CN113281328A - Method for detecting total nitrogen in water body and application thereof - Google Patents
Method for detecting total nitrogen in water body and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of water quality detection, and particularly provides a method for detecting total nitrogen in a water body and application thereof. The detection method comprises the following steps: adding an alkaline potassium persulfate solution into a water sample, and performing first digestion treatment at 90-100 ℃ to obtain a first digestion solution; adding acid liquor into the first digestion solution to adjust the first digestion solution to be neutral, and carrying out secondary digestion treatment on the neutral first digestion solution under the ultraviolet condition capable of releasing ozone to obtain a second digestion solution; adding a reducing solution into the second digestion solution, and carrying out reduction reaction under the ultraviolet condition capable of releasing ozone to obtain a reduction mixed solution; adding a color development liquid into the reduction mixed liquid to obtain a detection liquid; and carrying out total nitrogen detection treatment on the detection liquid. According to the method for detecting the total nitrogen in the water body, the digestion temperature is reduced to be below 100 ℃, the whole digestion time is less than 22min, and the total nitrogen detection efficiency is high.
Description
Technical Field
The invention relates to the technical field of water quality detection, in particular to a method for detecting total nitrogen in a water body and application thereof.
Background
The total nitrogen is one of important parameter indexes for monitoring water quality, and the existing total nitrogen detection methods mainly comprise an ultraviolet dual-wavelength detection method, a potassium persulfate high-temperature digestion-cadmium column reduction method and an ultraviolet digestion-ultraviolet reduction method. The ultraviolet dual-wavelength detection method needs to be resolved at 120 ℃ and under high pressure, and then needs two ultraviolet lamps with fixed wavelengths for detection, which has strict structural requirements on an on-line instrument; the potassium persulfate high-temperature digestion-cadmium column reduction rule needs to be carried out for 30min at the temperature of 110-120 ℃ and under the condition of 1.1-1.4 kPa, if the temperature is lower than the specified temperature, the potassium persulfate is not completely decomposed, the incomplete digestion can be caused, the digestion rate is low, in addition, the cadmium column reduction has high requirement on the environment of an experimental system, the damage of peracid and alkali on the cadmium column can not be reversed, so that the cadmium column becomes a consumable, and the cost is high; the ultraviolet digestion-ultraviolet reduction method needs to turn on the ultraviolet lamps for a long time, has high power consumption, and the service life of each ultraviolet lamp is 5000-6000 h, so that the ultraviolet lamps become consumables and have high cost.
Based on the current state of the art, there is a need to provide a new solution to the problems of total nitrogen detection.
Disclosure of Invention
The embodiment of the invention mainly aims to provide a method for detecting total nitrogen in a water body and application thereof, and aims to solve the problems of high digestion temperature, long detection time, high cost and the like of the conventional water body total nitrogen detection.
In a first aspect, an embodiment of the present invention provides a method for detecting total nitrogen in a water body, including the following steps:
adding an alkaline potassium persulfate solution into a water sample, and performing first digestion treatment at 90-100 ℃ to obtain a first digestion solution; the potassium persulfate solution is alkaline;
adding acid liquor into the first digestion solution to adjust the first digestion solution to be neutral, and performing secondary digestion treatment on the neutral first digestion solution under the ultraviolet condition capable of releasing ozone to obtain a second digestion solution;
adding a reducing solution into the second digestion solution, and carrying out reduction reaction under the ultraviolet condition capable of releasing ozone to obtain a reduction mixed solution;
adding a color development liquid into the reduction mixed solution to obtain a detection liquid;
and carrying out total nitrogen detection treatment on the detection liquid so as to obtain the content of total nitrogen in the water body.
Optionally, the time of the first digestion treatment is 6min-10 min; the time of the second digestion treatment is 3min-6 min; the time of the reduction reaction is 3min-6 min.
Optionally, the reducing solution is neutral, and the reducing solution contains diethylenetriamine pentaacetic acid, a buffering agent and a first pH value regulator.
Optionally, the content of diethylenetriamine pentaacetic acid is 4.5g/100mL-5.0g/100 mL; the content of the buffer is 12.0g/100mL-13.0g/100 mL; the first pH value regulator comprises at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide; and/or the presence of a gas in the gas,
the buffer comprises at least one of disodium hydrogen phosphate and dipotassium hydrogen phosphate.
Optionally, the color development liquid is acidic, and the color development liquid contains sulfanilamide, naphthyl ethylenediamine hydrochloride and a second pH value regulator.
Optionally, the content of the sulfanilamide is 1.8g/100mL-2.2g/100 mL; the content of the naphthyl ethylenediamine hydrochloride is 0.025g/100mL-0.075g/100 mL; the second pH value regulator comprises at least one of sulfuric acid and hydrochloric acid.
Optionally, the acid solution comprises at least one of hydrochloric acid and sulfuric acid.
Optionally, the step of performing total nitrogen detection processing on the detection solution includes performing total nitrogen detection processing on the detection solution by using a colorimetric method.
Optionally, the ultraviolet irradiation intensity in the ozone-releasing ultraviolet condition is 11.0 mu W/cm2-15.0μW/cm2And the ozone output of 1.5W is 5 mg/h.
In a second aspect, an embodiment of the present invention further provides an application of the method for detecting total nitrogen in a water body, where the method for detecting total nitrogen in a water body is applied to detection of total nitrogen in at least one of sea water quality, fresh water quality, and non-fresh water lake water quality.
Has the advantages that:
compared with the prior art, the method for detecting the total nitrogen in the water body provided by the embodiment of the invention firstly uses the alkaline potassium persulfate solution to perform digestion at 90-100 ℃, and then performs digestion under the ultraviolet condition capable of releasing ozone, so that the digestion temperature is reduced to be within 100 ℃ on the premise that the digestion effect is equivalent to that of the prior art, and meanwhile, the whole digestion process is not more than 22min, so that the whole total nitrogen detection time is effectively shortened, and the detection efficiency of the total nitrogen in the water body is improved; in addition, the digestion cost can be reduced. The method for detecting the total nitrogen in the water body provided by the embodiment of the invention is beneficial to the wide application of the online detection of the total nitrogen in the water body.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for detecting total nitrogen in a water body according to an embodiment of the present invention;
fig. 2 is a total nitrogen content curve detected by the method for detecting total nitrogen in a water body provided in embodiment 4 of the present invention;
FIG. 3 is a total nitrogen content curve obtained by the detection method for total nitrogen in water provided by comparative example 4 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The flow diagrams depicted in the figures are merely illustrative and do not necessarily include all of the elements and operations/steps, nor do they necessarily have to be performed in the order depicted. For example, some operations/steps may be decomposed, combined or partially combined, so that the actual execution sequence may be changed according to the actual situation.
It is to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
Fig. 1 is a schematic flow chart of a method for detecting total nitrogen in a water body according to an embodiment of the present invention.
And step S01, adding a potassium persulfate solution into the water sample, and performing first digestion treatment at 90-100 ℃ to obtain a first digestion solution, wherein the potassium persulfate solution is alkaline.
In step S01, the water sample may be collected from the ocean, fresh water (such as river, fresh water lake, groundwater, etc.), or non-fresh water lake. In some embodiments, the collected water sample is subjected to a pretreatment, such as a filtration or precipitation treatment, to filter out impurities or particles, thereby reducing the influence of the impurities or particles on the detection of total nitrogen in the water body. The potassium persulfate solution is acidic and an appropriate amount of a soluble base, such as sodium hydroxide, potassium hydroxide, etc., is added to the potassium persulfate solution to render it alkaline. In some embodiments, the concentration of the potassium persulfate solution is from 0.015mol/L to 0.020mol/L, such as may be 0.0185 mol/L. In some embodiments, the temperature of the first digestion process is 95 ℃, or 90 ℃, 100 ℃, and any other suitable temperature between 90 ℃ and 100 ℃. The time for the first digestion is shortened along with the increase of the digestion temperature between 90 ℃ and 100 ℃. In some embodiments, the time of the first digestion treatment is 6min to 10min, such as digestion for 10 min.
And step S02, adding acid liquor into the first digestion solution to adjust the first digestion solution to be neutral, and performing secondary digestion treatment on the neutral first digestion solution under the ultraviolet condition capable of releasing ozone to obtain a second digestion solution.
In step S02, the main purpose of adding the acid solution is to adjust the first digestion solution to neutral, i.e., to adjust the pH of the first digestion solution to about 7, and the acid solution can be dilute hydrochloric acid or dilute sulfuric acid. The ozone-releasing ultraviolet conditions may be achieved by ozone-bearing ultraviolet lamps, which may be low pressure mercury lamps or LED lamps. In some embodiments, the ozone-releasing ultraviolet radiation is at an intensity of 11.0 μ W/cm2-15.0μW/cm2And the ozone output of 1.5W is 5 mg/h. In some embodiments, the second digestion treatment may be performed at normal temperature, and in some embodiments, the time of the second digestion treatment is 3min to 6min, such as digestion for 5 min. Therefore, the total time of the first digestion treatment and the second digestion treatment is not more than 20min, the time required for digestion can be effectively shortened, and all nitrogen-containing substances are converted into orthonitrates through two times of digestion.
And step S03, adding a reducing solution into the second digestion solution, and carrying out reduction reaction under the ultraviolet condition capable of releasing ozone to obtain a reduction mixed solution.
In step S03, the reducing solution contains diethylenetriaminepentaacetic acid (DTPA), a buffer and a first pH adjuster. The diethylenetriamine pentaacetic acid is used as a reducing agent, the buffering agent has a buffering effect, the reducing liquid is neutral through the first pH value regulator, and the whole reduction process achieves a good reduction effect at the pH value of 7.0 or about 7.0. In some embodiments, the content of the diethylenetriamine pentaacetic acid in the reducing liquid is 4.5g/100mL-5.0g/100mL, the content of the buffering agent in the reducing liquid is 12.0g/100mL-13.0g/100mL, and the buffering agent can be any one of disodium hydrogen phosphate and dipotassium hydrogen phosphate; the addition amount of the first pH value regulator can be added according to the pH value of the reducing solution; the first pH regulator is any one of sodium hydroxide, potassium hydroxide and lithium hydroxide. In some embodiments, the ozone-releasing ultraviolet radiation is at an intensity of 11.0 μ W/cm2-15.0μW/cm2And the ozone output of 1.5W is 5 mg/h. In some embodiments, the time for the reduction reaction is 3min to 6min, such as 5 min. So far, the total time consumption is not more than 22min after two times of digestion treatment and reduction reaction treatment.
And step S04, adding color development liquid into the reduction mixed liquid to obtain detection liquid.
In step S04, the color developing solution contains sulfanilamide (NH)2C6H4SO2NH2) Naphthalene ethylene diamine (C)12H14N2) And a second pH adjustor. In particular to sulfanilamide and naphthyl ethylenediamine hydrochloride (C)12H14N22HCl) and a second pH value regulator are dissolved in deionized water to obtain a color developing solution, wherein the second pH value regulator is any one of sulfuric acid and hydrochloric acid. And after the color developing solution is added into the reduction mixed solution, color development is realized. In some embodiments, the content of the sulfanilamide in the color developing solution is 1.8g/100mL-2.2g/100mL, and the content of the naphthyl ethylenediamine hydrochloride in the color developing solution is 0.025g/100mL-0.075g/100 mL. In some embodiments, the developing time of the developing liquid is not more than 1 min.
And step S05, carrying out total nitrogen detection treatment on the detection liquid so as to obtain the content of total nitrogen in the water body.
In step S05, the total nitrogen detection process is performed by colorimetry. The detection solution is placed in a colorimetric tube, a cuvette or a colorimetric pool for detection, so that the content of total nitrogen in the water sample is obtained, the content of the total nitrogen in the water sample is also the water body corresponding to the water sample, and the content of the total nitrogen in the water body is obtained. In some embodiments, the total nitrogen detection processing time of the detection solution is 1min-3min, so that the time from digestion to total nitrogen detection is less than 25min, and the total nitrogen detection time in the water body can be greatly shortened.
In order to better illustrate the technical solutions of the embodiments of the present invention, the following further explains the embodiments and comparative examples.
Example 1
A method for detecting total nitrogen in a water body comprises the following steps:
(1) preparing a water sample: converting purchased glutamic acid into total nitrogen, preparing the total nitrogen and deionized water into a water sample, and dividing the water sample into six equal parts;
(2) preparing an alkaline potassium persulfate solution: 0.5g of potassium persulfate and 1.2g of sodium hydroxide are dissolved in deionized water, the volume is determined to be 100mL, and the solution is shaken up for standby.
(3) Preparing acid liquor: 2.5mL of concentrated hydrochloric acid is put into 70mL of deionized water, and the volume is adjusted to 100mL, and the concentrated hydrochloric acid is shaken up for standby.
(4) Preparing a reducing solution: adding 4.75g of diethylenetriamine pentaacetic acid and 12.6g of disodium hydrogen phosphate into 80mL of deionized water, dissolving, adding 1g of sodium hydroxide, adjusting the pH value to 7.0, fixing the volume to 100mL, and shaking up for later use.
(5) Preparing a color developing solution: and (3) putting 13.2mL of concentrated sulfuric acid into 70mL of deionized water, cooling to room temperature, sequentially adding 2g of sulfanilamide and 0.05g of naphthyl ethylenediamine hydrochloride, diluting the deionized water to 100mL, and shaking up for later use.
(6) And (3) adding the alkaline potassium persulfate solution prepared in the step (2) into three water samples, wherein the amount of the alkaline potassium persulfate solution added into each water sample is equal, and then performing first digestion treatment at the temperature of 95 ℃ for 10min to obtain three first digestion solutions.
(7) Adding an equal amount of acid liquor into each part of the first digestion liquor obtained in the step (6), wherein the acid liquor is the hydrochloric acid liquor obtained in the step (3), adjusting each part of the first digestion liquor to be neutral, and then carrying out secondary digestion treatment on the neutral first digestion liquor under the irradiation condition of a low-pressure mercury lamp with ozone, wherein the digestion time is 5min, so as to obtain three parts of second digestion liquor; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(8) Adding an equal amount of reducing liquid into each part of the second digestion solution obtained in the step (7), wherein the reducing liquid is the reducing liquid prepared in the step (4), uniformly mixing, and then carrying out reduction reaction under the condition of irradiation of a low-pressure mercury lamp with ozone for 5min to obtain three parts of reduction mixed solution; wherein, the ultraviolet radiation intensity of the low-pressure mercury lamp with ozoneThe degree is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(9) Adding equal amount of color development liquid into each part of the reduction mixed liquid obtained in the step (8), and uniformly mixing to obtain detection liquid, wherein the color development liquid is the color development liquid prepared in the step (5);
(10) and (4) respectively placing the three detection solutions obtained in the step (9) into a colorimetric pool for total nitrogen detection treatment, wherein the detection time of each detection solution is 10min, obtaining the total nitrogen content in the three water samples, calculating the digestion rate and the average digestion rate value according to the total nitrogen content of the three water samples, and recording the digestion rate and the average digestion rate value in table 1.
Comparative example 1
Detecting the total nitrogen of the remaining 3 parts of the water sample in the example 1 by adopting a potassium persulfate high-temperature digestion-cadmium column reduction method, wherein the specific detection method is as follows in GB 17378.4-2007 ocean monitoring Specification part 4: seawater analysis and section 4 of the GB/T12763.4-2007 Marine survey Specification: the sea water chemical element survey was conducted, and the digestion rate and the average digestion rate were calculated from the total nitrogen content of the three water samples and recorded in table 1.
Example 2
A method for detecting total nitrogen in a water body comprises the following steps:
(1) preparing a water sample: converting purchased lysine into total nitrogen, preparing a water sample with deionized water, and dividing the water sample into six equal parts;
(2) adding the alkaline potassium persulfate solution prepared in the step (2) in the example 1 into three water samples, wherein the amount of the alkaline potassium persulfate solution added into each water sample is equal, and then performing first digestion treatment at the temperature of 95 ℃ for 10min to obtain three first digestion solutions.
(3) Adding an equal amount of acid liquor into each part of the first digestion liquor obtained in the step (2), wherein the acid liquor is the hydrochloric acid solution prepared in the step (3) in the embodiment 1, adjusting each part of the first digestion liquor to be neutral, and then carrying out secondary digestion treatment on the neutral first digestion liquor under the irradiation condition of a low-pressure mercury lamp with ozone, wherein the digestion time is 5min, so as to obtain three parts of second digestion liquor; wherein, the ultraviolet radiation of the low-pressure mercury lamp with ozoneThe illumination intensity was 13.0. mu.W/cm21.5W of ozone output of 5 mg/h.
(4) Adding an equal amount of reducing liquid into each part of the second digestion solution obtained in the step (3), wherein the reducing liquid is the reducing liquid prepared in the step (4) in the example 1, uniformly mixing, and then carrying out reduction reaction under the irradiation condition of a low-pressure mercury lamp with ozone for 5min to obtain three parts of reduction mixed solution; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(5) Adding equal amount of color development liquid into each part of the reduction mixed liquid obtained in the step (4), and uniformly mixing to obtain detection liquid, wherein the color development liquid is the color development liquid prepared in the step (5);
(6) and (3) respectively placing the three detection solutions obtained in the step (5) into a colorimetric pool for total nitrogen detection treatment, wherein the detection time of each detection solution is 10min, obtaining the total nitrogen content in the three water samples, calculating the digestion rate and the average digestion rate value according to the total nitrogen content of the three water samples, and recording the digestion rate and the average digestion rate value in table 1.
Comparative example 2
Detecting the total nitrogen of the remaining 3 parts of the water sample in the example 2 by adopting a potassium persulfate high-temperature digestion-cadmium column reduction method, wherein the specific detection method is as follows in GB 17378.4-2007 ocean monitoring Specification part 4: seawater analysis and section 4 of the GB/T12763.4-2007 Marine survey Specification: the sea water chemical element survey was conducted, and the digestion rate and the average digestion rate were calculated from the total nitrogen content of the three water samples and recorded in table 1.
Example 3
A method for detecting total nitrogen in a water body comprises the following steps:
(1) preparing a water sample: converting purchased ammonia nitrogen into total nitrogen, preparing the total nitrogen and deionized water into a water sample, and dividing the water sample into six equal parts;
(2) adding the alkaline potassium persulfate solution prepared in the step (2) in the example 1 into three water samples, wherein the amount of the alkaline potassium persulfate solution added into each water sample is equal, and then performing first digestion treatment at the temperature of 95 ℃ for 10min to obtain three first digestion solutions.
(3) Adding an equal amount of acid liquor into each part of the first digestion liquor obtained in the step (2), wherein the acid liquor is the hydrochloric acid solution prepared in the step (3) in the embodiment 1, adjusting each part of the first digestion liquor to be neutral, and then carrying out secondary digestion treatment on the neutral first digestion liquor under the irradiation condition of a low-pressure mercury lamp with ozone, wherein the digestion time is 5min, so as to obtain three parts of second digestion liquor; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(4) Adding an equal amount of reducing liquid into each part of the second digestion solution obtained in the step (3), wherein the reducing liquid is the reducing liquid prepared in the step (4) in the example 1, uniformly mixing, and then carrying out reduction reaction under the irradiation condition of a low-pressure mercury lamp with ozone for 5min to obtain three parts of reduction mixed solution; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(5) Adding equal amount of color development liquid into each part of the reduction mixed liquid obtained in the step (4), and uniformly mixing to obtain detection liquid, wherein the color development liquid is the color development liquid prepared in the step (5);
(6) and (3) respectively placing the three detection solutions obtained in the step (5) into a colorimetric pool for total nitrogen detection treatment, wherein the detection time of each detection solution is 10min, obtaining the total nitrogen content in the three water samples, calculating the digestion rate and the average digestion rate value according to the total nitrogen content of the three water samples, and recording the digestion rate and the average digestion rate value in table 1.
Comparative example 3
Detecting the total nitrogen of the remaining 3 parts of the water sample in the example 3 by adopting a potassium persulfate high-temperature digestion-cadmium column reduction method, wherein the specific detection method is as follows in GB 17378.4-2007 ocean monitoring Specification part 4: seawater analysis and section 4 of the GB/T12763.4-2007 Marine survey Specification: the sea water chemical element survey was conducted, and the digestion rate and the average digestion rate were calculated from the total nitrogen content of the three water samples and recorded in table 1.
TABLE 1 digestion rates of Total Nitrogen in Water samples of examples 1-3 and comparative examples 1-3
As can be seen from Table 1, when the detection method provided by the embodiment of the invention is adopted for digestion treatment, the average digestion rate of glutamic acid is 99.7%, the average digestion rate of lysine is 99.8%, and the average digestion rate of ammonia nitrogen is 99.1%; in the potassium persulfate high-temperature digestion-cadmium column reduction method, when digestion is carried out under the condition of 120 degrees, the average digestion rate of glutamic acid is 99.6 percent, the average digestion rate of lysine is 99.6 percent, and the average digestion rate of ammonia nitrogen is 91.0 percent; therefore, the digestion rate of the same substance by the digestion method and the potassium persulfate high-temperature digestion-cadmium column reduction method of the embodiment of the invention has little difference and good repeatability.
Example 4
Drawing a calibration curve of total nitrogen in a water body, comprising the following steps:
(1) preparing an ammonia nitrogen standard solution: preparing standard solutions with the concentrations of 0.00mg/L, 0.20mg/L, 0.40mg/L, 0.60mg/L, 0.80mg/L and 1.00mg/L by taking ammonia nitrogen as a nitrogen source and deionized water as a solvent;
(2) taking a standard solution with each concentration as a water sample, adding six parts of the standard solution, adding the alkaline potassium persulfate solution prepared in the step (2) in the example 1 into each water sample, wherein the amount of the alkaline potassium persulfate solution added into each water sample is equal, and then performing first digestion treatment at the temperature of 95 ℃ for 10min to obtain six first digestion solutions.
(3) Adding an equal amount of acid liquor into each part of the first digestion liquor obtained in the step (2), wherein the acid liquor is the hydrochloric acid solution prepared in the step (3) in the embodiment 1, adjusting each part of the first digestion liquor to be neutral, and then carrying out secondary digestion treatment on the neutral first digestion liquor under the irradiation condition of a low-pressure mercury lamp with ozone, wherein the digestion time is 5min, so as to obtain six parts of second digestion liquor; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(4) And (3) determination: the absorbance of six digestion solutions was measured and a calibration curve was drawn, and the results are shown in fig. 2.
Comparative example 4
Taking one part of each of six standard solutions with six concentrations in example 4, wherein the total is six parts, digesting six water samples by adopting a potassium persulfate high-temperature digestion-cadmium column reduction method, and specifically detecting according to GB 17378.4-2007 ocean monitoring specification part 4: seawater analysis and section 4 of the GB/T12763.4-2007 Marine survey Specification: carrying out seawater chemical element survey to obtain six digestion solutions; the absorbance of six digestion solutions was measured and a calibration curve was drawn, and the results are shown in fig. 3.
As can be seen from fig. 2 and 3, the calibration curve, R, obtained by digesting the standard solution and drawing the calibration curve by using the method for detecting total nitrogen in water provided by the embodiment of the present invention20.9998 is reached; and digesting the standard solution by adopting a potassium persulfate high-temperature digestion-cadmium column reduction method and drawing a calibration curve R2Up to 0.9994; therefore, the linear R of the method for detecting total nitrogen in water and the potassium persulfate high-temperature digestion-cadmium column reduction method provided by the embodiment of the invention2All are larger than 0.9993, and the linearity meets the requirement, and all can be used.
Example 5
A method for detecting total nitrogen in a water body comprises the following steps:
(1) obtaining a water sample: randomly taking a proper amount of seawater in Shenzhen bay, standing for 2 hours, filtering with filter paper, taking filtrate to obtain a water sample, and dividing the water sample into 6 parts with equal amount;
(2) the alkaline potassium persulfate solution prepared in example 1 was added to 3 of the water samples in equal amounts, and then the first digestion treatment was carried out at 95 ℃ for 10min to obtain three first digestion solutions.
(3) Adding an equal amount of acid liquor into each part of the first digestion liquor obtained in the step (2), wherein the acid liquor is the hydrochloric acid solution prepared in the step (3) in the example 1, adjusting each part of the first digestion liquor to be neutral, and then carrying out second digestion treatment on the neutral first digestion liquor under the irradiation condition of a low-pressure mercury lamp with ozone, wherein the digestion time is 5min, so as to obtain three parts of second digestion liquor(ii) a Wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(4) Adding an equal amount of reducing liquid into each part of the second digestion solution obtained in the step (3), wherein the reducing liquid is the reducing liquid prepared in the step (4) in the example 1, uniformly mixing, and then carrying out reduction reaction under the irradiation condition of a low-pressure mercury lamp with ozone for 5min to obtain three parts of reduction mixed solution; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(5) Adding equal amount of color developing solution into each part of the reduction mixed solution obtained in the step (4), and uniformly mixing to obtain detection solution, wherein the color developing solution is the color developing solution prepared in the step (5) in the embodiment 1;
(6) and (3) respectively placing the three detection solutions obtained in the step (5) into a colorimetric pool for total nitrogen detection treatment, wherein the detection time of each detection solution is 10min, obtaining the total nitrogen content in the three water samples, recording the total nitrogen content in the three water samples in a table 2, and calculating the average value and the Relative Standard Deviation (RSD).
Comparative example 5
Detecting the total nitrogen of the remaining 3 parts of the water sample in the example 5 by adopting a potassium persulfate high-temperature digestion-cadmium column reduction method, wherein the specific detection method is as follows in GB 17378.4-2007 ocean monitoring Specification part 4: seawater analysis and section 4 of the GB/T12763.4-2007 Marine survey Specification: the sea water chemical element survey was conducted, and the test results were recorded in table 2, and the mean value and the Relative Standard Deviation (RSD) were calculated.
Example 6
A method for detecting total nitrogen in a water body comprises the following steps:
(1) obtaining a water sample: randomly taking a proper amount of seawater in the south Australia sea area, standing for 2 hours, filtering by using filter paper, taking filtrate to obtain a water sample, and dividing the water sample into 6 parts with equal amount;
(2) the alkaline potassium persulfate solution prepared in example 1 was added to 3 of the water samples in equal amounts, and then the first digestion treatment was carried out at 95 ℃ for 10min to obtain three first digestion solutions.
(3) Adding an equal amount of acid liquor into each part of the first digestion liquor obtained in the step (2), wherein the acid liquor is the hydrochloric acid solution prepared in the step (3) in the embodiment 1, adjusting each part of the first digestion liquor to be neutral, and then carrying out secondary digestion treatment on the neutral first digestion liquor under the irradiation condition of a low-pressure mercury lamp with ozone, wherein the digestion time is 5min, so as to obtain three parts of second digestion liquor; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(4) Adding an equal amount of reducing liquid into each part of the second digestion solution obtained in the step (3), wherein the reducing liquid is the reducing liquid prepared in the step (4) in the example 1, uniformly mixing, and then carrying out reduction reaction under the irradiation condition of a low-pressure mercury lamp with ozone for 5min to obtain three parts of reduction mixed solution; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(5) Adding equal amount of color developing solution into each part of the reduction mixed solution obtained in the step (4), and uniformly mixing to obtain detection solution, wherein the color developing solution is the color developing solution prepared in the step (5) in the embodiment 1;
(6) and (3) respectively placing the three detection solutions obtained in the step (5) into a colorimetric pool for total nitrogen detection treatment, wherein the detection time of each detection solution is 10min, obtaining the total nitrogen content in the three water samples, recording the total nitrogen content in the three water samples in a table 2, and calculating the average value and the Relative Standard Deviation (RSD).
Comparative example 6
Detecting the total nitrogen of the remaining 3 parts of the water sample in the example 6 by adopting a potassium persulfate high-temperature digestion-cadmium column reduction method, wherein the specific detection method is as follows in GB 17378.4-2007 ocean monitoring Specification part 4: seawater analysis and section 4 of the GB/T12763.4-2007 Marine survey Specification: the sea water chemical element survey was conducted, and the test results were recorded in table 2, and the mean value and the Relative Standard Deviation (RSD) were calculated.
Example 7
A method for detecting total nitrogen in a water body comprises the following steps:
(1) obtaining a water sample: randomly taking a proper amount of seawater in the waxberry pit sea area, standing for 2 hours, filtering by using filter paper, taking filtrate to obtain a water sample, and dividing the water sample into 6 parts with equal amount;
(2) the alkaline potassium persulfate solution prepared in example 1 was added to 3 of the water samples in equal amounts, and then the first digestion treatment was carried out at 95 ℃ for 10min to obtain three first digestion solutions.
(3) Adding an equal amount of acid liquor into each part of the first digestion liquor obtained in the step (2), wherein the acid liquor is the hydrochloric acid solution prepared in the step (3) in the embodiment 1, adjusting each part of the first digestion liquor to be neutral, and then carrying out secondary digestion treatment on the neutral first digestion liquor under the irradiation condition of a low-pressure mercury lamp with ozone, wherein the digestion time is 5min, so as to obtain three parts of second digestion liquor; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(4) Adding an equal amount of reducing liquid into each part of the second digestion solution obtained in the step (3), wherein the reducing liquid is the reducing liquid prepared in the step (4) in the example 1, uniformly mixing, and then carrying out reduction reaction under the irradiation condition of a low-pressure mercury lamp with ozone for 5min to obtain three parts of reduction mixed solution; wherein the ultraviolet radiation intensity of the low-pressure mercury lamp with ozone is 13.0 muW/cm21.5W of ozone output of 5 mg/h.
(5) Adding equal amount of color developing solution into each part of the reduction mixed solution obtained in the step (4), and uniformly mixing to obtain detection solution, wherein the color developing solution is the color developing solution prepared in the step (5) in the embodiment 1;
(6) and (3) respectively placing the three detection solutions obtained in the step (5) into a colorimetric pool for total nitrogen detection treatment, wherein the detection time of each detection solution is 10min, obtaining the total nitrogen content in the three water samples, recording the total nitrogen content in the three water samples in a table 2, and calculating the average value and the Relative Standard Deviation (RSD).
Comparative example 7
Detecting the total nitrogen of the remaining 3 parts of the water sample in the example 7 by adopting a potassium persulfate high-temperature digestion-cadmium column reduction method, wherein the specific detection method is as follows in GB 17378.4-2007 ocean monitoring Specification part 4: seawater analysis and section 4 of the GB/T12763.4-2007 Marine survey Specification: the sea water chemical element survey was conducted, and the test results were recorded in table 2, and the mean value and the Relative Standard Deviation (RSD) were calculated.
TABLE 2 detection results of Total Nitrogen in Water samples of examples 5 to 7 and comparative examples 5 to 7
As can be seen from Table 2, the detection results of the total nitrogen in the same water body are relatively close and have little difference, and the Relative Standard Deviation (RSD) is less than 5.0 percent in the examples 5-7 for detecting the total nitrogen in the water body by adopting the method for detecting the total nitrogen in the water body provided by the embodiment of the invention and the comparative examples 5-7 for detecting the total nitrogen in the water body by adopting the potassium persulfate high-temperature digestion-cadmium column reduction method, and both the detection methods have good accuracy and high detection stability.
As can be seen from the conclusions of table 1, fig. 3 and table 2, the digestion temperature is low, the digestion time is shortened, and the total time for detecting the total nitrogen in the water body is shortened because the time for developing and detecting occupies very little time for the whole detection, and the detection time mainly depends on the digestion step, so that the total time for detecting the total nitrogen in the water body can be effectively shortened, the total nitrogen detection efficiency is improved, the detection cost of the total nitrogen is effectively reduced, and the method can be used for monitoring the quality of ocean water, the quality of fresh water and the quality of non-fresh water lake water, such as on-line monitoring of seawater nutritive salt; in addition, the method for detecting the total nitrogen in the water body provided by the embodiment of the invention can be used together with an on-line instrument and a laboratory instrument.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments. While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art without departing from the scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A method for detecting total nitrogen in a water body is characterized by comprising the following steps:
adding an alkaline potassium persulfate solution into a water sample, and performing first digestion treatment at 90-100 ℃ to obtain a first digestion solution;
adding acid liquor into the first digestion solution to adjust the first digestion solution to be neutral, and performing secondary digestion treatment on the neutral first digestion solution under the ultraviolet condition capable of releasing ozone to obtain a second digestion solution;
adding a reducing solution into the second digestion solution, and carrying out reduction reaction under the ultraviolet condition capable of releasing ozone to obtain a reduction mixed solution;
adding a color development liquid into the reduction mixed solution to obtain a detection liquid;
and carrying out total nitrogen detection treatment on the detection liquid so as to obtain the content of total nitrogen in the water body.
2. The method for detecting the total nitrogen in the water body according to claim 1, wherein the time of the first digestion treatment is 6min to 10 min; the time of the second digestion treatment is 3min-6 min; the time of the reduction reaction is 3min-6 min.
3. The method for detecting the total nitrogen in the water body according to any one of claims 1 or 2, wherein the reducing solution is neutral, and the reducing solution contains diethylenetriaminepentaacetic acid, a buffering agent and a first pH value regulator.
4. The method for detecting the total nitrogen in the water body according to claim 3, wherein the content of the diethylenetriaminepentaacetic acid is 4.5g/100mL-5.0g/100 mL; the content of the buffer is 12.0g/100mL-13.0g/100 mL; the first pH value regulator comprises at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide; and/or the presence of a gas in the gas,
the buffer comprises at least one of disodium hydrogen phosphate and dipotassium hydrogen phosphate.
5. The method for detecting the total nitrogen in the water body according to any one of claims 1 or 2, wherein the color development liquid is acidic, and the color development liquid contains sulfanilamide, naphthyl ethylenediamine hydrochloride, and a second pH regulator.
6. The method for detecting the total nitrogen in the water body according to claim 5, wherein the content of the sulfanilamide is 1.8g/100mL-2.2g/100 mL; the content of the naphthyl ethylenediamine hydrochloride is 0.025g/100mL-0.075g/100 mL; the second pH value regulator comprises at least one of sulfuric acid and hydrochloric acid.
7. The method as claimed in any one of claims 1 or 2, wherein the acid solution comprises at least one of hydrochloric acid and sulfuric acid.
8. The method according to any one of claims 1 or 2, wherein the step of subjecting the detection solution to total nitrogen detection treatment comprises subjecting the detection solution to total nitrogen detection treatment by colorimetry.
9. The method for detecting total nitrogen in a water body according to any one of claims 1 or 2, wherein the ultraviolet irradiation intensity in the ozone-releasable ultraviolet condition is 11.0 μ W/cm2-15.0μW/cm2And the ozone output of 1.5W is 5 mg/h.
10. The application of the method for detecting the total nitrogen in the water body is characterized in that the method for detecting the total nitrogen in the water body according to any one of claims 1 to 9 is applied to the detection of at least one of the total nitrogen in the water quality of ocean water, the water quality of fresh water and the water quality of non-fresh water lake water.
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