidative effect Effects 0.000 abstract description 5
- 238000001228 spectrum Methods 0.000 abstract description 5
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 abstract description 3
- 150000002897 organic nitrogen compounds Chemical class 0.000 abstract description 3
- 239000007800 oxidant agent Substances 0.000 abstract description 3
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 125000001477 organic nitrogen group Chemical group 0.000 description 3
- 238000004847 absorption spectroscopy Methods 0.000 description 2
- 150000001412 amines Chemical class 0.000 description 2
- 150000001413 amino acids Chemical class 0.000 description 2
- 150000003863 ammonium salts Chemical class 0.000 description 2
- 235000013405 beer Nutrition 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 102000004169 proteins and genes Human genes 0.000 description 2
- 108090000623 proteins and genes Proteins 0.000 description 2
- 238000002798 spectrophotometry method Methods 0.000 description 2
- 238000004566 IR spectroscopy Methods 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000012851 eutrophication Methods 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000008213 purified water Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
Classifications
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- 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
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- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The invention relates to a method for measuring total nitrogen content in water, belonging to the technical field of environmental protection; in the prior art, a strong oxidant is used for oxidizing most organic nitrogen compounds, ammonia nitrogen and nitrite into nitrate; the oxidized water sample not only comprises nitrate, but also comprises carbon dioxide generated in the oxidation process, and the spectrum measurement of the N = O bond is interfered by the C = O bond; the method provided by the invention measures the absorbance under two wave bands, constructs a linear equation of two elements to obtain the content of the total nitrogen in the water, and solves the equation set to achieve the purpose of accurate measurement.
Description
Technical Field
The invention relates to the technical field of environmental protection, in particular to a method for measuring the total nitrogen content in water.
Background
Total nitrogen, referred to as TN, is one of the important indexes for measuring water quality. Total nitrogen is defined as the total amount of various forms of inorganic and organic nitrogen in the water. Including inorganic nitrogen such as nitrate, nitrite and ammonium salt, and organic nitrogen such as protein, amino acid and organic amine, calculated by the nitrogen-containing milligram per liter of water. Is often used to indicate the degree of nutrient contamination of a water body. The measurement of the method is helpful for evaluating the polluted and self-purification conditions of the water body. When the nitrogen and phosphorus substances in the surface water exceed the standard, the microorganisms propagate in a large quantity, plankton grows vigorously, and a eutrophication state appears.
In the prior art, the most common methods for measuring the total nitrogen content are alkaline potassium persulfate ultraviolet spectrophotometry and gas phase molecular absorption spectrometry.
Wherein, the alkaline potassium persulfate ultraviolet spectrophotometry has complicated steps and long time consumption; gas phase molecular absorption spectroscopy is mainly used in laboratories, and equipment is expensive and complex to maintain, so a new method for measuring the total nitrogen content is urgently needed.
Disclosure of Invention
In view of the problems in the prior art, the invention provides the following technical scheme: a method for measuring the total nitrogen content in water is characterized by comprising the following steps: the method comprises the following steps:
step (1): acquiring a water sample to be detected;
step (2): adding a potassium persulfate solution into the water sample for oxidation;
putting two water samples under an infrared spectrometer, and measuring the two water samples under two different wavelengths respectively to obtain spectral absorption values a and b; the two different wavelengths are both near 1500nm;
step (4) of obtaining the absorbance C of the carbonate and the nitrate under two different wavelengths 1 、N 1 、C 2 、N 2 ；
And (5) obtaining the total nitrogen content in the water by solving a component linear equation in a binary manner.
In the step (5), the linear equation of two elements is C 1 X+N 1 Y＝a；C 2 X+N 2 Y = b; wherein X is the content of carbon dioxide in the water sample, and Y is the content of nitrate in the water sample.
Preferably, in the step (3), the two different wavelengths are 1480nm and 1520nm, respectively.
Preferably, in the step (4), the absorbance C of the carbonate and nitrate at the two different wavelengths is 1 、N 1 、C 2 、N 2 Obtained by querying an existing spectrogram.
Preferably, in the step (4), the absorbance C of the carbonate and nitrate at the two different wavelengths is 1 、N 1 、C 2 、N 2 Is obtained by detection.
Compared with the prior art, the invention at least has the following invention points and corresponding beneficial effects:
(1) Oxidizing most of organic nitrogen compounds, ammonia nitrogen and nitrite into nitrate by using a strong oxidant; the oxidized water sample not only comprises nitrate, but also comprises carbon dioxide generated in the oxidation process, and the spectrum measurement of the N = O bond is interfered by the C = O bond; the total nitrogen content in the water is obtained by measuring the absorbance at two wave bands and constructing a linear equation of two elements.
(2) By selecting a specific wavelength, i.e. a wavelength around 1500nm, since this wavelength around this wavelength is the overlapping area of the C = O bond and the pair of N = O bonds.
(3) The detection method provided by the invention can quickly perform subsequent steps after the oxidation process is finished, does not need other treatment or additional reagents, and is high in speed and environment-friendly.
Detailed Description
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
To better illustrate the invention and to facilitate the understanding of the technical solutions thereof, typical but non-limiting examples of the invention are as follows:
example 1
The total nitrogen content in water usually comprises inorganic nitrogen such as nitrate, nitrite and ammonium salt, and organic nitrogen such as protein, amino acid and organic amine; if the total nitrogen is measured, a strong oxidizer is firstly used for oxidizing most organic nitrogen compounds, ammonia nitrogen and nitrite into nitrate; the oxidized water sample contains not only nitrate but also carbon dioxide generated in the oxidation process, and when infrared spectroscopy is used as a light source to measure absorbance, the spectrum measurement of the N = O bond is interfered by the C = O bond spectrum absorption region and the N = O bond spectrum absorption region, and a certain overlapping region exists.
Lambert beer's law, when a bundle of parallel monochromatic light of fixed wavelength is perpendicularly incident to the material to be detected, the absorption of the material to be detected to light is directly proportional to the product of the concentration of the material to be detected and the optical path of the light passing through the material.
According to the Lambert beer law, when light passes through a sample, the concentration of the sample can be calculated by detecting the absorbance of the sample and combining the light path length of the light passing through the sample.
And finally, measuring the absorbance of the oxidized water sample under two wavelengths with the light source being about 1500 wavelengths, establishing a linear equation of two variables by combining the absorbance of the nitrate and the carbon dioxide under the two wavelengths, and solving the equation to obtain the total nitrogen content in the water.
The invention provides a method for measuring total nitrogen content in water, which comprises the following steps:
step (1): obtaining a sample to be detected and filtering;
step (2): sucking a plurality of 20ml water samples, respectively placing the water samples into 25ml test tubes, then adding 5ml of potassium persulfate (40 g/l) solution into the water samples, plugging the test tubes by using plugs, wrapping a piece of gauze at the tube openings, and fastening by using fine wires; placing the test tube in a large beaker, heating in a high-pressure steam sterilizer, keeping the temperature at 120-240 ℃ for about 30 minutes when the pressure reaches 1-1.1kg/cm < 2 >, stopping heating, taking out the test tube after the reading of a pressure gauge is reduced to 0, and cooling;
placing the two water samples under an infrared spectrometer, and respectively measuring under the wavelengths 1520 and 1500 to obtain spectral absorption values a and b;
respectively placing a certain amount of carbonate and nitrate into a 25ml test tube, adding purified water to 25ml, and respectively measuring the absorbance of the carbonate and the nitrate at infrared wavelengths 1500 and 1520, namely C 1 (absorbance of carbonate at 1500 wavelength), N 1 (absorbance of nitrate at wavelength 1500), C 2 (absorbance of carbonate at wavelength 1520), N 2 (absorbance of nitrate at wavelength 1520);
step (5) component equation of linear two-in-two, C 1 X+N 1 Y＝a；C 2 X+N 2 Y = b; wherein X is the content of carbon dioxide in the water sample, Y is the content of nitrate in the water sample, the value Y, namely the content of nitrate in water, is obtained by solving an equation, and the total nitrogen content in water is obtained by conversion.
Example 2
The invention provides a method for measuring total nitrogen content in water, which comprises the following steps:
step (1): obtaining a sample to be detected and filtering;
step (2): sucking a plurality of 20ml water samples, respectively placing the water samples into 25ml test tubes, then adding 5ml of potassium persulfate (40 g/l) solution into the water samples, plugging the test tubes by using plugs, wrapping a piece of gauze at the tube openings, and fastening by using fine wires; placing the test tube in a large beaker, heating in a high-pressure steam sterilizer, keeping the temperature at 120-240 ℃ for about 30 minutes when the pressure reaches 1-1.1kg/cm < 2 >, stopping heating, and taking out and cooling after the reading of a pressure gauge is reduced to 0;
placing the two water samples under an infrared spectrometer, and respectively measuring at a wavelength of 1480 and a wavelength of 1520 to obtain spectral absorption values a and b;
step (4) obtaining absorption values at infrared wavelengths 1480 and 1520 of C = O bond and N = O bond by inquiry; c 1 (absorbance of carbonate at wavelength 1480), N 1 (absorbance of nitrate at wavelength 1500), C 2 (absorbance of carbonate at wavelength 1520), N 2 (absorbance of nitrate at wavelength 1520);
step (5) component equation of linear two-in-two, C 1 X+N 1 Y＝a；C 2 X+N 2 Y = b; wherein X is the content of carbon dioxide in the water sample, Y is the content of nitrate in the water sample, the value Y, namely the content of nitrate in water, is obtained by solving an equation, and the total nitrogen content in water is obtained by conversion.
The applicant states that the present invention is described by the above embodiments to explain the detailed structural features of the present invention, but the present invention is not limited to the above detailed structural features, that is, it is not meant to imply that the present invention must be implemented by relying on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that, in the above embodiments, the various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present invention does not separately describe various possible combinations.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (3)
1. A method for measuring the total nitrogen content in water is characterized by comprising the following steps: the method comprises the following steps:
step (1): acquiring a water sample to be detected;
step (2): adding a potassium persulfate solution into the water sample for oxidation;
and (3): placing two water samples under an infrared spectrometer, and respectively measuring at two different wavelengths to obtain spectral absorption values a and b; the two different wavelengths are 1480nm and 1520nm, respectively;
and (4): obtaining the absorbance C of the carbonate and the nitrate under the two different wavelengths 1 、N 1 、C 2 、N 2 ；
And (5): constructing a linear equation of two-dimensional, and solving the equation to obtain the total nitrogen content in the water;
in the step (5), the one-dimensional equation of two is C 1 X+ N 1 Y=a；C 2 X+ N 2 Y = b; wherein X is the content of carbon dioxide in the water sample, and Y is the content of nitrate in the water sample.
2. The method of claim 1, wherein: in the step (4), carbonate and nitrate are added at two different wavelengthsAbsorbance C of acid salt 1 、N 1 、C 2 、N 2 Is obtained by querying the spectrogram.
3. The method of claim 1, wherein: in the step (4), the absorbance C of the carbonate and nitrate at the two different wavelengths 1 、N 1 、C 2 、N 2 Is obtained by detection.
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