Device and method for detecting As (III) content of water body based on paper-based micro-fluidic chip

Abstract

The invention discloses a device and a method for detecting the content of As (III) in a water body based on a paper-based micro-fluidic chip. The method is based on the chemical principle that arsenite reacts with potassium iodate under the acidic condition to generate an iodine simple substance, and rhodamine B is oxidized by the generated iodine simple substance under the catalytic action of a sulfuric acid medium and potassium bromide, so that the rhodamine B is subjected to a color fading reaction. According to the device, a fluid channel is prepared on a filter paper material, reagent dropwise adding areas and a reaction area are sequentially arranged, corresponding reagents are dropwise added into the reagent dropwise adding areas in sequence, then the reagents are converged to a main channel step by step through a micro-fluidic channel and are communicated to the reaction area, and the reagents are mixed in the micro-fluidic channel and subjected to a chromogenic reaction in the reaction area. The method comprises the following steps: shooting an image of a reaction area, extracting color parameters by using image processing software, and performing contrast calculation with a pre-established standard working curve to obtain the content of As (III) in the water sample. The technical problems that in the prior art, operation steps are complex, the detection period is too long, the detection portability of the arsenic content in the water body is poor, and the detection cost is too high are solved.

Description

Technical Field

[0001] This invention relates to the field of arsenic content detection in water, and specifically to a device and method for detecting As(III) content in water based on a paper-based microfluidic chip. Background Technology

[0002] Arsenic (As) is a nonmetallic element widely distributed in the environment, mainly existing in both inorganic and organic forms. Inorganic arsenic is far more toxic than organic arsenic, and trivalent arsenic is approximately 60 times more toxic than pentavalent arsenic. In groundwater environments, As(III) often exists in an electroneutrally neutral form under reducing conditions, making it difficult to remove and posing a particularly serious threat to human health. Long-term arsenic exposure can cause various diseases such as skin cancer, lung cancer, liver cancer, and bladder cancer, and even lead to death. Therefore, arsenic pollution in drinking water has become a major global public health issue.

[0003] According to reports, more than 70 countries and regions worldwide have discovered excessive levels of arsenic in their groundwater, with over 140 million people having arsenic concentrations exceeding safe levels in their drinking water, and millions experiencing varying degrees of arsenic poisoning symptoms. The World Health Organization (WHO), the International Agency for Research on Cancer (IARC), and my country's Ministry of Ecology and Environment have all classified arsenic and inorganic arsenic compounds as Group 1 carcinogens and priority controlled toxic and hazardous water pollutants.

[0004] Paper-based microfluidic chips are a novel detection platform using paper as a substrate. Leveraging the capillary effect of paper fibers, liquids can spontaneously migrate within the porous network without external power. When a sample enters the chip, it travels along pre-designed hydrophilic channels to the reaction region, generating measurable signals such as color or fluorescence, thus enabling detection. This chip offers advantages such as simple fabrication, low cost, and ease of operation, and shows broad promise in environmental monitoring and medical diagnostics.

[0005] The existing invention patent application document CN107941726A, entitled "A Method for Determining Arsenic Content in Water," describes a method that includes: dispersing oxidizing manganese dioxide in water, heating and stirring to oxidize all trivalent arsenic ions in the water to pentavalent arsenic ions, thereby reducing the toxicity of arsenic in the water during detection and increasing the safety of the test. Pentavalent arsenic interacts with molybdic acid to form an arsine-molybdic acid mixture, which is finally reduced to molybdenum blue and detected by color development in boiling water. This prior art method for determining total arsenic oxidizes all trivalent arsenic to pentavalent arsenic; however, trivalent arsenic is far more toxic than pentavalent arsenic, making it impossible to measure the concentration of trivalent arsenic alone. Furthermore, this prior art requires water sample pretreatment, making the detection operation complex.

[0006] In summary, existing technologies suffer from technical problems such as complex operation procedures, excessively long detection cycles, poor portability in detecting arsenic content in water, and excessively high detection costs. Summary of the Invention

[0007] The technical problem to be solved by this invention is: how to solve the technical problems of complex operation steps, long detection cycle, poor portability of arsenic content detection in water and high detection cost in the prior art.

[0008] The present invention solves the above-mentioned technical problems by adopting the following technical solution: a device for detecting As(III) content in water based on a paper-based microfluidic chip includes:

[0009] The paper-based chip used in this invention is square in shape with a side length of 138 mm.

[0010] Fluid channels are fabricated on filter paper material, forming multi-channel converging structures to facilitate the mixing and reaction of multiple reagents. Paraffin wax is filled around the fluid channels to form a hydrophobic barrier structure, ensuring liquid flow on the hydrophilic paper substrate. The reagent addition zone comprises four areas: A (first area), B (second area), C (third area), and D (fourth area), each designed as a circle with a diameter of 8 mm. Pre-prepared reagents are sequentially added dropwise to these areas to provide the reaction environment, catalyst, and acidic conditions, inducing a series of chemical reactions in the arsenic-containing sample, ultimately resulting in the decolorization of Rhodamine B in the pre-prepared chemical system. The reagent addition zones are connected to a fluid channel. Driven by capillary forces, the reagents flow downwards along their respective hydrophilic branches, merging sequentially before finally converging into a single main channel connecting to reaction zone E, which is designed as a circle with a diameter of 12 mm. The color development results of reaction zone E were captured to obtain the color change image of the reaction zone. The image was then imported into image processing software, and the RGB values ​​of the reaction zone were extracted using a color picker (in actual analysis, only the intensity of the red channel is used, hereinafter referred to as the R value). The obtained data were compared with the standard working curve of As(III) concentration - R value to calculate the As(III) content of the water sample.

[0011] This invention utilizes a paper-based microfluidic chip for convenient detection of As(III) content in water. Using paper as the substrate, the required materials are simple and inexpensive, and the amount of reagents needed is also small, resulting in low overall cost. Color change images are captured using the same smartphone and then converted into RGB numerical signals, establishing a correlation with As(III) concentration. The operation is simple and easy to perform, does not rely on large analytical instruments, and yields accurate results.

[0012] In a more specific technical solution, a mixed solution of hydrochloric acid and potassium iodate is added to the first region A to provide a reaction environment.

[0013] In a more specific technical solution, 5 μL of a 10 g / L potassium iodate solution is added to the first region A. The pH of this solution is adjusted to 1.5 by adding 0.4 mol / L hydrochloric acid solution dropwise beforehand.

[0014] In a more specific technical solution, 5 μL of As(III) standard solutions of different concentrations are added dropwise to the second region B.

[0015] In a more specific technical solution, add 1-30 μg / L As(III) standard solution; weigh 0.132 g of As2O3 dried to constant weight in a sulfuric acid desiccator, warmly dissolve it in 1.2 mL of NaOH solution at a concentration of 100 g / L, transfer it to a 1000 mL volumetric flask, add deionized water to the mark, and prepare a 0.1 g / L As(III) standard solution stock solution. Dilute the stock solution to 1-30 μg / L as needed.

[0016] The detection range of this invention is 1-30 μg / L, and it can sensitively detect trace amounts of arsenic in water. The entire detection device is compact, portable, and easy to operate, making it suitable for on-site testing.

[0017] In a more specific technical solution, 5 μL of a mixed solution of 0.06 mol / L sulfuric acid and 0.1 mol / L potassium bromide, mixed in a 1:1 volume ratio, is added dropwise to the third region C to provide a catalyst and acidic conditions.

[0018] In a more specific technical solution, 5 μL of Rhodamine B solution is added to the fourth region D; the degree of decolorization of Rhodamine B is related to the concentration of As(III); By utilizing the capillary action of paper fibers, the solution flows in the channel, and the paper-based chip is allowed to react at room temperature for a predetermined time until the reaction is complete.

[0019] In a more specific technical solution, the concentration of the Rhodamine B solution can be set to, for example, 0.02 g / L.

[0020] In a more specific technical solution, the color development result of reaction zone E is captured, the color change image of the reaction zone is imported into image processing software, and the RGB values ​​of the reaction zone are extracted using a color picker to realize the digital analysis of the color signal. The RGB values ​​of the chip reaction zone were determined using standard solutions of As(III) at different concentrations, and a standard working curve of As(III) concentration versus R value was plotted. By comparing the R value of the sample to be tested with the standard curve, the As(III) content of the water sample can be obtained.

[0021] The detection results of this invention can be obtained by taking pictures of the reaction zone color with a regular smartphone, and quantitative interpretation can be achieved through RGB image analysis. No large analytical instruments are required, allowing for rapid on-site assessment of water quality. The same smartphone should be used for both sample testing and As(III) standard solution testing.

[0022] In a more specific technical solution, a method for detecting As(III) content in water based on a paper-based microfluidic chip includes: S1. A multi-channel converging fluid channel structure is prepared on filter paper material to facilitate the mixing and reaction of multiple reagents. Paraffin wax is filled around the fluid channel to form a hydrophobic barrier structure, ensuring that the liquid flows on the hydrophilic paper substrate; S2. The pre-prepared reagents are added dropwise to the first region A, the second region B, the third region C, and the fourth region D in sequence to provide a reaction environment, catalyst, and acidic conditions, so that the arsenic-containing sample undergoes a series of chemical reactions, ultimately causing Rhodamine B to decolorize in the pre-prepared chemical system. The reagent addition area is connected to the fluid channel. Driven by capillary force, the fluids flow downward along their respective hydrophilic branch channels. After merging step by step, they finally merge into a main channel that connects to the reaction zone E. S3. Capture the color development results of reaction zone E to obtain the color change image of the reaction zone. Import the image into the image processing software and use the color picker to extract the RGB values ​​of the reaction zone. Compare the obtained data with the standard working curve of As(III) concentration-R value to calculate the As(III) content of the water sample.

[0023] The present invention has the following advantages over the prior art: This invention utilizes a paper-based microfluidic chip for convenient detection of arsenic content in water. Using paper as the substrate, the required materials are simple and inexpensive, and the amount of reagents needed is also small, resulting in low overall cost. Color change images are captured using a smartphone and then converted into RGB numerical signals, establishing a correlation with arsenic concentration. The operation is simple and easy to perform, does not rely on large analytical instruments, and yields accurate results.

[0024] The detection range of this invention is 1-30 μg / L, and it can sensitively detect trace amounts of arsenic in water. The entire detection device is compact, portable, and easy to operate, making it suitable for on-site testing.

[0025] The detection results of this invention can be obtained by taking a picture of the reaction zone color with a regular smartphone and then performing quantitative analysis through RGB image analysis. No large analytical instruments are required, and water quality can be quickly assessed on-site.

[0026] This invention solves the technical problems of complex operation steps, long detection cycle, poor portability of arsenic content detection in water, and high detection cost in the prior art.

[0027] In the future, the method proposed in this invention is expected to be integrated into a single mobile terminal, developing a mobile application that integrates image acquisition, red channel signal analysis, concentration calculation, and output functions, providing an integrated solution for the rapid on-site detection of As(III) in water samples. Furthermore, this invention only detects As(III) in water bodies; it can reduce As(IV) to As(III) by adding ascorbic acid to the water sample, and then determine the total arsenic, As(III), and As(IV) in the water sample using the difference method. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the basic steps of a method for detecting As(III) content in water based on a paper-based microfluidic chip according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram illustrating the operation of a method for detecting As(III) content in water based on a paper-based microfluidic chip according to Embodiment 1 of the present invention. Figure 3 This is a schematic diagram of the structure of a device for detecting As(III) content in water based on a paper-based microfluidic chip according to Embodiment 1 of the present invention; Figure 4 These are colorimetric images of the Rhodamine B decolorization reaction in As(III) solutions of different concentrations in Example 1 of this invention. Figure 5 This is a schematic diagram of the color picker display interface of Embodiment 1 of the present invention; Figure 6 This is a standard curve graph showing the relationship between the R value and concentration of different concentrations of As(III) solutions and Rhodamine B on a paper chip in Example 1 of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1 like Figure 1 and Figure 2 As shown, a method for detecting As(III) content in water based on a paper-based microfluidic chip includes the following basic steps: S1. Prepare a multi-channel converging fluid channel on filter paper material, and fill the fluid channel with paraffin to form a hydrophobic barrier structure to ensure that the liquid flows on the hydrophilic paper substrate. This invention utilizes the principle that arsenite reacts with potassium iodate under acidic conditions to generate elemental iodine, which can then oxidize Rhodamine B in a sulfuric acid medium and under the catalysis of potassium bromide solution, causing Rhodamine B to decolorize. This is combined with a microfluidic paper-based chip, and a smartphone is used to capture the color development image of the solution after the reaction. The RGB values ​​are then extracted and analyzed using image processing software.

[0031] like Figure 3 As shown, in this embodiment, the paper-based chip uses microfabrication technology to fabricate fluid channels on filter paper material, and fills the periphery of the channels with paraffin to form a hydrophobic barrier structure. The chip has five functional regions: A, B, C, D, and E. Regions A, B, C, and D are reagent addition areas, and region E is the colorimetric reaction area. The reagent addition area is connected to the fluid channels. Driven by capillary forces, the fluid flows downwards along its respective hydrophilic branch channels, merging step by step before finally converging into a main channel connecting to reaction region E. See attached figure for dimensions. Figure 3 .

[0032] S2. The pre-prepared reagent is added dropwise to the first region A, the second region B, the third region C, and the fourth region D in sequence to provide a reaction environment, catalyst and acidic conditions, so that the arsenic-containing sample undergoes a series of chemical reactions, and finally the Rhodamine B undergoes a decolorization reaction in the pre-prepared chemical system. In this embodiment, the prepared reagents are precisely added to each functional area sequentially using a pipette. First, add 5 μL of a hydrochloric acid-potassium iodate mixed solution to zone A (adjust the pH to 1.5 by adding 0.4 mol / L hydrochloric acid solution dropwise to 10 g / L potassium iodate solution) to provide the reaction environment. Then, add 5 μL of As(III) standard solutions of different concentrations (1-30 μg / L) to zone B; weigh 0.132 g of As2O3 dried to constant weight in a sulfuric acid desiccator, warmly dissolve it in 1.2 mL of NaOH solution (100 g / L), transfer it to a 1000 mL volumetric flask, add deionized water to the mark to prepare a 0.1 g / L arsenic standard solution stock solution, and dilute the stock solution to 1-30 μg / L as needed. Next, add 5 μL of a mixed solution of sulfuric acid (0.06 mol / L) and potassium bromide (0.1 mol / L) dropwise to zone C, which are mixed in a 1:1 volume ratio to provide the catalyst and acidic conditions. In this embodiment, 5 μL of Rhodamine B solution (0.02 g / L) was added to region D. Rhodamine B can undergo a fading reaction in certain chemical systems, and the degree of fading is related to the As(III) concentration: the higher the As(III) concentration, the color changes from red to yellow to light yellow. After the above reagents were added, the solution flowed in the hydrophilic channels by means of the capillary action of the paper fibers. The paper-based microfluidic chip was allowed to stand at room temperature for about 1 min to ensure that the system reaction was complete. S3. Capture the color development results of reaction zone E, obtain the chip color change image, extract the RGB values ​​of the reaction zone, and calculate the As(III) content of the water sample by referring to the standard working curve of As(III) concentration-R value.

[0033] After the reaction was completed, the color development results of reaction region E were captured using the same smartphone camera to obtain an image of the color change in the reaction region, as shown in the attached image. Figure 4 and Figure 5 As shown. The image is then imported into image processing software, and the RGB values ​​of the reaction area are extracted using a color picker to achieve digital analysis of the color signal.

[0034] The RGB values ​​of the chip reaction region were determined using standard solutions of As(III) at different concentrations, and a standard working curve of As(III) concentration versus R value was plotted: y = -0.3219x + 212.37, as shown in the attached figure. Figure 6 As shown, a standard curve is obtained by combining the R values ​​of As(III) standard solutions of different concentrations with their concentrations. By correlating the R values ​​of the sample to be tested with the standard curve, the As(III) content in the water sample can be calculated.

[0035] This method, through strict volume control and standardized dropping procedures, not only ensures the accuracy of the results but also provides a reliable reference for the detection of actual samples.

[0036] Traditional methods for detecting arsenic pollution in water bodies still primarily rely on large-scale laboratory analytical instruments, such as atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma mass spectrometry (ICP-MS), and their combined techniques. While these methods offer high sensitivity and accuracy, their testing procedures are complex, susceptible to numerous interfering factors, have long testing cycles, and are costly per test. Furthermore, they depend on expensive, bulky analytical equipment that requires specialized personnel to operate, making them unsuitable for emergency on-site detection.

[0037] In comparison, the paper-based microfluidic chip As(III) detection method proposed in this invention has significant advantages. This method requires only a trace amount of water sample and low-cost reagents to complete the analysis, without the need for external power equipment. All liquids are automatically transported and react colorimetrically via capillary action. The cost of a single detection is less than 10 yuan, and the detection time can be shortened to approximately 5 minutes, thus meeting the needs of rapid on-site screening. The detection results can be quantitatively interpreted by taking a picture of the reaction area with a regular smartphone and analyzing the RGB image, without the need for any large analytical instruments, allowing for rapid on-site assessment of water quality. The detection range is 1-30 μg / L, covering the World Health Organization's concentration limit for arsenic ions (10 μg / L), and the detection is highly sensitive.

[0038] Compared with traditional technologies, this invention has significant advantages in terms of instrument dependence, cost, portability, ease of operation, sensitivity and applicable scenarios, and is more suitable for grassroots testing and rapid on-site emergency testing.

[0039] In summary, this invention utilizes a paper-based microfluidic chip for convenient detection of As(III) content in water. Using paper as the substrate simplifies the material requirements, reduces costs, and minimizes the need for reagents, resulting in low overall cost. The invention employs a smartphone to capture color change images, which are then converted into RGB numerical signals and correlated with arsenic concentration. The operation is simple and easy to perform, does not rely on large analytical instruments, and yields accurate results.

[0040] The detection range of this invention is 1-30 μg / L, and it can sensitively detect trace amounts of arsenic in water. The entire detection device is compact, portable, and easy to operate, making it suitable for on-site testing.

[0041] The detection results of this invention can be obtained by taking a picture of the reaction zone color with a regular smartphone and then performing quantitative analysis through RGB image analysis. No large analytical instruments are required, and water quality can be quickly assessed on-site.

[0042] This invention solves the technical problems of complex operation steps, long detection cycle, poor portability of arsenic content detection in water, and high detection cost in the prior art.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for detecting As(III) content in water based on a paper-based microfluidic chip, characterized in that, The chip includes: Fluid channels are prepared on filter paper material to form multi-channel converging fluid channels for mixing and reacting multiple reagents. Paraffin wax is filled around the fluid channels to form a hydrophobic barrier structure, allowing liquid to flow on a hydrophilic paper substrate. The reagent addition zone includes: a first zone A, a second zone B, a third zone C, and a fourth zone D. Pre-prepared reagents are sequentially added to the reagent addition zone to provide a reaction environment, catalyst, and acidic conditions, causing a series of chemical reactions in the arsenic-containing sample. Ultimately, Rhodamine B undergoes a decolorization reaction in the pre-prepared chemical system. The reagent addition zone is connected to a fluid channel. Driven by capillary forces, the fluids flow downwards along their respective hydrophilic branch channels, and after merging step by step, they finally merge into a main channel that connects to the reaction zone E. The color development results of reaction zone E were captured to obtain the chip color change image. The RGB values ​​of the reaction zone were extracted, and the As(III) content of the water sample was calculated by comparison with the standard working curve of As(III) concentration-R value.

2. The device for detecting As(III) content in water based on a paper-based microfluidic chip according to claim 1, characterized in that, A mixture of hydrochloric acid solution and potassium iodate solution is added to the first region A to provide the reaction environment.

3. The device for detecting As(III) content in water based on a paper-based microfluidic chip according to claim 2, characterized in that, Add 5 μL of 10 g / L potassium iodate solution to the first region A. The pH of this solution was adjusted to 1.5 beforehand by adding 0.4 mol / L hydrochloric acid solution dropwise.

4. The device for detecting As(III) content in water based on a paper-based microfluidic chip according to claim 1, characterized in that, Add 5 μL of arsenic standard solutions of different concentrations to region B in the second region.

5. The device for detecting As(III) content in water based on a paper-based microfluidic chip according to claim 3, characterized in that, Add 1-30 μg / L of the As(III) standard solution dropwise; weigh 0.132 g of As2O3 dried to constant weight in a sulfuric acid desiccator, dissolve it warmly in 1.2 mL of NaOH solution at 100 g / L, transfer it to a 1000 mL volumetric flask, add deionized water to the mark, and prepare a 0.1 g / L As(III) standard solution stock solution. Dilute the stock solution to 1-30 μg / L as needed.

6. The device for detecting As(III) content in water based on a paper-based microfluidic chip according to claim 1, characterized in that, Add 5 μL of a mixed solution of 0.06 mol / L sulfuric acid and 0.1 mol / L potassium bromide in a volume ratio of 1:1 to the third region C to provide the catalyst and acidic conditions.

7. The device for detecting As(III) content in water based on a paper-based microfluidic chip according to claim 1, characterized in that, Add 5 μL of Rhodamine B solution to the fourth region D; the degree of decolorization of Rhodamine B is related to the concentration of As(III); By utilizing the capillary action of paper fibers, the solution flows in the channel, and the paper-based microfluidic chip is allowed to react at room temperature for a preset time until the reaction is complete.

8. The device for detecting As(III) content in water based on a paper-based microfluidic chip according to claim 6, characterized in that, The concentration of the Rhodamine B solution is 0.02 g / L.

9. The device for detecting As(III) content in water based on a paper-based microfluidic chip according to claim 1, characterized in that, The color change image of the chip is imported into image processing software, and the RGB values ​​of the reaction area are extracted using a color picker in the color display area to realize digital analysis of the color signal. The RGB values ​​of the chip reaction zone were determined using standard solutions of As(III) at different concentrations, and a standard working curve of As(III) concentration versus R value was plotted. The R value of the sample to be tested was compared with the standard curve to determine the As(III) content of the water sample.

10. A method for detecting As(III) content in water based on a paper-based microfluidic chip, characterized in that, The method includes: S1. Prepare multi-channel converging fluid channels on filter paper material for mixing and reaction of multiple reagents. Fill the fluid channels with paraffin to form a hydrophobic barrier structure, so that the liquid flows on the hydrophilic paper substrate. S2. The pre-prepared reagent is sequentially added to the first region A, the second region B, the third region C, and the fourth region D to provide a reaction environment, catalyst, and acidic conditions, so that the arsenic-containing sample undergoes a series of chemical reactions, ultimately causing Rhodamine B to decolorize in the pre-prepared chemical system. The reagent addition area is connected to the fluid channel. Driven by capillary force, the fluid flows downward along its respective hydrophilic branch channels, and after merging step by step, it finally merges into a main channel connected to the reaction zone E. S3. Capture the color development results of reaction zone E to obtain the color change image of the reaction zone. Import the image into the image processing software and use the color picker to extract the RGB values ​​of the reaction zone. Compare the obtained data with the standard working curve of As(III) concentration-R value to calculate the As(III) content of the water sample.

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