Dual-mode paper-based analysis device integrating multiple paper materials and preparation method and application of dual-mode paper-based analysis device

Abstract

The invention discloses a dual-mode paper-based analysis device integrating multiple paper materials. The dual-mode paper-based analysis device is composed of a 3D paper chip and a three-electrode system, wherein the 3D paper chip comprises chromatographic paper (1), a double-sided adhesive tape (2) and glass fiber paper (3) which are sequentially fixed from bottom to top. The chromatographic paper (1) comprises a first detection part (101) and a second detection part (102), and the first detection part (101) is provided with a sample addition / electrochemical detection area (103); the double-faced adhesive tape (2) and the glass fiber paper (3) are fixed on the second detection part (102), and a third Y-shaped channel (301) and two third colorimetric detection areas (302) are arranged on the glass fiber paper (3). According to the device, synchronous detection of multiple targets is realized, electrochemical detection of Pb (II), Cu (II) and Hg (II) and colorimetric detection of Cr (VI) can be realized at the same time through one-time sample adding, and the detection efficiency is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inspection detection, in particular to a double-mode paper-based analysis device integrated with multiple paper materials and a preparation method and application thereof. BACKGROUND

[0002] Pb(II), Cu(II), Hg(II) and Cr(Ⅵ) are of great concern due to their irreversible toxic effects on human health, and it is of great importance to detect the content of these heavy metals in consumer products quickly and accurately. Therefore, it is of great significance to establish a portable device that can realize rapid and sensitive detection of Pb(II), Cu(II), Hg(II) and Cr(Ⅵ) in a single sample.

[0003] Currently, the preparation process of the electrochemical / colorimetric dual-mode paper-based microfluidic analysis device is complex, often requiring special equipment such as a wax printing machine (which has been discontinued), a silk screen printing device, etc., and complex modification of the electrode is required to achieve high sensitivity, which hinders the popularization and application of the paper-based microfluidic analysis device.

[0004] The existing electrochemical / colorimetric dual-mode paper-based microfluidic analysis device is mostly constructed from a single paper material, which cannot simultaneously achieve the best detection performance of electrochemistry / colorimetry, resulting in low detection sensitivity of certain targets or large differences in detection performance between different targets when multiple targets are detected simultaneously, thereby being not conducive to practical application. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a double-mode paper-based analysis device integrated with multiple paper materials, which has a simple structure, low cost and simple operation, a preparation method and application thereof.

[0006] The double-mode paper-based analysis device integrated with multiple paper materials according to the present application is composed of a 3D paper chip and a three-electrode system, the 3D paper chip includes chromatographic paper, double-sided tape and glass fiber paper fixed in order from bottom to top, the chromatographic paper includes a first detection part and a second detection part, the first detection part is provided with a sample addition / electrochemical detection zone, the double-sided tape and the glass fiber paper are fixed on the second detection part, a first Y-shaped channel and two first colorimetric detection zones are arranged on the second detection part, a second Y-shaped channel and two second colorimetric detection zones are arranged on the double-sided tape, and a third Y-shaped channel and two third colorimetric detection zones are arranged on the glass fiber paper.

[0007] The double-mode paper-based analysis device integrated with multiple paper materials according to the present application, wherein the first Y-shaped channel includes one main channel in the lower part and two branch channels in the upper part connected with the main channel, the lower part of the main channel is connected with the sample addition / electrochemical detection zone, and the upper ends of the branch channels are connected with one of the first colorimetric detection zones.

[0008] The sample adding / electrochemical detection area, the upper part of the branch channel and the first colorimetric detection area are hydrophilic regions, and other regions of the chromatographic paper are hydrophobic regions.

[0009] The double-mode paper-based analysis device integrating multiple paper materials, wherein the second Y-shaped channel on the double-sided tape is a Y-shaped through hole consistent with the size and position of the first Y-shaped channel, and the second colorimetric detection area is a through hole consistent with the size and position of the first colorimetric detection area.

[0010] The double-mode paper-based analysis device integrating multiple paper materials, wherein the third Y-shaped channel on the glass fiber paper is consistent with the size and position of the first Y-shaped channel, and the third colorimetric detection area is consistent with the size and position of the first colorimetric detection area; the third Y-shaped channel includes a main channel in the lower part and two branch channels in the upper part connected thereto, the upper part of the branch channel is a hydrophilic region, and the hydrophobic region of the third Y-shaped channel is smaller than the hydrophilic region of the first Y-shaped channel.

[0011] Except for the upper part of the branch channel, the other parts of the third Y-shaped channel and the third colorimetric detection area are hydrophilic regions; except for the above hydrophilic regions, other regions of the glass fiber paper are hydrophobic regions.

[0012] The double-mode paper-based analysis device integrating multiple paper materials, wherein the sample adding / electrochemical detection area is a circle with a diameter of 10 mm, the first colorimetric detection area, the second colorimetric detection area and the third colorimetric detection area are circles with a diameter of 6 mm; the width of the main channel of the first Y-shaped channel, the second Y-shaped channel and the third Y-shaped channel is 4 mm, the length is 4.5 mm, the width of the branch channel is 3 mm, and the length is 7 mm.

[0013] The size of the hydrophilic region of the upper part of the first Y-shaped channel is 3 mm*3 mm, and the size of the hydrophobic region of the upper part of the third Y-shaped channel is 3 mm*1 mm, that is, the distance between the top end of the hydrophilic region of the branch channel of the third Y-shaped channel and the third colorimetric detection area is 1 mm.

[0014] The size of the chromatographic paper is 3 cm*3 cm, the size of the first detection part is 3 cm*1.15 cm, and the size of the second detection part, the double-sided tape and the glass fiber paper is 3 cm*1.85 cm.

[0015] The three-electrode system includes a three-electrode support and a gold-plated plastic working electrode, the three-electrode support includes a platinum wire counter electrode, an Ag / AgCl wire reference electrode and a working electrode connector, and the whole support is fixed by screws and springs.

[0016] The sample adding / electrochemical detection area of the 3D paper chip is added on the circular reaction area of the gold-plated plastic working electrode, and is fixed by using the three-electrode support, the platinum wire counter electrode and the Ag / AgCl wire reference electrode contact the sample adding / electrochemical detection area of the 3D paper chip, the working electrode connector contacts the conductive area of the gold-plated plastic working electrode, the three-electrode system is connected with the electrochemical workstation through a data line, and a complete three-electrode detection system is formed.

[0017] The preparation method of the double-mode paper-based analysis device integrating multiple paper materials provided by the application comprises the following steps:

[0018] (A) Pattern design and preparation: device patterns are designed by using software, and are printed on chromatographic paper and glass fiber paper by using a laser printer, and the printed paper chips are heated in an oven;

[0019] (B) 3D paper chip assembly and modification: the first Y-shaped channel, the second Y-shaped channel and the third Y-shaped channel in the paper chip are aligned, the first colorimetric detection area, the second colorimetric detection area and the third colorimetric detection area are aligned, the three-layer structure is stacked and fixed, and a 3D microfluidic channel is established; after the assembly of the 3D paper chip is completed, the third colorimetric detection area is modified.

[0020] In the heating treatment in the oven, the glass fiber paper is heated for 30 minutes, and the chromatographic paper is heated for 3 hours; the method for modifying the third colorimetric detection area comprises the following steps: first, 10 muL of 0.1mol / L H3PO4 solution is added to the right third colorimetric detection area, and after drying, 10 muL of a mixed solution of 25mg / mL 1,5-diphenylcarbazide and 40mg / mL phthalic anhydride is added, and the addition is divided into 5 times, 2 muL each time; the left third colorimetric detection area is used as a control area, and only 10 muL of 0.1mol / L H3PO4 solution is added;

[0021] The sample solution is a standard solution or an actual sample solution, wherein:

[0022] The preparation method of the standard solution comprises the following steps: using 0.01 mol / L hydrochloric acid solution as a solvent to prepare heavy metal mixed standard solutions with different concentrations, i.e., 0.01 mg / L Pb(II), Cu(II), Hg(II) and 0.1 mg / L Cr(VI) mixed solution, 0.025 mg / L Pb(II), Cu(II), Hg(II) and 0.3 mg / L Cr(VI) mixed solution, 0.05 mg / L Pb(II), Cu(II), Hg(II) and 0.5 mg / L Cr(VI) mixed solution, 0.1 mg / L Pb(II), Cu(II), Hg(II) and 0.7 mg / L Cr(VI) mixed solution, 0.3 mg / L Pb(II), Cu(II), Hg(II) and 1.0 mg / L Cr(VI) mixed solution, 0.5 mg / L Pb(II), Cu(II), Hg(II) and 2.0 mg / L Cr(VI) mixed solution, and 0.5 mg / L Pb(II), Cu(II), Hg(II) and 3.0 mg / L Cr(VI) mixed solution.

[0023] The preparation method of the actual sample solution comprises the following steps: the leather toy and the plastic toy are respectively cut into test samples with a size less than 6 mm, then 1 g of each test sample is transferred into a 250 mL sealed light-proof container, 50 mL of 37 DEG C 0.07 mol / L hydrochloric acid is added, and the mixture is shaken for 1 minute; the acidity of the mixed solution is checked, if the pH value is greater than 1.5, 2 mol / L hydrochloric acid solution is added dropwise while shaking the mixture until the pH value reaches 1.0-1.5; then the mixture is continuously shaken at 37 DEG C for 1 hour, and then is statically placed at 37 DEG C for 1 hour; finally, the mixed solution is filtered by using a 0.45 mu m membrane, and the obtained filtrate is used for subsequent detection; before detection, the pH value of the filtrate is adjusted to 2.0 by using 2 mol / L sodium hydroxide, and all the samples must be analyzed within 24 hours after preparation.

[0024] The application of the double-mode paper-based analysis device integrating multiple paper materials to simultaneously realize electrochemical detection of Pb(II), Cu(II) and Hg(II) and colorimetric detection of Cr(VI) in a single sample.

[0025] The application, wherein the application detection method specifically comprises the following steps:

[0026] The sample adding / electrochemical detection area of the 3D paper chip is added on the circular reaction area of the gold-plated plastic working electrode, and then the two are fixed by using a three-electrode support; the three-electrode system is connected to an electrochemical workstation through a data line to form a complete three-electrode detection system. 100 muL of sample solution is added to the sample adding / electrochemical detection area, and under the capillary action, the liquid rapidly penetrates the paper and diffuses to the electrode surface and the colorimetric detection area; differential pulse anodic stripping voltammetry is used to electrochemically measure Pb(II), Cu(II) and Hg(II);

[0027] After the electrochemical detection is completed, the image of the colorimetric detection area is taken by using a smart phone, in order to ensure that the light conditions are consistent, the chip is placed in a black box equipped with an LED light belt for shooting; the obtained image is analyzed in an inverted mode in ImageJ software, and the average color intensity of the green channel in the detection area is extracted to perform colorimetric quantitative analysis on Cr(Ⅵ).

[0028] The application of the application has the following related parameters of the differential pulse anodic stripping voltammetry experiment: the scanning potential range is-400 to 600 mV, the deposition potential is-500 mV, the duration is 360 seconds, the pulse height is 50 mV, the pulse width is 0.01 second, the pulse period is 0.1 second, and the potential increment is 10 mV.

[0029] The integrated multi-paper material dual-mode paper-based analysis device of the application is different from the prior art in that:

[0030] 1) The application first designs and prepares a novel electrochemical / colorimetric dual-mode paper-based microfluidic analysis device, integrates two different types of paper materials (chromatographic paper and glass fiber paper) in the same three-dimensional (3D) paper chip, and can simultaneously realize the optimal detection performance of electrochemical and colorimetric detection.

[0031] 2) Through the matching optimization of paper types and detection modes, the electrochemical detection of Pb(II), Cu(II) and Hg(II) and the colorimetric detection of Cr(Ⅵ) in a single sample are simultaneously realized. Compared with other dual-mode paper-based devices, the device of the application not only has high sensitivity, but also can control the detection limit difference between target analytes in a relatively narrow range, thereby improving the convenience in practical application.

[0032] 3) The preparation process of the device of the application is simple, and the required materials are easy to obtain. A disposable, low-cost, and complex equipment-free multi-element heavy metal synchronous detection platform is constructed, which is suitable for on-site rapid screening.

[0033] The integrated multi-paper material dual-mode paper-based analysis device, method and application of the application will be further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The schematic diagram of the layer structure of the 3D paper chip in the double-mode paper-based analysis device integrated with multiple paper materials of the application; wherein, from left to right, the chromatographic paper, double-sided tape and glass fiber paper are arranged in sequence;

[0035] Figure 2 The schematic diagram of the assembly and modification of the 3D paper chip in the double-mode paper-based analysis device integrated with multiple paper materials of the application;

[0036] Figure 3 The design principle diagram of the double-mode paper-based analysis device integrated with multiple paper materials of the application;

[0037] Figure 4 The structural schematic diagram of the three-electrode system in the application;

[0038] Figure 5 The schematic diagram of the electrochemical colorimetric simultaneous detection in the application;

[0039] Figure 6 The electrochemical detection result diagram in the application; wherein: (A) differential pulse stripping voltammogram curves of Pb(II), Cu(II) and Hg(II) with different concentrations; (B) Pb(II) standard curve; (C) Cu(II) standard curve; (D) Hg(II) standard curve;

[0040] Figure 7 The colorimetric detection result diagram in the application; wherein: (A) colorimetric detection of Cr(Ⅵ) photo; (B) Cr(Ⅵ) standard curve;

[0041] Figure 8 The reproducibility result diagram of the electrochemical detection of Pb(II), Cu(II) and Hg(II) in the application;

[0042] Figure 9 The paper chip comparison experiment result diagram in the application; wherein: (A) one-dimensional paper chip colorimetric detection of Cr(Ⅵ); (B) three-dimensional paper chip colorimetric detection of Cr(Ⅵ). DETAILED DESCRIPTION

[0043] The application designs and prepares an electrochemical / colorimetric double-mode paper-based microfluidic analysis device based on different paper materials, which realizes the electrochemical detection of Pb(II), Cu(II) and Hg(II) and the colorimetric detection of Cr(Ⅵ) in a single sample.

[0044] I. Device part

[0045] As shown in Figure 5 , a double-mode paper-based analysis device integrated with multiple paper materials is composed of a 3D paper chip and a three-electrode system:

[0046] 1. 3D paper chip

[0047] As Figure 1 and Figure 2 shown, the 3D paper chip includes chromatography paper 1, double-sided tape 2 and glass fiber paper 3 fixed in turn from bottom to top, the chromatography paper 1 includes a first detection part 101 and a second detection part 102, the first detection part 101 is provided with a sample adding / electrochemical detection area 103, the double-sided tape 2 and the glass fiber paper 3 are fixed on the second detection part 102, a first Y-shaped channel 104 and two first colorimetric detection areas 105 are arranged on the second detection part 102, a second Y-shaped channel 201 and two second colorimetric detection areas 202 are arranged on the double-sided tape 2, and a third Y-shaped channel 301 and two third colorimetric detection areas 302 are arranged on the glass fiber paper 3.

[0048] The first Y-shaped channel 104 includes a main channel in the lower part and two branch channels in the upper part connected with the main channel, the lower part of the main channel is connected with the sample adding / electrochemical detection area 103, and the upper ends of the branch channels are connected with a first colorimetric detection area 105.

[0049] The sample adding / electrochemical detection area 103, the upper part of the branch channel and the first colorimetric detection area 105 are all hydrophilic regions, and other regions of the chromatography paper 1 are all hydrophobic regions.

[0050] The second Y-shaped channel 201 on the double-sided tape 2 is a Y-shaped through hole consistent in size and position with the first Y-shaped channel 104, and the second colorimetric detection area 202 is a through hole consistent in size and position with the first colorimetric detection area 105.

[0051] The third Y-shaped channel 301 on the glass fiber paper 3 is consistent in size and position with the first Y-shaped channel 104, and the third colorimetric detection area 302 is consistent in size and position with the first colorimetric detection area 105; the third Y-shaped channel 301 includes a main channel in the lower part and two branch channels in the upper part connected with the main channel, the upper part of the branch channel is a hydrophobic region, and the hydrophobic region of the third Y-shaped channel 301 is smaller than the hydrophilic region of the first Y-shaped channel 104.

[0052] Except for the upper part of the branch channel, the other parts of the third Y-shaped channel 301 and the third colorimetric detection area 302 are hydrophilic regions; except for the above-mentioned hydrophilic regions, other regions of the glass fiber paper 3 are hydrophobic regions.

[0053] The sample adding / electrochemical detection area 103 is a circle with a diameter of 10 mm, the first colorimetric detection area 105, the second colorimetric detection area 202 and the third colorimetric detection area 302 are circles with a diameter of 6 mm; the main channel of the first Y-shaped channel 104, the second Y-shaped channel 201 and the third Y-shaped channel 301 has a width of 4 mm and a length of 4.5 mm, and the branch channel has a width of 3 mm and a length of 7 mm.

[0054] The size of the hydrophilic region of the upper part of the first Y-shaped channel 104 is 3mm x 3mm, and the size of the hydrophobic region of the upper part of the third Y-shaped channel 301 is 3mm x 1mm, that is, the distance between the top end of the hydrophilic region of the branch channel of the third Y-shaped channel 301 and the third colorimetric detection area 302 is 1mm;

[0055] The size of the chromatographic paper 1 is 3cm x 3cm, the size of the first detection part 101 is 3cm x 1.15cm, and the size of the second detection part 102, the double-sided adhesive tape 2 and the glass fiber paper 3 is 3cm x 1.85cm.

[0056] Figure 3 It is the design principle diagram of the device of the application, which is described as follows: the existing electrochemical / colorimetric dual-mode paper-based microfluidic analysis device is mostly constructed by a single paper material, which cannot simultaneously consider the best electrochemical / colorimetric detection performance. As shown in Figure 3 When the glass fiber paper is used to construct the electrochemical / colorimetric dual-mode paper-based microfluidic analysis device, better colorimetric detection effect can be obtained, but the electrochemical detection performance is poor; on the contrary, when the chromatographic paper is used to construct the electrochemical / colorimetric dual-mode paper-based microfluidic analysis device, better electrochemical detection effect can be obtained, but the colorimetric detection performance is poor. Therefore, in the present application, two kinds of paper materials are innovatively integrated in one paper-based device, and the best electrochemical and colorimetric detection performance can be simultaneously realized by one sample injection. In addition, the hydrophobic spacing between the third Y-shaped channel 301 and the third colorimetric detection area 302 can effectively avoid the diffusion of the color developing reagent, so that the colorimetric detection result is more accurate.

[0057] II. Preparation method of the device

[0058] A preparation method of a dual-mode paper-based analysis device integrating multiple paper materials, comprising the following steps:

[0059] (A) Pattern design and preparation: using AutoCAD software to design the pattern, using a common office equipment laser printer to print it on the chromatographic paper 1 and the glass fiber paper 3 respectively, and heating the printed paper chip in an oven; the printed paper chip is heated in an oven at 170℃: the glass fiber paper is heated for 30 minutes, and the chromatographic paper is heated for 3 hours. The heating process enables the toner to penetrate the paper material, thereby forming a hydrophobic barrier.

[0060] (B) 3D paper chip assembly and modification:

[0061] 3D paper chip (3 cm x 3 cm) is composed of three layers. The bottom layer is made of chromatography paper 1 for electrochemical detection of Pb(II), Cu(II), Hg(II); the middle layer is made of double-sided tape 2 with customized structure for connecting the top layer and the bottom layer and forming a closed channel; the top layer is made of glass fiber paper 3 for colorimetric detection of Cr(VI). Align the first Y-shaped channel 104, the second Y-shaped channel 201 and the third Y-shaped channel 301 in the paper chip, align the first colorimetric detection area 105, the second colorimetric detection area 202 and the third colorimetric detection area 302, and stack and fix the three-layer structure to obtain a 3D microfluidic channel Figure 2 );After the assembly of the 3D paper chip, the third colorimetric detection area 302 is modified. First, add 10 μL of 0.1 mol / L H3PO4 solution to the right third colorimetric detection area 302, and after drying, add 10 μL of 25 mg / mL 1,5-diphenylcarbazide and 40 mg / mL phthalic anhydride mixed solution, add 2 μL at a time for 5 times; The left third colorimetric detection area 302 is used as a control area and only 10 μL of 0.1 mol / L H3PO4 solution is added. The control area is used as a reference to correct the color change.

[0062] 2, Three-electrode system

[0063] As shown in Figure 4 , the three-electrode system is composed of two parts: a reusable three-electrode holder 4 and a disposable gold-plated plastic working electrode 5 (Au / PET electrode). The preparation steps of the three-electrode system refer to the "electrical signal acquisition and transmission device for flat plate working electrode" (invention patent, patent number: ZL201610479208.5). The three-electrode holder 4 is composed of a 3D printed polylactic acid plastic base layer, a conductive connection layer composed of a printed circuit board, and a platinum wire counter electrode 401, an Ag / AgCl wire reference electrode 402 and a working electrode connector 403. The entire holder is fixed by screws and springs. The gold-plated plastic working electrode 5 is prepared by ion sputtering process: first, put the plastic sheet (60 x 40 mm) of appropriate size into the sputtering instrument for gold plating layer treatment, the sputtering current is 30 mA, and the sputtering time is 80 s. Subsequently, the electrode is trimmed to the appropriate size (10 x 20 mm) to match the three-electrode system. Finally, a piece of transparent tape with a diameter of 8 mm is pasted on the electrode to define the working area of the electrode. Connect the three-electrode system to the electrochemical workstation through the data line to collect electrochemical data.

[0064] The fixing mode of the 3D paper chip is as follows: the sample adding / electrochemical detection area 103 of the 3D paper chip is added on the circular reaction area of the gold-plated plastic working electrode 5, and is fixed by using a three-electrode support 4, the platinum wire counter electrode 401 and the Ag / AgCl wire reference electrode 402 contact the sample adding / electrochemical detection area 103 of the 3D paper chip, the working electrode connector 403 contacts the conductive area of the gold-plated plastic working electrode 5, the three-electrode system is connected with an electrochemical workstation through a data line, and a complete three-electrode detection system is formed.

[0065] III. Detection method

[0066] 1. Application of the double-mode paper-based analysis device integrating multiple paper materials in simultaneously realizing electrochemical detection of Pb(II), Cu(II) and Hg(II) and colorimetric detection of Cr(Ⅵ) in a single sample.

[0067] The application detection method specifically includes the following steps:

[0068] The preparation method of the sample solution (herein, a standard solution) is as follows: 0.01mol / L hydrochloric acid solution is used as a solvent to prepare heavy metal mixed standard solutions with different concentrations, and the concentrations are respectively 0.01mg / L Pb(II), Cu(II), Hg(II) and 0.1mg / L Cr(Ⅵ) mixed solution, 0.025mg / L Pb(II), Cu(II), Hg(II) and 0.3mg / L Cr(Ⅵ) mixed solution, 0.05mg / L Pb(II), Cu(II), Hg(II) and 0.5mg / L Cr(Ⅵ) mixed solution, 0.1mg / L Pb(II), Cu(II), Hg(II) and 0.7mg / L Cr(Ⅵ) mixed solution, 0.3mg / L Pb(II), Cu(II), Hg(II) and 1.0mg / L Cr(Ⅵ) mixed solution, 0.5mg / L Pb(II), Cu(II), Hg(II) and 2.0mg / L Cr(Ⅵ) mixed solution, and 0.5mg / L Pb(II), Cu(II), Hg(II) and 3.0mg / L Cr(Ⅵ) mixed solution.

[0069] The sample adding / electrochemical detection area 103 of the 3D paper chip is added on the circular reaction area of the gold-plated plastic working electrode 5, and then the two are fixed by using the three-electrode holder 4; the three-electrode system is connected to the electrochemical workstation through a data line to form a complete three-electrode detection system. 100 μL of sample solution is added to the sample adding / electrochemical detection area 103, and under the capillary action, the liquid rapidly penetrates the paper and diffuses to the electrode surface and the colorimetric detection area; differential pulse anodic stripping voltammetry (DPSV) is used for electrochemical measurement of Pb(II), Cu(II) and Hg(II). The related parameters of the DPSV experiment are as follows: the scanning potential range is -400 to 600 mV, the deposition potential is -500 mV, the duration is 360 seconds, the pulse height is 50 mV, the pulse width is 0.01 second, the pulse period is 0.1 second, and the potential increment is 10 mV. Unless otherwise specified, all electrochemical detections of the present application use this parameter.

[0070] After the electrochemical detection is completed, the image of the colorimetric detection area is taken by using a smart phone. In order to ensure the consistency of the light conditions, the chip is placed in a black box equipped with an LED light belt for shooting; the obtained image is analyzed in the ImageJ software in the inverted mode to extract the average color intensity of the green channel in the detection area for colorimetric quantitative analysis of Cr(Ⅵ).

[0071] The schematic diagram of the electrochemical colorimetric simultaneous detection device is shown in Figure 5 The electrochemical detection results are shown in Figure 6 Figure 6 A is the differential pulse stripping voltammogram of Pb(II), Cu(II) and Hg(II) with different concentrations, and the peak current gradually increases with the increase of the concentration of Pb(II), Cu(II) and Hg(II) solution. After linear fitting, it is found that the concentration of 0.01-0.5 mg / L Pb(II), Cu(II) and Hg(II) is linearly related to the peak current. The standard curves of Pb(II), Cu(II) and Hg(II) are shown in Figure 6 B-6D, and according to the linear relationship equation, the detection limit of Pb(II), Cu(II) and Hg(II) can be calculated as 0.005, 0.002 and 0.002 mg / L, respectively. The colorimetric detection results of Cr(Ⅵ) are shown in Figure 7 With the gradual increase of the concentration of Cr(Ⅵ), the color intensity also gradually deepens Figure 7 A). The standard curve is shown in Figure 7 B, and the linear equation is Y=27.485X(mg / L)+0.893 when the concentration of Cr(Ⅵ) is in the range of 0.1-3 mg / L, and the correlation coefficient is 0.999. According to the linear relationship equation, the detection limit of Cr(Ⅵ) can be calculated as 0.029 mg / L.

[0072] ​2. Reproducibility of electrochemical detection of Pb(II), Cu(II), and Hg(II)

[0073] The reproducibility of the method of the present invention was studied using 0.1 mg / L Pb(II), Cu(II), and Hg(II) standard solutions. A new working electrode and 3D paper chip were used for each detection. The results of six electrochemical detections are as follows: Figure 8 As shown, the relative standard deviations of 0.1 mg / L Pb(II), Cu(II), and Hg(II) were 2.34%, 1.88%, and 2.43%, respectively, which proves that the method of the present invention has good reproducibility.

[0074] 3. Paper chip comparison experiment

[0075] A 1 mm hydrophobic gap was intentionally placed between the third Y-type channel 301 and the third colorimetric detection area 302. This gap prevents the diffusion of the chromogenic reagent, thereby improving the accuracy of the detection. To demonstrate its effectiveness, a comparative experiment was conducted, performing colorimetric detection of a 2 mg / L Cr(VI) standard solution on both a single-layer paper-based chip and the 3D paper chip of this invention. Except for replacing the 3D paper chip with a single-layer paper chip, all other samples and methods were identical. The experimental results are as follows: Figure 9 As shown, when using a single-layer paper chip for colorimetric detection, the colorimetric reagent diffuses into the channel during the detection process because the colorimetric detection area is directly connected to the channel, introducing systematic errors into the quantitative analysis. The 3D paper chip of this invention effectively solves this problem by introducing a gap between the colorimetric detection area and the channel. This design allows the colorimetric reagent to be precisely preloaded in the colorimetric detection area, effectively controlling its diffusion and thus improving the accuracy of colorimetric detection. The relative standard deviation of Cr(VI) in six colorimetric detections was 1.79%, demonstrating that the detection effect of the 3D paper chip of this invention is significantly better than that of the one-dimensional paper chip.

[0076] 4. Actual sample testing

[0077] The preparation method of the actual sample solution is as follows: cut the leather toy and the plastic toy into test samples with a size of less than 6 mm respectively, then transfer 1 test sample of each into a 250 mL sealed light-proof container. Add 50 mL of 0.07 mol / L hydrochloric acid at 37°C, shake for 1 minute, and check the acidity of the mixture. If the pH value is greater than 1.5, add about 2 mol / L hydrochloric acid solution drop by drop while shaking the mixture until the pH value reaches 1.0-1.5. Then continuously oscillate at 37°C for 1 hour, and then stand at 37°C for 1 hour. Finally, filter the mixed solution using a 0.45 μm membrane, and the obtained filtrate is used for subsequent detection. Before detection, adjust the pH value of the filtrate to 2.0 with 2 mol / L sodium hydroxide. All samples must be analyzed within 24 hours after preparation. Except for the sample solution, the other method steps are consistent with the method of the standard solution.

[0078] Table 1 Determination results of Pb(II), Cu(II), Hg(II), Cr(VI) contents in actual samples (n = 3)

[0079]

[0080] The Pb(II), Cu(II), Hg(II), Cr(VI) in plastic and leather toy samples were actually verified using the device and method of the present application. At the same time, inductively coupled plasma optical emission spectrometry (ICP-OES) was used as a reference technology to compare the results. The detection results are shown in Table 1. Statistical comparison by independent sample two-tailed t-test gives a p value of 0.968, which exceeds the significance level of 0.05, indicating that there is no significant difference between the two groups of data in statistics. In order to further evaluate the accuracy, 0.05 mg / L Pb(II), Cu(II), Hg(II) and 0.5 mg / L Cr(VI) were added to the sample solution for standard addition recovery experiment, and the recovery rate was between 93% and 110%. These results confirm the reliable performance of the proposed device and method, and prove its practical application value in heavy metal screening in consumer products.

[0081] Technical effects achieved by the present application:

[0082] 1) The device of the present application realizes simultaneous detection of multiple targets: Pb(II), Cu(II), Hg(II) are simultaneously detected by electrochemical detection and Cr(VI) is detected by colorimetric detection, which significantly improves the detection efficiency.

[0083] 2) The device optimizes the matching of paper types and detection modes, which significantly improves the sensitivity of sample detection. The detection limits of Pb(II), Cu(II), Hg(II) can reach 0.005, 0.002, 0.002 mg / L respectively; Figure 6 ) and the detection limit of Cr(VI) is 0.029 mg / L.Figure 7 ). Moreover, the device makes the detection limit difference between different analytes within one order of magnitude, which helps to improve the convenience in practical applications.

[0084] 3) The device has good reproducibility for different target detection, the relative standard deviations of 0.1 mg / L Pb(II), Cu(II), and Hg(II) are 2.34%, 1.88%, 2.43% respectively Figure 8 ). The gap between the top colorimetric detection detection area and the channel effectively prevents the diffusion of the color developing reagent, which helps to improve the accuracy of colorimetric detection, and the relative standard deviation of 2 mg / L Cr(Ⅵ) is 1.79% Figure 9 ).

[0085] 4) The verification results are reliable, the detection results of Pb(II), Cu(II), Hg(II), and Cr(Ⅵ) in leather toys and plastic toys are consistent with the ICP-OES standard method, and in the standard addition experiment, the sample recovery rate is 93-110%.

[0086] 5) The device preparation process is simple, low cost, and does not require special equipment, and can realize batch preparation. It can provide a new idea for the preparation of other dual-mode paper-based analysis systems.

[0087] 6) The device has strong universality and can be extended to detect other analytes other than heavy metals; it also provides a promising tool for dual-mode detection, and the experimental operation is simple and does not require large instruments, which is suitable for on-site rapid screening.

[0088] The above-described embodiments are merely preferred embodiments of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope of the present application as defined by the claims.

Claims

1. A dual-mode paper-based analysis device integrating multiple paper materials, characterized in that: The device consists of two parts: a 3D paper chip and a three-electrode system. The 3D paper chip includes a chromatography paper (1), a double-sided adhesive (2), and a glass fiber paper (3) fixed from bottom to top. The chromatography paper (1) includes a first detection section (101) and a second detection section (102). The first detection section (101) is provided with a sample addition / electrochemical detection area (103). The double-sided adhesive (2) and the glass fiber paper (3) are fixed on the second detection section (102). The second detection section (102) is provided with a first Y-shaped channel (104) and two first colorimetric detection areas (105). The double-sided adhesive (2) is provided with a second Y-shaped channel (201) and two second colorimetric detection areas (202). The glass fiber paper (3) is provided with a third Y-shaped channel (301) and two third colorimetric detection areas (302).

2. The dual-mode paper-based analysis device integrating multiple paper materials according to claim 1, characterized in that: The first Y-shaped channel (104) includes a main channel at the bottom and two branch channels at the top connected thereto. The lower part of the main channel is connected to the sample addition / electrochemical detection area (103), and the upper end of the branch channels is connected to a first colorimetric detection area (105). The sample addition / electrochemical detection area (103), the upper part of the branch channel and the first colorimetric detection area (105) are all hydrophilic areas, while the other areas of the chromatographic paper (1) are all hydrophobic areas.

3. The dual-mode paper-based analysis device integrating multiple paper materials according to claim 2, characterized in that: The second Y-shaped channel (201) on the double-sided tape (2) is a Y-shaped through hole with the same size and position as the first Y-shaped channel (104), and the second colorimetric detection area (202) is a through hole with the same size and position as the first colorimetric detection area (105).

4. The dual-mode paper-based analysis device integrating multiple paper materials according to claim 3, characterized in that: The third Y-shaped channel (301) on the glass fiber paper (3) has the same size and position as the first Y-shaped channel (104), and the third colorimetric detection area (302) has the same size and position as the first colorimetric detection area (105). The third Y-shaped channel (301) includes a lower main channel and two upper branch channels connected to it. The upper part of the branch channels is a hydrophobic area, and the hydrophobic area of ​​the third Y-shaped channel (301) is smaller than the hydrophilic area of ​​the first Y-shaped channel (104). Except for the upper part of the branch channel, the other parts of the third Y-shaped channel (301) and the third colorimetric detection area (302) are hydrophilic areas; except for the above hydrophilic areas, the other areas of the glass fiber paper (3) are hydrophobic areas.

5. The dual-mode paper-based analysis device integrating multiple paper materials according to claim 4, characterized in that: The sample addition / electrochemical detection area (103) is a circle with a diameter of 10 mm, and the first colorimetric detection area (105), the second colorimetric detection area (202) and the third colorimetric detection area (302) are circles with a diameter of 6 mm; the main channel of the first Y-type channel (104), the second Y-type channel (201) and the third Y-type channel (301) has a width of 4 mm and a length of 4.5 mm, and the branch channel has a width of 3 mm and a length of 7 mm; The size of the hydrophilic region at the top of the first Y-shaped channel (104) is 3mm×3mm, and the size of the hydrophobic region at the top of the third Y-shaped channel (301) is 3mm×1mm. That is, the distance between the top of the hydrophilic region of the branch channel of the third Y-shaped channel (301) and the third colorimetric detection area (302) is 1mm. The size of the chromatographic paper (1) is 3cm×3cm, the size of the first detection part (101) is 3cm×1.15cm, and the size of the second detection part (102), the double-sided adhesive (2) and the glass fiber paper (3) is 3cm×1.85cm. The three-electrode system includes a three-electrode support (4) and a gold-plated plastic working electrode (5). The three-electrode support (4) includes a platinum wire counter electrode (401), an Ag / AgCl wire reference electrode (402), and a working electrode connector (403). The entire support is fixed by screws and springs. The sample addition / electrochemical detection area (103) of the 3D paper chip is placed on the circular reaction area of ​​the gold-plated plastic working electrode (5) and fixed by the three-electrode support (4). The platinum wire counter electrode (401) and the Ag / AgCl wire reference electrode (402) are in contact with the sample addition / electrochemical detection area (103) of the 3D paper chip, and the working electrode connector (403) is in contact with the conduction area of ​​the gold-plated plastic working electrode (5). The three-electrode system is connected to the electrochemical workstation through a data cable to form a complete three-electrode detection system.

6. A method for preparing the dual-mode paper-based analytical device integrating multiple paper materials as described in any one of claims 1 to 5, characterized in that: Includes the following steps: (A) Pattern design and preparation: The device pattern is designed using software and printed on chromatographic paper (1) and glass fiber paper (3) respectively using a laser printer. The printed paper chips are then heated in an oven. (B) 3D paper chip assembly and modification: Align the first Y-type channel (104), the second Y-type channel (201) and the third Y-type channel (301) in the paper chip, align the first colorimetric detection area (105), the second colorimetric detection area (202) and the third colorimetric detection area (302), stack and fix the three-layer structure to establish a 3D microfluidic channel; after the 3D paper chip is assembled, modify the third colorimetric detection area (302).

7. The preparation method according to claim 6, characterized in that: When heat treatment is performed in an oven, glass fiber paper (3) is heated for 30 minutes and chromatographic paper (1) is heated for 3 hours; the method for modifying the third colorimetric detection area (302) includes the following steps: first, add 10 μL of 0.1 mol / L H3PO4 solution to the right third colorimetric detection area (302), and after it dries, add 10 μL of a mixed solution of 25 mg / mL 1,5-diphenylcarbazide and 40 mg / mL phthalic anhydride, adding 2 μL in 5 portions each time; the left third colorimetric detection area (302) is used as a control area, and only 10 μL of 0.1 mol / L H3PO4 solution is added; The sample solution is a standard solution or an actual sample solution, wherein: The preparation method of the standard solution includes the following steps: Using 0.01 mol / L hydrochloric acid solution as the solvent, prepare mixed standard solutions of heavy metals with different concentrations: 0.01 mg / L Pb(II), Cu(II), Hg(II) and 0.1 mg / L Cr(VI) mixed solution; 0.025 mg / L Pb(II), Cu(II), Hg(II) and 0.3 mg / L Cr(VI) mixed solution; 0.05 mg / L Pb(II), Cu(II), Hg(II) and 0.5 mg / L Cr(VI) mixed solution; 0.1 mg / L Pb(II), Cu(II), Hg(II) and 0.7 mg / L Cr(VI) mixed solution; 0.3 mg / L Pb(II), Cu(II), Hg(II) and 1.0 mg / L Cr(VI) mixed solution; 0.5 mg / L Pb(II), Cu(II), Hg(II) and 1.0 mg / L Cr(VI) mixed solution; and 0.5 mg / L Pb(II), Cu(II), Hg(II) and Cr(VI) mixed solution. A mixed solution of Pb(II), Cu(II), Hg(II) and 2.0 mg / L Cr(VI), and a mixed solution of 0.5 mg / L Pb(II), Cu(II), Hg(II) and 3.0 mg / L Cr(VI); The preparation method of the actual sample solution includes the following steps: cut leather toys and plastic toys into test specimens with a size of less than 6 mm, then weigh 1 gram of each specimen and transfer it to a 250 mL sealed light-proof container, add 50 mL of 0.07 mol / L hydrochloric acid at 37 °C, shake for 1 minute, check the acidity of the mixture, if the pH value is greater than 1.5, add 2 mol / L hydrochloric acid solution dropwise while shaking the mixture until the pH value reaches 1.0-1.5; then continue shaking at 37 °C for 1 hour, then let it stand at 37 °C for 1 hour, and finally filter the mixture using a 0.45 μm membrane. The obtained filtrate is used for subsequent detection; before detection, adjust the pH value of the filtrate to 2.0 with 2 mol / L sodium hydroxide. All samples must be analyzed within 24 hours after preparation.

8. The application of the dual-mode paper-based analysis device integrating multiple paper materials as described in any one of claims 1 to 5 in simultaneously realizing the electrochemical detection of Pb(II), Cu(II), and Hg(II) and the colorimetric detection of Cr(VI) in a single sample.

9. The application according to claim 8, characterized in that: The application detection method specifically includes the following steps: The sample addition / electrochemical detection area (103) of the 3D paper chip was placed on the circular reaction area of ​​the gold-plated plastic working electrode (5), and then the two were fixed together using a three-electrode holder (4). The three-electrode system was connected to the electrochemical workstation via a data cable to form a complete three-electrode detection system. 100 μL of sample solution was added to the sample addition / electrochemical detection area (103). Under capillary action, the liquid quickly penetrated the paper and diffused to the electrode surface and the colorimetric detection area. The differential pulse anodic stripping voltammetry was used to electrochemically measure Pb(II), Cu(II) and Hg(II). After the electrochemical detection was completed, an image of the colorimetric detection area was taken using a smartphone. To ensure consistent lighting conditions, the chip was placed in a black box with LED light strips for the photo. The resulting image was analyzed in ImageJ software in inverted mode, and the average color intensity of the green channel in the detection area was extracted for colorimetric quantitative analysis of Cr(VI).

10. The application according to claim 9, characterized in that: The relevant parameters for the differential pulse anodic stripping voltammetry experiment are as follows: scanning potential range of -400 to 600 mV, deposition potential of -500 mV, duration of 360 seconds, pulse height of 50 mV, pulse width of 0.01 seconds, pulse period of 0.1 seconds, and potential increment of 10 mV.

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