CN112683889B - A binary chromogenic test paper and a method for rapid and semi-quantitative detection of Cd(Ⅱ) - Google Patents

Abstract

The invention discloses a binary color-developing type test paper and a method for rapid and semi-quantitative detection of Cd(II), comprising using PAN and dithizone (Dz) as composite color-developing agents, attaching them to medium-speed filter paper, and preparing Cd(II) ) binary color-developing test paper; prepare binary color-developing test paper standard color guide; through the control of the type and amount of masking agent, the purpose of selective and rapid determination of Cd(II) is achieved. The invention has the advantages of simple operation method, simple operation, wide color developing range, high accuracy, easy carrying and storage, widening the detection range of Cd(II) by the test paper method, and the like.

Description

A binary chromogenic test paper and a method for rapid and semi-quantitative detection of Cd(Ⅱ)

technical field

The invention belongs to the technical field of test paper preparation and application, relates to a preparation method of Cd(II) semi-quantitative detection test paper, and also relates to a method for detecting Cd(II) content.

Background technique

With the rapid development of mining, metallurgy and other industries, the heavy metal ions in the environment are increasing day by day. Mineral wastewater contains a large amount of heavy metal ions, such as Pb(II) and Cd(II), which will continuously migrate to surface water and groundwater over time. Cd(II) is a common heavy metal ion in water, which has strong toxicity to the biological community in water, and accumulates layer by layer through the food chain, and finally enters the human body, causing serious damage to the heart, liver and bone tissue of the human body; In addition, Cd(II) has the characteristics of strong enrichment and refractory degradation, so it is very important to develop a sensitive detection method for low concentration of Cd(II).

Patent CN103969258A discloses a test paper and method for rapid detection of Cd(II) with the naked eye. Although the operation technical requirements are low and the on-site detection is convenient, the color range is 1×10 ^-6 ~ 1×10 ^-2 mol·L ^-1 , For water samples with a Cd(II) concentration lower than 1×10 ^-6 mol L ^-1 , color development and quantification cannot be performed; patent CN111307778A discloses a preparation method and detection method of a test paper for semi-quantitative detection of copper ions, but the preparation steps of the test paper are cumbersome. And need vacuum drying. Therefore, it is necessary to develop a detection method with simple operation, wide color range and high accuracy.

Contents of the invention

Aiming at the deficiency that the current test paper method has a narrow range of Cd(II) color development, the object of the present invention is to provide a binary color development type test paper and a method for fast semi-quantitative detection of Cd(II), which is simple to operate and has the advantages of color development Wide range, high accuracy, convenient use of test paper, easy to carry and store, widened the detection range of Cd(II) by test paper method and other advantages.

The present invention is achieved through the following technical solutions.

A method for the rapid semi-quantitative detection of Cd(II) of a binary chromogenic test paper, comprising the following steps:

Step 1, prepare PAN/Dz binary color test paper

According to the mass ratio of 0.3/0.2, PAN (1-(2-pyridylazo)-2 naphthol) chloroform solution is mixed with Dz (dithizone) chloroform solution to prepare PAN/Dz chloroform solution binary color developer, and the test paper Immerse in it, take it out after a certain period of time and dry it to get a binary color test paper;

Step 2, prepare PAN/Dz binary color test paper standard color guide

Prepare a series of concentration gradient Cd(II) solutions, add them dropwise on the binary color-developing test paper prepared in step 1, develop color for a certain period of time, blot the remaining Cd(II) solution with absorbent paper, dry, inspect and Take the reaction fragments and make PAN/Dz binary color test paper standard color comparison plate;

Step 3, detection of unknown concentration of Cd(II) solution

Adjust the pH value of the Cd(II) solution to be tested, add masking agents respectively, drop the Cd(II) solution to be tested onto the binary color test paper prepared in step 1, check the color change, and compare it with the standard prepared in step 2 The color plates were compared and its concentration was semi-quantitatively determined.

For above-mentioned technical scheme, the present invention also has further preferred scheme:

Preferably, in the step 1, the test paper is a medium-speed qualitative filter paper, soaked in PAN/Dz chloroform solution for 30-60 minutes, then taken out, and dried in an oven at 40-60°C.

Preferably, in the step 1, the mass concentration of the PAN chloroform solution is 0.003-0.015%, and the mass concentration of the Dz chloroform solution is 0.0015-0.0075%.

Preferably, in the step 2, the color development time is 30-90s.

Preferably, in step 3, the pH of the Cd(II) solution to be tested is adjusted to 5-8.

Preferably, in the step 2, the concentration ranges of the series of Cd(II) standard solutions are 8.90×10 ^-7 to 8.90×10 ^-4 mol·L ^-1 respectively.

Preferably, in the step 3, the masking agent includes the following raw materials in parts by mass:

2-6 parts of thiourea, 2-6 parts of o-phenanthroline, 2-9 parts of citric acid, 13-26 parts of thioglycolic acid.

The present invention has the following beneficial effects due to the adoption of the above technical solutions:

1) The binary color-developing test paper and the method for rapid semi-quantitative detection of Cd(II) provided by the present invention have a color development and inspection time of 30-90 s, which is short in time and is an ideal rapid determination method.

2) The binary chromogenic test paper and the method for rapid semi-quantitative detection of Cd(II) provided by the present invention can realize the detection of Cd(II) with a concentration between 8.90×10 ^-7 and 8.90×10 ^-4 mol/L Semi-quantitative detection, LOD is 8.90×10 ^-7 mol/L.

3) The binary color-developing type test paper and the method for fast semi-quantitative detection of Cd(II) provided by the present invention, compared with the expensive detection instruments used in the laboratory, have low equipment requirements, simple operation methods, wide color range, and accurate High precision, convenient for on-site inspection.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention, constitute a part of the application, and do not constitute an improper limitation of the present invention. In the accompanying drawings:

Figure 1(a) and Figure 1(b) are the UV-visible absorption spectra of PAN(a), Dz(b) and Cd(Ⅱ) before and after complexation, respectively;

Figure 2 is the standard color guide of PAN/Dz binary color cadmium test paper.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, where the schematic embodiments and descriptions of the present invention are used to explain the present invention, but not to limit the present invention.

The embodiment of the present invention provides a binary color test paper and a method for rapid semi-quantitative detection of Cd(II), comprising the following steps:

Step 1, preparing PAN (1-(2-pyridylazo)-2 naphthol)/Dz (dithizone) binary color-developing type test paper.

According to the mass ratio of 0.3/0.2, PAN chloroform solution and Dz chloroform solution are mixed to prepare PAN/Dz chloroform solution binary color developer, wherein, the mass concentration of PAN chloroform solution is 0.003-0.015%, and the mass concentration of Dz chloroform solution is 0.0015-0.0075%. %; Immerse a disc-type medium-speed qualitative filter paper with a diameter of 6 mm in it, soak it in PAN/Dz chloroform solution for 30-60 minutes, take it out, and dry it in an oven at 40-60 ° C to obtain a binary color test paper.

Figure 1(a) and Figure 1(b) show the UV-vis absorption spectra of PAN, Dz and Cd(II) before and after complexation. Mixing PAN and Dz as a composite chromogenic agent can enhance the color change of the reaction on the one hand, and widen the semi-quantitative detection range of Cd(II) on the other hand.

Step 2, prepare PAN/Dz binary color test paper standard color guide

Prepare a series of Cd(II) solutions with concentration gradients, the solution concentrations range from 8.90×10 ^-7 to 8.90×10 ^{- 4} mol·L ^-1 , and add them dropwise on the binary color test paper prepared in step 1 , develop color for 30-90s, blot the residual Cd(II) solution with absorbent paper, dry, examine and take up the reaction fragments, and make a PAN/Dz binary color test paper standard color comparison plate.

Figure 2 shows the standard color guide of PAN/Dz binary colorimetric cadmium test paper.

Step 3, detection of unknown concentration of Cd(II) solution

Adjust the pH value of the Cd(II) solution to be tested to 5-8, and add masking agents for eliminating the interference of other coexisting ions respectively. The masking agents include the following raw materials in parts by mass: 2-6 parts of thiourea, 2-6 parts of phenanthrene Roline, 2-9 parts of citric acid, 13-26 parts of thioglycolic acid.

Pipette the Cd(II) solution to be tested with a rubber dropper, drop it onto the test paper prepared in step 1, check the color change, compare it with the standard color guide prepared in step 2, and conduct a semi-quantitative determination of its concentration .

The present invention is further illustrated below through different embodiments.

Example 1: Detection of Cd(II) concentration in unknown water sample 1

Step 1, prepare PAN/Dz binary color test paper

Prepare a binary chromogenic agent with 0.3/0.2 mass ratio PAN and Dz solution, wherein, the mass concentration of PAN chloroform solution is 0.005%, and the mass concentration of Dz chloroform solution is 0.0075%; immerse a disc-shaped test paper with a diameter of 6mm in it for 30min Afterwards, it was taken out and dried in an oven at 60°C to obtain a binary color-developing test paper.

Step 2, prepare PAN/Dz binary color test paper standard color guide

Prepare a series of Cd(II) solutions with concentration gradients, the solution concentrations range from 8.90×10 ^-7 to 8.90×10 ^{- 4} mol·L ^-1 , and add them dropwise on the binary color test paper prepared in step 1 , develop color for 30 s, blot the residual Cd(II) solution with absorbent paper, dry, inspect and take up the reaction fragments, and make a PAN/Dz binary color test paper standard color comparison plate.

Step 3, detection of unknown concentration of Cd(II) solution

Adjust the pH of the Cd(II) solution to be tested to 7, and add masking agents respectively. The masking agents include the following raw materials in parts by mass: 6 parts of thiourea, 5 parts of phenanthroline, 7 parts of citric acid, and 20 parts of thioglycolic acid.

Take a group of water samples for three parallel experiments, pipette the Cd(II) solution to be tested (pH 7) with a rubber dropper, add it dropwise to the test paper prepared in step 1, and check the color change. Standard color guide for comparison, and semi-quantitative determination of its concentration.

The results of colorimetry showed that the concentration of Cd(Ⅱ) in the solution was between 4.45×10 ^-6 ～8.90×10 ^-6 mol/L. The data obtained by ICP detection are 7.36×10 ^-6 mol/L, which is consistent with the range of results obtained after comparison with the color guide, and the colors appearing among the three groups of parallel samples are also the same, indicating that the test paper has good accuracy and stability.

Embodiment 2: Detection of Cd(II) concentration in unknown water sample 2

Step 1, prepare PAN/Dz binary color test paper

Prepare a binary chromogenic agent with 0.3/0.2 mass ratio PAN and Dz solution, wherein, the mass concentration of PAN chloroform solution is 0.0075%, and the mass concentration of Dz chloroform solution is 0.003%; immerse a disc-shaped test paper with a diameter of 6mm in it for 40min Afterwards, it was taken out and dried in an oven at 50°C to obtain a binary color-developing test paper.

Step 2, prepare PAN/Dz binary color test paper standard color guide

Prepare a series of Cd(II) solutions with concentration gradients, the solution concentrations range from 8.90×10 ^-7 to 8.90×10 ^{- 4} mol·L ^-1 , and add them dropwise on the binary color test paper prepared in step 1 , develop color for 40 s, blot the residual Cd(II) solution with absorbent paper, dry, inspect and take up the reaction fragments, and make a PAN/Dz binary color test paper standard color comparison plate.

Step 3, detection of unknown concentration of Cd(II) solution

Adjust the pH of the Cd(II) solution to be tested to 7, and add masking agents respectively. The masking agents include the following raw materials in parts by mass: 4 parts of thiourea, 6 parts of phenanthroline, 8 parts of citric acid, and 13 parts of thioglycolic acid.

Take a group of water samples for three parallel experiments, pipette the Cd(II) solution to be tested (pH 7) with a rubber dropper, add it dropwise to the test paper prepared in step 1, and check the color change. Standard color guide for comparison, and semi-quantitative determination of its concentration.

The results of colorimetry showed that the concentration of Cd(Ⅱ) in the solution was between 4.45×10 ^-6 ～8.90×10 ^-6 mol/L. The data obtained by ICP detection are 4.59×10 ^-6 mol/L, which is consistent with the range of results obtained after comparison with the color guide, and the colors appearing among the three parallel samples are also the same, indicating that the test paper has good accuracy.

Embodiment 3: the detection of Cd(II) concentration in simulated water sample 1

Step 1, prepare PAN/Dz binary color test paper.

Prepare binary chromogen with 0.3/0.2 mass ratio of PAN and Dz solution, wherein, the mass concentration of PAN chloroform solution is 0.003%, and the mass concentration of Dz chloroform solution is 0.0015%; immerse a disc-shaped test paper with a diameter of 6mm in it for 50min Afterwards, it was taken out and dried in an oven at 40°C to obtain a binary color-developing test paper.

Step 2, prepare PAN/Dz binary color test paper standard color guide

Prepare a series of Cd(II) solutions with concentration gradients, the solution concentrations range from 8.90×10 ^-7 to 8.90×10 ^{- 4} mol·L ^-1 , and add them dropwise on the binary color test paper prepared in step 1 , develop color for 80 s, blot the residual Cd(II) solution with absorbent paper, dry, examine and take up the reaction fragments, and make a PAN/Dz binary color test paper standard color comparison plate.

In step 3, the simulated water sample contains Zn(II), Cu(II) and other interfering ions. Before pipetting the water sample, add a masking agent to eliminate the interference of other coexisting ions. The masking agent is 4 parts of thiourea , 6 parts of o-phenanthroline, 9 parts of citric acid, 13 parts of thioglycolic acid.

Semi-quantitative detection with binary chromogenic test paper, the result is between 4.45×10 ^-4 and 8.90×10 ^-4 mol/L, and the data obtained by ICP detection is 5.21×10 ^-4 mol/L, which is consistent with the color guide After the comparison, the range of results obtained is consistent, and the colors appearing among the three groups of parallel samples are also the same, indicating that the accuracy of the test paper is better.

Embodiment 4: the detection of Cd(II) concentration in simulated water sample 2

Step 1, prepare PAN/Dz binary color test paper.

Prepare binary chromogen with 0.3/0.2 mass ratio of PAN and Dz solution, wherein, the mass concentration of PAN chloroform solution is 0.025%, and the mass concentration of Dz chloroform solution is 0.0035%; immerse a disc-shaped test paper with a diameter of 6mm in it for 40min Afterwards, it was taken out and dried in an oven at 55°C to obtain a binary color-developing test paper.

Step 2, prepare PAN/Dz binary color test paper standard color guide

Prepare a series of Cd(II) solutions with concentration gradients, the solution concentration ranges from 8.90×10 ^-5 to 8.90×10 ^{- 4} mol·L ^-1 , and add them dropwise on the binary color test paper prepared in step 1 , develop color for 75s, blot the residual Cd(II) solution with absorbent paper, dry, inspect and take up the reaction fragments, and make a PAN/Dz binary color test paper standard color comparison plate.

In step 3, the simulated water sample contains Zn(II), Cu(II) and other interfering ions. Before pipetting the water sample, add a masking agent to eliminate the interference of other coexisting ions. The masking agent is 5 parts of thiourea , 5 parts of o-phenanthroline, 7 parts of citric acid, 15 parts of thioglycolic acid.

Semi-quantitative detection with binary chromogenic test paper, the result is between 4.45×10 ^-4 and 8.90×10 ^-4 mol/L, and the data obtained by ICP detection is 7.09×10 ^-4 mol/L, which is consistent with the color guide After the comparison, the range of the results obtained is consistent, and the colors appearing among the three groups of parallel samples are also the same, indicating that the accuracy of the test paper is better.

Example 5: Detection of Cd(II) concentration in smelting wastewater 1

Step 1, prepare PAN/Dz binary color test paper.

Prepare a binary developer with 0.3/0.2 mass ratio of PAN and Dz solutions, wherein the mass concentration of PAN chloroform solution is 0.003%, and the mass concentration of Dz chloroform solution is 0.0055%; immerse a disc-shaped test paper with a diameter of 6mm in it for 60min Afterwards, it was taken out and dried in an oven at 50°C to obtain a binary color-developing test paper.

Step 2, prepare PAN/Dz binary color test paper standard color guide

Prepare a series of Cd(II) solutions with concentration gradients, the solution concentrations range from 8.90×10 ^-7 to 8.90×10 ^{- 4} mol·L ^-1 , and add them dropwise on the binary color test paper prepared in step 1 , develop color for 90s, blot the residual Cd(II) solution with absorbent paper, dry, inspect and take up the reaction fragments, and make a standard color comparison plate of PAN/Dz binary color test paper.

In step 3, the measured water sample is the preliminary treated wastewater from a non-ferrous metal smelter in Shaanxi Province. The waste contains Zn(II), Cu(II), Ni(II), Pb(II) and other interfering ions. Before taking the water sample, add a masking agent for eliminating the interference of coexisting ions in the water sample. The masking agent includes the following raw materials in parts by mass: 2 parts of thiourea, 2 parts of phenanthroline, 2 parts of citric acid, and 26 parts of thioglycolic acid .

Compared with the standard color guide, the concentration of Cd(II) in the measured water sample is between 4.45×10 ^-5 ~ 8.90×10 ^-5 mol/L, and the data obtained by ICP detection is 6.28×10 ^-5 mol/L, The range of the results compared with the color guide is consistent, and the colors appearing between the parallel samples are also the same, indicating that the test paper has good accuracy and applicability.

Example 6: Detection of Cd(II) concentration in smelting wastewater 2

Step 1, prepare PAN/Dz binary color test paper.

Prepare a binary chromogenic agent with 0.3/0.2 mass ratio PAN and Dz solution, wherein, the mass concentration of PAN chloroform solution is 0.0075%, and the mass concentration of Dz chloroform solution is 0.003%; immerse a disc-shaped test paper with a diameter of 6mm in it for 50min Afterwards, it was taken out and dried in an oven at 60°C to obtain a binary color-developing test paper.

Step 2, prepare PAN/Dz binary color test paper standard color guide

Prepare a series of Cd(II) solutions with concentration gradients, the solution concentrations range from 8.90×10 ^-7 to 8.90×10 ^{- 4} mol·L ^-1 , and add them dropwise on the binary color test paper prepared in step 1 , develop color for 60 s, blot the residual Cd(II) solution with absorbent paper, dry, inspect and take up the reaction fragments, and make a PAN/Dz binary color test paper standard color comparison plate.

In step 3, the measured water sample is the preliminary treated wastewater from a non-ferrous metal smelter in Shaanxi Province, which contains Zn(II), Cu(II), Ni(II), Pb(II) and other interfering ions. Before taking water samples, add a masking agent for eliminating the interference of coexisting ions in the water sample. The masking agent includes the following raw materials in parts by mass: 4 parts of thiourea, 6 parts of phenanthroline, 8 parts of citric acid, and 13 parts of thioglycolic acid .

Compared with the standard color guide, the concentration of Cd(II) in the measured water sample is between 4.45×10 ^-5 and 8.90×10 ^-5 mol/L, and the data obtained by ICP detection is 8.63×10 ^-5 mol/L, The range of the results compared with the color guide is consistent, and the colors appearing between the parallel samples are also the same, indicating that the test paper has good accuracy and applicability.

In summary, the present invention provides a binary chromogenic test paper and a method for rapid semi-quantitative detection of Cd(II), the detection range of ^Cd (II) is relatively wide, and the concentration of Semi-quantitative detection of Cd(II) between ×10 ^-4 mol/L, LOD is 8.90×10 ^-7 mol/L, color development and inspection time are both 60s, which takes a short time and has good accuracy , stability and applicability, and the test paper is easy to prepare and easy to operate.

The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solutions disclosed in the present invention, those skilled in the art can make some replacements and modifications to some of the technical features according to the disclosed technical content without creative work. Deformation, these replacements and deformations are all within the protection scope of the present invention.

Claims (6)

1. A method for rapidly and semi-quantitatively detecting Cd (II) by using binary chromogenic test paper is characterized by comprising the following steps:

step 1, preparing PAN/Dz binary color-developing test paper

Mixing the PAN chloroform solution and the Dz chloroform solution according to the mass ratio of 0.3/0.2 to prepare a PAN/Dz chloroform solution binary color developing agent, soaking the test paper in the PAN/Dz chloroform solution binary color developing agent, taking out the test paper after a certain time, and drying the test paper to obtain a binary color developing test paper;

the test paper is medium-speed qualitative filter paper, is soaked in PAN/Dz chloroform solution for 30-60 min and then taken out, and is dried in an oven at 40-60 ℃;

the mass concentration of the PAN chloroform solution is 0.003 to 0.015 percent, and the mass concentration of the Dz chloroform solution is 0.0015 to 0.0075 percent;

step 2, preparing a PAN/Dz binary color development type test paper standard colorimetric plate

Preparing a series of concentration gradient Cd (II) solutions, dropwise adding the solutions on the binary color-developing test paper prepared in the step (1), developing for a certain time, sucking the residual Cd (II) solutions by using absorbent paper, drying, inspecting and taking reaction fragments to prepare a PAN/Dz binary color-developing test paper standard colorimetric plate;

step 3, detecting Cd (II) solution with unknown concentration

And (3) adjusting the pH value of the Cd (II) solution to be detected, respectively adding a masking agent, dropwise adding the Cd (II) solution to be detected onto the binary color-developing test paper prepared in the step (1), detecting the color change, comparing the color change with the standard colorimetric plate prepared in the step (2), and carrying out semi-quantitative determination on the concentration of the Cd (II) solution to be detected.

2. The method for rapidly and semi-quantitatively detecting Cd (II) by using the binary chromogenic test paper as claimed in claim 1, wherein in the step 2, the chromogenic time is 30-90 s.

3. The method for quickly and semi-quantitatively detecting Cd (II) by using the binary color test paper as claimed in claim 1, wherein in step 3, the pH of a solution of Cd (II) to be detected is adjusted to 5-8.

4. The method for rapidly and semi-quantitatively detecting Cd (II) by using the binary chromogenic test paper as claimed in claim 1, wherein in the step 2, the concentration range of the series Cd (II) standard solution is 8.90 x 10 ^-7 ～8.90×10 ^-4 mol·L ^-1 。

5. The method for rapidly and semi-quantitatively detecting Cd (II) by using the binary chromogenic test paper as claimed in claim 1, wherein in the step 3, the masking agent comprises the following raw materials in parts by mass:

2-6 parts of thiourea, 2-6 parts of phenanthroline, 2-9 parts of citric acid and 13-26 parts of thioglycolic acid.

6. A test paper for binary color development used in accordance with any one of claims 1 to 5, wherein the test paper is obtained by immersing medium-speed quantitative filter paper in 0.003 to 0.015% PAN and 0.0015 to 0.0075% dz chloroform solution at a ratio of 0.3/0.2 for 30 to 60 minutes and drying the immersed paper in an oven at 40 to 60 ℃.

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