On-site rapid detection method for hydrogen sulfide

Abstract

The invention discloses a hydrogen sulfide on-site rapid detection method, and belongs to the technical field of hydrogen sulfide gas detection. The method disclosed by the invention comprises the following steps: preparing a cadmium telluride solution with known concentration, wherein the cadmium telluride solution shows red fluorescence; after the carbon quantum dots are mixed with a blue carbon quantum dot solution, to-be-detected gas containing hydrogen sulfide is added for reaction, the color of fluorescence can change along with the change of the content of hydrogen sulfide, and based on the principle, the color change can be recorded by adopting a photographing technology, so that the content of hydrogen sulfide is obtained. According to the detection method disclosed by the invention, the reaction of the gas to be detected and the mixed solution can be realized through the detection device with a simple structure, so that on-site rapid detection is realized. The method disclosed by the invention has the advantages of simplicity in operation, low cost, high sensitivity and high safety performance, and can be suitable for various hydrogen sulfide detection environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen sulfide detection, and particularly relates to a rapid on-site detection method for hydrogen sulfide. Background Art

[0002] Currently, the commonly used detection techniques for hydrogen sulfide include iodine-based probes, lead acetate impregnated test papers, electrochemistry, and spectrophotometry.

[0003] Among them, (1) the classical method for determining hydrogen sulfide is to titrate sulfide with iodine. This technique is simple but lacks sensitivity and selectivity and is usually used for sulfide standardization.

[0004] (2) A common and off-the-shelf sensor for detecting H 2 S is the commercial lead acetate test strip. These white strips turn black when PbS is formed. Although the lead acetate test paper has been proven to be superior to the iodine measurement probe in terms of convenience, the test paper uses the toxic metal lead and has low sensitivity and defects.

[0005] (3) Electrochemical methods are often much more sensitive than these two techniques. This technique can use silver or mercury electrodes to react with H 2 S to form the corresponding metal sulfide. Then, by applying an appropriate negative potential (essentially cathodic stripping technique), the metal sulfide is reduced to metal. However, electrochemical methods may be significantly interfered with by factors including humidity and oxygen concentration, resulting in low sensitivity and uncertain detection effects. In addition, different from commercial lead acetate test papers, the instruments usually used in electrochemical sensing technology may also lack portability and are too expensive for consumers and researchers, so they are not applicable.

[0006] (4) Several spectrophotometric methods have also been used to detect H 2 S, such as the methylene blue test. This test involves the reaction of hydrosulfide ions with N,N-dimethylphenyl-1,4-diamine to form the thiazine dye methylene blue with a characteristic blue color. A variant of this test involves pre-concentrating H 2 S gas in a fixed alkaline acceptor solution, and a detection limit of 10 ppb can be achieved using standard ultraviolet-visible spectroscopy. Although this method does provide an attractive detection limit (LOD) for industrial and commercial applications, the pre-concentration step makes it difficult to implement commercially, so it is also limited in use.

[0007] Therefore, if a portable method for on-site detection of hydrogen sulfide can be provided, rapid on-site detection of hydrogen sulfide can be achieved. Summary of the Invention

[0008] To solve the defects in the prior art, the present invention provides a method for rapid on-site detection of hydrogen sulfide. Through obvious fluorescence color changes, the hydrogen sulfide gas to be detected can be directly quantified using a smartphone or the naked eye. Therefore, the detection method of the present invention can be applied to the monitoring of hydrogen sulfide in industrial production, landfills, and sewage treatment plants.

[0009] In the first aspect, the present invention provides a method for rapid on-site detection of hydrogen sulfide, including the following steps:

[0010] Prepare a cadmium telluride quantum dot solution, and determine the concentration of cadmium telluride nanocrystals after purification;

[0011] Prepare a carbon quantum dot solution, mix it with the cadmium telluride quantum dot solution, place it in a detection device, and introduce the gas to be detected containing hydrogen sulfide for reaction;

[0012] Take a photo and pick the color of the reacted solution to determine the hydrogen sulfide concentration.

[0013] In the above solution of the present invention, the principle is as follows: H 2 S can react with Cd on the surface of cadmium telluride quantum dots 2+ to generate CdS to eliminate vacancies, thereby causing FL quenching. Then, carbon dots are added as a reference fluorescence to construct a ratio fluorescence system of cadmium telluride - carbon dots. The reaction of cadmium telluride quantum dots with hydrogen sulfide gas at different concentrations causes different degrees of quenching of the red fluorescence of cadmium telluride quantum dots, while the fluorescence of blue carbon dots is not affected. Therefore, with the successive increase of hydrogen sulfide concentration, the ratio of the red fluorescence cadmium telluride quantum dots and blue carbon dots in the ratio fluorescence system will also show different fluorescence intensity ratios, resulting in a change trend of fluorescence color from red to blue. Then, in combination with the portable detection device in the present invention, a photo is taken of the ratio fluorescence probe test solution, and then the color is picked through a smartphone Color Picker or a computer Image J software. It is quantified according to the RGB values corresponding to different colors of hydrogen sulfide at different concentrations.

[0014] Further, the cadmium telluride quantum dot solution is prepared by the following method:

[0015] Dissolve Cd(NO 3 ) 2 ·4H 2 O and trisodium citrate dehydrate solution in water, add MPA (or 16.6L TGA, 29.1μL Lcys and 36.0mg MSA) solution, and then adjust the pH to alkaline;

[0016] Then add Na 2 TeO 3 and KBH 4Recirculate to obtain a CdTe QDs solution. After precipitation, remove the supernatant. Redisperse the purified cadmium telluride quantum dots, and obtain cadmium telluride nanocrystals with an accurate concentration through a purification procedure and standard atomic absorption measurement.

[0017] Further, the molar ratio of Cd(NO 3 ) 2 ·4H 2 O to Na 2 TeO 3 is 5:1.

[0018] Further, the carbon quantum dot solution is prepared by the following method:

[0019] Co-dissolve ethylenediamine and citric acid in deionized water, and react at 150 - 180 °C for 4 - 6 h;

[0020] After the reaction, purify the reaction product to obtain it.

[0021] Further, the concentration of the cadmium telluride quantum dot solution is 0.4 μM, and the volume ratio of the cadmium telluride quantum dot solution to the carbon quantum dot solution is 250:100;

[0022] Dilute the mixed solution with ultrapure water to 40 times the volume of the carbon quantum dot solution.

[0023] Further, the rate of the hydrogen sulfide gas is 350 - 450 mL / min, and the introduction time is 8 - 12 min.

[0024] Further, the detection device includes a device body and a housing. Inside the device body, a feeding component and a detection component are provided. The detection component includes a light source, a cuvette, and a power supply. The cuvette is arranged above the light source, the power supply supplies power to the light source, and a heat sink is arranged outside the light source.

[0025] In the above solution of the present invention, the detection device has a simple structure. It only needs to react the gas to be detected with the mixed solution under specific conditions, and then take color by taking a photo with a smartphone, which can meet the detection and monitoring of hydrogen sulfide gas in various places.

[0026] Further, the feeding component includes an air pump and a headspace bottle connected to the air outlet end of the air pump. The air outlet end of the headspace bottle is communicated with the detection component, and a flow meter is arranged on the air outlet end of the headspace bottle.

[0027] Further, a first switch, a second switch, and a third switch are arranged outside the power supply. The first switch is used to control the startup of the detection device, the second switch is used to control the startup of the air pump, and the third switch is used to control the startup of the light source.

[0028] Further, when using the detection device, turn on the first switch, place the mixed solution in a headspace vial, turn on the air pump through the second switch, pump in the test gas containing hydrogen sulfide to react with the mixed solution, and obtain the reacted solution.

[0029] Turn off the air pump, start the light source through the third switch, place the reacted solution in a cuvette, take a photo to obtain the color, and determine the hydrogen sulfide concentration.

[0030] The above technical solutions provided by the embodiments of the present application have at least the following advantages compared with the prior art:

[0031] 1. The present invention discloses a rapid on-site detection method for hydrogen sulfide, which meets the requirements of on-site sample measurement. Compared with the current national standard method and other commercial methods, this method has high sensitivity. The detection limit of this method is 14 ppb, which can basically meet the monitoring of hydrogen sulfide gas in various places. The response time only requires 8 - 12 minutes, and the portable device designed by 3D printing and the smart phone in the present invention can directly meet the equipment required for on-site sample measurement, which is convenient, fast, and has high sensitivity.

[0032] 2. The present invention discloses a rapid on-site detection method for hydrogen sulfide. The method is simple and sensitive. Only by introducing the test hydrogen sulfide gas into the mixed solution of cadmium telluride and carbon dots can a ratio fluorescence system be constructed. The concentration of hydrogen sulfide can be quantified by the change in fluorescence color without the need for the regulation of other reagents, and then the smart phone can be directly used to take a photo for quantification. The operation is extremely simple and does not require the support of large equipment.

[0033] 3. The present invention discloses a rapid on-site detection method for hydrogen sulfide, which solves the problem of the cumbersome process of the national standard methods of methylene blue spectrophotometry and iodometry. The detection device can be directly used in the on-site environment, and can also be remotely operated by using equipment such as drones, improving the portability and safety performance of the operation. On the basis of improving the reuse rate (the detection device can be repeatedly used after being printed and formed), the cost is reduced, thereby improving the economic benefits of hydrogen sulfide detection. Description of the Drawings

[0034] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments in line with the present application, and are used together with the specification to explain the principles of the present application.

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 The connection relationship between the headspace vial and the air pump in the detection device used in the present invention;

[0037] Figure 2 Schematic diagram of the colorimetric cell and the lamp beads in the detection device used in the present invention;

[0038] Figure 3 Schematic diagram of the power supply and the switch in the detection device used in the present invention;

[0039] Figure 4 Structure block diagram of the detection device used in the present invention;

[0040] Figure 5 The control relationship between the hydrogen sulfide concentration detected by the on-site rapid detection method for hydrogen sulfide disclosed in the present invention and the color;

[0041] Figure 6 Specific photos for assisting in taking pictures with a smart phone when using the detection device in the present invention for detection;

[0042] Figure 7 Different signal output values of B / R, G / R, (B + G) / R, and (R + G + B) / R;

[0043] Figure 8 Fitting curve with the ratio of (B + G) / R value as the signal output. Detailed implementation mode

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0045] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchase or can be prepared by existing methods.

[0046] The principles and features of the present invention will be described below in conjunction with the embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. For those not specifically indicated in the examples, they are carried out under conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through market purchase.

[0047] Example 1

[0048] This example provides a method for on-site rapid detection of hydrogen sulfide, including the following steps:

[0049] S1. Preparation of cadmium telluride quantum dots with red fluorescence

[0050] Dissolve 0.5 mmol of Cd(NO 3 ) 2 ·4H 2 O and 0.20 g of trisodium citrate dehydrate solution in 50 mL of water, and then immediately add 52 μL of MPA (3-mercaptopropionic acid) (or 16.6 μL of TGA mercaptoacetic acid, 29.1 μL of L-cysteine, and 36.0 mg of MSA mercaptosuccinic acid).

[0051] Adjust the pH of the solution to 10.5, add 0.1 mmol of Na 2 TeO 3 and 50 mg of KBH 4 , reflux for 1 h, precipitate the obtained CdTe QDs solution with n-propanol, and then centrifuge (11000 rpm) to remove the supernatant.

[0052] Redisperse the purified CdTe quantum dots in double distilled water (DIW), measure the concentration of the nanocrystals by standard atomic absorption (AA) measurement, and determine that the concentration of cadmium telluride in the solution is 0.4 μM.

[0053] S2. Preparation of carbon quantum dots with blue fluorescence

[0054] Dissolve 335 μL of ethylenediamine and 1.0507 g of citric acid in 10 mL of deionized water. Then, transfer the solution to a polytetrafluoroethylene-lined autoclave (50 mL) and react at 160 °C for 5 hours.

[0055] After the reaction is completed, cool the reaction product to room temperature, and then purify it by chromatography to obtain the final carbon quantum dot solution. Take 28 mg of carbon quantum dots and dissolve them in 1 mL of ultrapure water.

[0056] S3. Construction of ratio fluorescence

[0057] Mix 250 μL (0.4 μM) of cadmium telluride quantum dot solution and 100 μL of carbon quantum dot solution, and dilute to 4 mL with ultrapure water.

[0058] Take 15 μL of the diluted mixed solution and dilute it to 1 mL, and then take 1 mL and transfer it into a 20 mL brown headspace vial.

[0059] This step can also be carried out by mixing 250 μL (0.4 μM) of cadmium telluride quantum dot solution and 100 μL of carbon quantum dot solution, diluting to about 266.66 mL, and then taking 1 mL and adding it to the headspace vial.

[0060] S4. Reaction

[0061] Introduce the hydrogen sulfide-containing gas to be measured into the headspace vial for 10 minutes at a flow rate of 400 mL / min, and react with the mixed solution to obtain the reacted solution.

[0062] S5. Detection

[0063] Take out the reacted solution and put it into a cuvette. Turn on the 365 nm ultraviolet LED lamp bead and take a color photo with the professional mode of a smartphone. The photo-taking parameters of the professional mode are: ISO, 100; S, 1 / 60; AF, AF-C; WB, 6500.

[0064] It can be seen that the detection method of the present invention can be quickly detected using the detection device as Figure 1-4 shown. The specification of the device is 12*15*10 cm, and its structure is simple and convenient to carry. It specifically includes a device body and a housing. An inlet component and a detection component are arranged inside the device body. The detection component includes a light source, a cuvette, and a power supply. The cuvette is arranged above the light source, and the power supply supplies power to the light source. A heat sink is arranged outside the light source. It can be seen that the light source is a 365 nm ultraviolet LED lamp bead.

[0065] The inlet component includes an air pump and a headspace vial connected to the air outlet end of the air pump. The headspace vial serves as a carrier device for reaction raw materials and a reaction occurrence device. A flow meter, which is a glass rotor flow meter, is arranged at the air outlet end of the headspace vial.

[0066] A first switch, a second switch, and a third switch are arranged outside the power supply. The first switch is used to control the startup of the detection device, the second switch is used to control the startup of the air pump, and the third switch is used to control the startup of the light source.

[0067] During use, as shown in steps S4 and S5, place the mixed cadmium telluride quantum dot solution and carbon quantum dot solution in the headspace vial, pump the hydrogen sulfide-containing gas sample to be measured into the headspace vial from the air pump, and react in the headspace vial. Take out the reacted mixed solution, place it in a cuvette, and take a photo with a photo-taking tool. The taken photo is as Figure 6 shown. Use a professional color-picking tool, such as a smartphone Color Picker or a computer Image J software, to pick the color of the photo, and quantify it according to the RGB values corresponding to different colors of hydrogen sulfide at different concentrations.

[0068] Considering that the red fluorescence gradually quenches with the increase of hydrogen sulfide concentration, the present invention studies different signal output values of B / R, G / R, (B + G) / R, and (R + G + B) / R, as Figure 7As shown, it is found that the RGB signal value of the (B+G) / R value is the highest after deducting the blank (such as Figure 8 The concentration of hydrogen sulfide detected has a good linear relationship (r 2 =0.996), which is beneficial to improve the sensitivity of this method to hydrogen sulfide analysis. Therefore, the ratio of (B+G) / R value is selected as the signal output.

[0069] The present invention directly uses standard gas to mix nitrogen through a gas diluter to dilute hydrogen sulfide of different concentrations and directly introduces it into a headspace bottle for determination. The method is simple and fast, has a rapid and sensitive response, is applicable to various detection environments, and can be detected anytime and anywhere.

[0070] like Figure 5 As shown, the color detected in an environment without hydrogen sulfide gas is pink-purple (or red). As the hydrogen sulfide content increases, it gradually turns to purple, then increases to blue-purple, and finally turns blue when the concentration reaches 1000ppb. Compared with the current national standard method and other commercial methods, this method has high sensitivity. The detection limit of this method is 14ppb, which can basically meet the monitoring of hydrogen sulfide gas in various places, and the response time only takes 10min.

[0071] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A rapid on-site detection method for hydrogen sulfide, characterized in that, it includes the following steps: Prepare a cadmium telluride quantum dot solution, and determine the concentration of cadmium telluride nanocrystals after purification; Prepare a carbon quantum dot solution, mix it with the cadmium telluride quantum dot solution, place it in a detection device, and introduce a test gas containing hydrogen sulfide to react; Take a photo of the reacted solution to obtain the color, and determine the hydrogen sulfide concentration.

2. The rapid on-site detection method for hydrogen sulfide according to claim 1, characterized in that, the cadmium telluride quantum dot solution is prepared by the following method: Dissolve Cd(NO 3 ) 2 ·4H 2 O and trisodium citrate dehydrate solution in water, add MPA solution and adjust the pH to alkaline; Add Na again 2 TeO 3 and KBH 4 Reflux to obtain a CdTe QDs solution. After precipitation, remove the supernatant. Redisperse the purified cadmium telluride quantum dots, and obtain cadmium telluride nanocrystals with an accurate concentration through a purification procedure and standard atomic absorption measurement.

3. The rapid on-site detection method for hydrogen sulfide according to claim 2, characterized in that, The Cd(NO 3 ) 2 ·4H 2 O and Na 2 TeO 3 have a molar ratio of 5:

1.

4. The rapid on-site detection method for hydrogen sulfide according to claim 1, characterized in that, the carbon quantum dot solution is prepared by the following method: Co-dissolve ethylenediamine and citric acid in deionized water, and react at 150-180 °C for 4-6 h; After the reaction is completed, purify the reaction product to obtain it.

5. The rapid on-site detection method for hydrogen sulfide according to claim 1, characterized in that, the concentration of the cadmium telluride quantum dot solution is 0.4 μM, and the volume ratio of the cadmium telluride quantum dot solution to the carbon quantum dot solution is 250:

100.

6. The rapid on-site detection method for hydrogen sulfide according to claim 1, characterized in that, the rate of the hydrogen sulfide gas is 350-450 mL / min, and the introduction time is 8-12 min.

7. The rapid on-site detection method for hydrogen sulfide according to claim 1, characterized in that, the detection device includes a device body and a housing. Inside the device body, a feeding component and a detection component are provided. The detection component includes a light source, a colorimetric cell and a power supply. The colorimetric cell is arranged above the light source, the power supply supplies power to the light source, and a heat sink is arranged outside the light source.

8. The rapid on-site detection method for hydrogen sulfide according to claim 7, characterized in that, the feeding component includes an air pump and a headspace bottle connected to the air outlet end of the air pump. The headspace bottle is used to load the mixed carbon quantum dot solution and cadmium telluride quantum dot solution, and a flow meter is arranged on the headspace bottle.

9. The rapid on-site detection method for hydrogen sulfide according to claim 8, characterized in that, a first switch, a second switch and a third switch are arranged outside the power supply. The first switch is used to control the start of the detection device, the second switch is used to control the start of the air pump, and the third switch is used to control the start of the light source.

10. The rapid on-site detection method for hydrogen sulfide according to claim 9, characterized in that, when using the detection device, turn on the first switch, place the mixed solution in the headspace bottle, turn on the air pump through the second switch, pump in a test gas containing hydrogen sulfide to react with the mixed solution to obtain a reacted solution; Turn off the air pump, start the light source through the third switch, place the reacted solution in the colorimetric cell, take a photo to obtain the color, and determine the hydrogen sulfide concentration.

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