A kind of water quality selenium detection reagent and method

Abstract

The present application discloses a kind of water quality selenium detection reagent and method, the detection reagent includes a first reagent, a second reagent and a third reagent; the first reagent is a mixed aqueous solution of a masking agent, a buffer, a stabilizer and a developer; the second reagent is an alkaline buffer solution; the third reagent is an extractant; in the first reagent, by weight percentage concentration, the buffer is 1% to 10%; the masking agent is 1% to 10%; the stabilizer is 0.01% to 5%, and the developer is 1% to 10%; in the second reagent, by weight percentage concentration, sodium hydroxide 1%-20%, sodium carbonate 1%-20%, borax 1-20%, and the remaining components are water; the extractant is ethyl acetate or n-butanol. The present application provides a new detection reagent and method, the reagent is more environmentally friendly, suitable for non-professional operation, the reagent has a long shelf life and is simple to operate, the color development time is significantly shortened, and the detection efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of water quality detection, and in particular to a detection reagent and method for high-concentration water selenium. Background Art

[0002] Selenium in people's daily diet includes inorganic selenium and organic selenium. Organic selenium, such as selenoprotein and selenoamino acid, can be converted into active substances beneficial to the human body in the body and absorbed and utilized by the human body. Inorganic selenium, especially hexavalent selenium, is highly toxic, and the limit between the poisoning amount and the required amount is very close. In addition, its absorption and utilization rate are poor, and its biological effectiveness is low. Therefore, its use is strictly limited. Therefore, when conducting ecological environment surveys and monitoring, it is of great significance to accurately detect the content of inorganic selenium in water quality.

[0003] Traditional detection methods include atomic spectrophotometry, absorption spectroscopy, mass spectrometry, electrochemical technology, chromatography, etc. (Table 1):

[0004] Table 1 National and local standard detection methods for selenium in water

[0005]

[0006] Among the traditional methods, spectrophotometry is widely used, among which the diaminobenzidine spectrophotometry method of the water quality industry standard HJ811-2016 is a relatively commonly used standard method. However, on the one hand, the reagents used in this method need to be prepared and used immediately, and have a short shelf life; the extraction agent toluene is relatively toxic, and the reagents are not environmentally friendly and are not suitable for non-professionals to operate; the color development time is too long, which affects the detection efficiency. Summary of the invention

[0007] As can be seen from the relevant standard methods listed in Table 1, various standard methods are mainly aimed at the determination of low-concentration selenium. The present application provides a new detection reagent and method, which can determine high-concentration selenium, with the highest detection concentration reaching 10 mg / L, which can be used as a supplement to the relevant standard methods; and the color developer is a non-hazardous chemical as inquired on the Sinopharm website, and the extractant is more environmentally friendly than the toluene used in the industry standard HJ811-2016, suitable for non-professional operation, the reagent has a long shelf life and is simple to operate, the color development time is significantly shortened, and the detection efficiency is improved.

[0008] A water quality selenium detection reagent, comprising a first reagent, a second reagent and a third reagent; the first reagent is a mixed aqueous solution of a masking agent, a buffer, a stabilizer and a color developer; the second reagent is an alkaline buffer solution; the third reagent is an extractant;

[0009] In the first reagent, the buffer is 1% to 10% by weight; the masking agent is 1% to 10%; the stabilizer is 0.01% to 5%; the color developer is 1% to 10%; the color developer is 4,5-diaminophthalonitrile or its salts;

[0010] The second reagent comprises, by weight percentage, 1%-20% sodium hydroxide, 1%-20% sodium carbonate, 1%-20% borax, and the remaining component is water;

[0011] The extractant is ethyl acetate or n-butanol.

[0012] Several optional methods are also provided below, but they are not intended to be additional limitations on the above-mentioned overall solution, but are merely further supplements or preferences. Under the premise that there are no technical or logical contradictions, each optional method can be combined with the above-mentioned overall solution separately, and multiple optional methods can also be combined.

[0013] Optionally, in the first reagent: the buffer is citric acid or tartaric acid to maintain the pH value of the first reagent between 1-3.

[0014] Optionally, in the first reagent: the stabilizer is a mixture of sodium sulfite and 2-hydroxy-4-methoxybenzophenone in a mass ratio of 1:1 or a mixture of sodium sulfite and 2-hydroxy-4-n-octyloxybenzophenone in a mass ratio of 1:1.

[0015] Optionally, in the first reagent: the masking agent is one or a combination of ethylenediaminetetraacetic acid and EDTA sodium salt thereof; the color developer is 4,5-diaminophthalonitrile or its salts.

[0016] Optionally, the detection reagent is used for detecting selenium in water with a selenium concentration of 0.2-10 mg / L.

[0017] Optionally, the water quality selenium refers to inorganic selenium in the water body.

[0018] Most preferably, the first reagent is a mixed aqueous solution of a masking agent, a buffer, a stabilizer and a developer: wherein the masking agent is ethylenediaminetetraacetic acid and has a weight percentage concentration of 2.5% in the mixed aqueous solution, the buffer is citric acid or tartaric acid and has a weight percentage concentration of 2.5% in the mixed aqueous solution, the stabilizer is a mixture of sodium sulfite and 2-hydroxy-4-methoxybenzophenone in a mass ratio of 1:1 and has a weight percentage concentration of 0.5% in the mixed aqueous solution, and the developer is 4,5-diaminophthalonitrile or its salts and has a weight percentage concentration of 5% in the mixed aqueous solution;

[0019] The second reagent contains, by weight percentage, 10% sodium hydroxide, 5% sodium carbonate, 5% borax, and the remaining component is water;

[0020] The third reagent is ethyl acetate.

[0021] The present application also provides a method for detecting selenium in water quality using the detection reagent, wherein the concentration range of selenium in water quality is 0.2-10 mg / L, comprising:

[0022] (1) Take the test water sample, add the first reagent, fully dissolve it and let it react for 10 to 15 minutes;

[0023] (2) adding the second reagent to the reaction solution of step (1), mixing thoroughly, and then adding the third reagent for extraction;

[0024] (3) Detect the absorbance value of the extract obtained in step (2) at 420 nm, and substitute the obtained absorbance value into the standard curve to calculate the selenium concentration in the water sample.

[0025] Optionally, in step (1), based on 5 mL of the test water sample, the amount of the first reagent added is 0.2 g, the amount of the second reagent added is 1 mL, and the amount of the third reagent added is 5 mL.

[0026] Optionally, the standard curve is: y = 6.1146x - 0.1644, R 2 = 0.9999, where y is the selenium concentration in mg / L and x is the absorbance.

[0027] This method belongs to spectrophotometry. Compared with HJ811-2016 and SLT272-2016, this application has at least one of the following beneficial effects:

[0028] (1) The color development time is reduced. The color development time of HJ811-2016 is 30 minutes, while that of this method is 10 to 15 minutes, which shortens the color development time by 1 / 3 to 1 / 2. SLT272-2016 requires a gas production reaction, and the gas production time is at least 30 minutes, not including the color development reaction time.

[0029] (2) HJ811-2016 requires toluene as an extractant, which is highly toxic, while ethyl acetate and n-butanol are relatively more environmentally friendly and easier to operate, making them suitable for non-professionals. SLT272-2016 requires perchloric acid, potassium borohydride tablets, etc. These reagents are highly corrosive, produce gas and are prone to leakage. The production of marking lines requires high professionalism and is a test of the professional's proficiency.

[0030] (3) The shelf life of the reagents in this application is more than 1 year, and there is no need to prepare them before each measurement. The reagents in HJ811-2016 need to be prepared before the measurement and have a short shelf life, especially the hydrochloric acid solution and the color developer solution, which will deteriorate every other day.

[0031] (4) Have good precision and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the standard test graph of the extractant cyclohexane;

[0033] Figure 2 This is the standard test graph of the extraction agent n-butanol;

[0034] Figure 3 This is a curve diagram of Example 1. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0037] Relevant description of the reagents and detection methods of this application:

[0038] About the first reagent: the acidity required for the reaction of this method is around pH 2, and citric acid can provide a reaction environment of around pH 2. At the same time, citric acid has a certain reducing property, which can reduce the high-valent selenium in the water sample to tetravalent selenium that can react, thereby promoting detection accuracy; since the reaction may be interfered by some metal ions, a masking agent is added to the first reagent to mask some common metal ions, thereby promoting detection accuracy; the color developer contained in the first reagent will be degraded by light and oxygen, and the detection reaction will also be affected by light and oxides. This application adds a stabilizer, which includes an ultraviolet absorber such as 2-hydroxy-4-methoxybenzophenone, and a reducing agent with strong reducing property, sodium sulfite. The stabilizer ensures the stability of the color developer during the shelf life and avoids interference from light and water sample oxides during the reaction.

[0039] About the second reagent:

[0040] The present application adopts a buffer solution to stabilize the acid-base environment of the reaction during different reaction steps, thereby promoting the reaction to proceed stably and rapidly.

[0041] About the third reagent:

[0042] This application uses ethyl acetate and n-butanol as extractants to extract the reactants from the water sample into the organic phase. The selection of the extractant needs to be screened and tested, and a standard curve is required to be established according to the concentration of selenium. During the screening process, this application tested ethyl acetate, n-butanol and cyclohexane. The test results use the absorbance value as the horizontal axis and the selenium concentration value as the vertical axis. The standard curve was established and it was found that cyclohexane can extract the reactants, but it is not linear ( Figure 1 ), it is impossible to make a standard curve, while the linearity of n-butanol and ethyl acetate is very good ( Figure 2 , Figure 3 ).

[0043] The following is a description of specific examples, and all reagents used are commercially available:

[0044] Example 1

[0045] Detection reagent components:

[0046] The first reagent (mass percentage concentration): buffer (citric acid) 2.5%, masking agent (ethylenediaminetetraacetic acid) 2.5%, stabilizer (sodium sulfite and 2-hydroxy-4-methoxybenzophenone mixed in a mass ratio of 1:1) 0.5%, color developer (4,5-diaminophthalonitrile) 5%, and the solvent is water.

[0047] The second reagent (mass percentage concentration): sodium hydroxide 10%, sodium carbonate 5%, borax 5%, the solvent is water.

[0048] The third reagent, ethyl acetate.

[0049] The process of making a standard curve:

[0050] Purchase Aladdin selenium standard solution (100 mg / L in 1% HCl) S115455-80mL. 1, 3, 5, 10 mg / L concentrations are obtained by diluting the 100 mg / L selenium standard solution, and 0.2, 0.3, 0.5 mg / L concentrations are obtained by diluting the 10 mg / L selenium standard solution, see Table 2.

[0051]

[0052] The test was performed according to the following test process. The test results were taken as absorbance value as the horizontal axis and selenium concentration value as the vertical axis to establish a standard curve. The standard curve is: y = 6.1146x - 0.1644, R 2 = 0.9999, where y is the selenium concentration in mg / L and x is the absorbance. Figure 3 shown.

[0053] The detection process is as follows:

[0054] (1) Turn on the water quality detector (such as ZY-360 Multi-parameter Water Quality Analyzer, Zhejiang Luheng Environmental Technology Co., Ltd.), select the selenium measurement position, or select 420nm wavelength, and add an appropriate amount of the third reagent into the colorimetric tube for zero adjustment.

[0055] (2) Add 5 ml of water sample and 0.2 g of the first reagent to the reaction bottle, shake well to fully dissolve it, and let it stand for 15 minutes for color development reaction. The reaction solution will turn yellow.

[0056] (3) Add 1 mL of the second reagent to the reaction bottle after the reaction, cover it and shake it for 10 seconds to mix it thoroughly. Take 5 mL of the third reagent and add it to the reaction bottle. Cover it and shake it vigorously for 1 minute.

[0057] (4) After standing for 2 minutes, use a pipette to draw an appropriate amount of the extract into a 10 mm colorimetric tube. Place the colorimetric tube in the detection tank of the water quality detector and read its absorbance value after 1 minute.

[0058] (5) After the test, long press the power button to turn off the instrument.

[0059] Precision test results:

[0060] The relative standard deviations of inorganic selenium concentrations determined by three laboratories using this method are shown in Table 3:

[0061]

[0062] From the results in Table 3, we can see that the relative standard deviations within the laboratory are 2.32%~6.89%, -2.67%~1.50%, and -0.17%~4.19%, respectively, and the precision error is less than 7%.

[0063] Accuracy test results:

[0064] Two types of tap water and two types of river water samples were taken for spiked determination. The results are shown in Table 4:

[0065]

[0066] From the results in Table 4, we can see that the recovery rate of tap water spiked is 96.58%~103.55%, the recovery rate of river water spiked is 99.56%~109.93%, the recovery rate of seawater spiked is 88.12%~102.25%, and the recovery rate of wastewater spiked is 101.88~112.65%. The deviation of the spiked recovery rate of natural water samples and wastewater samples is ≤13%. Compared with HJ811, the recovery rate of sewage samples spiked is the highest at 114%, and the recovery rate deviation is ≤14%, which is basically the same.

[0067] Water samples with different selenium concentrations were taken for testing, and the results are shown in Table 5:

[0068]

[0069] It can be seen from the results in Table 5 that the detection reagent and method of the present application can measure high concentration selenium, and the highest detection concentration reaches about 10 mg / L.

[0070] Stability test results:

[0071] The reagent produced in September 2023 randomly carried out two groups of measurements on selenium standard solutions of different concentrations, and the concentration values ​​were compared with the data measured by the reagent in 2024, as shown in Table 6:

[0072]

[0073] From the results in Table 6, we can see that the relative deviation of each concentration in September 2023 is 89%~108%, and the relative deviation of each concentration in September 2024 is 90%~106%. The relative standard deviation of each concentration in 2023-2024 is less than 5%. Therefore, the performance of the reagents is basically the same. The reagents in 2023 are put into 2024. After one year, the measurement accuracy is consistent, and the shelf life is at least one year.

[0074] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A water quality selenium detection reagent, characterized in that, It includes a first reagent, a second reagent and a third reagent; the first reagent is a mixed aqueous solution of a masking agent, a buffer, a stabilizer and a developer; the second reagent is an alkaline buffer solution; the third reagent is an extractant; In the first reagent, the buffer is 1% to 10% by weight; the masking agent is 1% to 10%; the stabilizer is 0.01% to 5%; the color developer is 1% to 10%; the color developer is 4,5-diaminophthalonitrile or its salts; the stabilizer is a mixture of sodium sulfite and 2-hydroxy-4-methoxybenzophenone in a mass ratio of 1:1 or a mixture of sodium sulfite and 2-hydroxy-4-n-octyloxybenzophenone in a mass ratio of 1:1; The second reagent comprises, by weight percentage, 1%-20% sodium hydroxide, 1%-20% sodium carbonate, 1%-20% borax, and the remaining component is water; The extractant is ethyl acetate or n-butanol; The detection reagent is used for detecting selenium in water with a selenium concentration of 0.2-10 mg / L.

2. The detection reagent according to claim 1, characterized in that In the first reagent: the buffer is citric acid or tartaric acid to maintain the pH value of the first reagent between 1-3.

3. The detection reagent according to claim 1, characterized in that In the first reagent: the masking agent is one or a combination of ethylenediaminetetraacetic acid and EDTA sodium salt.

4. The detection reagent according to claim 1, characterized in that The water quality selenium refers to the inorganic selenium in the water body.

5. The detection reagent according to claim 1, characterized in that The first reagent is a mixed aqueous solution of a masking agent, a buffer, a stabilizer and a developer: wherein the masking agent is ethylenediaminetetraacetic acid and its weight percentage concentration in the mixed aqueous solution is 2.5%, the buffer is citric acid or tartaric acid and its weight percentage concentration in the mixed aqueous solution is 2.5%, the stabilizer is a mixture of sodium sulfite and 2-hydroxy-4-methoxybenzophenone in a mass ratio of 1:1 and its weight percentage concentration in the mixed aqueous solution is 0.5%, and the developer is 4,5-diaminophthalonitrile or its salts and its weight percentage concentration in the mixed aqueous solution is 5%; The second reagent contains, by weight percentage, 10% sodium hydroxide, 5% sodium carbonate, 5% borax, and the remaining component is water; The third reagent is ethyl acetate.

6. A method for detecting selenium in water quality using the detection reagent according to claim 1, characterized in that: The concentration of selenium in the water is in the range of 0.2-10 mg / L, including: (1) Take the test water sample, add the first reagent, fully dissolve it and let it react for 10 to 15 minutes; (2) adding the second reagent to the reaction solution of step (1), mixing thoroughly, and then adding the third reagent for extraction; (3) Detecting the absorbance value of the extract obtained in step (2) at 420 nm, and substituting the obtained absorbance value into the standard curve to calculate the selenium concentration in the water sample; Based on 5 mL of the test water sample, the amount of the first reagent added is 0.2 g, the amount of the second reagent added is 1 mL, and the amount of the third reagent added is 5 mL.

7. The method according to claim 6, characterized in that The standard curve is: y = 6.1146x - 0.1644, R 2 = 0.9999, where y is the selenium concentration in mg / L and x is the absorbance.

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